研究者データベース

佐田 和己(サダ カズキ)
理学研究院 化学部門 物理化学分野
教授

基本情報

所属

  • 理学研究院 化学部門 物理化学分野

職名

  • 教授

学位

  • 博士(工学)(京都大学)

ホームページURL

科研費研究者番号

  • 80225911

J-Global ID

研究キーワード

  • 高吸水性樹脂   架橋   MOF   配位高分子   ネットワーク材料   相転移   温度応答性高分子   分子認識   水素結合   X線構造解析   結晶工学   分子グラフィックス   包接化合物   固相重合   ジエン   高分子電解質   ゲル   イオン対   結晶構造解析   環境材料   静電斥力   カルボン酸   ジスルフィド   金属イオン   立体選択的重合   金基板   ラジカル重合   高分子合成   有機溶媒   光スイッチ   結晶重合   高分子化学   有機結晶   ナノ多孔質結晶   精密重合   ナノ材料   刺激応答性高分子   ナノ分子機械   有機合成化学   超分子化学   分子集合体   

研究分野

  • ナノテク・材料 / 高分子化学
  • ナノテク・材料 / ナノ構造物理
  • ナノテク・材料 / ナノ構造化学
  • ナノテク・材料 / 高分子材料
  • ナノテク・材料 / 機能物性化学
  • ナノテク・材料 / 生体化学
  • ナノテク・材料 / 複合材料、界面
  • ナノテク・材料 / 有機合成化学
  • ナノテク・材料 / 有機合成化学

職歴

  • 2010年04月 - 現在 北海道大学大学院 理学研究院 教授
  • 2007年04月 - 2010年03月 九州大学大学院 工学研究院 准教授
  • 2002年04月 - 2007年03月 九州大学大学院 工学研究院 助教授
  • 1998年04月 - 2002年04月 大阪大学大学院 工学研究科 助手
  • 1995年10月 - 1998年03月 大阪大学 工学部 助手
  • 1990年04月 - 1995年09月 岐阜大学 工学部 助手

学歴

  • 1987年04月 - 1990年03月   京都大学大学院   工学研究科   合成化学専攻 博士後期課程
  • 1985年04月 - 1987年03月   京都大学大学院   工学研究科   合成化学専攻 博士前期課程
  • 1981年04月 - 1985年03月   京都大学   工学部   合成化学科

所属学協会

  • 高分子学会   米国化学会   日本化学会   

研究活動情報

論文

  • M. Akter, J. J. Keya, K. Kayano, A. M. R. Kabir, D. Inoue, H. Hess, K. Sada, A. Kuzuya, H. Asanuma, A. Kakugo
    Science Robotics 7 65 2022年04月20日
  • Hiroshi Inaba, Arif Md. Rashedul Kabir, Akira Kakugo, Kazuki Sada, Kazunori Matsuura
    Chemistry Letters 51 4 348 - 351 2022年04月05日
  • Arif Md. Rashedul Kabir, Tasrina Munmun, Tomohiko Hayashi, Satoshi Yasuda, Atsushi P. Kimura, Masahiro Kinoshita, Takeshi Murata, Kazuki Sada, Akira Kakugo
    ACS Omega 7 4 3796 - 3803 2022年02月01日
  • Hiroshi Inaba, Yurina Sueki, Muneyoshi Ichikawa, Arif Md. Rashedul Kabir, Takashi Iwasaki, Hideki Shigematsu, Akira Kakugo, Kazuki Sada, Kazunori Matsuura
    2022年01月28日 
    AbstractMicrotubules (MTs) play important roles in biological functions by forming superstructures, such as doublets, triplets, and branched structures, in vivo. Formation of these superstructures by exogenous molecules in vitro will be useful not only for understanding the functions of MTs but also as components of MT-based nanomaterials. Here, we developed a tetrameric fluorescent protein Azami-Green (AG) fused with a His-tag and Tau-derived peptide (TP), TP–AG, which can bind to the inside or outside of MTs depending on the polymerization conditions. The binding of TP–AG to the inside of MTs induced the formation, stabilized, and increased the rigidity of the MTs. The binding of TP–AG to the outside of MTs induced various types of MT superstructures, including doublets, multiplets, and branched structures, by recruiting tubulins to MTs. The formation of motile MT aster structures by TP–AG was also observed. The generation of MT superstructures by these exogenous proteins provides guidelines for the design of MT-based nanomaterials.
  • Kentaro Kawai, Kazuki Ikeda, Akane Sato, Akira Kabasawa, Masahiro Kojima, Kenta Kokado, Akira Kakugo, Kazuki Sada, Tatsuhiko Yoshino, Shigeki Matsunaga
    Journal of the American Chemical Society 2022年01月18日
  • Soei Watari, Hiroshi Inaba, Tomonori Tamura, Arif Md. Rashedul Kabir, Akira Kakugo, Kazuki Sada, Itaru Hamachi, Kazunori Matsuura
    Chemical Communications 2022年 
    Stabilization of microtubules was achieved in vitro and in living cells by photo-crosslinking of a Tau-derived peptide using a photo-reactive diazirine group.
  • Syeda Rubaiya Nasrin, Christian Ganser, Seiji Nishikawa, Arif Md. Rashedul Kabir, Kazuki Sada, Takefumi Yamashita, Mitsunori Ikeguchi, Takayuki Uchihashi, Henry Hess, Akira Kakugo
    Science Advances 7 42 2021年10月15日
  • Farhana Afroze, Daisuke Inoue, Tamanna Ishrat Farhana, Tetsuya Hiraiwa, Ryo Akiyama, Arif Md. Rashedul Kabir, Kazuki Sada, Akira Kakugo
    Biochemical and Biophysical Research Communications 563 73 - 78 2021年07月 
    Flocking is a fascinating coordinated behavior of living organisms or self-propelled particles (SPPs). Particularly, monopolar flocking has been attractive due to its potential applications in various fields. However, the underlying mechanism behind flocking and emergence of monopolar motion in flocking of SPPs has remained obscured. Here, we demonstrate monopolar flocking of kinesin-driven microtubules, a self-propelled biomolecular motor system. Microtubules with an intrinsic structural chirality preferentially move towards counter-clockwise direction. At high density, the CCW motion of microtubules facilitates monopolar flocking and formation of a spiral pattern. The monopolar flocking of microtubules is accounted for by a torque generated when the motion of microtubules was obstructed due to collisions. Our results shed light on flocking and emergence of monopolar motion in flocking of chiral active matters. This work will help regulate the polarity in collective motion of SPPs which in turn will widen their applications in nanotechnology, materials science and engineering.(c) 2021 Elsevier Inc. All rights reserved.
  • Dora-M. Răsădean, Takashi Machida, Kazuki Sada, Christopher R. Pudney, G. Dan Pantoș
    Tetrahedron 82 131925 - 131925 2021年02月
  • Arif Md. Rashedul Kabir, Kazuki Sada, Akira Kakugo
    Chemical Communications 57 4 468 - 471 2021年 

    The length of a self-assembled, micro-scale tubular structure is tightly regulated through scission under tensile and compressive stress.

  • Levente Cseri, Rifan Hardian, Shizuka Anan, Hakkim Vovusha, Udo Schwingenschlögl, Peter M. Budd, Kazuki Sada, Kenta Kokado, Gyorgy Szekely
    Journal of Materials Chemistry A 2021年 [査読有り]
     
    Porous nanoparticles with interfacial adhesiveness boost the selectivity of separation membranes to achieve size-selective nanofiltration.
  • Masami Naya, Kenta Kokado, Kazuki Sada
    ACS Applied Polymer Materials 2 11 4415 - 4424 2020年11月13日 
    Multi-thermoresponsiveness which exhibits more than triple phase transitions has not been achieved yet. Current research studies have reported double thermoresponsive copolymers having two kinds of polymer chains. However, the molecular design strategy of triple thermoresponsiveness remains unclear. Herein, we report a triple thermoresponsive chiral homopolymer which exhibits UCST- LCST-UCST-type phase transitions. The polymer contains the alpha,alpha,alpha',alpha'-tetraaryl-2,2-disubstituted 1,3-dioxolane-4,5-dimethanol moiety in the side chains, where multiple supramolecular complexes between the host polymer and guest molecules are formed. The formations and dynamic changes in the multiple complexes of model compounds were monitored by H-1 NMR spectroscopy. We concluded that the key factor of the triple thermoresponsive behavior is the stoichiometric change in the multiple complexes. This work can extend the molecular design of the thermoresponsive polymer and lead to the next stage of functional polymer materials.
  • Yuma Tanaka, Takashi Machida, Toshiaki Noumi, Kazuki Sada, Kenta Kokado
    ORGANIC CHEMISTRY FRONTIERS 7 18 2649 - 2656 2020年09月 [査読有り][通常論文]
     
    The structural change in the excited state evidently plays a crucial role in the quenching process of organic molecules exhibiting aggregation-induced emission (AIE, thus AIEgens) in the solution state. In this report, we synthesized a series of tetraphenylethylene (TPE) macrocycles having a covalent oligoethylene glycol (OEG) linkage between vicinal phenyl rings with various chain lengths and substituting positions. As a result, the obtained TPE macrocycles which are tightly fastened by short OEG chains showed strong emission even in the solution state. The tight fastener efficiently restricted the pi twist around the central C-C bond in TPE macrocycles, which was also supported by theoretical computations. These results provide very important information about the origin of the AIE properties of TPE derivatives, which will lead to the rational design of new AIEgens.
  • Hiroshi Inaba, Miyuu Nagata, Kyeongmi Juliano Miyake, Arif Md Rashedul Kabir, Akira Kakugo, Kazuki Sada, Kazunori Matsuura
    Polymer Journal 52 9 1143 - 1151 2020年09月01日 [査読有り][通常論文]
     
    © 2020, The Society of Polymer Science, Japan. The cyclization of peptides is a valuable strategy for the development of binding motifs to target proteins with improved affinity. Microtubules (MTs) are important targets for therapeutics, and a variety of MT-targeted drugs and peptides have recently been developed. We have previously designed a Tau-derived peptide (TP) that binds to the interior of MTs. In the present study, the development of a cyclic TP (TCP) for enhanced binding to tubulin and the stabilization of MTs are described. The fluorescently labeled cyclic peptide containing three glycine linkers (TCP3-TMR) exhibited a remarkably enhanced binding affinity to tubulin. The cyclic peptide was also demonstrated to stabilize MTs by enhancing polymerization and reducing depolymerization. Moreover, MTs were effectively formed by the treatment of cyclic peptides in the presence of guanosine triphosphate (GTP), while the linear peptide showed no such effect. These findings indicate that TCP is a useful binding motif that can stabilize MTs and is valuable for various therapeutic and material applications.
  • Syeda Rubaiya Nasrin, Tsukasa Ishihara, Arif Md Rashedul Kabir, Akihiko Konagaya, Kazuki Sada, Akira Kakugo
    Polymer Journal 52 8 969 - 976 2020年08月01日 [査読有り][通常論文]
     
    © 2020, The Society of Polymer Science, Japan. Microtubules, one of the major components of the cytoskeleton, play important roles as pathways for neuronal transport of cellular traffic. The loss of structural stability of microtubules causes detrimental effects on neurons and may contribute to several neurodegenerative diseases, such as Alzheimer’s disease, amyotrophic lateral sclerosis, Huntington’s disease, etc. The triazolopyrimidine class compound cevipabulin is a synthetic microtubule-stabilizing agent that has recently emerged as a drug for the treatment of Alzheimer’s disease. However, the mechanism of microtubule stabilization by cevipabulin has not yet been revealed. Here, we explored the effect of cevipabulin on stabilizing microtubules polymerized from purified tubulins in vitro. We observed the effects of the concentration of microtubule-stabilizing drugs, incubation time, and modification of the cevipabulin structure on the stabilization of microtubules in comparison to those of the most commonly used anticancer drug, paclitaxel. This study will provide insight into the action of cevipabulin in the treatment of neurodegenerative diseases.
  • Mousumi Akter, Jakia Jannat Keya, Arif Md Rashedul Kabir, Hiroyuki Asanuma, Keiji Murayama, Kazuki Sada, Akira Kakugo
    Chemical Communications 56 57 7953 - 7956 2020年07月21日 [査読有り][通常論文]
     
    © 2020 The Royal Society of Chemistry. We regulate the persistency in motion of kinesin-driven microtubules (MTs) simply using a photoresponsive DNA (pDNA) and ultraviolet (UV)-visible light. The path persistence length of MTs, which is a measure of the persistency in their motion, increases and decreases upon illuminating the MTs with UV and visible light respectively. Moreover, pDNA is found to work as a shield for MTs against damage under UV irradiation.
  • Hiroshi Inaba, Mayuki Yamada, Mst Rubaya Rashid, Arif Md Rashedul Kabir, Akira Kakugo, Kazuki Sada, Kazunori Matsuura
    Nano Letters 20 7 5251 - 5258 2020年07月08日 [査読有り][通常論文]
     
    Copyright © 2020 American Chemical Society. Construction of magnetotactic materials is a significant challenge in nanotechnology applications such as nanodevices and nanotransportation. Artificial magnetotactic materials can be designed from magnetotactic bacteria because these bacteria use magnetic nanoparticles for aligning with and moving within magnetic fields. Microtubules are attractive scaffolds to construct magnetotactic materials because of their intrinsic motility. Nonetheless, it is challenging to magnetically control their orientation while retaining their motility by conjugating magnetic nanoparticles on their outer surface. Here we solve the issue by encapsulating magnetic cobalt-platinum nanoparticles inside microtubules using our developed Tau-derived peptide that binds to their internal pockets. The in situ growth of cobalt-platinum nanoparticles resulted in the formation of a linear-chain assembly of nanoparticles inside the microtubules. The magnetic microtubules significantly aligned with a high order parameter (0.71) along the weak magnetic field (0.37 T) and showed increased motility. This work provides a new concept for designing magnetotactic materials.
  • Daisuke Inoue, Arif Md Rashedul Kabir, Kiyotaka Tokuraku, Kazuki Sada, Akira Kakugo
    Advanced Materials Interfaces 7 13 2020年07月01日 [査読有り][通常論文]
     
    © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Biomolecular motors are the smallest natural machines that can convert chemical energy into mechanical work with much higher energy efficiencies compared to man-made machineries. Nowadays, reconstructed biomolecular motors, such as microtubules–kinesin, are successfully utilized for nanotechnological applications, e.g., in nanotransportation, parallel computation, molecular robotics, and so on. However, stochastic nature of their motion poses a limitation to their applications, which is difficult to control particularly under spatial constraints. In this work, top-down and bottom-up approaches are combined to address this problem in a gliding assay of microtubules. Through mechanical stimulation of the motile microtubule filaments, parallelization of the filaments is demonstrated concurrently in hundreds of microwells. The orientation of plenty of motile microtubules in confined space should further accelerate nanotechnological applications of biomolecular motors.
  • Takashi Machida, Takeshi Iwasa, Tetsuya Taketsugu, Kazuki Sada, Kenta Kokado
    CHEMISTRY-A EUROPEAN JOURNAL 26 36 8028 - 8034 2020年06月 [査読有り][通常論文]
     
    Aggregation-induced emission (AIE) is a fascinating phenomenon because of the applications of luminescent materials in the aggregated state, which exploit the large structural changes of the molecules in the excited state. Recently, it was reported that triphenylphosphane derivatives show AIE behavior in which they undergo potentially large structural changes in the excited state. Inspired by this report, photoinduced pyramidal inversion behavior of phosphanes was investigated. In photochemical experiments, the prepared P-stereogenic phosphanes exhibited photoracemization in dilute solution, and a negative correlation was observed between the photoracemization and the AIE phenomenon. Theoretical computations revealed that the inversion barrier in the excited state was much smaller than that in the ground state. This is the first report on the photoinduced pyramidal inversion behavior of phosphanes, which will provide new and unexplored applications.
  • Syeda Rubaiya Nasrin, Arif Md Rashedul Kabir, Kazuki Sada, Akira Kakugo
    Polymer Journal 52 6 655 - 660 2020年06月01日 [査読有り][通常論文]
     
    © 2020, The Society of Polymer Science, Japan. Abstract: The glutaraldehyde fixation method for fixing tissues is attractive for its ease of use and straightforward surface chemistry. We investigated the effect of glutaraldehyde-induced microtubule immobilization on kinesin-driven cargo transport along microtubules and found that at low glutaraldehyde concentrations, the microtubule–kinesin interaction remains unperturbed. Such findings may facilitate the application of the glutaraldehyde fixation method for many in vitro studies aiming to build nanodevices powered by the microtubule–motor protein interaction.
  • Radial alignment of microtubules through tubulin polymerization in an evaporating droplet
    Syeda Rubaiya Nasrin, Tanjina Afrin, Arif Md. Rashedul Kabir, Daisuke Inoue, Takayuki Torisawa, Kazuhiro Oiwa, Kazuki Sada, Akira Kakugo
    PLOS ONE 0231352  2020年04月 [査読有り][通常論文]
  • Arif Md Rashedul Kabir, Kazuki Sada, Akira Kakugo
    Biochemical and Biophysical Research Communications 524 1 249 - 254 2020年03月26日 [査読有り][通常論文]
     
    © 2020 Elsevier Inc. Microtubule is the most rigid component of eukaryotic cytoskeleton that plays pivotal roles in many important cellular events. Microtubules are known to undergo bending or buckling in cells which often results in breaking of this cytoskeletal protein filament. Various cellular events such as cell migration, chromosome segregation, etc. are dependent on the buckling induced breaking of microtubules. However, the reason behind the breaking of buckled microtubules in cell has remained obscure yet. In this work, we have demonstrated breaking of microtubules on a 2D elastic medium by applying compressive stress. The applied compressive stress caused buckling of the microtubules which ultimately resulted in their breaking. We show that breaking of the buckled microtubules cannot be accounted for by considering the changes in curvature of the microtubules due to mechanical deformation. Our results confirm that, it is the interaction of kinesin, a microtubule-associated motor protein, with microtubules which plays the key role in breaking of the buckled microtubules on the 2D elastic medium. The breaking of buckled microtubules is ascribed to decrease in rigidity of microtubules upon interaction with kinesins. This work for the first time confirms the involvement of a microtubule-associated motor protein in breaking of microtubules under compressive stress, which will help further clarify the mechanism of breaking of buckled microtubules in cells and its significance in the cellular events.
  • Masami Naya, Kenta Kokado, Kira Beth Landenberger, Shokyoku Kanaoka, Sadahito Aoshima, Kazuki Sada
    Macromolecular Chemistry and Physics 221 5 2020年03月01日 [査読有り][通常論文]
     
    © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Thermoresponsive polymers in water, for example, poly(N-isopropylacrylamide) (PNIPAM) are investigated extensively, due to a wide range of biomedical applications. However, the attempts to control thermoresponsiveness are still rare in less or nonpolar media. Herein, the three thermoresponsive homopolymers tethering an N-butylurea group in the side chain with a different polymer backbone are reported. They exhibit lower critical solution temperature (LCST)-type and upper critical solution temperature (UCST)-type thermoresponsiveness depending on association of the urea group in the polymer chain and hydrogen bonding small molecules (effectors) in ternary systems (polymer/effector/organic solvent). The difference of polymer backbone appears as their change of solvophobicity in organic solvents. Poly(methacrylate) backbone needs more amount of the effector in nonpolar organic solvents, and poly(vinyl ether) backbone needs more amount in polar organic solvents. However, the influence of polymer backbone is too little to change the phase transition behavior, and the thermoresponsiveness is dominated by association and dissociation of hydrogen bondings between polymers and effectors. The supramolecular design of the thermoresponsive polymers is strong and extensible for the design of their phase transitions.
  • Shunjiro Nagata, Kenta Kokado, Kazuki Sada
    CrystEngComm 22 6 1106 - 1111 2020年02月14日 [査読有り][通常論文]
     
    This journal is © The Royal Society of Chemistry. The controlled release of small molecules from carrier materials by manipulating the environmental conditions has potential for use in drug delivery. In the present study, we demonstrate the controlled release of a guest molecule (procainamide) from a metal-organic framework (MOF). The MOF is covered with a copolymer of N-isopropyl acrylamide (NIPAM) and acrylic acid (AA) by post-synthetic modification. The polymer exhibits a rapid and reversible coil-globule transition that is both pH- and thermoresponsive, thereby allowing the guest molecules to be released from the MOF in an "on-off" manner. At high pH (6.86) or low temperatures (<25 °C) - when the polymer adopts a coil conformation - the guest molecules are rapidly released from the MOF, whereas at low pH (4.01) or high temperatures (>40 °C) - when the polymer adopts a globule conformation - the release of the guest molecules is suppressed. The release can be halted by applying external stimuli even after starting the release. The MOF-derived controllable container introduced here will facilitate targeted drug delivery and controlled release of therapeutic agents.
  • Tasrina Munmun, Arif Md Rashedul Kabir, Kazuki Sada, Akira Kakugo
    Sensors and Actuators, B: Chemical 304 2020年02月01日 [査読有り][通常論文]
     
    © 2019 Elsevier B.V. Nanoscale transportation in engineered environments is critical towards designing efficient and smart hybrid bio-nanodevices. Biomolecular motors, the smallest natural machines, are promising as actuators as well as sensors in hybrid nanodevices and hold enormous potentials in nanoscale transportation. Highly specific regulation of the activity of biomolecular motors is the key to control such integrated nanodevices. We present a simple method to regulate the activity of a biomolecular motor system, microtubule (MT)-kinesin by using a natural osmolyte trimethylamine-N-oxide (TMAO). Motility of kinesin-driven MTs in an in vitro gliding assay is regulated over a broad spectrum by using TMAO in a concentration dependent manner. The regulation of MT motility is rapid, reversible and repeatable over multiple cycles. Interestingly, the motility of MTs can be completely turned off using TMAO of a relatively high concentration. The halted motility of MTs is fully restored upon elimination of TMAO. Repeated cycles of TMAO addition and removal enable cyclical inhibition and restoration of the motility of MTs. These results demonstrate an ability to control nanoscale motion of a biomolecular motor in an artificial environment. This work facilitates further tunability over functions of biomolecular motors, which in turn will foster their nanotechnological applications, such as in nano-transportation.
  • Tasrina Munmun, Arif Md Rashedul Kabir, Yukiteru Katsumoto, Kazuki Sada, Akira Kakugo
    Chemical Communications 56 8 1187 - 1190 2020年 [査読有り][通常論文]
     
    © The Royal Society of Chemistry. Trimethylamine N-oxide is found to be effective in regulating the interaction between microtubules and kinesins over a wide temperature range. The lifetime of the motility of microtubules on kinesins at high temperatures is prolonged using trimethylamine N-oxide. The activation energy of microtubule motility is increased by trimethylamine N-oxide. Prolonged operation at high temperatures decreased the activation energy of MT motility despite the increase in concentration of trimethylamine N-oxide.
  • Takashi Machida, Takeshi Iwasa, Tetsuya Taketsugu, Kazuki Sada, Kenta Kokado
    Chemistry - A European Journal 26 36 7965 - 7965 2020年 [査読無し][通常論文]
     
    © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Invited for the cover of this issue is Kenta Kokado and co-workers at Hokkaido University. The cover picture describes the interesting pyramidal inversion behavior of phosphanes in the excited state, like entering “the Mirror World”, which we found in this research. Read the full text of the article at 10.1002/chem.202000264.
  • Syeda Rubaiya Nasrin, Tanjina Afrin, Arif Md Rashedul Kabir, Daisuke Inoue, Takayuki Torisawa, Kazuhiro Oiwa, Kazuki Sada, Akira Kakugo
    ACS Applied Materials and Interfaces 2020年 [査読有り][通常論文]
     
    Copyright © 2020 American Chemical Society. Mechanical stress on cells has profound influences on biological processes, such as cell shape regulation, the formation of tissue patterns, and development. Recently, mechanosensing properties of the microtubule, an important cytoskeletal component, have drawn attention. In this work, we studied cargo transport by dynein, a microtubule-associated motor protein, along microtubules deformed under mechanical stress. We reveal that the microtubule deformation took place as a response to the applied stress and that the deformation of microtubules facilitated the transport of dynein-driven quantum dots. This finding will provide opportunities to explore the role of microtubules as molecular mechanotransducers in cellular processes.
  • Daisuke Inoue, Greg Gutmann, Takahiro Nitta, Arif Md Rashedul Kabir, Akihiko Konagaya, Kiyotaka Tokuraku, Kazuki Sada, Henry Hess, Akira Kakugo
    ACS Nano 13 11 12452 - 12460 2019年11月26日 [査読有り][通常論文]
     
    © 2019 American Chemical Society. Boundary conditions are important for pattern formation in active matter. However, it is still not well-understood how alterations in the boundary conditions (dynamic boundary conditions) impact pattern formation. To elucidate the effect of dynamic boundary conditions on the pattern formation by active matter, we investigate an in vitro gliding assay of microtubules on a deformable soft substrate. The dynamic boundary conditions were realized by applying mechanical stress through stretching and compression of the substrate during the gliding assay. A single cycle of stretch-and-compression (relaxation) of the substrate induces perpendicular alignment of microtubules relative to the stretch axis, whereas repeated cycles resulted in zigzag patterns of microtubules. Our model shows that the orientation angles of microtubules correspond to the direction to attain smooth movement without buckling, which is further amplified by the collective migration of the microtubules. Our results provide an insight into understanding the rich dynamics in self-organization arising in active matter subjected to time-dependent boundary conditions.
  • Kenta Kokado, Masami Naya, Kazuki Sada
    Sustainable Nanoscale Engineering: From Materials Design to Chemical Processing 351 - 372 2019年09月19日 [査読有り][通常論文]
  • Syeda Rubaiya Nasrin, Arif Md Rashedul Kabir, Akihiko Konagaya, Tsukasa Ishihara, Kazuki Sada, Akira Kakugo
    Biochemical and Biophysical Research Communications 516 3 760 - 764 2019年08月27日 [査読有り][通常論文]
     
    © 2019 Elsevier Inc. We report the utility of cevipabulin as a stabilizing agent for microtubules. Cevipabulin-stabilized microtubules were more flexible compared to the microtubules stabilized by paclitaxel, the most commonly used microtubule stabilizing agent. Similar to the paclitaxel-stabilized microtubules, cevipabulin-stabilized microtubules were driven by kinesins in an in vitro gliding assay. The velocity of cevipabulin-stabilized microtubules was significantly higher than that of paclitaxel-stabilized microtubules. These findings will enrich the variety of microtubules with difference in mechanical and dynamic properties and widen their applications in nanotechnology.
  • Hiroshi Inaba, Takahisa Yamamoto, Takashi Iwasaki, Arif Md Rashedul Kabir, Akira Kakugo, Kazuki Sada, Kazunori Matsuura
    ACS Omega 4 6 11245 - 11250 2019年06月27日 [査読有り][通常論文]
     
    © 2019 American Chemical Society. Microtubules (MTs) are key cytoskeletal components that modulate various cellular activities with their dynamic structural changes, including polymerization and depolymerization. To monitor the dynamics of MTs in living cells, many drug-based fluorescent probes have been developed; however, these also potentially disturb the polymerization/depolymerization of MTs. Here, we report nondrug, peptide-based fluorescent probes to monitor MTs in living cells. We employed a Tau-derived peptide (TP) that has been shown to bind MTs without inhibiting polymerization/depolymerization in vitro. We show that a tetramethylrhodamine (TMR)-labeled TP (TP-TMR) is internalized into HepG2 cells and binds to intracellular MTs, enabling visualization of MTs as clear, fibrous structures. The binding of TP-TMR shows no apparent effects on polymerization/depolymerization of MTs induced by MT-targeted drugs and temperature change. The main uptake mechanism of TP-TMR was elucidated as endocytosis, and partial endosomal escape resulted in the binding of TP-TMR to MTs. TP-TMR exhibited no cytotoxicity compared with MT-targeted drug scaffolds. These results indicate that TP scaffolds can be exploited as useful MT-targeted tools in living cells, such as in long-term imaging of MTs.
  • Kenta Kokado, Kazuki Sada
    Angewandte Chemie - International Edition 58 26 8632 - 8639 2019年06月24日 [査読無し][通常論文]
     
    © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Aggregation-induced emission (AIE) is a photoluminescence phenomenon in which an AIE luminogen (AIEgen) exhibits intense emission in the aggregated or solid state but only weak or no emission in the solution state. Understanding the mechanism of AIE requires consideration of excited state molecular geometry (for example, a π twist). This Minireview examines the history of AIEgens with a focus on the representative AIEgen, tetraphenylethylene (TPE). The mechanisms of solution-state quenching are reviewed and the crucial role of excited-state molecular transformations for AIE is discussed. Finally, recent progress in understanding the relationship between excited state molecular transformations and AIE is overviewed for a range of different AIEgens.
  • Kento Matsuda, Arif Md Rashedul Kabir, Naohide Akamatsu, Ai Saito, Shumpei Ishikawa, Tsuyoshi Matsuyama, Oliver Ditzer, Md Sirajul Islam, Yuichi Ohya, Kazuki Sada, Akihiko Konagaya, Akinori Kuzuya, Akira Kakugo
    Nano Letters 19 6 3933 - 3938 2019年06月12日 [査読有り][通常論文]
     
    © 2019 American Chemical Society. DNA has been well-known for its applications in programmable self-assembly of materials. Nonetheless, utility of DNA origami, which offers more opportunity to realize complicated operations, has been very limited. Here we report self-assembly of a biomolecular motor system, microtubule-kinesin mediated by DNA origami nanostructures. We demonstrate that a rodlike DNA origami motif facilitates self-assembly of microtubules into asters. A smooth-muscle like molecular contraction system has also been realized using the DNA origami in which self-assembled microtubules exhibited fast and dynamic contraction in the presence of kinesins through an energy dissipative process. This work provides potential nanotechnological applications of DNA and biomolecular motor proteins.
  • Shizuka Anan, Yumi Mochizuki, Kenta Kokado, Kazuki Sada
    Angewandte Chemie - International Edition 58 24 8018 - 8023 2019年06月11日 [査読有り][通常論文]
     
    © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim The A–A/B–B step-growth copolymerization between a monomer immobilized in the crystalline state and a monomer mobile in the solution state is demonstrated. One of the two monomers was immobilized as organic ligands of the metal–organic framework (MOF) and polymerized with the mobile guest monomer, resulting in the formation of linear polymers. The polymerization behavior was completely different from that of the solution polymerizations. In particular, the degrees of polymerization (DP) converged to a specific value depending on the MOF structures. The inevitable termination is caused not by imperfectness of the polymerization reaction, but by the selection of the two polymerization partners among the several adjacent immobilized monomers. This is fully supported by the Monte Carlo simulation on the basis of the polymerization mechanism. Precise immobilization of monomers in the supramolecular assemblies is a promising way for the controlled A–A/B–B step-growth polymerization.
  • Nobuhito Sakamoto, Masahiko Ohta, Kenta Kokado, Kazuki Sada
    New Journal of Chemistry 43 37 14853 - 14858 2019年 [査読有り][通常論文]
     
    © 2019 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique. In the present study, we designed tetrahedral tetraarylborate pentads which were synthesized by a typical click reaction, copper-catalyzed azide-alkyne cyclization. The synthesis of the borate pentads was confirmed by FT-IR and NMR spectroscopies, and NMR measurements indicated a rapid exchange of bound and unbound counter cations. The obtained borate pentads exhibited a representative behavior of weak electrolytes, and thus a decrease of their concentration caused a rapid increase of their molar conductivity, especially at the limit of dilution. Additionally, the observed association constant did not correspond to the theoretical association constant, probably because of the multivalent ionic dissociation dependent on the dielectric constant of the media.
  • Shizuka Anan, Kenta Kokado, Kazuki Sada
    Chemistry Letters 48 3 285 - 287 2019年 [査読有り][通常論文]
     
    © 2019 The Chemical Society of Japan. An octahedral metal-organic framework (MOF), UiO-68, with two hydroxymethyl groups (UiO68-hyd) was synthesized for the first time and the hydroxy groups were post-synthetically modified with iso(thio)cyanates to form (thio)urethanes. Several organotins and tertiary amines were used as catalysts for the modification of UiO68-hyd with butyl isocyanate (BuNCO), and 70% of hydroxy groups reacted after 7 days. Moreover, various isocyanate and isothiocyanate compounds were successfully modified on UiO68-hyd.
  • Md Jahirul Islam, Kazuya Matsuo, Halley M. Menezes, Masayuki Takahashi, Hidehiko Nakagawa, Akira Kakugo, Kazuki Sada, Nobuyuki Tamaoki
    Organic and Biomolecular Chemistry 17 1 53 - 65 2019年 [査読有り][通常論文]
     
    © 2019 The Royal Society of Chemistry. Linear motor proteins including kinesin and myosin are promising biomaterials for developing nano-devices. Photoswitchable substrates of these biomotors can be used to optically regulate the motility of their associated cytoskeletal filaments in in vitro systems. Here, we describe the discovery of the myosin selective azobenzene-tethered triphosphate. It enables the specific photocontrol over myosin in a reversible mode with the composite motility assay composed of both kinesin and myosin. The mechanistic insight into this myosin selectivity is also explained with the docking simulation study.
  • Hiroshi Inaba, Takahisa Yamamoto, Takashi Iwasaki, Arif Md Rashedul Kabir, Akira Kakugo, Kazuki Sada, Kazunori Matsuura
    Chemical Communications 55 62 9072 - 9075 2019年 [査読無し][通常論文]
     
    © 2019 The Royal Society of Chemistry. We constructed GFP-encapsulated microtubules (MTs) using a Tau-derived peptide which binds to their interior. The encapsulation of the GFP dramatically increased the rigidity of MTs, resulting in their enhanced velocity on a kinesin-coated substrate. Moreover, the GFP-encapsulated MTs were significantly more stable than normal MTs.
  • Jakia Jannat Keya, Ryuhei Suzuki, Arif Md Rashedul Kabir, Daisuke Inoue, Hiroyuki Asanuma, Kazuki Sada, Henry Hess, Akinori Kuzuya, Akira Kakugo
    Nature Communications 9 1 2018年12月01日 [査読有り][通常論文]
     
    © 2018 The Author(s). In nature, swarming behavior has evolved repeatedly among motile organisms because it confers a variety of beneficial emergent properties. These include improved information gathering, protection from predators, and resource utilization. Some organisms, e.g., locusts, switch between solitary and swarm behavior in response to external stimuli. Aspects of swarming behavior have been demonstrated for motile supramolecular systems composed of biomolecular motors and cytoskeletal filaments, where cross-linkers induce large scale organization. The capabilities of such supramolecular systems may be further extended if the swarming behavior can be programmed and controlled. Here, we demonstrate that the swarming of DNA-functionalized microtubules (MTs) propelled by surface-adhered kinesin motors can be programmed and reversibly regulated by DNA signals. Emergent swarm behavior, such as translational and circular motion, can be selected by tuning the MT stiffness. Photoresponsive DNA containing azobenzene groups enables switching between solitary and swarm behavior in response to stimulation with visible or ultraviolet light.
  • Jakia Jannat Keya, Arif Md Rashedul Kabir, Daisuke Inoue, Kazuki Sada, Henry Hess, Akinori Kuzuya, Akira Kakugo
    Scientific Reports 8 1 2018年12月01日 [査読有り][通常論文]
     
    © 2018, The Author(s). Recently we demonstrated swarming of a self-propelled biomolecular motor system microtubule (MT)-kinesin where interactions among thousands of motile MTs were regulated in a highly programmable fashion by using DNA as a processor. However, precise control of this potential system is yet to be achieved to optimize the swarm behavior. In this work, we systematically controlled swarming of MTs on kinesin adhered surface by different physicochemical parameters of MT-kinesin and DNA. Tuning the length of DNA sequences swarming was precisely controlled with thermodynamic and kinetic feasibility. In addition, swarming was regulated using different concentration of DNA crosslinkers. Reversibility of swarming was further controlled by changing the concentration of strand displacement DNA signal allowing dissociation of swarm. The control over the swarm was accompanied by variable stiffness of MTs successfully, providing translational and circular motion. Moreover, the morphology of swarm was also found to be changed not only depending on the stiffness but also body length of MTs. Such detail study of precise control of swarming would provide new insights in developing a promising molecular swarm robotic system with desired functions.
  • Hiroshi Inaba, Takahisa Yamamoto, Arif Md Rashedul Kabir, Akira Kakugo, Kazuki Sada, Kazunori Matsuura
    Chemistry - A European Journal 24 56 14958 - 14967 2018年10月09日 [査読有り][通常論文]
     
    © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. Microtubules are cytoskeletal filaments that serve as attractive scaffolds for developing nanomaterials and nanodevices because of their unique structural properties. The functionalization of the outer surface of microtubules has been established for this purpose. However, no attempts have been made to encapsulate molecules inside microtubules with 15 nm inner diameter. The encapsulation of various molecular cargos inside microtubules constitutes a new concept for nanodevice and nanocarrier applications of microtubules. Here, we developed peptide motifs for binding to the inner surface of microtubules, based on a repeat domain of the microtubule-associated protein Tau. One of the four Tau-derived peptides, 2N, binds to a taxol binding pocket of β-tubulin located inside microtubules by preincubation with tubulin dimer and subsequent polymerization of the peptide-tubulin complex. By conjugation of 2N to gold nanoparticles, encapsulation of gold nanoparticles inside microtubules was achieved. The methodology for molecular encapsulation inside microtubules by the Tau-derived peptide is expected to advance the development of microtubule-based nanomaterials and nanodevices.
  • Takahiro Jimbo, Mikako Tsuji, Ryosuke Taniguchi, Kazuki Sada, Kenta Kokado
    Crystal Growth and Design 18 7 3863 - 3869 2018年07月05日 [査読有り][通常論文]
     
    Copyright © 2018 American Chemical Society. We aim to control the photoluminescence property of co-crystals derived from an aggregation-induced emission luminogen (AIEgen) through other components in the co-crystal. For this purpose, we prepared co-crystals of a typical AIEgen, tetraphenylethene having four hydroxy groups (THPE), and hydrogen-bond acceptors (HBAs) containing nitrogen atoms. The crystallographic study showed that the hydrogen-bonding pattern and inclusion of crystallization solvents are significantly influenced by the employed HBA, depending on the size, position of nitrogen atoms, and basicity of the HBA, thanks to the moderate hydrogen-bonding ability of THPE. The photoluminescence properties of the co-crystals are governed by the employed HBA, and thus, co-crystals derived from imidazole derivatives or 1,4-diazabicyclo[2.2.2]octane exhibit intense photoluminescence, while those from pyridine derivatives and an electron-deficient imidazole derivative do not show any photoluminescence. The involvement of photoinduced electron transfer causes quenching of the co-crystals derived from pyridine derivatives, which is confirmed by theoretical computations. These observations imply that the photoluminescence properties of co-crystals derived from AIEgens can be tuned through other components in the co-crystal. ©
  • Kazuki Sada
    Polymer Journal 50 6 473 - 473 2018年06月01日 [査読有り][通常論文]
     
    © 2018 The Society of Polymer Science, Japan. In the original version of this article, owing to an error during the production process, the author biography was unfortunately missed. The correct author biography is given below.
  • Kazuki Sada, Kenta Kokado, Sokuro Sunaga
    Kobunshi 67 5 257 - 261 2018年05月 [査読有り][通常論文]
     
    © 2018 the Society of Polymer Science, Japan. After the disaster in Deepwater Horizon oil spill in 2010, the development of sorbents for organic solvents including oil has been attracting considerable interest among material scientists, due to increase of social interest against the large-scale pollution to natural environment. In this account we summarize recent advances in designing such sorbents with high efficiency by the two different approaches. One is super-absorbent polymers for organic solvents with high swelling ability. The other is highly porous and hydrophobic materials with large surface areas such as sponges and carbon aerogels. Both of them have high sorption efficiency for organic solvents, and most of the latter have good performances for separation of oil from oil-water mixture.
  • Kazuki Sada
    Polymer Journal 50 4 285 - 299 2018年04月 [査読無し][通常論文]
     
    © 2018 The Society of Polymer Science, Japan. This review demonstrates our approaches for developing functional polymer systems using dissociation processes in nonpolar media. One is the molecular design of highly swellable gels known as superabsorbent polymers in nonpolar organic solvents, and the other is the supramolecular design of thermo-responsive polymers. Both of them are well documented in water, but no practical molecular design for other media have ever been proposed. For designing these behaviors, the dissociation or release of the low-molecular component from macromolecular complexes should play a key role. Therefore, controlling the dissociation processes in supramolecular chemistry should be another important strategy for developing functional polymer materials.
  • Ren Sasaki, Arif Md Rashedul Kabir, Daisuke Inoue, Shizuka Anan, Atsushi P. Kimura, Akihiko Konagaya, Kazuki Sada, Akira Kakugo
    Nanoscale 10 14 6323 - 6332 2018年04月 [査読有り][通常論文]
     
    © 2018 The Royal Society of Chemistry. Self-organized structures of biomolecular motor systems, such as cilia and flagella, play key roles in the dynamic processes of living organisms, like locomotion or the transportation of materials. Although fabrication of such self-organized structures from reconstructed biomolecular motor systems has attracted much attention in recent years, a systematic construction methodology is still lacking. In this work, through a bottom-up approach, we fabricated artificial cilia from a reconstructed biomolecular motor system, microtubule/kinesin. The artificial cilia exhibited a beating motion upon the consumption, by the kinesins, of the chemical energy obtained from the hydrolysis of adenosine triphosphate (ATP). Several design parameters, such as the length of the microtubules, the density of the kinesins along the microtubules, the depletion force among the microtubules, etc., have been identified, which permit tuning of the beating frequency of the artificial cilia. The beating frequency of the artificial cilia increases upon increasing the length of the microtubules, but declines for the much longer microtubules. A high density of the kinesins along the microtubules is favorable for the beating motion of the cilia. The depletion force induced bundling of the microtubules accelerated the beating motion of the artificial cilia and increased the beating frequency. This work helps understand the role of self-assembled structures of the biomolecular motor systems in the dynamics of living organisms and is expected to expedite the development of artificial nanomachines, in which the biomolecular motors may serve as actuators.
  • Yumi Mochizuki, Chihiro Oka, Takumi Ishiwata, Kenta Kokado, Kazuki Sada
    GELS 4 1 16  2018年03月 [査読有り][通常論文]
     
    Biomineralization has been given a great deal of attention by materials chemists because of its low environmental load and sustainability. With the goal of synthesizing such processes, various methods have been developed, especially for inorganic salts of calcium. In this report, we focused on the deposition of inorganic salts, such as calcium carbonate and calcium phosphate using crystal crosslinked gels (CCG), which are prepared by crystal crosslinking of metal-organic frameworks (MOFs). Due to the crystalline nature of MOFs, CCGs intrinsically possess polyhedral shapes derived from the original MOF crystals. As the result of deposition, the obtained inorganic salts also exhibited a polyhedral shape derived from the CCG. The deposition mainly occurred near the surface of the CCG, and the amorphous nature of the deposited inorganic salts was also confirmed.
  • Kazuya Iseda, Kenta Kokado, Kazuki Sada
    ChemistryOpen 7 3 269 - 274 2018年03月 [査読有り][通常論文]
     
    © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. In this study, we performed conductometry in various organic solvents to directly detect the transformation from tetrabutylammonium chloride (TBACl) ion-pair salt to the free ions through complexation with meso-octamethylcalix[4]pyrrole (CP), which is a well-known receptor for chloride anions. In the presence of CP, the conductivity of TBACl increases in various non-polar solvents, indicating that complexation with CP enhances the ionic dissociation of TBACl in such non-polar solvents. In other words, CP recognizes chloride as an ion-paired salt as well as a free anion in non-polar solvents. Additionally, the TBA(CP–Cl) complex exhibited a considerably lower ion-pairing constant (Kip) than TBACl in non-polar solvents, resulting in enhanced conductivity. Based on these findings, we can conclude that complexation of an anion with a hydrophobic anion receptor will be useful for creating functional and stimuli-responsive soft materials in organic solvents using coulombic forces.
  • Kenta Kokado, Takashi Machida, Takeshi Iwasa, Tetsuya Taketsugu, Kazuki Sada
    Journal of Physical Chemistry C 122 1 245 - 251 2018年01月11日 [査読有り][通常論文]
     
    © 2017 American Chemical Society. Aggregation-induced emission (AIE) has emerged as a new class of attractive photoluminescence behavior. Understanding the precise mechanism of the AIE phenomenon will lead to the rational molecular design of novel molecules with AIE properties (AIEgens). In this work, we selected disubstituted derivatives of tetraphenylethene (TPE), a well-known archetypal AIEgen, as the model compounds to elucidate the AIE mechanism. As the result of photochemical experiments and quantum chemical computations, π-bond twist (π twist), including E-Z isomerization (EZI), was found to be the major factor for quenching the photoexcited state of TPE derivatives in the solution state, differently from the well-accepted propeller-like rotation of the side phenyl groups in earlier research. In photochemical experiments, the prepared TPE derivatives exhibited EZI in the solution state upon photoirradiation, and a negative correlation was observed between this isomerization and the AIE phenomenon. The theoretical computations verified the crucial role of π twist triggered by photoirradiation in the solution state, rather than intramolecular rotation. In the crystal state, π twist was efficiently suppressed by the surrounding molecules. Our results will support the realization of novel smart AIEgens that can respond to various external stimuli.
  • 有機溶媒高吸収性材料の分子デザイン
    佐田 和己, 小門 憲太, 須永 総玄
    高分子 67 5 257 - 261 2018年 [査読有り][通常論文]
  • Sokuro Sunaga, Kenta Kokado, Kazuki Sada
    Soft Matter 14 4 581 - 585 2018年 [査読有り][通常論文]
     
    © 2018 The Royal Society of Chemistry. Herein, we demonstrate a polyelectrolyte gel which can absorb a wide range of organic solvents from dimethylsulfoxide (DMSO, permittivity: ϵ = 47.0) to tetrahydrofuran (ϵ = 5.6). The gel consists of polystyrene chains with small amounts (∼5 mol%) of lipophilic electrolytes derived from triphenylphosphonium tetraaryl borate. The swelling ability of the polyelectrolyte gel was higher than that of the alkyl ammonium tetraaryl borate previously reported by us, and this is attributed to the higher compatibility with organic solvents, as well as the higher dissociating ability, of the triphenyl phosphonium salt. The role of the ionic moieties was additionally confirmed by post modification of the polyelectrolyte gel via a conventional Wittig reaction, resulting in a nonionic gel. Our findings introduced here will lead to a clear-cut molecular design for polyelectrolyte gels which absorb all solvents.
  • Takumi Ishiwata, Ayano Michibata, Kenta Kokado, Sylvie Ferlay, Mir Wais Hosseini, Kazuki Sada
    Chemical Communications 54 12 1437 - 1440 2018年 [査読有り][通常論文]
     
    © 2018 The Royal Society of Chemistry. New polymer capsules (PCs) were obtained using a crystal crosslinking (CC) method on core-shell MOF crystals. The latter are based on the epitaxial growth of two isostructural coordination polymers which are then selectively crosslinked. Decomposition of the non-reticulated phase leads to new PCs, possessing a well-defined hollow cubic shape reflecting the heterostructure of the template.
  • Kazuki Sada
    Bulletin of the Chemical Society of Japan 91 8 1282 - 1292 2018年 [査読有り][通常論文]
     
    © 2018 The Chemical Society of Japan. This review focuses on our trial to control the swelling and collapsing of polymer gels by two different approaches. One is the introduction of ion-pairs from bulky and hydrophobic ions into hydrophobic polymers to form ionic polymer gels as "lipophilic polyelectrolyte gels". Partial dissociation of these ion-pairs in nonpolar media, such as chloroform and THF, provides them a high swelling ability as superabsorbent polymers. Compatibility of the polymers with the media and ion dissociation are crucial for the superabsorbency. The other is preparation of polymer gels by controlling the size, shape and crosslinking points with the aid of nanoporous metal-organic frameworks (MOF). It includes polymerization between the organic ligands as host monomers fixed on the open framework and the guest monomers that penetrate into the nanopores. Thus, all the components in a crystal are polymerized, which is called "crystal crosslinking". Hydrolysis of the coordination bonds produces insoluble polymer gels without metal ions. The shapes of the polymer gels are essentially identical to those of the template crystals, and the swelling ability is controlled by arrangements of the host monomers in the template crystals. These two approaches should be unique and effective for controlling the swelling ability of the polymer gels.
  • Jakia Jannat Keya, Daisuke Inoue, Yuki Suzuki, Toshiya Kozai, Daiki Ishikuro, Noriyuki Kodera, Takayuki Uchihashi, Arif Md Rashedul Kabir, Masayuki Endo, Kazuki Sada, Akira Kakugo
    Scientific Reports 7 1 6166  2017年12月01日 [査読有り][通常論文]
     
    © 2017 The Author(s). In vitro gliding assay of microtubules (MTs) on kinesins has provided us with valuable biophysical and chemo-mechanical insights of this biomolecular motor system. Visualization of MTs in an in vitro gliding assay has been mainly dependent on optical microscopes, limited resolution of which often render them insufficient sources of desired information. In this work, using high speed atomic force microscopy (HS-AFM), which allows imaging with higher resolution, we monitored MTs and protofilaments (PFs) of tubulins while gliding on kinesins. Moreover, under the HS-AFM, we also observed splitting of gliding MTs into single PFs at their leading ends. The split single PFs interacted with kinesins and exhibited translational motion, but with a slower velocity than the MTs. Our investigation at the molecular level, using the HS-AFM, would provide new insights to the mechanics of MTs in dynamic systems and their interaction with motor proteins.
  • Mikako Tsuji, Arif Md Rashedul Kabir, Masaki Ito, Daisuke Inoue, Kenta Kokado, Kazuki Sada, Akira Kakugo
    Langmuir 33 43 12108 - 12113 2017年10月31日 [査読有り][通常論文]
     
    © 2017 American Chemical Society. Water-in-oil emulsion systems have recently attracted much attention in various fields. However, functionalization of water-in-oil emulsion systems, which is required for expanding their applications in industries and research, has been challenging. We now demonstrate the functionalization of a water-in-oil emulsion system by anchoring a target protein molecule. A microtubule (MT)-associated motor protein kinesin-1 was successfully anchored to the inner surface of water-in-oil emulsion droplets by employing the specific interaction of nickel-nitrilotriacetic acid-histidine tag. The MTs exhibited a gliding motion on the kinesin-functionalized inner surface of the emulsion droplets, which confirmed the success of the functionalization of the water-in-oil emulsion system. This result would be beneficial in exploring the roles of biomolecular motor systems in the cellular events that take place at the cell membrane and might also contribute to expanding the nanotechnological applications of biomolecular motors and water-in-oil emulsion systems in the future.
  • Masami Naya, Yoshimi Hamano, Kenta Kokado, Kazuki Sada
    ACS Macro Letters 6 9 898 - 902 2017年09月19日 [査読有り][通常論文]
     
    © 2017 American Chemical Society. Molecular design of stimuli-sensitive polymers has been attracting considerable interest of chemists because of their latent ability to achieve smart materials. Heat, light, pH, and chemicals have been often utilized as a stimuli-inducing polymer phase transition from solution to aggregation and vice versa. In this report, as a new trigger for lower critical solution temperature (LCST)-type polymer phase transition, we introduce organic reaction of small organic molecules, not to the polymer chain itself. The addition of the reactant for the "effector", which can interact with the polymer chain for increasing the compatibility of the polymer chain with the media, caused a polymer phase separation, due to reduction of the solvation ability of the effector to the polymer chain. In other words, decrease of the "effector" concentration induced the polymer phase separation. Within our knowledge, this is the first report to connect a polymer phase separation with organic reaction dynamics. This process will be the first step for the development of artificial allosteric enzyme mimics from a combination of a simple synthetic polymer and a product or reactant in organic reactions.
  • Kenta Kokado, Takumi Ishiwata, Shizuka Anan, Kazuki Sada
    Polymer Journal 49 9 685 - 689 2017年09月01日 [査読有り][通常論文]
     
    © 2017 The Society of Polymer Science, Japan (SPSJ). The artificial construction of anisotropic deforming materials is one of the great challenges in materials and polymer chemistry. In this paper, we demonstrate a unidirectionally deformable material with reversibility. First, crystal crosslinking of a pillared-layer metal-organic framework (PLMOF) was accomplished, followed by the exchange of the pillar ligand with the monotopic ligand. The obtained crosslinked MOF crystal showed reversible unidirectional compression and expansion during cycles of drying and immersion in good solvents. The macroscopic unidirectional deformation was derived from microscopic variations in the layer distance in the MOF crystal. The polymerization between the organic ligand and the crosslinker effectively reinforced the MOF crystal, which had enough durability for reversible unidirectional deformation. Our strategy is a promising general method for the construction of anisotropic deforming materials, which are often seen in biological systems and mechanical devices.
  • 生体分子モーターと光応答性DNAを用いた分子輸送技術の構築(Construction of a nano-transportation system by using a biomolecular motor and photoresponsive DNA)
    Kayano Kentaro, Suzuki Ryuhei, Kabir Arif Md. Rashedul, Sada Kazuki, Kuzuya Akinori, Asanuma Hiroyuki, Kakugo Akira
    生物物理 57 Suppl.1-2 S291 - S291 2017年08月
  • 人工筋肉の創成に向けたサルコメアユニットの設計(Designing of sarcomere unit from microtubules and kinesins for construction of artificial muscles)
    Saito Ai, Rashedul Kabir Arif Md., Hiratsuka Yuichi, Kuzuya Akinori, Konagaya Akihiko, Sada Kazuki, Kakugo Akira
    生物物理 57 Suppl.1-2 S321 - S321 2017年08月
  • Shogo Amemori, Kazuya Iseda, Shizuka Anan, Toshikazu Ono, Kenta Kokado, Kazuki Sada
    Polymer Chemistry 8 26 3921 - 3925 2017年07月14日 [査読有り][通常論文]
     
    © 2017 The Royal Society of Chemistry. The preparation of the polymers having a self-attractive urea unit via hydrogen bonding and a self-repulsive lipophilic ion unit via electrostatic interaction was carried out to achieve the thermoresponsivity of polymer solution. The solubility of the obtained copolymers depended on the balance between the attractive force induced by hydrogen bonding among the urea units and the repulsive force attributed to the dissociation of the ionic units. In aprotic and nonpolar solvents, the solubility of the polymers was changed from insoluble to soluble with the increasing content of the ionic units. Moreover, in acetonitrile and 1,2-dichloroethane, the UCST-type thermoresponsivity was observed. This result indicated that the UCST-type thermoresponsivity was induced by cleavage of the hydrogen bonds among urea units upon heating, and at the cloud point, the repulsive force among the ionic units overwhelmed the attractive force. From the result of this research, we would like to emphasize that the combination of a lipophilic ion pair and other self-attractive units can be a simple principle for the molecular design of UCST-type thermoresponsive polymers in any media.
  • Kenji Hirai, Bongjun Yeom, Kazuki Sada
    ACS Nano 11 6 5309 - 5317 2017年06月27日 [査読有り][通常論文]
     
    © 2017 American Chemical Society. Fabrication of chiroptical materials with broadband response in the visible light region is vital to fully realize their potential applications. One way to achieve broadband chiroptical activity is to fabricate chiral nanostructures from materials that exhibit broadband absorption in the visible light region. However, the compounds used for chiroptical materials have predominantly been limited to materials with narrowband spectral response. Here, we synthesize Ag2S-based nanohelices derived from helical coordination polymers. The right- and left-handed coordination helices used as precursors are prepared from l- and d-glutathione with Ag+ and a small amount of Cu2+. The pyrolysis of the coordination helices yields right- and left-handed helices of Cu0.12Ag1.94S/C, which exhibit chiroptical activity spanning the entire visible light region. Finite element method simulations substantiate that the broadband chiroptical activity is attributed to synergistic broadband light absorption and light scattering. Furthermore, another series of Cu0.10Ag1.90S/C nanohelices are synthesized by choosing the l- or d-Glu-Cys as starting materials. The pitch length of nanohelicies is controlled by changing the peptides, which alters their chiroptical properties. The pyrolysis of coordination helices enables one to fabricate helical Ag2S-based materials that enable broadband chiroptical activity but have not been explored owing to the lack of synthetic routes.
  • Shinya Tajima, Yoshiki Kuroshima, Tetsuro Katayama, Naoto Tamai, Kazuki Sada, Kenji Hirai
    European Journal of Inorganic Chemistry 2017 18 2444 - 2449 2017年05月10日 [査読有り][通常論文]
     
    © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim The development of synthetic routes to nanomaterials has been motivated by their potential applications in electronics, optics, and catalytic reactions. Solution-based synthesis has relied on organic stabilizers to regulate the crystal growth. Despite the beneficial effect on crystal growth, organic stabilizers attached to the resulting particles reduce the accessibility of reactants and inhibit charge transport, resulting in a lower catalytic activity than expected. In this work we have demonstrated that coordination polymers (CPs) can be used as precursors for photocatalysts without stabilizers. The pyrolysis of CP nanowires of [Cd(l-cysteinate)]n gave CdS/C nanowires (CdS/C-NWs) that exhibit photocatalytic activity for hydrogen generation superior to CdS nanowires with organic stabilizers (CdS/stb-NWs). Transient absorption spectroscopy showed that CdS/C-NWs provide an active surfaces to facilitate catalytic reactions associated with electron migration. Moreover, Zn-doped CdS nanowires (ZnxCd1-xS/C-NWs) obtained by the pyrolysis of CPs exhibited higher photocatalytic activity than nondoped CdS/C-NWs. The improvement in photocatalytic activity is attributable to the prolonged lifetime of photoexcited electrons. The pyrolysis of CPs provides a facile means to design nanocomposites that realize efficient catalytic reactions associated with facile charge transfer.
  • Taihei Yamada, Kenta Kokado, Kazuki Sada
    Langmuir 33 10 2610 - 2616 2017年03月14日 [査読有り][通常論文]
     
    © 2017 American Chemical Society. According to the design of disassembly using electrostatic repulsion, novel amphiphiles consisting of a lipophilic ion part and a hydrophilic saccharide part were synthesized via the facile copper-catalyzed click reaction, and their molecular assemblies in water and chloroform were studied. The amphiphiles exhibited a molecular orientation opposite to that of the conventional amphiphiles in each case. ζ Potential measurements indicated that the lipophilic ion part is exposed outside in chloroform. The size of a solvophobic part in the amphiphiles dominates the size of an assembling structure; that is, in water, these amphiphiles tethering different lengths of the saccharide part exhibited almost identical assembling size, whereas in chloroform, the size depends on the length of the saccharide part in the amphiphiles.
  • 鈴木 隆平, Arif Md. Rashedul Kabir, 佐田 和己, 角五 彰
    オレオサイエンス 17 2 49 - 53 公益社団法人 日本油化学会 2017年 

    微小管/キネシン系に代表される生体分子モーターはアデノシン三リン酸(ATP)を加水分解することにより得られるエネルギーを使って運動するタンパク質である。これらの生体分子モーターはナノメートルサイズでありながら,高いエネルギー変換効率,高い比出力を有する。本項では生体分子モーターを動力源とした生体分子ロボットの開発を目的とした研究を紹介する。

  • Shinya Sudo, Kenta Kokado, Kazuki Sada
    RSC Advances 7 2 678 - 683 2017年 [査読有り][通常論文]
     
    © The Royal Society of Chemistry 2017. We report on the synthesis of nanosized single-crystalline spherical β-Ga2O3 particles (GONP) by thermal annealing of gallium nanoparticles (GaNP), which previously has been prepared under ultrasonication. GONP displayed a spherical morphology and the particle size reflected that of GaNP. The nanoparticles have been confirmed as crystalline β-Ga2O3 by powder X-ray diffraction. The selected area electron diffraction patterns obtained from a whole particle of one GONP represented production of single-crystalline nanoparticle. Furthermore, the dispersibility and stability of GONP in solvent dramatically improved through silica coating (GO@SiO2 NP). Photoluminescence spectroscopy indicated that the GO@SiO2 NP exhibited a light blue emission at 445 nm under excitation at 240 nm. Diffuse reflectance spectroscopy demonstrated that the band gap of GO@SiO2 NP (Eg = 4.89 eV) was hypsochromically shifted compared to that of bulk Ga2O3 (Eg(bulk) = 4.56 eV) due to the quantum size effect of β-Ga2O3. Additionally, silica particle-supported GONP (GONP/MCM-41) showed catalytic activity for the benzylation of benzene with benzyl chloride. Thus, the GONP presented here will have potential applications in LED phosphors, optoelectronic devices, and supported catalysts.
  • Ai Saito, Tamanna Ishrat Farhana, Arif Md Rashedul Kabir, Daisuke Inoue, Akihiko Konagaya, Kazuki Sada, Akira Kakugo
    RSC Advances 7 22 13191 - 13197 2017年 [査読有り][通常論文]
     
    © The Royal Society of Chemistry. We investigated the role of the concentration of microtubules and depletion force in the emergence of collective motion of microtubules driven by kinesins. Critical concentrations were found for both microtubules and the depletant to demonstrate the collective motion of microtubules. More importantly, the kinetics of the collective motion were found to be significantly dependent on the concentration of microtubules and the depletant. Substantial variations in the time course of emergence of the collective motion of microtubules were observed in response to the changes in concentration of the microtubules and the depletant. This study provides new insights into the kinetics of the collective motion of microtubules driven by kinesins, which might also be useful in understanding the coordinated behavior of other self-propelled systems.
  • Tsuyoshi Oura, Ryosuke Taniguchi, Kenta Kokado, Kazuki Sada
    Polymers 9 1 2017年 [査読有り][通常論文]
     
    © 2017 by the authors. The synthesis and photoluminescence properties of crystal crosslinked gels (CCGs) with an aggregation-induced emission (AIE) active crosslinker derived from tetraphenylethene (TPE) is discussed in this article. The CCG was prepared from a metal organic framework (MOF) with large pore aperture to allow the penetration of TPE crosslinker. The obtained CCG possessed a rectangular shape originated from the parent MOF, KUMOF. The CCG showed stimuli-responsive photoluminescence behavior depending on the swelling degree, thus the photoluminescence intensity was higher at higher swelling degree. By changing the solvent, water content, or ionic strength, the photoluminescence intensity was controllable, accompanying the change of swelling degree. Moreover, emission color tuning was also achieved by the introduction of luminescent rare earth ions to form a coordination bonding with residual carboxylate inside the CCG.
  • Arif Md Rashedul Kabir, Masaki Ito, Kyohei Uenishi, Shizuka Anan, Akihiko Konagaya, Kazuki Sada, Miwa Sugiura, Akira Kakugo
    Chemistry Letters 46 2 178 - 180 2017年 [査読有り][通常論文]
     
    © 2017 The Chemical Society of Japan. We have demonstrated in vitro motility assay of microtubules on a kinesin-coated substrate by using adenosine triphosphate (ATP) generated from microsphere gels containing thylakoid membranes. Upon photoirradiation, the gels generated ATP, which was utilized for performing gliding motions of microtubules. This work may facilitate the development of a localized ATP generation system in the in vitro motility assay, which consequently would widen the applications of biomolecular motors in nanotechnology.
  • Takashi Machida, Ryosuke Taniguchi, Tsuyoshi Oura, Kazuki Sada, Kenta Kokado
    Chemical Communications 53 15 2378 - 2381 2017年 [査読有り][通常論文]
     
    © The Royal Society of Chemistry. A typical AIE dye, TPE, was liquefied by attaching long and branched alkyl chains. The obtained liquid dye showed intense emission compared to the solid dye or TPE. The linkage between TPE and the alkyl chain led to significant difference in their photoluminescent and thermal properties.
  • Takumi Ishiwata, Kenta Kokado, Kazuki Sada
    Angewandte Chemie - International Edition 56 10 2608 - 2612 2017年 [査読有り][通常論文]
     
    © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Anisotropically deforming objects have attracted considerable interest for use in molecular machines and artificial muscles. Herein, we focus on a new approach based on the crystal crosslinking of organic ligands in a pillared-layer metal–organic framework (PLMOF). The approach involves the transformation from crosslinked PLMOF to polymer gels through hydrolysis of the coordination bonds between the organic ligands and metal ions, giving a network polymer that exhibits anisotropic swelling. The anisotropic monomer arrangement in the PLMOF underwent axis-dependent crosslinking to yield anisotropically swelling gels. Therefore, the crystal crosslinking of MOFs should be a useful method for creating actuators with designable deformation properties.
  • K. Hirai, K. Sada
    Chemical Communications 53 38 5275 - 5278 2017年 [査読有り][通常論文]
     
    © 2017 The Royal Society of Chemistry. An infrared (IR) laser machine is used for the synthesis of metal-organic frameworks (MOFs). Solutions containing metal ions and organic ligands are casted on glass substrates. MOF crystals are formed at the positions the IR laser irradiated, resulting in the patterning of MOFs.
  • Md Sirajul Islam, Kaori Kuribayashi-Shigetomi, Arif Md Rashedul Kabir, Daisuke Inoue, Kazuki Sada, Akira Kakugo
    Sensors and Actuators, B: Chemical 247 53 - 60 2017年 [査読有り][通常論文]
     
    © 2017 Elsevier B.V. Self-organization is one of the most spectacular phenomena exhibited in the wide spectrum of biologically active systems. Many studies have attempted to investigate different parameters that regulate the self-organization of moving objects. Recent theoretical and analytical-based approaches have revealed that physical confinement has regulatory effect on the self-organization of moving objects. However, a detailed experimental study on how the varying shapes and sizes of the confinement affect the self-organization of moving objects is still lacking. Recently, biomolecular motor systems F-actin/myosin and microtubule/kinesin or microtubule/dynein have been promising to experimentally study the self-organization of moving objects. Here, we experimentally investigated the shape and size effect of confinement on the self-organization of microtubules (MTs) by employing the in vitro motility assay of MT/kinesin motor system. The MTs were confined by a lipid layer on a glass surface micro-patterned by photolithography. We demonstrated that shapes and sizes of the confinements largely influenced the self-organization of MTs. The MTs showed distinct orientations in different shapes and sizes of the confinements. This work clearly unveiled how physical confinement influences the self-organization of MTs and would help understand the effect of confinement on the self-organization of more complex biologically active systems in nature.
  • Tanjina Afrin, Arif Md Rashedul Kabir, Kazuki Sada, Akira Kakugo, Takahiro Nitta
    Biochemical and Biophysical Research Communications 480 1 132 - 138 2016年11月04日 [査読有り][通常論文]
     
    © 2016 Elsevier Inc. Buckling of microtubules observed in cells has been reconstructed on a two-dimensional elastic medium consisting of kinesins grafted over compressible substrates, enabling precise control of experimental conditions and quantitative analysis. However, interpretations of the observations have ambiguities due to inevitable experimental difficulties. In this study, with computer simulations, we investigated importance of the mode of interaction of microtubule with elastic medium in the buckling behavior of microtubule. By taking into consideration of forced-induced detachments of kinesins from microtubules, our simulations reproduced the previous experimental results, and showed deviations from predictions of the elastic foundation model. On the other hand, with hypothetical linkers permanently bound to microtubules, our simulation reproduced the predictions of the elastic foundation model. By analyzing the results of the simulations, we investigated as to why the difference arose. These findings indicate the importance of the mode of interaction of microtubule with the medium in the buckling behavior of microtubule. Our findings would bring new insights on buckling of microtubules in living cells.
  • Daisuke Inoue, Takahiro Nitta, Arif Md Rashedul Kabir, Kazuki Sada, Jian Ping Gong, Akihiko Konagaya, Akira Kakugo
    Nature Communications 7 2016年10月03日 [査読有り][通常論文]
     
    © 2016 The Author(s). Studying mechanical deformation at the surface of soft materials has been challenging due to the difficulty in separating surface deformation from the bulk elasticity of the materials. Here, we introduce a new approach for studying the surface mechanical deformation of a soft material by utilizing a large number of self-propelled microprobes driven by motor proteins on the surface of the material. Information about the surface mechanical deformation of the soft material is obtained through changes in mobility of the microprobes wandering across the surface of the soft material. The active microprobes respond to mechanical deformation of the surface and readily change their velocity and direction depending on the extent and mode of surface deformation. This highly parallel and reliable method of sensing mechanical deformation at the surface of soft materials is expected to find applications that explore surface mechanics of soft materials and consequently would greatly benefit the surface science.
  • 枯渇力が誘起する微小管集団運動に関する研究(Study of the collective motion of microtubules induced by depletion force)
    Saito Ai, Suzuki Ryuhei, Fahana Tamanna Ishrat, Kabir Arif Md. Rashedul, Sada Kazuki, Kakugo Akira
    生物物理 56 Suppl.1-2 S200 - S200 2016年10月
  • 自律的な振動運動を示す微小管リング状集合体(Mechanical Oscillation of Dynamic Microtubule Rings)
    Ito Masaki, Arif Md. Rashedul Kabir, Islam Md. Sirajul, Inoue Daisuke, Wada Shoki, Sada Kazuki, Konagaya Akihiko, Kakugo Akira
    生物物理 56 Suppl.1-2 S222 - S222 2016年10月
  • 微小管の集団的な運動に対する外因性の機械的ストレスの影響(Effect of external mechanical stress on collective motion of microtubules)
    Farhana Tamanna Ishrat, Kabir Arif Md. Rashedul, Inoue Daisuke, Sada Kazuki, Kakugo Akira
    生物物理 56 Suppl.1-2 S306 - S306 2016年10月
  • DNAにプログラムされた生体分子モーター系から調製した分子ロボットの統制された集団形成(Regulated swarming of molecular robots prepared from a DNA programmed biomolecular motor system)
    Keya Jakia Jannat, Suzuki Ryuhei, Kabir Arif Md. Rashedul, Inoue Daisuke, Sada Kazuki, Kuzuya Akinori, Kakugo Akira
    生物物理 56 Suppl.1-2 S306 - S306 2016年10月
  • 微小管の力学応答特性と生化学的な機能変調
    Kakugo Akira, Tanjina Afrin, Arif Md. Rashedul Kabir, Sada Kazuki
    日本分析化学会講演要旨集 65年会 35 - 35 2016年08月
  • Md Sirajul Islam, Arif Md Rashedul Kabir, Daisuke Inoue, Kazuki Sada, Akira Kakugo
    Biophysical Chemistry 211 1 - 8 2016年04月 [査読有り][通常論文]
     
    © 2015 Published by Elsevier B.V. Reactive oxygen species (ROS), one of the regulators in various biological processes, have recently been suspected to modulate microtubule (MT) dynamics in cells. However due to complicated cellular environment and unavailability of any in vitro investigation, no detail is understood yet. Here, by performing simple in vitro investigations, we have unveiled the effect of ROS on MT dynamics. By studying dynamic instability of MTs in a ROS free environment and comparing with that in the presence of ROS, we disclosed that MTs showed enhanced dynamics in the ROS free environment. All the parameters that define dynamic instability of MTs e.g., growth and shrinkage rates, rescue and catastrophe frequencies were significantly affected by the presence of ROS. This work clearly reveals the role of ROS in modulating MT dynamics in vitro, and would be a great help in understanding the role of ROS in regulation of MT dynamics in cells.
  • Masahiko Ohta, Toshikazu Ono, Kenta Kokado, Akira Kakugo, Kazuki Sada
    Macromolecular Chemistry and Physics 217 3 433 - 444 2016年02月01日 [査読有り][通常論文]
     
    © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. In this study, polystyrene (PS) ionomers having tetraalkylammonium with a series of counterions are prepared with various feed ratio of the ionic units and blended with nonionic poly(n-butyl methacrylate) (PBMA) which is originally immiscible with PS. According to differential scanning calorimetry analysis, in the blends of ionomers with tetraarylborate and PBMA, the ionomers with more than 1 mol% of the ionic units are completely miscible with PBMA. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction measurements reveal that the bulky and lipophilic ion-pair inhibits the association of ions and instead induces the attractive interaction to alkyl groups of PBMA. Tensile tests of the miscible specimen exhibit both characteristic behavior, that is, high tensile strength as PS and high elongation property of PBMA. Employment of lipophilic ion-pair as a compatibilizing component is produced for homogeneous polymer blends consisting of polystyrene (PS) and poly(n-butyl methacryrate) (PBMA). The lipophilic ion-pair is tethered on the PS chain and only 1 mol% introduction is adequate to obtain the homogeneous polymer blends. The obtained polymer blends show combined characteristics, thus high tensile strength of PS and high elongation property of PBMA.
  • ISLAM Md. Sirajul, Kuribayashi-SHIGETOMI Kaori, KABIR Arif Md. Rashedul, INOUE Daisuke, SADA Kazuki, KAKUGO Akira
    バイオフロンティア講演会講演論文集 2016 0 A205  一般社団法人 日本機械学会 2016年
  • 小門憲太, 佐田和己
    ネットワークポリマー 37 2 88 - 99 2016年 [査読有り][通常論文]
  • Masaki Ito, Arif Md Rashedul Kabir, Md Sirajul Islam, Daisuke Inoue, Shoki Wada, Kazuki Sada, Akihiko Konagaya, Akira Kakugo
    RSC Advances 6 73 69149 - 69155 2016年 [査読有り][通常論文]
     
    © 2016 The Royal Society of Chemistry. Mechanical oscillation is a ubiquitous phenomenon observed in living systems, which emerges from a wide range of well-organized self-assembled structures, and plays important roles in many biological processes. Although considerable efforts have been devoted to demonstrate the mechanical oscillation of organized structures produced through self-assembly in vitro, it has rarely been documented. Here we report the mechanical oscillation of ring-shaped structures, composed of multiple microtubule (MT) filaments, obtained through energy dissipative self-assembly of MT filaments at an air-buffer interface. The MT rings exhibit autonomous oscillation manifested through periodic changes in the size and shape. We propose the oscillation of the MT rings is attributed to mechanical feedback arising from accumulated stress induced by the driving force of the motor protein system. This work might offer new insights to our current understanding on the mechanical feedback driven oscillation of organized structures and its effect on dynamic processes in living systems.
  • Yusuke Nishikori, Kazuya Iseda, Kenta Kokado, Kazuki Sada
    Polymers 8 4 2016年 [査読有り][通常論文]
     
    © 2016 by the authors. In this paper, mesogenic polyelectrolyte gels (MPEgels) tethering mesogenic groups on the side chains were synthesized from a mesogenic monomer and ionic monomer via a conventional radical polymerization process. The obtained MPEgels absorbed various organic solvents in a wide range of dielectric constants from chloroform (ε = 7.6) to DMSO (ε = 46.5). The electrostatic repulsion among the polymer chains and the osmotic pressure between the interior and exterior of the MPEgel is responsible for the high swelling ability, revealed by the common ion effect using tetra(n-hexyl)ammonium tetra(3,5-bis(trifluoromethyl)phenylborate (THATFPB). The obtained MPEgels could also absorb liquid crystalline molecules such as 4-cyano-4'-pentylbiphenyl (5CB), analogously caused by the above-mentioned polyelectrolyte characteristic. The MPEgels exhibited liquid crystal transition temperature (TNI) on differential scanning calorimetry (DSC) measurement, and the increase of the ionic group content lowered TNI. The MPEgels absorbing liquid crystalline molecules exhibited differing TNI, dependent on the compatibility of the mesogenic group on the side chain to the liquid crystalline molecule.
  • Masaki Ito, Takumi Ishiwata, Shizuka Anan, Kenta Kokado, Daisuke Inoue, Arif M.R. Kabir, Akira Kakugo, Kazuki Sada
    ChemistrySelect 1 16 5358 - 5362 2016年 [査読有り][通常論文]
     
    © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Metal-organic frameworks (MOFs) are well-ordered microporous crystalline materials synthesized from metal cluster nodes and organic ligands. Using organic ligands with functional and reactive moieties enables post-synthetic modification (PSM) for further functionalization of MOFs. In this study, bioconjugation of MOFs with functional motor proteins, such as kinesin-microtubule (MT) system was investigated by employing PSM. Kinesin-MT system, energy diffusive gliding motion of MT was performed by consuming chemical energy of adenosine-tri-phosphate (ATP) in vitro. Thus, we attempted establishment of gliding of MOF by applying bio-motor system, in which reconstituted MT filaments are propelled over a kinesin-coated substrate in the presence of ATP.
  • Kenji Hirai, Shigehito Isobe, Kazuki Sada
    SCIENTIFIC REPORTS 5 2015年12月 [査読有り][通常論文]
     
    Central in material design of metal oxides is the increase of surface area and control of intrinsic electronic and optical properties, because of potential applications for energy storage, photocatalysis and photovoltaics. Here, we disclose a facile method, inspired by geochemical process, which gives rise to mesoporous anion-doped metal oxides. As a model system, we demonstrate that simple calcination of a multinuclear coordination cluster results in synchronic chemical reactions: thermal oxidation of Ti8O10(4-aminobenzoate)(12) and generation of gases including amino-group fragments. The gas generation during the thermal oxidation of Ti8O10(4-aminobenzoate)(12) creates mesoporosity in TiO2. Concurrently, nitrogen atoms contained in the gases are doped into TiO2, thus leading to the formation of mesoporous N-doped TiO2. The mesoporous N-doped TiO2 can be easily synthesized by calcination of the multinuclear coordination cluster, but shows better photocatalytic activity than the one prepared by a conventional sol-gel method. Owing to an intrinsic designability of coordination compounds, this facile synthetic will be applicable to a wide range of metal oxides and anion dopants.
  • Arif Md. Rashedul Kabir, Daisuke Inoue, Tanjina Afrin, Hiroyuki Mayama, Kazuki Sada, Akira Kakugo
    SCIENTIFIC REPORTS 5 2015年11月 [査読有り][通常論文]
     
    We have demonstrated compression stress induced mechanical deformation of microtubules (MTs) on a two-dimensional elastic medium and investigated the role of compression strain, strain rate, and a MT-associated protein in the deformation of MTs. We show that MTs, supported on a two-dimensional substrate by a MT-associated protein kinesin, undergo buckling when they are subjected to compression stress. Compression strain strongly affects the extent of buckling, although compression rate has no substantial effect on the buckling of MTs. Most importantly, the density of kinesin is found to play the key role in determining the buckling mode of MTs. We have made a comparison between our experimental results and the 'elastic foundation model' that theoretically predicts the buckling behavior of MTs and its connection to MT-associated proteins. Taking into consideration the role of kinesin in altering the mechanical property of MTs, we are able to explain the buckling behavior of MTs by the elastic foundation model. This work will help understand the buckling mechanism of MTs and its connection to MT-associated proteins or surrounding medium, and consequently will aid in obtaining a meticulous scenario of the compression stress induced deformation of MTs in cells.
  • Kazuki Sada, Takumi Ishiwata, Kenta Kokado
    Advances in Organic Crystal Chemistry: Comprehensive Reviews 2015 517 - 530 2015年08月06日 [査読有り][通常論文]
     
    Topochemical polymerizations have been attracting continuous interest as one of the precise polymerizations in a confined space. However, it is still not easy for designing new monomers due to difficulty in designing and controlling the arrangement suitable for topochemical polymerization. In this chapter, we shortly review polymerization in a confined space and demonstrate recent advances in topochemical polymerizations, providing the molecular orientations for various topochemical polymerization monomers. Then, we propose a new type of topochemical polymerization by use of metal organic framework (MOF). MOF is nano-porous crystalline materials constructed by metal ions and rigid organic ligands equipped with two or more ligation sites to form robust 3D host framework with nano-pores. The void space between them is wide and stable, which prompted us to investigate cross-linking of the organic ligands as the host monomers by the external guest monomers by means of two chemical reactions: (1) azide-tagged MOF (AzMOF) cross-linked by multi-alkyne cross-linkers via click reaction and (2) cyclodextrinMOF (CDMOF) cross-linked by diglycidyl ethers. They should be new crystalline-state polymerization, because the cross-linking took place without any movement of the host monomers in the open-host framework.
  • キネシン上でのDNAにプログラムされた微小管の能動的自己組織化(DNA programmed active self-organization of microtubules on kinesin)
    Keya Jakia Jannat, Inoue Daisuke, Kabir Arif Md. Rashedul, Sada Kazuki, Kakugo Akira
    生物物理 55 Suppl.1-2 S318 - S318 2015年08月
  • Kengo Nishi, Saki Tochioka, Takashi Hiroi, Taihei Yamada, Kenta Kokado, Tae-Hwan Kim, Elliot Paul Gilbert, Kazuki Sada, Mitsuhiro Shibayama
    MACROMOLECULES 48 11 3613 - 3621 2015年06月 [査読有り][通常論文]
     
    Lipophilic polyelectrolyte gels capable of large swelling in low-polar solvents (3 <= epsilon <= 10) were developed by Ono et al. ( Nature Mater. 2007), where e is the dielectric constant. These gels were prepared by introducing tetraphenylborate as a lipophilic anion (tetrakis(3,5-bis(trifluoromethyl)phenyl)borate; TFPB) and tetraalkylammonium with long alkyl chains as a lipophilic cation (tetra(n-butyl)ammonium; TBA(+)) into a poly(octadecyl acrylate) (pODA) backbone chain. Here, we investigated the structure of the lipophilic polyelectrolyte gels and corresponding polymer solutions in CH2Cl2 with small-angle neutron scattering (SANS) and dynamic light scattering (DLS). From SANS, it was revealed that individual pODA chain is regarded as a rod with the cross-section radius of 15 angstrom and the length of ca. 160 angstrom and is little changed by introduction of charges or cross-linking. In addition to this, it was revealed from SANS measurements that the second virial coefficient of pODA in CH2Cl2 was positive. In combination with DLS measurements, we observed several characteristic features similar to polyelectrolyte aqueous systems such as (i) the clear appearance of slow diffusional motion in polymer solutions, (ii) an increase of diffusion coefficient in gels, and (iii) an increase of osmotic modulus in solutions and gels when ionic groups are incorporated in pODA. These experimental findings clearly show that [TBA(+)][TFPB-] dissociates enough and pODA, accompanying these ionic groups, acts as a polyelectrolyte even in a low-polar solvent such as CH2Cl2 (epsilon = 8.9). It is concluded that the good compatibility of pODA with CH2Cl2 and the introduction of dissociable ionic groups into pODA result in high-swelling capability of the lipophilic polyelectrolyte gels.
  • 眞山 博幸, Kabir Arif. Md., 井上 大介, 濱野 芳美, 佐田 和己, 角五 彰
    日本物理学会講演概要集 70 2947 - 2947 一般社団法人日本物理学会 2015年
  • 小門憲太, 佐田和己
    機能材料 35 3 45 - 51 シーエムシー出版 2015年 [査読有り][通常論文]
  • Desi H. Gharib, Shogo Amemori, Masami Naya, Kenta Kokado, Kazuki Sada
    RSC ADVANCES 5 108 89319 - 89322 2015年 [査読有り][通常論文]
     
    A novel gel LCST system consisting of a pyrene containing acrylate network polymer and external effectors is demonstrated. The LCST behaviour was conducted by switching of the CT interaction between the gel and effector, which was readily tuned by effector concentration or molecular structure of the effector.
  • Daisuke Inoue, Bulbul Mahmot, Arif Md. Rashedul Kabir, Tamanna Ishrat Farhana, Kiyotaka Tokuraku, Kazuki Sada, Akihiko Konagaya, Akira Kakugo
    NANOSCALE 7 43 18054 - 18061 2015年 [査読有り][通常論文]
     
    Collective motion is a fascinating example of coordinated behavior of self-propelled objects, which is often associated with the formation of large scale patterns. Nowadays, the in vitro gliding assay is being considered a model system to experimentally investigate various aspects of group behavior and pattern formation by self-propelled objects. In the in vitro gliding assay, cytoskeletal filaments F-actin or microtubules are driven by the surface immobilized associated biomolecular motors myosin or dynein respectively. Although the F-actin/myosin or microtubule/dynein system was found to be promising in understanding the collective motion and pattern formation by self-propelled objects, the most widely used biomolecular motor system microtubule/kinesin could not be successfully employed so far in this regard. Failure in exhibiting collective motion by kinesin driven microtubules is attributed to the intrinsic properties of kinesin, which was speculated to affect the behavior of individual gliding microtubules and mutual interactions among them. In this work, for the first time, we have demonstrated the collective motion of kinesin driven microtubules by regulating the mutual interaction among the gliding microtubules, by employing a depletion force among them. Proper regulation of the mutual interaction among the gliding microtubules through the employment of the depletion force was found to allow the exhibition of collective motion and stream pattern formation by the microtubules. This work offers a universal means for demonstrating the collective motion using the in vitro gliding assay of biomolecular motor systems and will help obtain a meticulous understanding of the fascinating coordinated behavior and pattern formation by self-propelled objects.
  • Kenta Kokado, Ryosuke Taniguchi, Kazuki Sada
    JOURNAL OF MATERIALS CHEMISTRY C 3 33 8504 - 8509 2015年 [査読有り][通常論文]
     
    In this paper, we prepared various network polymers with crosslinkers having two or four acryloyl groups derived from an AIE luminogen, and investigated the relationship between the rigidity of network polymers and emission behaviour. The crosslinkers showed representative AIE properties. A conventional radical polymerization with various vinyl monomers produced corresponding network polymers. The variation of vinyl monomers or the crosslinkers allowed us to obtain network polymers with different rigidities. Fluorescence spectroscopy of the network polymers revealed rigidity dependent emission enhancement accompanying the hypsochromic shift. In addition, the network polymer showed temperature and solvent dependent emission behaviour. The crosslinker with less crosslinkable substituents showed higher susceptibility toward the environmental conditions such as rigidity, temperature, and solvent.
  • Shoki Wada, Arif Md Rashedul Kabir, Ryuzo Kawamura, Masald Ito, Daisuke Inoue, Kazuki Sada, Akira Kakugo
    BIOMACROMOLECULES 16 1 374 - 378 2015年01月 [査読有り][通常論文]
     
    Biomolecular motor system microtubule (MT)-kinesin is considered a building block for developing artificial microdevices. Recently, an active self-organization method has been established to integrate MT filaments into ring-shaped assembly that can produce rotational motion both in the clockwise and in the counterclockwise directions. In this work, we have investigated the effect of parameters such as MT and kinesin concentration, length, and rigidity of MT and type of kinesin (structure of tail region) on the preferential rotation of the ring-shaped MT assembly produced in an active self-organization. We elucidated that these factors can significantly affect the bias of rotation of the ring-shaped MT assembly, which seems to be related to the fluctuation of leading tip of moving MT filaments. This new finding might be important for designing handedness regulated artificial biomachine using the ring-shaped MT assembly in future.
  • Shoki Wada, Arif Md. Rashedul Kabir, Masaki Ito, Daisuke Inoue, Kazuki Sada, Akira Kakugo
    SOFT MATTER 11 6 1151 - 1157 2015年 [査読有り][通常論文]
     
    The microtubule (MT)-kinesin biomolecular motor system has attracted considerable attention due to its possible applications in artificial biomachines. Recently, an active self-organization (AcSO) method has been established to integrate MT filaments into highly organized assembled structures. The ring-shaped MT assembly, one of the structures derived from the AcSO of MTs, can convert the translational motion of MTs into rotational motion. Due to this attractive feature, the ring-shaped MT assembly appears to be a promising candidate for developing artificial devices and for future nanotechnological applications. In this work, we have investigated the effect of length and rigidity of the MT filaments on the size of the ring-shaped MT assembly in the AcSO process. We show that the size of the ring-shaped MT assembly can be controlled by tuning the length and rigidity of MT filaments employed in the AcSO. Longer and stiffer MT filaments led to larger ring-shaped assemblies through AcSO, whereas AcSO of shorter and less stiff MT filaments produced smaller ring-shaped assemblies. This work might be important for the development of biomolecular motor based artificial biomachines, especially where size control of ring-shaped MT assembly will play an important role.
  • Shunjiro Nagata, Kenta Kokado, Kazuki Sada
    CHEMICAL COMMUNICATIONS 51 41 8614 - 8617 2015年 [査読有り][通常論文]
     
    A smart metal-organic framework (MOF) exhibiting controlled release was achieved by modification with a thermoresponsive polymer (PNIPAM) via a surface-selective post-synthetic modification technique. Simple temperature variation readily switches "open'' (lower temperature) and "closed'' (higher temperature) states of the polymer-modified MOF through conformational change of PNIPAM grafted onto the MOF, resulting in controlled release of the included guest molecules such as resorufin, caffeine, and procainamide.
  • Ryosuke Taniguchi, Taihei Yamada, Kazuki Sada, Kenta Kokado
    MACROMOLECULES 47 18 6382 - 6388 2014年09月 [査読有り][通常論文]
     
    We synthesized a tetravinyl ME luminogen based on tetraphenylethene (TPE-CL), followed by its reaction with H-terminated PDMS via hydrosilylation to construct ME elastomers. NMR and IR spectroscopy studies showed facile progress of the preparative reaction. The obtained sample strips represented typical elastomeric behavior revealed by tensile test, while the mechanical properties were varied by the chain length of employed PDMS. The homogeneous distribution of TPE-CL in an elastomer was confirmed by UV-vis absorption spectra variation upon increase of TPE-CL content. The elastomers exhibited stimuli-sensitive fluorescence against organic solvents and temperature, and the responsiveness was found to be reversible. These characteristics are clearly derived from ATE property of TPE-CL, which is sensitive to intramolecular rotation.
  • Shinya Sudo, Shunjiro Nagata, Kenta Kokado, Kazuki Sada
    CHEMISTRY LETTERS 43 8 1207 - 1209 2014年08月 [査読有り][通常論文]
     
    Facile mixing of a liquid metal, organic medium, and surfactant by sonication provided well-dispersed and uniformly sized gallium nanoparticles (GaNP). Furthermore, transformation to other noble metal nanoparticles having a similar size distribution was achieved via metal exchanging redox process utilizing the GaNP as the precursor.
  • Taihei Yamada, Kenta Kokado, Yuji Higaki, Atsushi Takahara, Kazuki Sada
    CHEMISTRY LETTERS 43 8 1300 - 1302 2014年08月 [査読有り][通常論文]
     
    Herein, we describe the preparation of lipophilic polyelectrolyte brush (LPB) and its morphology variation induced by immersing in various organic solvents. In particular, the use of 1,2-dichloroethane resulted in twining of large fibers due to the extension of polymer chains, caused by both good compatibility of nonionic moiety and dissociation of ionic moiety. To our best knowledge, this is the first example for PE brush functioning in nonpolar organic media.
  • Daisuke Inoue, Arif Md. Rashedul Kabir, Kazuki Sada, Jian Ping Gong, Akira Kakugo
    Soft Actuators: Materials, Modeling, Applications, and Future Perspectives 9784431547679 475 - 487 2014年07月01日 [査読有り][通常論文]
     
    Biomolecular motor systems microtubule/kinesin, actin/myosin are constituent components of biological power unit, which can perform mechanical work by converting chemical energy obtained from hydrolysis of adenosine triphosphate (ATP). The biomolecular motors are organized into highly complex and ordered structures as observed in muscle, stress fiber, contractile ring which exhibit various functions. Performance of these natural machines are much attractive compared to man-made machine. Therefore, to utilize the advantage of these natural machines biological motors have been proposed as the building blocks of ATP-driven bio-machine. In this chapter, different methodologies for designing biomolecular motor based bio-machines through non-equilibrium self-organization process are described.
  • Arif Md Rashedul Kabir, Daisuke Inoue, Yoshimi Hamano, Hiroyuki Mayama, Kazuki Sada, Akira Kakugo
    BIOMACROMOLECULES 15 5 1797 - 1805 2014年05月 [査読有り][通常論文]
     
    The microtubule (MT) is the stiffest cytoskeletal filamentous protein that takes part in a wide range of cellular activities where its mechanical property plays a crucially significant role. How a single biological entity plays multiple roles in cell has been a mystery for long time. Over the recent years, it has been known that modulation of the mechanical property of MT by different cellular agents is the key to performing manifold in vivo activities by MT. Studying the mechanical property of MT thus has been a prerequisite in understanding how MT plays such diversified in vivo roles. However, the anisotropic structure of MT has been an impediment in obtaining a precise description of the mechanical property of MT along its longitudinal and lateral directions that requires employment of distinct experimental approach and has not been demonstrated yet. In this work, we have developed an experimental system that enabled us to investigate the effect of tensile stress on MT. By using our newly developed system, (1) we have determined the Young's modulus of MT considering its deformation under applied tensile stress and (2) a new role of MT associated motor protein kinesin in modulating the mechanical property of MT was revealed for the first time. Decrease in Young's modulus of MT with the increase in interaction with kinesin suggests that kinesin has a softening effect on MT and thereby can modulate the rigidity of MT. This work will be an aid in understanding the modulation of mechanical property of MTs by MT associated proteins and might also help obtain a clear insight of the endurance and mechanical instability of MTs under applied stress.
  • Masaki Ito, Arif Md. Rashedul Kabir, Daisuke Inoue, Takayuld Torisawa, Yoko Toyoshima, Kazuld Sada, Akira Kakugo
    POLYMER JOURNAL 46 4 220 - 225 2014年04月 [査読有り][通常論文]
     
    Microtubule (MT)-kinesin, a biomolecular motor system, is a promising candidate for construction of artificial biomachines for a variety of nanotechnology applications. An active self-organization (AcSO) method involving a specific streptavidin (St)-biotin (Bt) interaction has been developed to assemble MTs into a highly ordered structure by exploiting their motility on a kinesincoated surface. Dynein is another biomolecular motor that moves along the MTs in the opposite direction from kinesin. Dynein has not yet been used to demonstrate the AcSO of MTs. In this study, we report the first successful demonstration of the AcSO of MTs on a dynein-coated surface to produce ring-shaped MT assemblies similar to those of kinesin. We found that ring-shaped MT assemblies obtained on dynein showed equal clockwise and counterclockwise rotational motion. This work will enrich the building blocks for designing future oriented motor protein-based artificial devices.
  • Wada Shoki, Ito Masaki, Inoue Daisuke, Sada Kazuki, Kakugo Akira
    生物物理 54 1 S193  一般社団法人 日本生物物理学会 2014年
  • Uenishi Kyohei, Wada Shoki, Inoue Daisuke, Sada Kazuki, Kakugo Akira
    生物物理 54 1 S194  一般社団法人 日本生物物理学会 2014年
  • 超分子相互作用を駆使した新しい温度応答性高分子の開発
    佐田和己, 小門憲太
    高分子 63 12 844 - 846 2014年 [査読有り][通常論文]
  • 小門憲太, 佐田和己
    現代化学 524 524 42 - 46 東京化学同人 2014年 [査読有り][通常論文]
  • Kazuki Sada, Kenta Kokado
    Kobunshi 63 225 - 226 2014年01月01日 [査読無し][通常論文]
  • Kazuki Sada, Kenta Kokado
    Kobunshi 63 844 - 846 2014年01月01日 [査読無し][通常論文]
  • Kazuya Iseda, Kenta Kokado, Kazuki Sada
    REACTIVE & FUNCTIONAL POLYMERS 73 7 951 - 957 2013年07月 [査読有り][通常論文]
     
    Stimuli-responsive polymer gels can drastically change their volume in response to various external physical and chemical stimuli. The smart polymer gels for specific chemical substances have been extensively studied as applications for molecular recognition or supramolecular chemistry in the material sciences toward intelligent materials. This review article highlights recent advances in the molecular design of stimuli-responsive polymer gels triggered by molecular recognition, especially by the recognition of ionic species. (C) 2013 Elsevier Ltd. All rights reserved.
  • Kouta Sugikawa, Shunjiro Nagata, Yuki Furukawa, Kenta Kokado, Kazuki Sada
    CHEMISTRY OF MATERIALS 25 13 2565 - 2570 2013年07月 [査読有り][通常論文]
     
    Practical and functional surface-enhanced Raman scattering (SERS)-active nanomaterials working in solution require a protecting shell. In this study, we demonstrate the fabrication of gold nanorods coated by metal organic frameworks of several hundred nanometers in size, which is one kind of crystalline porous materials, as s suspension-based SERS sensor. The composites also showed enough stability and reproducibility for detection of the guest molecules.
  • Takumi Ishiwata, Yuki Furukawa, Kouta Sugikawa, Kenta Kokado, Kazuki Sada
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 135 14 5427 - 5432 2013年04月 [査読有り][通常論文]
     
    Until now, seamless fusion of metal organic frameworks (MOFs) and covalently cross-linked polymer gels (PG) at molecular level has been extremely rare, since these two matters have been regarded as opposite, that is, hard versus soft. In this report, we demonstrate transformation of cubic MOF crystals to PG via inner cross-linking of the organic linkers in the void space of MOF, followed by decomposition of the metal coordination. The obtained PG behaved as a polyelectrolyte gel, indicating the high content of ionic groups inside. Metal ions were well adsorbed in the PG due to its densely packed carboxylate groups. A chimera-type hybrid material consisting of MOF and PG was obtained by partial hydrolysis of resulting cross-linked MOF. The shape of resulting PG network well reflected the crystal structure of MOF employed as a template. Our results will connect the two different network materials that have been ever studied in the two different fields to provide new soft and hard hybrid materials, and the unique copolymerization in the large void space of the MOF will open a new horizon toward "ideal network polymers" never prepared before now.
  • 理想的な高分子網目構造に向けて
    小門憲太, 佐田和己
    化学 68 9 68 - 69 2013年 [査読有り][通常論文]
  • Shogo Amemori, Kenta Kokado, Kazuki Sada
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 52 15 4174 - 4178 2013年 [査読有り][通常論文]
     
    Cool down and get it together! The lower critical solution temperature (LCST) behavior of a polymer containing pyrene units was controlled by a charge-transfer (CT) interaction with an electron-accepting effector (see picture). The appearance of CT bands enabled quantitative evaluation of the thermodynamics of the association. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • Daisuke Inoue, Arif Md Rashedul Kabir, Hiroyuki Mayama, Jian Ping Gong, Kazuki Sada, Akira Kakugo
    SOFT MATTER 9 29 7061 - 7068 2013年 [査読有り][通常論文]
     
    The microtubule (MT)-kinesin system is a promising candidate for constructing artificial biomachines. The active self-organisation (AcSO) method has been developed to integrate MT filaments into highly organised assembled structures. The creation of ring-shaped MT assemblies is one of the outcomes of the organisation process and holds prospects for use in future nano-technological applications. However, making use of ring-shaped MT assemblies in practical applications requires further control of the size of these assemblies, which has not yet been addressed. In this work, we demonstrated AcSO of MTs in a stepwise manner inside an inert atmosphere. We show that in an inert atmosphere, AcSO could be performed several times (at least nine times), and as a result, this method successfully increased the thickness of ring-shaped MT assemblies.
  • Toshikazu Ono, Masahiko Ohta, Kazuki Sada
    ACS MACRO LETTERS 1 11 1270 - 1273 2012年11月 [査読有り][通常論文]
     
    Polyelectrolytes are ubiquitous materials, and their unique properties originate from dissociation of ionic groups to the small number of macromolecular ions and the large number of small counterions. They have been exploited only in water or high-dielectric media and scarcely in nonpolar ones (epsilon < 10). Herein, we demonstrate that poly(octadecyl acrylate) bearing tetraalkylammonium tetraarylborate as ionic groups behaves as a polyelectrolyte in the common nonpolar organic solvents such as chloroform, THF, and 1,2-dichloroethane. Conductivity measurement, DOSY NMR spectroscopy, and viscosity measurements clearly indicate that they form the extended conformation in them. This result emphasizes that the ionic polymers bearing suitable ion pairs ionizable in the given media act as polyelectrolytes. Various characteristic properties and processes of polyelectrolytes should be realized in nonpolar media by designing ion pairs and polymer chains in the ionic polymers. Moreover, our results imply that electrostatic interaction is readily available as a long-range repulsive force even in the nonpolar media.
  • Yuki Furukawa, Kenta Kokado, Kazuki Sada
    CHEMISTRY LETTERS 41 7 667 - 668 2012年07月 [査読有り][通常論文]
     
    Novel anionic and lipophilic polymer networks have been successfully synthesized by imine formation between tetraphenylborates and 1,4-phenylenediamine. The obtained polymer networks showed various morphologies depending on the dielectric constant of media used in the synthesis. Moreover, the addition of water led to polymer networks with spherical structure presumably due to suppression of imine formation.
  • Arif Md Rashedul Kabir, Daisuke Inoue, Akira Kakugo, Kazuki Sada, Jian Ping Gong
    POLYMER JOURNAL 44 6 607 - 611 2012年06月 [査読有り][通常論文]
     
    Microtubule-kinesin system is considered as a building block for the construction of artificial biomachines, and active self-organization of microtubules has been used to integrate their structural organization and achieve amplified functions similar to those observed in natural systems. However, the short lifetime of assembled structures has limited their use in organized systems. In the present study, we demonstrated that the use of an inert atmosphere in the self-organization of microtubules allows the assembled structures to remain active for a prolonged period of time (10 times longer). The longer lifetime achieved in the present study will facilitate the development of assembled microtubules for designing biomolecular motor-based efficient artificial biomachines with prolonged lifetimes. Polymer Journal (2012) 44, 607-611; doi:10.1038/pj.2012.26; published online 4 April 2012
  • Shogo Amemori, Kenta Kokado, Kazuki Sada
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 134 20 8344 - 8347 2012年05月 [査読有り][通常論文]
     
    The de novo design of thermosensitive polymers in solution has been achieved by using the addition of small organic molecules (or "effectors"). Hydrogen bonding as an attractive polymer-polymer or polymer-effector interaction substantially dominates the responsivity, causing facile switching between LCST-type and UCST-type phase transitions, control of the transition temperature, and further coincidence of the two transitions. Small molecules having a high affinity for the polymer induce UCST-type phase behavior, whereas those having a low affinity for the polymer showed LCST-type phase behavior.
  • Tsuchiya Y, Shiraki T, Matsumoto T, Sugikawa K, Sada K, Yamano A, Shinkai S
    Chemistry - A European Journal 18 2 456 - 465 2012年01月 [査読有り][通常論文]
     
    In Nature, chromophoric groups play various roles, such as oxygen carriers, electron donors, light sensitizers, which are achieved in many cases by control of their aggregation modes in proteins. Hostguest chemistry between cyclodextrins and porphyrins has attracted great interest from supramolecular chemists because of their unique structures and functions that mimic those of proteins with chromophoric prosthetic groups. To mimic Natures contrivances, the hostguest systems between cyclodextrins and porphyrins have frequently been studied. It is really surprising, however, that to date no detailed structural information of these complexes has been obtained from single-crystal analysis. In 2011, we reported the first successful isolation of a dye inclusion single crystal (DISC) between 2,3,6-trimethyl-beta-cyclodextrin (TM beta CD) and 5,10,15,20-tetrapyridylporphyrin (TPyP), and analyzed its X-ray crystal structure. The crystal structure revealed not only the real complex mode but also the attractive orientation of TPyP in the DISC. Herein, we present new strategies to prepare DISCs of TM beta CD for several porphyrins and provide crystal structures, details of the complex modes, and optical properties. We believe that the present study has various important implications not only for the basic crystal analysis of inclusion complexes but also for potential applications that use these single crystals.
  • Toshikazu Ono, Masahiko Ohta, Kazuya Iseda, Kazuki Sada
    SOFT MATTER 8 13 3700 - 3704 2012年 [査読有り][通常論文]
     
    Molecular design of superabsorbent materials for organic solvents has attracted much attention due to their superior applications for the removal of hazardous leakages or spillages of volatile organic compounds (VOCs) and waste oils. One approach for preparing such soft matter is loosely crosslinked lipophilic polyelectrolytes. Here, we demonstrate the counter anion effect for superabsorbency for various organic solvents in a series of poly(octadecyl acrylate)-based lipophilic polyelectrolyte gels bearing tetraalkylammonium with relatively hydrophobic counter-anions: dodecyl sulfate (DS), tetrakis(3,5-bis(trifluoromethyl)phenyl) borate (TFPB) and (mu-(1H-imidazolato kappa-N1:kappa-N3) hexakis(pentafluorophenyl borate) (IM). The benefit of high-swelling abilities due to dissociation of ionpairs was observed in less-and non-polar media (3 < epsilon < 13), when TFPB and IM were selected as counter anions. These results indicate that molecular design of superabsorbent materials requires that the ionic groups have sufficient bulkiness and lipophilicity for ionic dissociation in nonpolar solvents.
  • Shunjiro Nagata, Hiroki Sato, Kouta Sugikawa, Kenta Kokado, Kazuki Sada
    CRYSTENGCOMM 14 12 4137 - 4141 2012年 [査読有り][通常論文]
     
    Facile conversion of azide to primary amine in metal-organic frameworks (MOFs) was accomplished by Staudinger reduction. After the reaction, MOFs retained high crystallinity confirmed by X-ray diffraction patterns, meaning a high usability of this method for post-synthetic modification of MOFs. Bulky phosphine groups provided surface-selective modification of MOFs via a reaction between resulting amine groups of MOF and activated ester with fluorescein, illustrated by confocal laser scanning microscope (CLSM) observation. This method opens up new possibilities for the preparation of MOFs having core-shell structures.
  • Kazuya Iseda, Yohei Haketa, Kenta Kokado, Hiromitsu Maeda, Hiroyuki Furuta, Kazuki Sada
    SOFT MATTER 8 28 7490 - 7494 2012年 [査読有り][通常論文]
     
    Stimuli-responsive gels that can change their volumes drastically in response to various external physical and chemical stimuli have been of much interest due to their various applications. Herein, novel stimuli-responsive gels were achieved through the complexation between anion receptors and the chloride anion of polystyrene ionomer gels in aprotic organic solvents. The volume expansions induced by the addition of the receptors originated from breaking the aggregation of ionic groups and enhancing the dissociation of the ion-pairs, accompanied by their colour changes.
  • Yuki Furukawa, Takumi Ishiwata, Kouta Sugikawa, Kenta Kokado, Kazuki Sada
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 51 42 10566 - 10569 2012年 [査読有り][通常論文]
  • Toshikazu Ono, Kazuki Sada
    JOURNAL OF MATERIALS CHEMISTRY 22 39 20962 - 20967 2012年 [査読有り][通常論文]
     
    Oil spills and other industrial chemical leaks to natural environments can cause long-term impact on ecosystems, and the use of polymer-based absorbent materials for such media is a promising technique for cleaning up contaminated sites. Here, we prepared a set of poly(octadecyl acrylate)-based lipophilic polyelectrolyte gels bearing tetraalkylammonium tetrakis(3,5-bis(trifluoromethyl)phenyl) borate (TFPB) with different contents of the ionic groups from 1.0 mol% (EG18(1%)) to 10 mol% (EG18(10%)), and investigated their swelling behaviours in organic solvents and oils. The swelling degrees of the polymer gels in non- or less-polar media (3 < epsilon < 14) increased both with increasing the contents of TFPB salt on the polymer chain and increasing the dielectric constants of the solvents. The swelling degrees of EG18(10%) in dichloromethane and 1,2-dichloroethane showed over 300 times as much as its dry weight. In nonpolar media (epsilon < 3) such as toluene and hexane, however, EG18(10%) collapsed and showed low swelling degrees owing to their low dielectric constants. But, the addition of ethanol (epsilon = 24.6) to them increased the solvent polarities as mixtures, resulting in the high swelling degrees over 100 times by polyelectrolyte effects. The lipophilic polyelectrolyte gels could find applications as protective barriers for volatile organic compounds (VOCs) spilled in the environment and as absorbents for waste oil.
  • Arif Md Rashedul Kabir, Shoki Wada, Daisuke Inoue, Yoshiki Tamura, Tamaki Kajihara, Hiroyuki Mayama, Kazuki Sada, Akira Kakugo, Jian Ping Gong
    SOFT MATTER 8 42 10863 - 10867 2012年 [査読有り][通常論文]
     
    Biopolymers such as actin, microtubules and DNA are well known for their fascinating in vivo self-organization phenomena. Considerable efforts have been devoted to mimicking their organization process in vitro that produced ring-shaped or toroid structures in an irreversible manner. However, understanding the factors that lead to formation of such assembled structures deserves more investigation to achieve a unified insight into the assembly process, particularly of the microtubules. Here, we report an active assembly process of microtubules (MTs) at an air-buffer interface that resulted in ring-shaped microtubule structures with a narrow size distribution and a high yield. Using an "air-buffer interface control system" combined with the newly developed "inert chamber system (ICS)" we have also successfully observed the reversible conformational transition between ring-and linear-shaped microtubules at the air-buffer interface. This is the first ever direct in situ observation of a reversible assembly process of MTs and probably provides us with valuable discernment to understand the in vivo organizational behavior of biopolymers.
  • Hiroyuki Tanaka, Tomohiro Ikeda, Masayuki Takeuchi, Kazuki Sada, Seiji Shinkai, Tomoji Kawai
    ACS NANO 5 12 9575 - 9582 2011年12月 [査読有り][通常論文]
     
    An alkyl chain-substituted multidecker porphyrin (a cerium double-decker porphyrin (CeDDP) and a lanthanum triple-decker porphyrin (LaTDP)) complexes were arranged in a monolayer array on Au(111) substrate. By using a pulse injection deposition method, both multidecker complexes were deposited on the surface intact to form a well-defined two-dimensional array. Low-temperature scanning tunneling microscopy (STM) allowed the measurement of the topographic heights of the multidecker porphyrin complexes and visualization of their internal structures clearly. The STM images suggest that the top porphyrin ligand in CeDDP rarely rotates under nondestructive imaging condition, while the top porphyrin ligand in LaTDP exhibits flip-flop rotation even under the nondestructive Imaging condition at sub-pA tunneling currents. These results provide the future applications of molecular-scale mechanical machines and single molecule storage memory.
  • Masahiko Ohta, Veera M. Boddu, Minori Uchimiya, Kazuki Sada
    POLYMER BULLETIN 67 5 915 - 926 2011年09月 [査読有り][通常論文]
     
    The development of absorbent materials for volatile organic compounds (VOCs) is in demand for a variety of environmental applications including protective barriers for VOCs point sources. One of the challenges for the currently available VOCs absorbents is their recyclability. In this study, we synthesized poly(stearylacrylate-co-ethylene glycol dimethacrylate) (NG-18) gels, and after rigorous characterization, investigated the absorption properties for VOCs. The synthesized gel could be recycled by immersing in ether and other chlorinated, aromatic, and aliphatic solvents and by cooling them at 0 A degrees C. These recycling processes resulted in approximately 25% weight loss compared to the fully swollen state, due to the crystallization of long-alkyl chain component of the gel. This property shows the possibility of recycling absorbed solvents easily and its usefulness as VOCs absorbent material.
  • Kouta Sugikawa, Yuki Furukawa, Kazuki Sada
    CHEMISTRY OF MATERIALS 23 13 3132 - 3134 2011年07月 [査読有り][通常論文]
  • Masahiko Ohta, Toshikazu Ono, Kazuki Sada
    CHEMISTRY LETTERS 40 6 648 - 650 2011年06月 [査読有り][通常論文]
     
    Two kinds of oppositely charged polystyrene ionomers bearing the bulky and lipophilic phosphazenium cation or diborateimidazolide anion that are soluble and dissociated partially into ions even in nonpolar solvents were prepared. Alternate complexes of them were fabricated in less-polar solvent, acetone, layer-by-layer onto a gold substrate and silica nanoparticles.
  • Takahiro Tani, Yuta Goto, Kyoshiro Nonaka, Seiji Shinkai, Kazuki Sada
    CHEMISTRY LETTERS 40 3 273 - 275 2011年03月 [査読有り][通常論文]
     
    Various eutectic mixtures and organic alloys have been prepared by changing combination of four-component mixtures of 1-naphthylmethylammonium n-alkanoates, which implies high-fidelity control of molecular recognition in the solid state.
  • Kouta Sugikawa, Munenori Numata, Daiki Kinoshita, Kenji Kaneko, Kazuki Sada, Atsushi Asano, Shu Seki, Seiji Shinkai
    ORGANIC & BIOMOLECULAR CHEMISTRY 9 1 146 - 153 2011年 [査読有り][通常論文]
     
    Creation of higher-ordered polymeric architectures composed of alternative assemblies of single-walled carbon nanotubes (SWNTs) and fibrous porphyrin J-aggregates can be easily achieved utilizing the cationic semi-artificial polysaccharide which can act not only as a tubular host for SWNTs but also as a one-dimensional template for porphyrin molecules. This new class of hierarchical polymer assembly is formed, for the first time, by the mutual template effect of two components, i.e., the cationic SWNT complexes and the anionic porphyrin supramolecular nanofibers. In the present system, the self-assembling behaviors of the SWNT complexes as well as the final properties of the SWNT nanoarchitectures are strongly affected by the packing mode of porphyrin molecules on the cationic semi-artificial polysaccharide. Furthermore, we have confirmed that the light energy captured by the porphyrin J-aggregates is effectively transferred to SWNTs.
  • Tomohiro Ikeda, Kazuki Sada, Seiji Shinkai, Masayuki Takeuchi
    SUPRAMOLECULAR CHEMISTRY 23 1-2 59 - 64 2011年 [査読有り][通常論文]
     
    A double-decker porphyrin 1R bearing one chiral substituent per porphyrin ring was synthesised. The host 1R showed highly cooperative binding towards chiral guest 2R with stoichiometry of the complex (1:2) and its stepwise association constants (K1 and K2) were evaluated to be log K1=1.6 and log K2=4.1, respectively. 1R also recognised 2S cooperatively and formed into a 1:3 complex in log K1=1.9, log K2=1.2 and log K3=3.8. When we use racemic 2, 1R exhibits unconventional enantioselectivity only towards 2R in a specific concentration region. It not only showed a chiral screening but also changed the stoichiometry depending on the guest chirality. These high enantioselectivity and stoichiometric modulation are effected by proper incorporation of the structural information of two enantiomers into the host and utilisation of multiple equilibrium characteristic of positive allosterism.
  • Youichi Tsuchiya, Youichi Tsuchiya, Akihito Yamano, Tomohiro Shiraki, Tomohiro Shiraki, Kazuki Sada, Seiji Shinkai, Seiji Shinkai, Seiji Shinkai
    Chemistry Letters 40 1 99 - 101 2011年01月 [査読有り][通常論文]
     
    Complexes formed between porphyrins and cyclodextrins are among the most fascinating targets of host-guest complexes. So far, the structural details have been discussed on the basis of the solution properties. However, the real complex structure determined from single-crystal analysis is not known up to the present. In this paper, we report the first successful example for formation of a single crystal and its X-ray analysis. We believe that the resultant dye-oriented crystalline material would lead to novel host-guest chemistry applicable to new photo and electronic devices.
  • Janakiraman Krishnamurthi, Toshikazu Ono, Shogo Amemori, Hiromu Komatsu, Seiji Shinkai, Kazuki Sada
    CHEMICAL COMMUNICATIONS 47 5 1571 - 1573 2011年 [査読有り][通常論文]
     
    Fluoride and acetate-responsive polymer gels were prepared by incorporation of p-nitrophenylthiourea into poly(octadecyl acrylate) gels, and the colours and volumes were changed selectively in the presence of these ions by complexation in THF.
  • Hanying Li, Yuzo Fujiki, Kazuki Sada, Lara A. Estroff
    CRYSTENGCOMM 13 4 1060 - 1062 2011年 [査読有り][通常論文]
     
    Calcium tartrate tetrahydrate and alpha-glycine single crystals grown in agarose hydrogels incorporate agarose polymer networks, resulting in polymer/single-crystal composites.
  • Kouta Sugikawa, Tomohiro Shiraki, Youichi Tsuchiya, Shuichi Haraguchi, Kazuki Sada, Seiji Shinkai
    SUPRAMOLECULAR CHEMISTRY 23 3-4 239 - 243 2011年 [査読有り][通常論文]
     
    We demonstrate the preparation of 1-D nanostructured polypyrrole wrapped by semi-artificial anionic -1,3-glucans via in situ polymerisation. The anionic polysaccharides act as both templating molecules for oxidative polymerisation of pyrrole and 1-D hosts for oligomer or polymer of pyrrole. This system would give a general design strategy for fabrication of 1-D nanostructures.
  • Kazuya Iseda, Masahiko Ohta, Toshikazu Ono, Kazuki Sada
    SOFT MATTER 7 13 5938 - 5940 2011年 [査読有り][通常論文]
     
    Molecular design of polymer gels that exhibit high swelling degrees at low temperature was demonstrated with the aid of repulsive interaction among the polymer chains in the ionic polymer gels and the utility of organic solvents with relative low melting points. A small amount of tetraalkylammonium tetraphenylborate as ionic groups was incorporated into cross-linked polystyrene to yield novel ionic polymer gels. The swelling degrees at room temperature (23 degrees C) were about 100 times as much as their dried weights in various organic solvents. Moreover, they swelled and absorbed some organic solvents such as THF and dichloromethane at low temperature (-80 degrees C), and the swelling degrees were similar to those at room temperature.
  • Kouta Sugikawa, Kouta Sugikawa, Kenji Kaneko, Kazuki Sada, Seiji Shinkai, Seiji Shinkai
    Langmuir 26 24 19100 - 19105 2010年12月 [査読有り][通常論文]
     
    We report the development of a new templating molecule designed by the modification of a helix-forming beta-1,3-glucan polysaccharide to the cationic semiartificial one and its application to the fabrication of one-dimensional (1D) gold nanostructures by simple photoirradiation. Transmission electron microscopy observation showed that Au(III) ions are primarily reduced to gold nanoparticles self-assembling into the ID array with the aid of the cationic beta-1,3-glucan polysaccharide, which gradually fuse into the ID gold nanostructure with the tapelike structure. The gold nanotape structure could not be created by neutral beta-1,3-glucan polysaccharides or random coil synthetic cationic polymers. These findings consistently support the view that Au(III) ions are reduced by unmodified OH groups to gold nanoparticles under the photoirradiation, which are wrapped in the helical structure of the cationic beta-1,3-glucan polysaccharide and eventually fuse into gold nanotapes. One may regard, therefore, that this cationic beta-1,3-glucan polysaccharide can act as an "all-in-one" template playing three roles of reduction, ID arrangement, and fusion of gold nanoparticles. In addition, we found an interesting phenomenon that the obtained gold nanotapes coated with cationic beta-1,3-glucan polysaccharides show unique surface-enhanced Raman scattering for anionic porphyrines organized on the surface of gold nanotapes through the electrostatic interaction.
  • ヘリックス形成能をもつ多糖との複合化による新材料の開発
    新海征治, 杉川幸太, 佐田和己
    未来材料 79 10 76 - 79 2010年09月 [査読無し][通常論文]
  • Kouta Sugikawa, Munenori Numata, Kazuki Sada, Seiji Shinkai
    CHEMISTRY LETTERS 39 7 710 - 711 2010年07月 [査読有り][通常論文]
     
    We have revealed unique template effects of a semiartificial polysaccharide on the self-assembly of anionic cyanine dyes. The inner space of the polysaccharide acts not only as a nanotemplate for the dye assembly but also as a protective space from unfavorable photobleaching.
  • Arnab Dawn, Tomohiro Shiraki, Shuichi Haraguchi, Hiroki Sato, Kazuki Sada, Seiji Shinkai
    CHEMISTRY-A EUROPEAN JOURNAL 16 12 3676 - 3689 2010年 [査読有り][通常論文]
     
    An organogelator (G) that contains 2-anthracenecarboxylic acid (2Ac) attached covalently to a gelator counterpart that consists of 3,4,5-tris(n-dodecan-1-yloxy)benzoic acid by means of a chiral amino alcohol linkage has been synthesized. G acts as an efficient gelator of organic solvents, including mixed solvents and chiral solvents. Photodimers isolated after the photoreaction of the gel samples display different degrees of stereoselectivity. In the gel state, the formation of head-to-head (h-h) photodimers is always favored over head-to-tail (h-t) photodimers. Enantiomeric excess (ee) values of the major h-h photodimers reached as high as -56% in the case of the gels with enantiomeric glycidyl methyl ethers. Here, the solvent chirality is outweighed by the intrinsic chirality of the gelator molecule. The packing of the chromophore in the gel state has been characterized by the absorption and the emission behaviors and their variations during, the course of gel-to-sol phase transition. Whereas for the hexane gel, emission intensity increases with an increase in temperature, other systems show a decrease in emission intensity. Redshift of the lambda(max) in the gel spectra indicates the J-aggregate arrangement of the chromophores. Chiral transcription in the gel state has been investigated by CD spectroscopy, which shows a decrease in CD intensity during the gel-to-sol phase transition. The X-ray diffraction study clearly differentiates among the gels in terms of the order of molecular arrangements. The gel systems are categorized as strong, moderately strong, and weak, that originate from the cooperative or individual participations of in hydrogen-bonding and pi-pi interactions, fine-tuned by the solvent polarity and the gelation temperature. A simple model based on the experimental findings and the molecular preorientation as evidenced by the stereochemistry of the photodimers has been proposed.
  • Yuzo Fujiki, Seiji Shinkai, Kazuki Sada
    CRYSTAL GROWTH & DESIGN 9 6 2751 - 2755 2009年06月 [査読有り][通常論文]
     
    Nanocrystals of a palladium complex 3 were deposited onto the specific surfaces of the single crystals of CT complex (CT1) between pyrene and naphthyldiimide bearing pyridine groups. They were characterized by X-ray powder diffraction (XRD) and scanning electron microscope equipped with energy-dispersive X-ray spectroscopy (SEM-EDX). Nanocrystals of 3 were deposited selectively onto {01 (1) over bar} faces. Comparison between the crystal structures and deposition preference of the crystal faces revealed that deposition of 3 occurred on the most hydrophobic face of the single crystals of CT1 that exposed no pyridine moieties. This indicated that accessibility or coordination of metal complexes to the pyridine moieties apparently suppressed deposition of the nanocrystals. As a result, the nanocrystals were easily deposited onto the hydrophobic crystal surfaces, and rapid growth provides the thin-film decoration of the selective crystal faces.
  • Tomohiro Ikeda, Seiji Shinkai, Kazuki Sada, Masayuki Takeuchi
    TETRAHEDRON LETTERS 50 17 2006 - 2009 2009年04月 [査読有り][通常論文]
     
    A macrocyclic host molecule that comprised two different rotating modules, cerum(IV) bis(porphyrinate)s and fenocenyl rotating, units, exhibiting contraction/expansion motion was synthesized, which call be regarded as a prototype of artificial molecular spring driven by cooperative guest binding in 1:6 stoichiometry. (C) 2009 Elsevier Ltd. All rights reserved.
  • Katsunari Inoue, Norimitsu Tohnai, Mikiji Miyata, Akikazu Matsumoto, Takahiro Tani, Yuta Goto, Seiji Shinkai, Kazuki Sada
    CRYSTAL GROWTH & DESIGN 9 2 1072 - 1076 2009年02月 [査読有り][通常論文]
     
    We report the formation of molecular solid solutions from the 1:1 binary mixtures of 1-naphthylmethylammonium n-alkanoates with different alkyl chain lengths. Systematic investigation of all the combinations from acetate to nonadecanoate concluded that a 1-naphthylmethylammonium n-alkanoate formed the molecular solid solutions with six or seven alkanoates due to similarity of their molecular structures. X-ray diffractions revealed that the molecular solid solutions had bilayered structures similar to those of pure alkanoates and that the two alkanoates formed steric complementary pairs and distributed randomly in the alkyl bilayers. When the differences of the numbers of the carbon atoms were less than three, the mixtures yielded selectively single-phased molecular solid solutions. When the differences became more than six, the mixtures yielded two-phased eutectic mixtures. Therefore, this size difference of the molecular structures (Delta V = ca. 100 angstrom(3) for six carbon atoms) should be critical to form the molecular solid solutions. The numbers of carbon atoms in the mixed alkanoates play a crucial role in the formation of the binary solid solutions or eutectic mixtures.
  • Darshak R. Trivedi, Yuzo Fujiki, Norifumi Fujita, Seiji Shinkai, Kazuki Sada
    CHEMISTRY-AN ASIAN JOURNAL 4 2 254 - 261 2009年 [査読有り][通常論文]
     
    A 2D colorimetric indicator array to discriminate isomers of dihydroxynaphthalene has been designed by using a crystal engineering concept combined with solid-state co-grinding and charge-transfer complexation. The N center dot center dot center dot H-O supramolecular synthon between the pyridyl N atom of the probe and hydroxy group of the analyte has been observed in all reported single-crystal X-ray structures of resultant CT complexes. Solid-state co-grinding with aromatic solids easily provided the highly concentrated solvent-free conditions required to promote the formation of charge-transfer complexes with brighter color changes. Probe D (N,N'-bis-(4-pyridyl)pyromellitic diimide) showed an excellent ability to discriminate eight isomers of dihydroxynaphthalene with a wide variety of colors of the resultant CT complexes.
  • Arnab Dawn, Norifumi Fujita, Shuichi Haraguchi, Kazuki Sada, Seiji Shinkai
    CHEMICAL COMMUNICATIONS 16 2100 - 2102 2009年 [査読有り][通常論文]
     
    A novel photoresponsive organogel with a binary gelator containing 2-anthracenecarboxylic acid shows a high degree of stereochemical control, resulting in head-to-head photocyclodimers exclusively together with significant enantiomeric excess induced by the chiral counterpart of the gelator.
  • Arnab Dawn, Norifumi Fujita, Shuichi Haraguchi, Kazuki Sada, Shun-ichi Tamaru, Seiji Shinkai
    ORGANIC & BIOMOLECULAR CHEMISTRY 7 21 4378 - 4385 2009年 [査読有り][通常論文]
     
    A new class of binary organogelator (G1, G2 and G3) based on 2-anthracenecarboxylic acid (2Ac), attached noncovalently with the gelator counterpart containing a 3,4,5-tris(n-dodecyloxy)-benzoylamide backbone has been developed. Among the three gelators, two (G2 and G3) are chiral containing D-alanine or L-2-phenylglycine moieties, respectively. They can act as efficient gelators of organic solvents with varying polarity depending upon the gelator systems. Gelator G1 even gelates chiral solvents. The photoirradiation of the gel samples produces photocyclodimers having different degrees of stereoselectivity for different systems. Gels with G1 and G2 produce head-to-head (h-h) photodimers as major products, whereas the stereoselectivity is reversed for the gels with G3 producing head-to-tail (h-t) photodimers as major products. Among those, G2/cyclohexane gel shows the highest degree of stereoselectivity, producing only h-h photodimers with some significant amount of chiral induction. Other chiral systems exhibit low to moderate chiral inductions. The gelator G1 can differentiate between the racemic and enantiomerically pure varieties of a solvent by exhibiting different gel melting temperatures (T-gel). For different gel systems, T-gel increases in all the cases as a consequence of photoreaction, except for the G2/cyclohexane gel, where a prominent gel-to-sol phase transition can be observed during the photoreaction. Hydrogen-bonding and pi-pi stacking interactions play the principal roles in constructing the gel structure. The morphologies of the gel systems vary between one-dimensional fibrils and a fibrillar network structure. In addition, the influences of the gelator and solvent polarity on the rate of photoreactions, photoproduct distributions as well as gel structures are investigated.
  • Shuichi Haraguchi, Youichi Tsuchiya, Tomohiro Shiraki, Kouta Sugikawa, Kazuki Sada, Seiji Shinkai
    CHEMISTRY-A EUROPEAN JOURNAL 15 42 11221 - 11228 2009年 [査読有り][通常論文]
     
    alpha-Conjugated polymers can finely tune their electrical and optical properties in response to their conformational changes. We believe that a deeper understanding of their higher-order structures will stimulate further development of their applications. We had revealed that one helix-forming natural polysaccharide (SPG) and one polythiophene derivative (PT-1) formed a stable one-dimensional complex and in the polythiophene main chain a helical conformation was induced through the dynamic conformational changes. The objective of our present research is to obtain a better mechanistic understanding on the interaction between SPG and polythiophenes. Here we have used particular left- and right-handed helix-forming polythiophene derivatives (D- and L-POWTs, respectively) and studied their influence on the helical motif of the complexes. We observed that SPG interacts with both D- and L-POWTs through their dynamic conformational changes and both D- and L-POWTs form the right-handed co-helical complexes with SPG according to the inherent helical motif of SPG. In addition, it was confirmed that 1) the complexes do not coagulate in aqueous solution, and 2) the exchange in the helical motif can occur only when the polymers experience the denature-renature process. We believe, therefore, that the mechanism of the helical induction of the SPG/POWT complexes is very unique, being different from conventional equilibrium reactions.
  • Shuichi Haraguchi, Youichi Tsuchiya, Tomohiro Shiraki, Kazuki Sada, Seiji Shinkai
    CHEMICAL COMMUNICATIONS 40 6086 - 6088 2009年 [査読有り][通常論文]
     
    A novel method to control polythiophene redox potentials based on supramolecular complexation with the native polysaccharide, schizophyllan (SPG) is reported, which can importantly improve air stability for easy handling and processing.
  • Kouta Sugikawa, Munenori Numata, Kenji Kaneko, Kazuki Sada, Seiji Shinkai, Seiji Shinkai
    Langmuir 24 23 13270 - 13275 2008年12月 [査読有り][通常論文]
     
    A great deal of attention has been focused on exploiting novel methods to fabricate thin carbonaceous capsules from multiple components for advanced materials. A layer-by-layer (LbL) method is therefore being introduced to synthesize thin and multi-carbon nanotube (CNT)-based hollow capsules from CNT complexes with cationic or anionic complementarily functionalized beta-1,3-glucans as building-blocks. These ionic beta-1,3-glucans wrap around single-walled carbon nanotubes (SWNTs) and double-walled carbon nanotubes (DWNTs) to form water-soluble complexes with ionic groups on their exterior surface. Alternate self-assembly of these CNT complexes on the silica particles is demonstrated in solution by electrostatic interactions. The LbL adsorption processes were carefully monitored by zeta-potential measurements, frequency shifts of a quartz crystal microbalance (QCM), and electron micrographs. Silica particles were then dissolved away by HF acid to obtain CNT-based hollow capsules composed of SWNTs and DWNTs. We believe that these novel surface adsorption methods are useful for potential design of CNT-based advanced functional materials.
  • Toshikazu Ono, Takahiro Sugimoto, Seiji Shinkai, Kazuki Sada
    ADVANCED FUNCTIONAL MATERIALS 18 24 3936 - 3940 2008年12月 [査読有り][通常論文]
     
    Molecular design of lipophilic polyelectrolyte gels as superabsorbent polymers that exhibit a high degree of swelling in less-polar and nonpolar organic solvents is demonstrated. A small amount of tetraalkylammonium tetraphenylborate with long alkyl chains as a lipopholic ion pair is incorporated into crosslinked polyacrylates with variable alkyl chain lengths to provide novel lipophilic polyelectrolyte gels. Their swelling degree becomes more than 100 times as much as their dried weights in various organic solvents. The high effectiveness of the swellable solvents shifts to the polar ones by decreasing the length of the alkyl chain. Swelling or collapsing of the lipophilic polyelectrolyte gels originates from both incompatibility of the polymer chains in the media and dissociation of ionic groups. Thus, a unique superabsorbency is observed when the polymer chains have good compatibility with the solvents and the solvents have relatively high polarities enough to dissociate the ionic groups. By varying the polarity of the neutral monomer in these polyelectrolyte gels, the design of gels that can absorb solvents of nearly any polarity is demonstrated.
  • Yuta Goto, Hiroki Sato, Seiji Shinkai, Kazuki Sada
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 130 44 14354 - + 2008年11月 [査読有り][通常論文]
     
    We demonstrated the metal-organic framework bearing the azide group in the organic linkers and in situ click reactions with some small alkynes. The XRPD patterns indicated that the click reaction proceeded without any decomposition of the original MOF network. Controlling the organic linkers and incorporation of the azide groups should provide the designer-made MOFs that have controlled molecular cavities with the desired steric dimensions and functionality.
  • Darshak R. Trivedi, Yuzo Fujiki, Yuta Goto, Norifumi Fujita, Seiji Shinkai, Kazuki Sada
    CHEMISTRY LETTERS 37 5 550 - 551 2008年05月 [査読有り][通常論文]
     
    A colorimetric indicating system has been developed using solid-state charge-transfer complexation to demonstrate color changes in response to various aromatic compounds and their isomers that provide no color changes under diluted solution conditions.
  • Kazuaki Aburaya, Kazunori Nakano, Kazuki Sada, Nungruethai Yoswathananont, Masashi Shigesato, Ichiro Hisaki, Norimitsu Tohnai, Mikiji Miyata
    CRYSTAL GROWTH & DESIGN 8 3 1013 - 1022 2008年03月 [査読有り][通常論文]
     
    Steroidal cholamide (CAM) has been found to form inclusion crystals with 23 aromatic compounds in 1:1 and 2:1 host-to-guest molar ratios. The 1:1 crystals have guest-dependent host frameworks, termed beta-trans-type, where weak hydrogen bonds such as N-H center dot center dot center dot pi, C-H center dot center dot center dot pi, and C-H center dot center dot center dot O play a key role in linking the host and guest molecules. The steroidal side-chains involving methyl, methylene, and amide groups serve as the hydrogen bond donors, and aromatic guest molecules serve as the acceptors. Three kinds of such weak hydrogen bonds are visualized by the Hirshfeld surfaces of the guest molecules. Comparisons of the inclusion crystals of CAM and cholic acid (CA) with the same guests clarify a profound effect of the weak hydrogen bonds. In the case of the 1:1 crystals, the N-H center dot center dot center dot pi hydrogen bonds explain the fact that CAM always employs the beta-trans-type framework, while CA employs either an alpha-gauche- or beta-trans-type framework. On the other hand, the 2:1 crystals, termed DCA-type, have only C-H center dot center dot center dot pi hydrogen bonds. The guest-dependent isomerization of these frameworks is examined in terms of the weak hydrogen bonds as well as compatibilities in size and shape.
  • Toshikazu Ono, Seiji Shinkai, Kazuki Sada
    SOFT MATTER 4 4 748 - 750 2008年 [査読有り][通常論文]
     
    Discontinuous volume changes of lipophilic polyelectrolyte gels in non-polar organic solvent mixtures are demonstrated towards the construction of stimuli-sensitive materials in media other than water.
  • Toshikazu Ono, Takahiro Sugimoto, Seiji Shinkai, Kazuki Sada
    NATURE MATERIALS 6 6 429 - 433 2007年06月 [査読有り][通常論文]
     
    Polyelectrolyte gels that are known as super- absorbent polymers swell and absorb water up to several hundred times their dried weights and have become ubiquitous and indispensable materials in many applications(1,2). Their superior swelling abilities originate from the electrostatic repulsion between the charges on the polymer chains and the osmotic imbalance between the interior and exterior of the gels(3). However, no superabsorbent polymers for volatile organic compounds ( VOCs), and especially for nonpolar organic solvents (epsilon < 10) have been reported, because common polyelectrolyte gels collapse in such solvents(4-6) owing to the formation of a higher number of aggregates of ions and ion pairs(7,8). Here, we report that a novel class of polyelectrolyte gels bearing tetra- alkylammonium tetraphenylborate(9,10) as a lipophilic and bulky ionic group swell in some nonpolar organic solvents up to 500 times their dry size. Dissociation of the ionic groups even in low- dielectricmedia ( 3 < epsilon < 10) enhances the swelling ability by expansion of the polymer networks(3). This expands the potential of polyelectrolytes that have been used only in aqueous solutions or highly polar solvents(11), and provides soft materials that swell in a variety of media. These materials could. nd applications as protective barriers for VOCs spilled in the environment and as absorbents for waste oil.
  • Yuzo Fujiki, Seiji Shinkai, Kazuki Sada
    CHEMISTRY LETTERS 36 5 608 - 609 2007年05月 [査読有り][通常論文]
     
    We demonstrate novel strategy to create the three-dimensional networks of the gold nanoparticle from organic crystals decorated by the gold nanoparticles via slow removal of the crystals by sublimation.
  • Takahiro Sugimoto, Takayuki Suzuki, Seiji Shinkai, Kazuki Sada
    CHEMISTRY LETTERS 36 2 248 - 249 2007年02月 [査読有り][通常論文]
     
    A 2,6-naphthalenediol-modified BisPYBOX (2,6-bis(benzoxazol-2-yl)pyridine (benzoPYBOX)) ligand and a naphthaldiimide-modified BisPYBOX ligand were newly designed and synthesized as a bar for ladder structure formation. The mixing of these two BisPYBOX ligands formed supramolecular ladders along a polymeric secondary dialkylammonium cations as templates to yield charge-transfer (CT) complexes in solution.
  • Molecular assemblies as templates toward the creation of functional superstructures
    M. Takeuchi, M. Numata, N. Fujita, K. Sada, S. Shinkai
    Chem. Soc. Rev. 36 415  2007年 [査読有り][通常論文]
  • Takahiro Sugimoto, Takayuki Suzuki, Seiji Shinkai, Kazuki Sada
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 129 2 270 - 271 2007年01月 [査読有り][通常論文]
     
    The first artificial double helix composed of achiral synthetic polymers have been constructed by twisting of a supramolecular ladders from poly(trimethylene imine) salts and porphyrin-bridged BisPYBOXs through hydrogen bonds between the PYBOX groups and secondary ammonium cations in the polymer.
  • Kazuki Sada, Masayuki Takeuchi, Norifumi Fujita, Munenori Numata, Seiji Shinkai
    CHEMICAL SOCIETY REVIEWS 36 2 415 - 435 2007年 [査読有り][通常論文]
     
    Combination of supramolecular chemistry with molecular recognition has been successfully applied to creating large superstructures with a wide variety of morphologies. Control of shapes and patterns of ordered molecular assemblies in nano and micro scales has attracted considerable interest as promising bottom- up technology. It is known, however, that these molecular assembling superstructures are fragile, reflecting the characteristic of the non- covalent interaction, a driving force operating in these molecular systems. In fact, they easily collapse or change by small perturbation in the environmental conditions. Thus, over the last decade, researchers have been seeking possible methods for the immobilization these superstructures. This critical review focuses on recent advances in in situ post- modification under the influence of the molecular assemblies as templates and polymerization of ordered molecular assemblies such as organogel fibers and crystals to preserve their original superstructures and intensify their mechanical strength.
  • Takayuki Suzuki, Yulchi Tateishl, Takahlro Sugimoto, Seiji Shinkai, Kazuki Sada
    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 7 7 605 - 608 2006年10月 [査読有り][通常論文]
     
    A bottom-up approach to construct nano-size architecture has attracted considerable attention. In this report, we demonstrate the formation of one-dimensional supramolecular assemblies of small organic compounds aligned by a template polymer. Complexation of linear poly(trimethylene iminium) salts and benzoxazylpyridine (bzpybox) ligands yielded linear supramolecular assemblies on the mica surface by electrostataic interaction. (c) 2006 NIMS and Elsevier Ltd. All rights reserved.
  • Akio Ojida, Yoshifumi Miyahara, Ararut Wongkongkatep, Shun-ichi Tamaru, Kazuki Sada, Itaru Hamachi
    CHEMISTRY-AN ASIAN JOURNAL 1 4 555 - 563 2006年10月 [査読有り][通常論文]
     
    Nucleoside pyrophosphate (nucleoside PP) derivatives are widespread in living cells and play pivotal roles in various biological events. We report novel fluorescence chemosensors for nucleoside PPs that make use of coordination chemistry. The chemosensors, which contain two Zn-II-dipicolylamine units, bind strongly to nucleoside PPs (K-app > 10(6) M-1) in aqueous solution and sense them by a dual-emission change. Detailed fluorescence and UV/Vis spectral studies revealed that the emission changes of the chemosensors upon binding to nucleoside PPs can be ascribed to the loss of coordination between Zn-II and the acridine fluorophore. This is a unique sensing system based on the anion-induced rearrangement of the coordination. Furthermore, we demonstrated the utility of these chemosensors in real-time monitoring of two important biological processes involving nucleoside PP conversion: the apyrase-catalyzed hydrolysis of nucleoside PPs and the glycosyl transfer catalyzed by beta-1,4-galactosyltransferase.
  • Kazuki Sada, Takahiro Tani, Seiji Shinkai
    SYNLETT 15 2364 - 2374 2006年09月 [査読有り][通常論文]
     
    Ion pairs and higher order aggregates of organic ammonium carboxylates have been recognized as important tools in supramolecular chemistry. The structures of these species are attributed to isotropic electrostatic interaction and hydrogen bonds between oppositely charged ions. This account describes the role of hydrogen bonding in the crystal structures of various organic ammonium carboxylates. The utility of these salts in the design of supramolecular assemblies such as organogels and higher order clusters in non-polar solutions is also demonstrated.
  • T Suzuki, S Shinkai, K Sada
    ADVANCED MATERIALS 18 8 1043 - + 2006年04月 [査読有り][通常論文]
     
    A photo- and thermoresponsive physical gel has been developed based on crosslinked supramolecular polymer networks. The gel shows reversible sol-gel phase transitions induced by heat or light irradiation. The photoinsol-gel phase transition shown in the figure results from the cis-trans photoisomerization of an azobenzene group present in the crosslinker.
  • A Ojida, M Inoue, Y Mito-oka, H Tsutsumi, K Sada, Hamachi, I
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 128 6 2052 - 2058 2006年02月 [査読有り][通常論文]
     
    Protein phosphorylation is ubiquitously involved in living cells, and it is one of the key events controlling protein-protein surface interactions, which are essential in signal transduction cascades. We now report that the small molecular receptors bearing binuclear Zn(ll)-Dpa can strongly bind to a bisphosphorylated peptide in a cross-linking manner under neutral aqueous conditions when the distance between the two Zn(ll) centers can appropriately fit in that of the two phosphate groups of the phosphorylated peptide. The binding property was quantitatively determined by ITC (isothermal titration calorimetry), induced CD (circular dichroism), and NMR. On the basis of these findings, we demonstrated that these types of small molecules were able to effectively disrupt the phosphoprotein-protein interaction in a phosphorylated CTD peptide and the Pin1 WW domain, a phosphoprotein binding domain, at a micromolar level. The strategy based on a small molecular disruptor that directly interacts with phosphoprotein is unique and should be promising in developing a designer inhibitor for phosphoprotein-protein interaction.
  • K Nakano, N Tohnai, K Sada, M Miyata
    KOBUNSHI RONBUNSHU 63 5 277 - 285 2006年 [査読有り][通常論文]
     
    We have systematically investigated the molecular assembly, guest-dependent polymorphism, dynamic behavior, and chiral recognition of the inclusion crystals of bile acid derivatives. A typical bile acid, i.e., cholic acid, and its derivative, i.e., cholamide, formed inclusion crystals with various organic compounds. The packing coefficients of the host cavities in the inclusion crystals indicated that the host frameworks isomerize in response primarily to the guest size. The enantio-selective enclathration in the chiral cavities of the two hosts was interpreted in terms of the four-location model for chiral recognition. In addition to the molecular recognition, the inclusion crystals showed reversible dynamic behavior, which is similar to intercalation and deintercalation observed in inorganic layer crystals. The formation of chiral molecular assembly, the molecular recognition, and the dynamic behavior of the bile acid derivatives seem to be virtually identical to those of proteins, leading to an idea that these behaviors of bile acid derivatives are the expressions of information contained in their molecular structures.
  • Motoshi Yamanaka, Kazuki Sada, Mikiji Miyata, Kenji Hanabusa, Kazunori Nakano
    CHEMICAL COMMUNICATIONS 21 2248 - 2250 2006年 [査読有り][通常論文]
     
    Superhydrophobic surfaces, characterized by water contact angles greater than 150 degrees, can be produced by means of intermediate organogels, which were formed by perfluoroalkyl chain-containing organogelators with volatile organic solvents.
  • Kazunori Nakano, Kazuki Sada, Kazuaki Aburaya, Kenji Nakagawa, Nungruethai Yoswathananont, Norimitsu Tohnai, Mikiji Miyata
    CRYSTENGCOMM 8 6 461 - 467 2006年 [査読有り][通常論文]
     
    Cholic acid, a typical asymmetric host, forms inclusion crystals with six 1,2,3-trisubstituted benzenes and five 1,2,4-trisubstituted benzenes as guests. All the eleven crystals have a bilayer structure composed of hydrophilic and lipophilic layers. The guest molecules are included in one-dimensional ( 1-D) cavities within the lipophilic layers, where the host molecules array in an antiparallel mode. On the other hand, in the absence of host-guest hydrogen bonds, the host arrangements in the hydrophilic layers change depending on the guest shape; 1,2,3- and 1,2,4-trisubstituted benzenes give the parallel and antiparallel arrangements that are categorized into shv and shv# patterns, respectively. The former crystals have a size-fit relationship between the guest molecule and the host cavity lesser than usual inclusion crystals involving the latter crystals. Therefore, the shape-fit relationship plays an important role in the formation of the host arrangements with the shv pattern. Moreover, the crystal structures of cholic acid with 1,2,3-trisubstituted benzenes are similar to those of deoxycholic acid with the identical guests. This is a rare example that hosts with a different number of hydroxyl groups in their molecular structure form an isomorphous crystal structure.
  • Yuzo Fujiki, Nami Tokunaga, Seiji Shinkai, Kazuki Sada
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 45 29 4764 - 4767 2006年 [査読有り][通常論文]
  • Akio Ojida, Hiroshi Nonaka, Yoshifumi Miyahara, Shun-ichi Tamaru, Kazuki Sada, Itaru Hamachi
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 45 33 5518 - 5521 2006年 [査読有り][通常論文]
  • Nami Tokunaga, Yuzo Fujiki, Seiji Shinkai, Kazuki Sada
    CHEMICAL COMMUNICATIONS 34 3617 - 3618 2006年 [査読有り][通常論文]
     
    Face-selective decoration of a single crystal constructed from 1-pyrenemethylammonium chloride by an anionic porphyrin dye is reported. CLSM observations indicated that the {001} face of the single crystal was selectively coated by the anionic porphyrin ( TPPS). This novel achievement could be the first step for preparation of multi-component composite materials mediated by anisotropy of organic single crystals toward photochemical devices.
  • N Yoswathananont, K Sada, K Nakano, K Aburaya, M Shigesato, Y Hishikawa, K Tani, N Tohnai, M Miyata
    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY 24 5330 - 5338 2005年12月 [査読有り][通常論文]
     
    Fifty eight inclusion crystals of cholamide (CAM) with aliphatic alcohols have been systematically investigated by Xray crystallography. The host frameworks of the inclusion crystals can be categorized into three structural types: bilayer, herringbone, and crossing structures. Most of the guests are included in bilayer structures, which can be further divided into four sub-types. The host frameworks isomerize depending on the size and shape of the guest molecules. This dependence is clearly evaluated by the relationship between the volume of the guest molecules and the packing coefficient of the void space in the host frameworks. Although the host frameworks with the cavities and the structural isomerization are very similar to those of the inclusion crystals of cholic acid (CA), the inclusion behavior of aliphatic alcohols in the two hosts is completely different: fifty four alcohols can be included in the bilayer-type structures of CAM, but only two in those of CA. This is attributed to their different functional groups, which lead to different hydrogen-bond networks with the guest alcohols. The result in the two hosts is a good example to understand the effect of host-guest hydrogen bonds on guest inclusion in cavities that are identical in size and shape.((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).
  • T Kishida, N Fujita, K Sada, S Shinkai
    LANGMUIR 21 21 9432 - 9439 2005年10月 [査読有り][通常論文]
     
    Porphyrins bearing four urea-linked dodecyl groups (3a) or four urea-linked triethoxysilylpropyl groups (3TEOS) at their peripheral positions were synthesized. 3a tends to assemble into a sheetlike two-dimensional structure due to the predominant hydrogen-bonding interaction among the urea groups and acts as a moderate gelator of organic solvents. On the other hand, its Cu(II) compelx (3a(.)Cu) tends to assemble into a fibrous one-dimensional structure due to the predominant porphyrin-porphyrin pi-pi stacking interaction and acts as an excellent gelator of many organic solvents. 3TEOS and 3TEOS(.)Cu, which also act as gelators, afforded similar superstructures as those of 3a and 3a(.)Cu, respectively, and as evidenced by SEM and TEM observations and XRD measurements, the original superstructures could be precisely immobilized by in situ sol-gel polycondensation of the triethoxysilyl groups. The TEM images of 3a gels and 3TEOS gels after sol-gel polycondensation showed a fine striped structure, the periodical distance of which was either 2 or 4 nm. X-ray crystallographic analysis of a single crystal obtained from a reference porphyrin bearing four urea-linked butyl groups revealed that there are two different porphyrin-stacked columns in the crystal and both the 2 nm distance and the 4 nm distance can appear, depending on the observation tilting angle. The hybrid gel prepared from 3TEOS(.)Cu by sol-gel polycondensation showed unique physicochemical properties such as a high sol-gel phase-transition temperature (> 160 degrees C), sufficient elasticity, high mechanical strength, etc. Thus, the present study has established new concepts for molecular design of porphyrin-based gelators on the basis of cooperative and/or competitive actions of hydrogen-bonding and pi-pi stacking interactions and for immobilization of their superstructures leading to development of new functional organic/inorganic hybrid materials.
  • T Sugimoto, K Sada, Y Tateishi, T Suzuki, Y Sei, K Yamaguchi, S Shinkai
    TETRAHEDRON LETTERS 46 32 5347 - 5350 2005年08月 [査読有り][通常論文]
     
    A new strategy to control the orientation and aggregation numbers of porphyrins by alignment along well-defined templates has been demonstrated. Porphyrin-bridged bisPYBOX ligands were arranged along the oligomeric secondary dialkylammonium cations as templates to form well-defined supramolecular complexes. The templates controlled the aggregations of the porphyrins. (c) 2005 Elsevier Ltd. All rights reserved.
  • T Kishida, N Fujita, K Sada, S Shinkai
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 127 20 7298 - 7299 2005年05月 [査読有り][通常論文]
  • K Nakano, K Sada, K Nakagawa, K Aburaya, N Yoswathananont, N Tohnai, M Miyata
    CHEMISTRY-A EUROPEAN JOURNAL 11 6 1725 - 1733 2005年03月 [査読有り][通常論文]
     
    Cholic acid (CA) forms inclusion crystals that have a sandwich-type lamellar structure constructed by the alternative stacking of host bilayers and guest layers. Five disubstituted benzenes, o-toluidine, m-fluoroaniline, o-chlorotoluene, o-bromotoluene, and indene, are accommodated in the two-dimensional void space between the host bilayers at 1:2 host-guest stoichiometries. Thermal gravimetric analysis of the inclusion crystals revealed that all the guest molecules, except o-toluidine, are released in two separate steps, indicating the formation of intermediate crystals after the first guest release. Adequate heat treatment of the four inclusion crystals induces release of half or three quarters of the guest molecules. X-ray diffraction patterns of the intermediate crystals revealed that the crystals have a bilayer structure the same as those of the common CA inclusion crystals. They have one-dimensional cavities, in which the guest molecules are included at a 1:1 or 2:1 host-guest stoichiometry. These facts indicate that the host bilayers move 1.6-4.5 angstrom perpendicular to the layer direction by desorption of the guest molecules. Furthermore, a reverse structural change is also achieved by absorption of the guest molecules to regenerate the starting sandwich-type inclusion crystals. This reversible change in the host bilayer by the guest sorption and desorption is a novel example of organic intercalation materials.
  • T Watabe, K Kobayashi, K Kato, M Miyata, K Sada
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 440 117 - 124 2005年 [査読有り][通常論文]
     
    Brucine inclusion crystals with neutral guest molecules exhibit guest-dependent polymorphism due to a hierarchical structure. Chiral brucine molecules are regarded as a primary structure and assemble to form a chiral tape with a 21 axis as a common secondary structure. Such tapes meet together in various modes to constitute different bundles as a tertiary structure. The bundle modes are theoretically classified into eight types, which were screened by alteration of guest compounds in the volume range from 39 to 150 angstrom(3).
  • K Sada, K Inoue, T Tanaka, A Epergyes, A Tanaka, N Tohnai, A Matsumoto, M Miyata
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 44 43 7059 - 7062 2005年 [査読有り][通常論文]
  • T Itoh, S Nomura, M Ohtake, T Yoshida, T Uno, M Kubo, A Kajiwara, K Sada, M Miyata
    MACROMOLECULES 37 22 8230 - 8238 2004年11月 [査読有り][通常論文]
     
    Solid-state alternating copolymerization took place by molecular oxygen insertion in the crystals of 7,7,8,8-tetrakis(ethoxycarbonyl)quinodimethane (1a) and 7,7-bis(ethoxycarbonyl)-8,8-bis(methoxycarbonyl)quinodimethane (1b) to form highly crystalline needle like white solids for la and amorphous ones for 1b. The polymer structures were confirmed by H-1 NMR, C-13 NMR, IR, elemental analysis, powder XRD, and TGA measurements. However, in vacuo polymerizations of 1a and 1b in the solid state with heating and photoirradiation did not take place. 7,7,8,8-Tetrakis(methoxycarbonyl)quinodimethane (1c) did not undergo solid-state alternating copolymerization with oxygen even in the presence of oxygen, but instead it homopolymerized to form highly crystalline homopolymer. The difference in the solid-state polymerization reactivity was discussed on the basis of molecular packing in the crystals obtained by X-ray crystallography. In addition, it was found by ESR measurement that the solid-state alternating copolymerizations with molecular oxygen proceed by means of a radical mechanism.
  • T Itoh, S Nomura, N Saitoh, T Uno, M Kubo, K Sada, K Inoue, M Miyata
    MACROMOLECULES 37 21 7938 - 7944 2004年10月 [査読有り][通常論文]
     
    Thermal polymerizations and photopolymerizations of 7-alkoxycarbonyl-7-cyano-1,4-benzoquinone methides (methoxy (2a), ethoxy (2b), propoxy (2c), isopropoxy (2d), butoxy (2e), and see-butoxy (2f)) were investigated in the solid state. In the thermal polymerization in the solid state, 2a, 2c, 2d, and 2e polymerized to give glassy solids or a mass of crystals, but both 2b and 2f did not polymerize. In the photopolymerization in the solid state, all monomer crystals except for 2a polymerized to give corresponding polymers as needlelike solids. The needlelike polymer obtained by photopolymerization of highly reactive 2c was amorphous by powder X-ray diffraction measurement. Crystal structure of 2c was determined by single-crystal X-ray structure analysis, and the molecular packing in the crystals was discussed.
  • T Suzuki, K Sada, Y Tateishi, T Tani, S Shinkai
    TETRAHEDRON LETTERS 45 44 8161 - 8163 2004年10月 [査読有り][通常論文]
     
    2,6-Bis(2-benzoxazoyl)pyridine (bzpybox) ligand is reported as a new artificial receptor for secondary dialkylammonium. (C) 2004 Elsevier Ltd. All rights reserved.
  • T Kishida, N Fujita, K Sada, S Shinkai
    CHEMISTRY LETTERS 33 8 1002 - 1003 2004年08月 [査読有り][通常論文]
     
    A porphyrin which assembles into a two-dimensional sheet structure by the hydrogen-bonding interaction among the peripheral urea groups has been designed. Introduction of triethoxysilyl groups into the terminal groups has enabled us to immobilize this novel porphyrin-based cluster by sol-gel polycondensation.
  • K Sada, Y Tateishi, S Shinkai
    CHEMISTRY LETTERS 33 5 582 - 583 2004年05月 [査読有り][通常論文]
     
    A new chiral shift reagent, a C-2 chiral phenylpybox ligand, targeted for secondary dialkylammonium cations has been exploited.
  • T Sugimoto, K Sada, S Sakamoto, K Yamaguchi, S Shinkai
    CHEMICAL COMMUNICATIONS 10 10 1226 - 1227 2004年05月 [査読有り][通常論文]
     
    Hydrogen bonded supramolecular ladders were constructed by complexation of PYBOX dimers with flexible oligo(sec-dialkyl-ammonium cations).
  • Kazunori Nakano, Shigendo Akita, Nungruethai Yoswathananont, Kazuki Sada, Mikiji Miyata
    Journal of Inclusion Phenomena 48 3-4 181 - 184 2004年04月 [査読有り][通常論文]
     
    Selective incorporation of two aromatic compounds, benzene and ethylbenzene, into an inclusion crystal of cholic acid was investigated. Addition of an excess amount of 1:1 mixture of benzene and ethylbenzene into saturated solution of cholic acid in 1-butanol led to a spontaneous formation of an inclusion crystal. The co-crystal contained benzene and ethylbenzene at the constant molar ratio of 8:2 irrespective of the relative concentrations of guest and host in the feed solution, indicating that the resulting crystal consists of the two guests mixed in a single host framework. The resulting ternary crystal had thermal behavior similar to a binary crystal obtained from benzene. In contrast to the guest/host ratio, the benzene/ethylbenzene ratio in the feed solution affected that in the inclusion crystal. Benzene was basically preferred in the cholic acid crystal over ethylbenzene, but the selectivity reversed at an excess amount of ethylbenzene. This separation behavior can be understood in terms of the structural flexibility of host frameworks.
  • K Nakano, S Akita, N Yoswathananont, K Sada, M Miyata
    JOURNAL OF INCLUSION PHENOMENA AND MACROCYCLIC CHEMISTRY 48 3-4 181 - 184 2004年04月 [査読有り][通常論文]
     
    Selective incorporation of two aromatic compounds, benzene and ethylbenzene, into an inclusion crystal of cholic acid was investigated. Addition of an excess amount of 1: 1 mixture of benzene and ethylbenzene into saturated solution of cholic acid in 1-butanol led to a spontaneous formation of an inclusion crystal. The co-crystal contained benzene and ethylbenzene at the constantmolar ratio of 8: 2 irrespective of the relative concentrations of guest and host in the feed solution, indicating that the resulting crystal consists of the two guests mixed in a single host framework. The resulting ternary crystal had thermal behavior similar to a binary crystal obtained from benzene. In contrast to the guest/host ratio, the benzene/ethylbenzene ratio in the feed solution affected that in the inclusion crystal. Benzene was basically preferred in the cholic acid crystal over ethylbenzene, but the selectivity reversed at an excess amount of ethylbenzene. This separation behavior can be understood in terms of the structural flexibility of host frameworks.
  • K Kato, M Sugahara, N Tohnai, K Sada, M Miyata
    CRYSTAL GROWTH & DESIGN 4 2 263 - 272 2004年03月 [査読有り][通常論文]
     
    A systematic structural study of asymmetric supramolecular assembly in the crystalline state has been performed by one-by-one insertions of methylene spacers into the side-chain of steroidal bile acids. Five derivatives of bile acid with different side-chain lengths, bisnorcholic acid (0), norcholic acid (1), cholic acid (2), homocholic acid (3), and bishomocholic acid (4), were recrystallized from many solvents. X-ray diffraction studies of the resulting crystals revealed that these derivatives form various bilayer and layerlike structures in which two steroidal planes are diversely aggregated by using the hydrophilic faces inside. Such asymmetric bimolecular aggregation modes are logically classified into 10 categories on the basis of the relative positions between two steroidal planes. Actually, four modes among them were observed by means of one-by-one methylene insertions. This is attributable to the fact that four hydrogen-bonding groups, three hydroxyl groups on the skeletons and one carboxyl group at the side-chain, work cooperatively to form various hydrogen-bonding networks with the corresponding host frameworks. In this way, the insertion of methylene spacers plays a decisive role to diversify the asymmetric bimolecular aggregation modes.
  • A Ojida, Y Mito-oka, K Sada, Hamachi, I
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 126 8 2454 - 2463 2004年03月 [査読有り][通常論文]
     
    The phosphorylation of proteins represents a ubiquitous mechanism for the cellular signal control of many different processes, and thus selective recognition and sensing of phosphorylated peptides and proteins in aqueous solution should be regarded as important targets in the research field of molecular recognition. We now describe the design of fluorescent chemosensors bearing two zinc ions coordinated to distinct dipicolylamine (Dpa) sites. Fluorescence titration experiments show the selective and strong binding toward phosphate derivatives in aqueous solution. On the basis of H-1 NMR and P-31 NMR studies, and the single-crystal X-ray structural analysis, it is clear that two Zn(Dpa) units of the binuclear receptors cooperatively act to bind a phosphate site of these derivatives. Good agreement of the binding affinity estimated by isothermal titration calorimetry with fluorescence titration measurements revealed that these two receptors can fluorometrically sense several phosphorylated peptides that have consensus sequences modified with natural kinases. These chemosensors display the following significant features: (i) clear distinction between phosphorylated and nonphosphorylated peptides, (ii) sequence-dependent recognition, and (iii) strong binding to a negatively charged phosphorylated peptide, all of which can be mainly ascribed to coordination chemistry and electrostatic interactions between the receptors and the corresponding peptides. Detailed titration experiments clarified that the phosphate anion-assisted coordination of the second Zn(II) to the binuclear receptors is crucial for the fluorescence intensification upon binding to the phosphorylated derivatives. In addition, it is demonstrated that the binuclear receptors can be useful for the convenient fluorescent detection of a natural phosphatase (PTP1B) catalyzed dephosphorylation.
  • K Kato, M Sugahara, N Tohnai, K Sada, M Miyata
    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY 5 981 - 994 2004年02月 [査読有り][通常論文]
     
    Nordeoxycholic acid (NDCA), which has a shorter side chain than the steroidal host compound, deoxycholic acid (DCA), forms inclusion crystals with various organic substances at 1:1 or 2:1 host-guest ratios. X-ray crystallographic studies reveal that four types of host frameworks (bilayer, monolayer, tape, and hexagonal) are generated by NDCA, in stark contrast to the robust and dominant bilayer frameworks formed from DCA, although they have the same functional groups capable of hydrogen bonding. The first three host frameworks are further divided into three, two, and four sub-types by arrangements of the hydrogen-bonded host columns, tapes, or layers, respectively. A total of nine types of open host frameworks are observed depending on the nature of the guest compounds. The sizes of the guest compounds induce isomerization of these host frameworks having molecular cavities, which is rationalized by the range of values of PCcavity, which are ratios of the volumes between the guest compound and the host cavities. Such a drastic increase of flexibility of the open host framework by the slight chemical modification from DCA to NDCA deserves attention with respect to crystal engineering. Unique 2(1) helical assemblies of DCA are linked by the carboxyl group at the side chain to form a robust sheet-like structural motif. In NDCA, on the other hand, the linkage between the helices becomes impossible because of the shortening of the side chain's length, which results in destruction of the sheet-like motif to yield renewed molecular voids among the unique 2(1) helical assemblies. These remarkable differences in the flexibility of the open host frameworks provide us with a possible strategy for designing of new host compounds. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
  • K Sada, T Watanabe, J Miyamoto, T Fukuda, N Tohnai, M Miyata, T Kitayama, K Maehara, K Ute
    CHEMISTRY LETTERS 33 2 160 - 161 2004年02月 [査読有り][通常論文]
     
    Ion-pair clusters of simple alkylammonium carboxylates in solution and in the crystalline state were described as a model of Lys salt bridge. tert-Butylammonium triphenyl acetate gives a well-defined tetrameric cluster by a cubic hydrogen bond (H-bond) network, and diisopropylammonium triphenyl acetate gives a dimeric cluster by a cyclic network.
  • A Matsumoto, A Matsumoto, T Kunisue, A Tanaka, N Tohnai, K Sada, M Miyata
    CHEMISTRY LETTERS 33 2 96 - 97 2004年02月 [査読有り][通常論文]
     
    Naphthylmethylammonium salts of a series of diacetylene-containing carboxylic acids with various sizes of alkyl chains were photopolymerized in the crystalline state. X-ray crystal structure analyses confirmed lamellar structures characterized with the two-dimensional hydrogen networks formed between carboxylate anion and countercation layers in the crystals. The absorption properties of the resulting polymers depended on the length of alkyl substituents.
  • K Sada, K Inoue, T Tanaka, A Tanaka, A Epergyes, S Nagahama, A Matsumoto, M Miyata
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 126 6 1764 - 1771 2004年02月 [査読有り][通常論文]
     
    A series of 1-naphthylmethylammonium n-alkanoates from acetate to triacontanoate produce isomorphic layered structures in the crystalline state. The interlayer distances, d-spacings, are proportional to the lengths of the alkyl chains. This is attributed to synergic intermolecular interactions; pi-pi and CH-pi interactions of the naphthalene rings between the cations, hydrophobic interactions of the alkyl chains, and two-dimensional hydrogen-bond networks between the primary ammonium cations and the carboxylate anions. Salts made from carboxylic acids wider than 5.5 Angstrom in the cross sections produce another columnar structure with a one-dimensional ladder-type hydrogen-bond network. Steric parameters of the acid components provide an explanation for the isomerism of the hydrogen-bond network.
  • S Nomura, T Itoh, H Nakasho, T Uno, M Kubo, K Sada, K Inoue, M Miyata
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 126 7 2035 - 2041 2004年02月 [査読有り][通常論文]
     
    Highly conjugated monomers, 7,7,8,8-tetrakis(alkoxycarbonyl)quinodimethanes (methoxy (1a), ethoxy (1b), isopropoxy (1c), benzyloxy (1d), chloroethoxy (1e), and bromoethoxy (1f)), were synthesized. Recrystallizations of 1a, 1c, 1e, and 1f yielded two crystal forms (prisms (1a-A) and needles (1a-1B), needles (1c-A) and plates (1c-1B), prisms (1e-A) and plates (1e-1B), and prisms (1f-A) and needles (1f-B)), which have different molecular packing modes by X-ray crystal structure analysis, indicating that the crystals are polymorphic. In the photopolymerizations of these monomer crystals in the solid state, 1a-A, 1e-A, and 1f-A polymerized topochemically to give crystalline polymers. For their thermal polymerizations in the solid state, in addition to 1a-A, 1e-A, and 1f-A, 1e-1B and 1f-1B polymerized, but polymers formed from the 1e-B and 1f-B were amorphous. The packing of quinodimethane molecules in the crystals was defined by four kinds of parameters, stacking distance (d(s)), the distance between the reacting exomethylene carbon atoms (d(cc)), the angles formed between the stacking axis and longer axis of the monomer molecule (theta(1)), and the shorter axis of the monomer molecule (theta(2)), and then the polymerization reactivity of these quinodimethanes in the solid state was discussed on the basis of these parameters.
  • S Kiyonaka, K Sada, Yoshimura, I, S Shinkai, N Kato, Hamachi, I
    NATURE MATERIALS 3 1 58 - 64 2004年01月 [査読有り][通常論文]
     
    The protein microarray is a crucial biomaterial for the rapid and high-throughput assay of many biological events where proteins are involved. In contrast to the DNA microarray, it has not been sufficiently established because of protein instability under the conventional dry conditions. Here we report a novel semi-wet peptide/protein microarray using a supramolecular hydrogel composed of glycosylated amino acetate. The spontaneous gel-formation and amphiphilic properties of this supramolecular hydrogel have been applied to a new type of peptide/protein gel array that is compatible with enzyme assays. Aqueous cavities created in the gel matrix are a suitable semi-wet reaction medium for enzymes, whereas the hydrophobic domains of the fibre are useful as a unique site for monitoring the reaction. This array system overcomes several drawbacks of conventional protein chips, and thus can have potential applications in pharmaceutical research and diagnosis.
  • T Tani, K Sada, M Ayabe, Y Iwashita, T Kishida, M Shirakawa, N Fujita, S Shinkai
    COLLECTION OF CZECHOSLOVAK CHEMICAL COMMUNICATIONS 69 6 1292 - 1300 2004年 [査読有り][通常論文]
     
    Crystal structure of hexylammonium anthracene-9-carboxylate was investigated. The salt was arranged by a one-dimensional hydrogen bond network to form a columnar structure in the crystalline state. This columnar structure should be the model of fibrous assemblies in the organogels of anthracene-9-carboxylate alkylammonium salts having a long alkyl chain.
  • K Sada, T Sugimoto, T Tani, Y Tateishi, T Yi, S Shinkai, H Maeda, N Tohnai, M Miyata
    CHEMISTRY LETTERS 32 8 758 - 759 2003年08月 [査読有り][通常論文]
     
    A novel supramolecular orthogonal joint via hydrogen bonds was constructed by a molecular complex between 2,6-bis(2-oxazolyl)pyridnes (pybox) and secondary dialkylammonium tetraphenylborates.
  • K Nakano, E Mochizuki, N Yasui, K Morioka, Y Yamauchi, N Kanehisa, Y Kai, N Yoswathananont, N Tohnai, K Sada, M Miyata
    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY 13 2428 - 2436 2003年07月 [査読有り][通常論文]
     
    Molecular recognition of o-, m-, and p-xylenes (oX, mX, and pX) through enclathration of cholic acid (CA) is described. All of the xylenes give lattice inclusion crystals with CA, and crystallographic studies reveal that they are included in different open host frameworks. In particular, oX has two polymorphs, depending on,the recrystallization temperatures. Competitive recrystallization from mixtures of xylenes resulted in selective enclathrations and the formation of racemic mixed crystals. In the presence of an equimolar amount of oX, CA selectively includes mX or pX in the host frameworks, which are identical to those obtained from the pure mX or pX, respectively. The low affinity of oX is explained in terms of a lower stability of CA.oX than of the other two complexes, as judged from the low PCcavity, the volume ratio of the guest compound to the host cavity. Mean-while, mixtures of mX and pX yield inclusion crystals that accommodate both of the guests. These have the same open host framework as obtained from pure mX, and the guest components are disordered statically in the host cavity. The ratios of the xylene mixtures in the single crystals are similar to those in the original recrystallization mixtures, and also in the bulk crystals, indicating that CA forms mixed crystals of mX and pX. This non-selectivity is attributed to the similar stabilities of CA.mX and CA.pX, according to the moderate PCcavity. The inclusion behavior of CA from mixtures of xylenes is quite similar to chiral recognition by diastereomer-salt methods. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).
  • M Shirakawa, S Kawano, N Fujita, K Sada, S Shinkai
    JOURNAL OF ORGANIC CHEMISTRY 68 13 5037 - 5044 2003年06月 [査読有り][通常論文]
     
    To obtain insights into a correlation relationship between the structure and the aggregation mode in an organogel system, we synthesized gelators 2a-4a bearing a porphyrin moiety as a one-dimensional aggregation unit and amide groups as peripheral hydrogen-bonding sites. Gelators 3a and 3b bearing the amide groups at the 4-position of the meso-phenyl groups are classified as versatile gelators, gelating 10 and 14 solvents, respectively, among 23 solvents tested herein. In contrast, gelators 2a and 4a bearing the amide groups at the 3,5-positions and 3-position, respectively, are classified as poor gelators. Examination by spectroscopic methods (UV-vis, ATR-FTIR, XRD, etc.) revealed that in the organogel phase porphyrins in 3a adopt the H aggregation mode whereas those in 2a and 4a adopt the J aggregation mode. X-ray analysis of the single crystals established that in fact 3b features a columnar stack of porphyrin moieties that can be classified as the H-aggregate, whereas 2a results in a two-dimensional a-b plane, in which porphyrin moieties are arranged in the J-aggregate. Very interestingly, the difference in the H versus J aggregation mode is well-reflected by the difference in the macroscopic aggregate morphology observed by SEM: 3a + cyclohexane gel results in a one-dimensionally aggregated fibrillar structure, whereas 2a + cyclohexane gel results in a two-dimensional sheetlike structure. These findings indicate that the H versus J aggregation mode of porphyrin stacks can be controlled by the peripheral hydrogen-bonding interactions and the microscopic hydrogen-bonding network structure is well-reflected by the macroscopic SEM-observed structure.
  • S Nagahama, K Inoue, K Sada, M Miyata, A Matsumoto
    CRYSTAL GROWTH & DESIGN 3 2 247 - 256 2003年03月 [査読有り][通常論文]
     
    Strong and weak hydrogen bonds, as intermolecular interactions, are used for the construction of designer crystals with organic small molecules as the building blocks. We report here crystal engineering for the synthetic plan of the topochemical polymerization using the ammonium derivatives of 1,3-diene mono- and dicarboxylic acids on the basis of intermolecular interactions such as NH/O and CH/pi interactions. The isomerism of hydrogen bond network structures obstructs the prediction of crystal structure and reactivity, although topochemical polymerization requires that monomer molecules stack in a column with a stacking distance of 5 Angstrom in the crystals. The structures of hydrogen bond networks are roughly classified into a two-dimensional type appropriate for topochemical polymerization, and the others consisting of two-dimensional sheets or one-dimensional ladders not for polymerization. We conclude that the CH/pi interaction of naphthylmethyl and benzyl substituents promises to give polymerizable lamella crystals, of which the interface is supported by robust two-dimensional hydrogen bond networks reinforced by lining with CH/pi interaction between benzylic and aromatic hydrogens and T-electrons.
  • M Ayabe, K Yamashita, K Sada, S Shinkai, A Ikeda, S Sakamoto, K Yamaguchi
    JOURNAL OF ORGANIC CHEMISTRY 68 3 1059 - 1066 2003年02月 [査読有り][通常論文]
     
    The construction of chirally twisted porphyrin-based molecular capsule 6 and polymeric capsule 8 was investigated by means of scanning electron microscopy (SEM) and H-1 NMR, LTV-visible, and CD spectroscopic observations. Molecular capsule 6 and polymeric capsule 8 were constructed by the reaction of chiral cis-Pd(II) complex 4 bearing a (R)-(+)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP) ligand with porphyrin 1 bearing four pyridyl groups and porphyrin 2 bearing eight pyridyl groups, respectively. The peak-splitting pattern of the beta-pyrrole protons in the 1H NMR spectrum and the specific CD spectral pattern bearing an exciton coupling band indicate that both molecular capsule 6 and polymeric capsule 8 are chirally twisted. Moreover, it was found that the CD intensity of the polymeric capsule plotted against [4]/([4] + [3]) shows a sigmoidal curvature, reflecting a unique cooperativity among the ligand groups; that is, the ligand existing in excess over the other dominates the twisting direction. These results consistently demonstrate that "chirality" in these molecular assembly systems is conveniently controlled by the use of chiral ligands.
  • Kazuaki Kato, Kazuaki Aburaya, Yasuhito Miyake, Kazuki Sada, Norimitsu Tohnai, Mikiji Miyata
    Chemical Communications 2872 - 2873 2003年 [査読有り][通常論文]
  • T Yi, K Sada, K Sugiyasu, T Hatano, S Shinkai
    CHEMICAL COMMUNICATIONS 3 344 - 345 2003年 [査読有り][通常論文]
     
    The controlled colour generation and colour erasing phenomena of alkylammonium polyoxomolybdate complexes were first observed in the trans-(1R, 2R)-1,2-bis( undecylcarbonylamino) cyclohexane organogel system using the sol-gel phase transition.
  • K Kato, K Aburaya, Y Miyake, K Sada, N Tohnai, M Miyata
    CHEMICAL COMMUNICATIONS 23 2872 - 2873 2003年 [査読有り][通常論文]
     
    Pure ( 2R, 3S)- 3- methyl- 2- pentanol is resolved from the racemates by a steroidal host; the interpretation of the recognition mechanism based on the crystal structure reveals that CH/ O interaction between the host and guest plays a decisive role in enantio- selective enclathration of the small aliphatic secondary alcohol.
  • M Ayabe, T Kishida, N Fujita, K Sada, S Shinkai
    ORGANIC & BIOMOLECULAR CHEMISTRY 1 15 2744 - 2747 2003年 [査読有り][通常論文]
     
    The gelation ability of 10 alkylammonium (CnH2n+1NH3+ where n = 4 - 11, 12 and 16) anthracene-9-carboxylates (1(n)) has been evaluated. In cyclohexane, 1(4), 1(5), 1(6) and 1(7) only provided precipitates whereas 1(11), 1(12) and 1(16) provided very viscous solutions. In contrast, 1(8), 1(9) and 1(10) resulted in gels. The critical gelation concentration of 1(10) was very low (5.0 x 10(-4) mol dm(-3)). SEM observations showed that in the gel phase the morphology changes from straight fibrils to frizzy fibrils with the increase in n, whereas in the sol phase the formation of the sheet-like, two-dimensional aggregate is recognized. When the cyclohexane 1(10) gel was photoirradiated (lambda > 300 nm), the UV-VIS absorption bands assignable to monomeric anthracene were decreased and the gel was changed into the sol. It was confirmed by dark-field optical microscopy that the fibrillar bundles supporting the gel formation gradually disappear with photoirradiation time. When this sol was warmed at 30 degreesC in the dark, the gel was not regenerated but the precipitation of 1(10) resulted. When this sol was heated once at the bp of cyclohexane and cooled to 15 degreesC, the solution was changed into the gel again. This finding indicates that the fibrillar structure required for the gel formation is not reconstructed at 30 degreesC but obtained only when the hot cyclohexane solution is cooled.
  • A Matsumoto, T Kunisue, S Nagahama, A Matsumoto, K Sada, K Inoue, T Tanaka, M Miyata
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 390 11 - 18 2003年 [査読有り][通常論文]
     
    We have investigated the crystal structures of several 1-naphthylmethylammonium salts of unsaturated carboxylic acids, i.e., sorbate, crotonate, tiglate, and methacrylate as the diene and vinyl monomers. In the crystals, the monomer molecules stack in a similar fashion to make a lamellar structure consisting of alternating naphthylmethylammonium cation and carboxylate anion layers. For the construction of the lamellar structure, weak intermolecular interaction such as pi-pi stacking and CH-pi interaction is important as well as the formation of robust two-dimensional hydrogen bond network. We discuss the relationship between the molecular packing in the crystals and photopolymerization reactivity of the unsaturated carboxylic acid derivatives in the solid state.
  • S Nomura, T Itoh, M Ohtake, T Uno, M Kubo, A Kajiwara, K Sada, M Miyata
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 42 44 5468 - 5472 2003年 [査読有り][通常論文]
  • K Kato, Y Aoki, M Sugahara, N Tohnai, K Sada, M Miyata
    CHIRALITY 15 1 53 - 59 2003年01月 [査読有り][通常論文]
     
    Nordeoxycholic acid (NDCA) forms three kinds of host frameworks, M1, M2, and M3, with channels where aliphatic alcohols (1-7) are accommodated. C-13-NMR studies clarified that racemic alcohols 1- or 2-6 are enclosed in the M1- or M2-type channel with lower than 15% enantiomeric excess, respectively, while 3-methyl-2-pentanol (7) is done in the M3-type with 47% ee. These inclusion phenomena can be explained due to the Difference Fourier maps of electron densities of their enantiomers in the channels. In addition, analysis of the manner of packing indicates that four locations in the channels should be fixed for the enantioresolution of the alcohols. These results support the four-location model, which has been proposed by Mesecar et al.(20) with respect to enantioresolution on protein surfaces. (C) 2002 Wiley-Liss, Inc.
  • N Yoswathananont, K Sada, M Miyata, S Akita, K Nakano
    ORGANIC & BIOMOLECULAR CHEMISTRY 1 1 210 - 214 2003年01月 [査読有り][通常論文]
     
    Competitive recrystallizations of cholic acid (CA) from I : I binary mixtures of seven mono-substituted benzenes are demonstrated. The order of preference for guests to be incorporated into the cholic acid crystals are as follows: benzene, toluene > n-amylbenzene, n-hexylbenzene > ethylbenzene, n-propylbenzene, n-butylbenzene. These seven compounds afford bilayer type inclusion crystals that are classified into four types based on the host frameworks and host-guest stoichiometries. The order of selective enclathration corresponds to the four types as follows: 1 : 1 alphaG > 2 : 1 alphaG > 1 : 1 betaT or 2 : 1 alphaT. The preference for the alphaG type was also confirmed by investigating the host frameworks of the crystals obtained from binary mixtures. The dependence of the selectivity on the different types of CA crystals can be understood in terms of the fit of the guest molecule in the host cavity.
  • N Yoswathananont, H Kita, N Tohnai, K Sada, M Miyata
    CHEMISTRY LETTERS 12 1234 - 1235 2002年12月 [査読有り][通常論文]
     
    Cholamide (1) exhibits a novel pseudopolymorphism in a three-component system composed of 1, acetonitrile, and water. Recrystallization of 1 from a guest solution composed of an equal amount of acetonitrile and water gave one polymorph (triangular, 1 : 1 : 1 molar ratio of 1 : acetonitrile : water). Diminished water in the guest solution provided the other polymorph (bilayer, 1 : 1 : 2).
  • A Matsumoto, K Sada, K Tashiro, M Miyata, T Tsubouchi, T Tanaka, T Odani, S Nagahama, T Tanaka, K Inoue, S Saragai, S Nakamoto
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 41 14 2502 - + 2002年 [査読有り][通常論文]
  • T Itoh, S Nomura, T Uno, M Kubo, K Sada, M Miyata
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 41 22 4306 - 4309 2002年 [査読有り][通常論文]
  • Nakano K, Hishikawa Y, Sada K, Miyata M, Hanabusa K
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 389 11 - 16 2002年 [査読有り][通常論文]
  • Yoswathananont N, Sada K, Miyata M
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 389 47 - 51 2002年 [査読有り][通常論文]
  • T Odani, A Matsumoto, K Sada, M Miyata
    CHEMICAL COMMUNICATIONS 19 2004 - 2005 2001年10月 [査読有り][通常論文]
     
    One-way EZ-isomerization of bis(n-butylammonium) (ZZ)muconate [(ZZ)-hexa-2,4-diene-1,6-dioate] to the corresponding (EE)-isomer quantitatively proceeded in the crystalline state under photoirradiation with a high-pressure mercury lamp, being a new type of crystal-to-crystal reaction.
  • K Sada, M Sugahara, K Kato, M Miyata
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 123 19 4386 - 4392 2001年05月 [査読無し][通常論文]
     
    Expansion of a molecular cavity is described by using elongation of the side chain of a bile acid host compound. Bishomocholic acid (2), which has a side chain that is longer by two methylene unit than cholic acid (1), includes many organic substances at 1:I host:guest ratios. X-ray crystallographic studies revealed that 2 has two types of open host frameworks: a bilayer type and a crossing type. Both of them are isostructural to those of 1, indicating that they are robust against the elongation of the side chain. In the former type, the increment of the width of the host channel corresponds to that of the length of the molecular structures. Larger aromatic guest components such as l-methylnaphthalene and 1-tetralone, are included in 2, but not in 1.
  • K Nakano, K Sada, Y Kurozumi, M Miyata
    CHEMISTRY-A EUROPEAN JOURNAL 7 1 209 - 220 2001年01月 [査読無し][通常論文]
     
    The crystal structures of inclusion compounds of cholic acid (CA) with 28 monosubstituted benzenes have been systematically investigated. All of the crystals belong to the monoclinic space group P2(1) and have bilayer structures with one-dimensional molecular channels that can include guest compounds. They are classified into four types of host frameworks that depend on the conformations and stacking modes of the host compound. The host frameworks and the host - guest ratios depend primarily on the molecular volumes of the guest compounds. The packing coefficient of the host cavity (PCcavity), which is the volume ratio of the guest compound to the host cavity, is used to clarify the relationship between the guest volume and isomerization of the host frameworks. The value of PCcavity for stable inclusion compounds lies in the range of 55-70%. Compounds out of this range induce isomerization of the host frameworks. The packing coefficients of other host-guest compounds, in which the guest components are included in the host cavities through steric dimensions and van der Waals forces, are also in this range. These results indicate that PCcavity is a useful parameter correlation for guest recognition and isomerization of the host frameworks.
  • Conformational Polymorphism in Inclusion Crystals of Cholid Acid with Ethyl Acetate
    Cryst. Eng. Comm. 11 1 1 - 2 2001年 [査読無し][通常論文]
  • K Nakano, K Sada, M Miyata
    POLYMER JOURNAL 33 2 172 - 176 2001年 [査読無し][通常論文]
     
    Inclusion polymerization of vinyl and diene monomers was studied using cholic acid (CA) as host. Polymorphism of CA inclusion crystals was found to play a decisive role in the polymerizability of the monomers. Polymorphic crystals were obtained by recrystallization and guest-exchange on intercalation. In the case of methacrylonitrile, CA forms two crystal structures; a bilayer structure with one-dimensional channels and crossing structure with cage-like cavities. The former structure is suitable for polymerization, but not the latter. In the case of 2,3-dimethyl-1,3-butadiene, intercalation yielded only bilayer crystals. The microstructure of the resulting polymer was compared with those of the polymers obtained by other steroidal hosts. Different stereoregularity may be explained on the basis of different channel sizes of hosts.
  • K Nakano, M Katsuta, K Sada, M Miyata
    CRYSTENGCOMM 11 art. no. - 11 2001年 [査読有り][通常論文]
     
    Conformational polymorphism is observed in the inclusion crystals of cholic acid 1 with ethyl acetate. Direct recrystallization of host 1 from ethyl acetate gives one polymorph (monoclinic P2(1)); in the presence of 1-naphthylmethylamine as a third component another polymorph (triclinic P1) is produced. The former has gauche conformation of the side chain (the dihedral angle of C17-C20-C22-C23, psi = 65 degrees) while the latter has trans conformation (psi = 158 and -168 degrees), although they have similar bilayer host frameworks with the same 1:1 host-guest stoichiometries. This results in differences between the hydrogen bond networks, the cavity shapes and the orientations of the guest molecules.
  • M Miyata, K Sada
    SOFT CHEMISTRY LEADING TO NOVEL MATERIALS 191 99 - 123 2001年 [査読有り][通常論文]
     
    Inclusion compounds have molecular-level spaces where monomers as guest components form low-dimensional and anisotropic assemblies. The polymerization consists of a cyclic process and proceeds via radical mechanism in most of the cases. Features of the polymerization are understood on the basis of low-dimensionality and space-dependence. Relative sizes between the monomers and the spaces play a decisive role in determining motions of propagating radicals, polymerizabilities and stereoregularities. The representative one- or two-dimensional polymerization are summarized. After the polymerization low-dimensional molecular composite materials are obtained. In the case of steroidal hosts, the polymerization can be controlled on the basis of chiral and sequential carbon-chains, leading to the idea that inclusion polymerization constitutes a process of molecular information and their expression, like biopolymers such as proteins.
  • K Sada, K Nakano, K Hirayama, M Miyata, S Sasaki, K Takemoto, N Kasai, K Kato, M Shigesato, K Miki
    SUPRAMOLECULAR CHEMISTRY 13 1 35 - + 2001年 [査読有り][通常論文]
     
    Molecular recognitions of medium size lactones by enclathration of cholic acid (CA) are described. Size and location of the substituents on the lactone rings play an important role for enclathration. Lactones within the limited steric dimensions are included in CA and larger or smaller ones are not included to give guest-free crystals of CA. Moreover, CA partially separates one enantiomer from racemic lactones by recystallization. X-ray crystallographic studies reveal that all included lactones form the beta -trans type bilayer structure having a pentagonal void channel with a side pocket. The cross-sections illustrate that the lactone rings are incorporated in the center of the channel and that the substituents of the guests are fixed in the side pockets. The asymmetric channel enables CA to discriminate size and chirality of medium size lactones.
  • M Sugahara, J Hirose, K Sada, M Miyata
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 356 155 - 162 2001年 [査読有り][通常論文]
     
    It was found that steroidal bile acids have greatly different inclusion abilities with decreasing or increasing their side chain length, Namely, the acids with intermediate side chains formed inclusion compounds with various organic compounds, while those with shorter or longer chains did not include so many. X-ray crystallographic studies clarified that the chains alter the hydrogen bonding networks among the host molecules, leading to the changes of the inclusion abilities and assembly modes.
  • N Yoswathananont, S Chirachanchai, K Tashiro, K Nakano, K Sada, M Miyata
    CRYSTENGCOMM 19 2001年 [査読有り][通常論文]
     
    A novel host framework of cholic acid (CA) has been observed in the crystal structure of m-chloroaniline clathrate. Crystallographic study reveals that CA forms a bilayer-type structure; however, slide and flip of the lipophilic layers give a different host framework to those of over 100 inclusion crystals previously reported. Structural comparison between the clathrates of aniline and m-chloroaniline indicates that the addition of a chlorine atom leads to isomerization of the open host framework due to a steric effect between adjacent guests within the host cavities.
  • K Nakano, Y Hishikawa, K Sada, M Miyata, K Hanabusa
    CHEMISTRY LETTERS 10 1170 - 1171 2000年10月 [査読有り][通常論文]
     
    A combinatorial library approach enables us to find new low molecular-weight organogelators composed of a bile acid -alkylamine salt; the gel phenomena are investigated by FT-LR spectroscopy, SEM, and X-ray crystallography.
  • 宮田 幹二, 佐田 和己
    日本油化学会誌 = Journal of Japan Oil Chemists' Society 49 5 447 - 454 Japan Oil Chemists' Society 2000年05月20日 
    コール酸誘導体は様々な有機物と結晶性包接化合物をつくる。二百以上の結晶構造データに基づいて, その包接化合物における分子認識が調べられた。ホスト分子は分子間水素結合により会合して, 層状あるいはらせん状の多様な集合体を形成することがわかった。これらの分子集合様式は, キラリティ・方向性・両親媒性などにおける, ホスト分子の独特な面状構造に基づいて解釈することができる。特に, ホスト分子の水素結合基は集合体形成に重要な役割を果たしている。分子構造のわずかな変化により, 水素結合網が変化して, 集合体が劇的に変化することがある。水素結合様式は複数あるため, ゲスト依存性の多形結晶が得られる。アルコールゲストに対する包接能は, ホストにより非常に異なっていた。このような包接能の違いは, ゲストを捕らえる水素結合基がホストの分子集合体に存在するかどうかにより決まる。包接空間は, ラセミ体の分割や重合反応の場として利用できる。このような研究から, コール酸誘導体とタンパク質との間に類似関係のあることが明らかになった。そのため, 定序性キラル炭素鎖が潜在的に持つ分子情報は, 分子集合のプロセスを通じて, その形質や機能の発現へと具現化されるものと考えられる。
  • Akikazu Matsumoto, Toru Odani, Kazuki Sada, Mikiji Miyata, Kohji Tashiro
    Nature 405 6784 328 - 330 2000年05月18日 [査読無し][通常論文]
     
    Organic solid-state synthesis allows formation of products that are difficult or impossible to produce by conventional methods. This feature, and the high degree of reaction selectivity that can be achieved, is a direct result of the control over the relative orientation of the reactants afforded by the solid state. But as the successful development of 'topochemical reactions' requires the careful design of suitable reactant crystals, the range of both reactions and products amenable to this approach has been limited. However, recent advances in organic crystal engineering, particularly the rational design of complex solid architectures through supramolecular preorganization, have renewed interest in topochemical reactions. Previously, we have orientated muconate monomers - diene moieties with a carboxylate group on each end - using long-chain n-alkylammonium ions, such that the topochemical photopolymerization of the solid-state reactants produces layered crystals of stereoregular and high-molecular-mass polymers. Here we show that these polymer crystals are capable of repeated, reversible intercalation by conversion to the analogous poly(carboxylic acid), followed by transformation into a number of poly(alkylammonium muconate)s upon addition of the appropriate amine. Introduction of functional groups into these crystals may allow the design of organic solids for applications such as molecular recognition, separation and catalysis, thereby extending the range and practical utility of current intercalation compounds.
  • RE Melendez, AJ Carr, K Sada, AD Hamilton
    MATERIALS OF SMART SYSTEMS III 604 335 - 340 2000年 [査読有り][通常論文]
     
    The use of organic molecules as gelators in certain organic solvents has been the target of recent research in materials science. The types of structures formed in the gel matrix have potential applications as porous solids that can be used as absorbents or in catalysis. We will present and discuss the organogelation properties of a family of bis-ureas. Studies presented will include a molecule structure activity relationship, thermodynamic properties, comparison to x-ray crystallographic data and potential functionalization of the gels formed by this class of compounds.
  • Y Aoki, Y Hishikawa, K Sada, M Miyata
    ENANTIOMER 5 1 95 - 104 2000年 [査読有り][通常論文]
     
    Lithocholamide (LCAM) forms inclusion compounds with aliphatic alcohols involving over five carbon atoms. Enantioresolution of the racemic alcohols was studied in channels of the inclusion compounds. X-ray crystallographic study clarified that host assemblies exhibit guest-dependent polymorphism. In each polymorphic crystal, the more longer or bulkier groups the alcohols have, the effective the resolutions become. The inclusion spaces were analyzed by a computed tomographic method, explaining the chiral recognition mechanism from a stereochemical viewpoint.
  • A Matsumoto, T Odani, M Chikada, K Sada, M Miyata
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 121 48 11122 - 11129 1999年12月 [査読無し][通常論文]
     
    A new type of photoreaction of the ammonium salts of butadiene-1,4-dicarboxylic acid in the solid state is reported. When the crystals of a series of di(benzylammonium) (Z,Z)-muconate (2,3-hexadienedioate) and its related derivatives were prepared and photoirradiated, either a tritactic polymer or an (E,E)-isomer was obtained as the photoproduct according to the structure of the ammonium part. The polymers produced were confirmed to be of high molecular weight and stereoregular by viscometry and NMR spectroscopy after solid-state polymer transformation. X-ray crystal structure analysis revealed that the crystal structures of benzylammonium muconates were classified into columnar-type and sheet-type on the basis of the molecular arrangement. Both types involve two-dimensional hydrogen bond networks between the primary ammonium cations and the carboxylate anions. In the former structure, the stacking of the diene moieties was suitable for topochemical polymerization to yield a tritactic polymer, while the latter has molecular packing favoring the isomerization or no reactivity. The stereocontrol of the tritactic polymer is in good agreement with the results expected from the crystal structure. This indicates that the molecular packing determines a reaction pathway in the crystalline state.
  • Design of organic gelators based on a family of bis-ureas.
    Melendez RE, Carr AJ, Sada K, Hamilton AD
    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 218 U39  1999年08月22日 [査読有り][通常論文]
  • M Sugahara, K Sada, M Miyata
    CHEMICAL COMMUNICATIONS 3 293 - 294 1999年02月 [査読無し][通常論文]
     
    Four norbile acids (norcholic, nordeoxycholic, norchenodeoxycholic and norlithocholic acids) include various organic compounds and have a common robust motif in their crystal structures based on a cyclic hydrogen bond network and steric complementarity in the lipophilic parts.
  • M Chikada, K Sada, M Miyata
    POLYMER JOURNAL 31 11 1061 - 1064 1999年 [査読有り][通常論文]
     
    Chenodeoxycholic acid (CDCA) was found to form hexagonal crystals including various vinyl and diene monomers. The crystals consist of helical assemblies of CDCA. The inner channels are one-dimensional spaces with a diameter of 0.7 to 0.8 nm. The monomers are incorporated into the channels through a guest exchange method (called intercalation), starting from the original compounds with n-octyl acetate. gamma-Ray irradiation from a Co-60 source yielded polymers with relatively narrow molecular weight distributions. The microstructures are similar to those obtained from usual radical polymerization. The crystals maintained their shape during the intercalation and polymerization. The propagating radicals were detected by ESR spectroscopy. The spectra were dependent on the temperature. These results indicate that the polymerization proceeds in the relativly large channels with a living-like radical mechanism. This reseach contributes to the establishment of the concept; molecular information and their expression through nano-organized systems of sequential and chiral carbon-chain oligomers.
  • Y Hishikawa, K Sada, M Miyata
    SUPRAMOLECULAR CHEMISTRY 11 2 101 - 108 1999年 [査読有り][通常論文]
     
    N-Methyldeoxycholamide (1) was recrystallized from over one hundred organic substances in a search for inclusion compounds. Only ethylene glycol (EG) was included into host assemblies together with water. Other solvents gave hemihydrate crystals without organic guests. X-ray structural analysis revealed that the former inclusion crystal has a three-leaved building block similar to that of glycodeoxycholic acid (2). Tomographical analysis of both the assemblies gave an insight about such an extremely specific inclusion behavior from the viewpoint of steric and hydrogen-bonding terms.
  • Y Hishikawa, Y Aoki, K Sada, M Miyata
    CHEMISTRY LETTERS 12 1289 - 1290 1998年12月 [査読無し][通常論文]
     
    The substitution of lithocholic acid (1) to lithocholamide (4) led to the finding of the formation of channel-type inclusion compounds with a limited range of organic substances, such as alcohols, ketones and so on. The inclusion behavior of 4 is greatly different from those of the known hosts of bile acids and their derivatives.
  • Y Hishikawa, K Sada, M Miyata
    JOURNAL OF CHEMICAL RESEARCH-S 12 738 - 739A 1998年12月 [査読有り][通常論文]
     
    Addition of water enables deoxycholamide to form a triangular pillar-like assembly with a core involving water and a surface involving organic compounds.
  • K Sada, N Shiomi, M Miyata
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 120 40 10543 - 10544 1998年10月 [査読無し][通常論文]
  • K Sada, T Kondo, M Ushioda, Y Matsuura, K Nakano, H Miyata, K Miki
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 71 8 1931 - 1937 1998年08月 [査読無し][通常論文]
     
    Clathrate formation and crystal structures of 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholan-24-amide (cholamide) have been investigated. Cholamide forms inclusion compounds with various organic compounds having hydrogen-bond (H-bond) donors. X-Ray crystallographic studies showed that cholamide has bilayer structures with molecular channels. The crystal structures are quite similar to those of channel-type inclusion crystals of cholic acid. Steric dimensions of the host cavities are identical, but cholamide has an H-bond 'hook' on the wall of the channels, while cholic acid does not. This difference is correlated with not only the inclusion abilities but also the molecular structures. Two H-bond donors of the amide group yield a hydrophilic inclusion cavity that includes H-bond accepters, and one H-bond donor of the carboxylic acid gives a lipophilic inclusion cavity that includes non-polar or less polar compounds.
  • K Sada, K Yoshikawa, M Miyata
    CHEMICAL COMMUNICATIONS 16 1763 - 1764 1998年08月 [査読無し][通常論文]
     
    Seventeen new ammonium carboxylate host compounds were screened from a combinatorial library of one hundred ammonium carboxylates formed by mixing ten amines and ten carboxylic acids.
  • Y Hishikawa, K Sada, R Watanabe, M Miyata, K Hanabusa
    CHEMISTRY LETTERS 8 795 - 796 1998年08月 [査読有り][通常論文]
     
    N-Isopropylcholamide afforded three kinds of matters in organic solvents; organogels, inclusion crystals, and guest-free crystals. The gelation occurred in aromatic liquids in the presence of methanol as a good solvent, while the inclusion crystals were formed when adding ethanol, I-propanol, or acetone as a good solvent. The guest-free crystals were obtained in benzene when using 2-butanone, 2-pentanone, or 3-pentanone. Electron microscopic image of the organogel exhibited that the network was formed by gathering of many colloidal particles of several hundreds nanometers in diameter.
  • Y Hishikawa, R Watanabe, K Sada, M Miyata
    CHIRALITY 10 7 600 - 618 1998年 [査読無し][通常論文]
     
    Chiral compounds, N-methyl-, N-ethyl-, and N-n-propylcholamides, form crystalline inclusion compounds with water or small organic substances. The compounds were analyzed by X-ray diffraction methods. It was found that the crystals have bilayered structures accumulated by chiral molecular sheets. The chiral molecules associate in a unique head-to-head/tail-to-tail and right-to-left motif to give chiral and amphiphilic sheets. Such sheets stack by adhesions between the hydrophilic sides and between the lipophilic sides. The alkyl groups of the amides prompt the formation of a hydrogen-bonding network between the tails instead of a cyclic one between the head and tail. The guest molecules are accommodated into small cavities between the steroidal side chains. (C) 1998 Wiley-Liss, Inc.
  • Y Miyake, J Hirose, Y Hasegawa, K Sada, M Miyata
    CHEMICAL COMMUNICATIONS 1 111 - 112 1998年01月 [査読無し][通常論文]
     
    A new host, 3-epiursodeoxycholic acid, forms inclusion crystals with naphthalene derivatives with 1:1 stoichiometry.
  • K Sada, M Sugahara, Y Nakahata, Y Yasuda, A Nishio, M Miyata
    CHEMISTRY LETTERS 1 31 - 32 1998年 [査読有り][通常論文]
     
    A new host, 23-nordeoxycholic acid, which forms inclusion compounds with many organic compounds, have a novel monolayer columnar structure in spite of a facially amphiphilic molecular structure.
  • Y Miyake, K Sada, M Miyata
    SUPRAMOLECULAR CHEMISTRY 10 2 107 - 109 1998年 [査読有り][通常論文]
     
    Hyocholic acid forms lattice-type inclusion compounds with specific aliphatic alcohols. In these compounds, water molecules are also included and they play an important role in the formation of inclusion spaces.
  • Mikiji Miyata, Kazuki Sada, Yasuhito Miyake
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS 313 173 - 178 1998年 [査読有り][通常論文]
     
    Steroidal acids and their derivatives form inclusion compounds with a variety of organic substances. Over one thousand derivatives are candidates for hosts of the compounds. The study on steroidal inclusion compounds provides systematic data for considering relationships between molecular structures and molecular assemblies, indicating that combinatorial chemistry can be applied to inclusion chemistry.
  • K Sada, M Miyata
    KOBUNSHI RONBUNSHU 54 10 754 - 755 1997年 [査読有り][通常論文]
     
    Inclusion compounds of cholamide with poly(ethylene glycol)s were prepared. X-Ray crystallographic study revealed that they had bilayer structures with molecular channels. The polymeric guest was incorported in the channel of the host lattice.
  • K Nakano, K Tani, K Sada, M Miyata
    FORMATION AND DYNAMICS OF SELF-ORGANIZED STRUCTURES IN SURFACTANTS AND POLYMER SOLUTIONS 106 249 - 251 1997年 [査読有り][通常論文]
     
    Selective acquisition of polymorphic inclusion crystals of cholic acid with acrylonitrile and methacrylonitrile is described. Two polymorphic inclusion crystals of 1 with methacrylonitrile have different hydrogen-bonded networks from those with acrylonitrile.
  • Y Miyake, Y Matsuura, K Sada, M Miyata
    CHEMISTRY LETTERS 12 1263 - 1264 1997年 [査読有り][通常論文]
     
    Hyodeoxycholic acid forms inclusion crystals with aromatic amines such as pyridine, aniline and toluidines. The crystal structure of a I:1 inclusion compound of hyodeoxycholic acid with pyridine was determined.
  • P Briozzo, T Kondo, K Sada, M Miyata, K Miki
    ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE 52 728 - 733 1996年08月 [査読有り][通常論文]
     
    The three types of inclusion compounds of cholanamide (CAM, 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholan-24-amide) have been crystallized from the solutions of (S)-butan-2-ol (CAMSB), (R)-butan-2-ol (CAMRB) and racemic butan-2-ol (CAMSRB), respectively. The crystal structures have been determined. The three crystal structures are isomorphous to each other and revealed that the host CAM molecules form the same layered arrangements, providing channel spaces for the guest butan-2-ol molecules. As expected, the CAMSB and CAMRB crystals include the pure (S)- and (R)-enantiomers of butan-2-ol, whereas the (S)-enriched mixture of enantiomers is accommodated in CAMSRB with a molar ratio between the host CAM and guest butan-2-ol molecules of 1:1. The hydrogen-bond network is rigidly formed between the CAM molecules and also between CAM and butan-2-ol molecules. CAMSB and CAMRB have slightly different unit-cell dimensions: the channels in CAMRB have a larger section, resulting in a larger unit-cell volume. In CAMSRB, although both enantiomers of the guest alcohol are included, the (S)-enantiomer is more abundant, indicating that the optical resolution occurs during the crystallization step.
  • K Nakano, K Sada, M Miyata
    CHEMICAL COMMUNICATIONS 8 989 - 990 1996年04月 [査読有り][通常論文]
     
    Addition of a third component enables cholic acid to form polymorphic inclusion crystals with different hydrogen-bonded networks with the same organic guest, indicating a novel additive effect on polymorphs.
  • K Sada, M Miyata
    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN 54 2 113 - 121 1996年02月 [査読無し][通常論文]
     
    Inclusion behavior and crystal structures of inclusion compounds of bile acids and their derivatives are described. Molecular recognition properties of the steroidal hosts are dependent on molecular structure. Especially, cholic acid, deoxycholic acid and their amides are found to be versatile hosts to include a wide variety of organic compounds. However, Some derivatives of cholic acid provide only guest-free crystals, and they can not form inclusion crystals with common organic solvents at all. X-ray crystallographic studies reveal that the crystal structures consist of stacked bilayers except that of lithocholic acid. Facially amphiphilic molecular structure of the bile acids gives the multibilayer structure in crystalline state. Side chain of the steroidal skeleton controls the structural variety of multibilayer structure. On the basis of molecular recognition and dynamic properties of inclusion crystals of the steroidal bile acid, we can say that bile acids have similar structure and function to proteins through molecular assembly.
  • K Sada, T Maeda, M Miyata
    CHEMISTRY LETTERS 10 837 - 838 1996年 [査読有り][通常論文]
     
    Chiral discrimination of 1-phenylethylamine (1) by diastereomeric salt formation with bile acids is described. X-ray crystallographic studies of the salts between cholic acid (2a) and (R)-, (S)-, and (RS)-1 reveal that more densely packed (S)-1+2a salt crystallizes preferentially by treatment of 2a from racemic 1.
  • K Nakano, K Sada, M Miyata
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS 276 129 - 132 1996年 [査読有り][通常論文]
     
    Cholic acid forms inclusion crystals with guest-dependent bilayered structures. Heat treatment induced a sliding of the bilayers accompanied by release of guests. The opposite sliding occurred by soaking the crystals into liquid guests.
  • K Sada, Y Matsuura, M Miyata
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS 276 121 - 127 1996年 [査読有り][通常論文]
     
    Crystal structure of an inclusion crystal of cholanamide with aniline is described. Comparison of the crystal structure with that of the cholic acid clathrate reveals both hosts have quite similar assembly mode. However, the most striking difference is hydrogen bonding. Aniline is included in host lattice of cholanamide by triple hydrogen bonds, whereas in that of cholic acid by double weak hydrogen bonds. Difference of the molecular structure between them gives raise to change the host-guest hydrogen bonding.
  • K SADA, A MATSUO, M MIYATA
    CHEMISTRY LETTERS 10 877 - 878 1995年10月 [査読有り][通常論文]
     
    A novel molecular arrangement in asymmetric bilayered crystals is described. 3 alpha, 12 alpha, 24-trihydroxy-5 beta-cholane with benzene clathrate (2:1) have multibilayer structure with parallel fashions both in the lipophilic sites and in the hydrophilc sites.
  • K NAKANO, K SADA, M MIYATA
    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS 9 953 - 954 1995年05月 [査読有り][通常論文]
     
    o-Xylene and 1,2,3-trimethylbenzene permit cholic acid to employ a reversed molecular arrangement in asymmetric multibilayers, in contrast to benzene, toluene and m- or p-xylene.
  • Reversible layer sliding in cholic acid crystals
    Mol. Cryst. Liq. Cryst 276 129  1995年 [査読無し][通常論文]
  • Y CHUJO, A NAKA, M KRAMER, K SADA, T SAEGUSA
    JOURNAL OF MACROMOLECULAR SCIENCE-PURE AND APPLIED CHEMISTRY A32 6 1213 - 1223 1995年 [査読有り][通常論文]
     
    This paper describes the synthesis of various star-shaped polymers by means of complexation of bipyridyl-terminated polyoxyethylene with Ru(II) ion. Three kinds of bipyridyl-terminated polyoxyethylenes of different molecular weights were prepared from the corresponding polyoxyethylene monomethyl ethers with narrow molecular weight distributions. Bipyridyl was found to be introduced quantitatively at the end of the polymers based on the results of UV spectra. The formation of a starshaped polymer was carried out by the reaction of RuCl3 with three equivalents of bipyridyl-terminated polyoxyethylene. The UV spectrum of the star-shaped polymer obtained supported the formation of a typical Ru(II) tris(bipyridyl) complex. From the results of GPC, the starshaped polymer obtained had a higher molecular weight than the prepolymer and showed a narrow molecular weight distribution. In the case of a Ni(II) or a Co(II) complex, however, the star-shaped polymer was found to be dissociated into three linear prepolymers under the conditions of GPC measurement.
  • K SADA, T KONDO, M MIYATA
    SUPRAMOLECULAR CHEMISTRY 5 3 189 - 191 1995年 [査読有り][通常論文]
     
    Deoxycholanamide forms lattice inclusion compounds with a variety of organic substances; the 1:1 inclusion crystal of the amide with 1-butanol has a bilayer structure involving channels with hydrogen bond hooks for the guests.
  • K SADA, Y HISHIKAWA, T KONDO, M MIYATA
    CHEMISTRY LETTERS 11 2113 - 2116 1994年11月 [査読有り][通常論文]
     
    N-Methyldeoxycholanamide specifically includes water instead of organic substances, which is in contrast to deoxycholic acid and deoxycholanamide. Such a specific inclusion behaviour is reasonably explained by the crystal structure of the hemihydrate. The N-methyl group induces a ladder-like hydrogen bonding scheme involving water. The resulting molecular arrangement inhibits an inclusion of organic guests.
  • K SADA, T KONDO, M MIYATA, K MIKI
    CHEMISTRY OF MATERIALS 6 8 1103 - 1105 1994年08月 [査読有り][通常論文]
  • K SADA, T KONDO, Y YASUDA, M MIYATA, K MIKI
    CHEMISTRY LETTERS 4 727 - 730 1994年04月 [査読有り][通常論文]
     
    5 beta-Petromyzonol does not form crystalline inclusion compounds with organic substances in contrast to cholic acid, cholanamide and methyl cholate. The crystal structures of these hosts give direct evidence for such an inclusion feature. 5 beta-Petromyzonol forms greatly different bilayered crystals from other hosts with respect to the hydrogen bonding networks, molecular arrangements, and stacking modes.
  • SADA, K, KONDO, T, YASUDA, Y, MIYATA, M, MIKI, K
    CHEMISTRY LETTERS 4 727 - 730 1994年04月 [査読有り][通常論文]
  • K SADA, T KITAMURA, M MIYATA
    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS 7 905 - 907 1994年04月 [査読有り][通常論文]
     
    Glycine-conjugated bile acids serve as new hosts for multimolecular inclusion compounds; a novel three-leaved assembly is found in the crystal structure of a 1:1 complex between glycodeoxycholic acid and THF.
  • M MIYATA, K SADA, Y YASUDA, K MIKI
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS 240 183 - 186 1994年 [査読有り][通常論文]
     
    Highly asymmetric and facially amphiphilic compounds, cholic acid and its derivatives, form asymmetric bilayers with variable hydrogen bonding networks. The bilayers are stacked in various modes to produce dynamical inclusion crystals suitable for molecular recognition and reaction.
  • K NAKANO, K SADA, M MIYATA
    CHEMISTRY LETTERS 1 137 - 140 1994年01月 [査読有り][通常論文]
     
    Cholic acid was found to form crystalline inclusion compounds with various hydrocarbons and related compounds. Some alcohols do not form inclusion crystals at all, but serve as solvents. The crystal structure of a 1:1 inclusion compound of cholic acid with benzene was determined. Comparative studies on inclusion behaviors of cholic acid and deoxycholic acid are now possible.
  • Y CHUJO, K SADA, T SAEGUSA
    MACROMOLECULES 26 24 6320 - 6323 1993年11月 [査読有り][通常論文]
     
    Redox behavior and thermally reversible nature were observed in an intermolecular cross-linked metal complex between bipyridyl-branched polyoxazoline and the cobalt(III) ion. The complex gels were much swollen in water and stable enough at ambient temperature for a few days, while they turned soluble in hot water within 30 min. The resulting brown orange solution was concentrated slowly to dryness under atmospheric pressure to regenerate the cross-linked product in a quantitative yield. This reversible interconversion between the gel and the soluble polymer was caused by the ligand exchange reaction. The initial intermolecular complex gel was converted to the entropically favorable intramolecular one (soluble polymer) by swelling in water. The thermal acceleration of the ligand exchange reaction changed these complex gels to the thermally reversible hydrogel. The results of the swelling behavior and the kinetics of the thermal cleavage reaction of the complex gel at 30-degrees-C revealed that the swelling equilibrium in water was the rate determining step at the first stage, then the rapid cleavage reaction took place, and simultaneously the water content of the gel increased rapidly. This gel was also completely dissolved in water by the rapid reduction of the central cobalt ion from the trivalent state to the divalent one. This interconversion from a hydrogel to a soluble polymer by reduction can be regarded as a novel redox reversible hydrogel system by means of kinetic control of the ligand exchange reaction coupled with the redox of the metal ions. Thus, this system can be recognized as the first example of a multisensitive hydrogel, i.e., the redox and thermally reversible hydrogel system.
  • Y CHUJO, K SADA, T SAEGUSA
    MACROMOLECULES 26 24 6315 - 6319 1993年11月 [査読有り][通常論文]
     
    An intermolecular cross-linked metal complex between bipyridyl-branched polyoxazoline and ferrous ion was prepared, in which the thermally reversible nature was observed. The red complex gels were much swollen in water and stable enough at ambient temperature for a few days, while they turned soluble in hot water within 30 min. The resulting red solution was concentrated slowly to dryness under atmospheric pressure to give a red gel again in quantitative yield. This reversible interconversion between the gel and the soluble polymer was caused by the ligand exchange reaction. The initial intermolecular complex gel was converted to the entropically favorable intramolecular one (soluble polymer) by swelling in water. The thermal reversibility of this hydrogel was caused by the thermal acceleration of the ligand exchange reaction. From the results of the swelling behavior and the kinetics of the thermal cleavage reaction of the coordination gel at 40-degrees-C, it was found that the swelling equilibrium in water was the rate determining step at the first stage, then the rapid cleavage reaction took place, and simultaneously, the water content of the gel increased rapidly. A series of poly(N-acetylethylenimine)s (PAEIs) having varying amounts of the functional groups were prepared and subjected to a cross-linking reaction. The degree of swelling and the stability of the gel in water depended on the content of the functional groups in the prepolymer. In the case of less substituted polymer, e.g., 3.3% bipyridyl-branched PAEI, the water uptake was up to 56 multiples of its own weight in the dry state. This gel was completely dissolved into water rapidly. This interconversion from a hydrogel to a soluble polymer by heating can be regarded as a novel thermally reversible hydrogel system by means of kinetic control of the ligand exchange reaction.
  • Y CHUJO, K SADA, R NOMURA, A NAKA, T SAEGUSA
    MACROMOLECULES 26 21 5611 - 5614 1993年10月 [査読有り][通常論文]
     
    Polyoxazoline having both anthracene and disulfide groups was prepared by the reaction of partially hydrolyzed poly(N-acetylethylenimine) (PAEI) with (9-anthracenyl)methyl hydrogen 3,3'-dithio-dipropanoate in the presence of dicyclohexylcarbodiimide (DCC) as a condensing agent. This photosensitive PAEI was irradiated with a 450-W high-pressure Hg lamp (lambda > 300 nm) to produce a PAEI gel, which was swollen in water and showed characteristic hydrogel properties. The equilibrium swelling degree in water was controlled both by the irradiation time and by the degree of substitution of the anthracene moieties. The water uptake was up to 20 times the weight of the dry gel. The photo-cross-linked PAEI gel became soluble by the reductive cleavage of disulfide cross-links. The gelation by photoreaction and the cleavage by reduction constitute a novel photosensitive and redox-sensitive hydrogel system.
  • Y CHUJO, K SADA, T KAWASAKI, E IHARA, T SAEGUSA
    POLYMER BULLETIN 31 3 311 - 316 1993年09月 [査読有り][通常論文]
     
    Telechelic bifunctional polyoxazoline (poly(N-acetylethylenimine), PAEI) was prepared by ring-opening polymerization of 2-methyl-2-oxazoline (1) in the presence of p-(alpha,alpha'-dibromo)xylene (2) as an initiator. The terminal propagating ends of this polyoxazoline were reacted with 3-aminopropyltrimethoxysilane (4) to give telechelic trimethoxysilyl-terminated polyoxazoline (5). Gelation of this telechelic polymer was carried out by hydrolysis and condensation of alkoxysilyl groups. By this method, the PAEI gels were obtained in good yields, and their degrees of swelling in the solvent could be controlled successfully by the feed ratios of the initiator to the monomer in the stage of the polymerization of 2-methyl-2-oxazoline. However, the cross-linked products were not stable and gradually dissolved in water. The gels were also swollen in N,N-dimethylformamide (DMF). The degrees of swelling of these gels were thus measured in DMF.
  • K SADA, T KONDO, M MIYATA, T TAMADA, K MIKI
    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS 9 753 - 755 1993年05月 [査読有り][通常論文]
     
    A new host, cholanamide (CAM), is described; CAM forms lattice inclusion compounds with a variety of organic substances, particularly hydrogen bond acceptors, which are trapped in channels by hydrogen bonding to the amide nitrogen.
  • Y CHUJO, K SADA, A NAKA, R NOMURA, T SAEGUSA
    MACROMOLECULES 26 5 883 - 887 1993年03月 [査読有り][通常論文]
     
    A polyoxazoline hydrogel having a disulfide bridge was prepared by the reduction-oxidation of thiol-protected poly(N-acetylethylenimine) (PAEI) (anthracene-SS-modified PAEI) or by the cross-linking reaction of the partially hydrolyzed PAEI with bifunctional disulfide compounds. As a disulfide cross-linking agent, dithiodi-2,1'-ethanediyl diisocyanate/1,8-diazabicyclo[5.4.0] undec-7-ene or 3,3'-dithiopropanoic acid/dicyclohexylcarbodiimide gave good results. The reduction of thiol-protected PAEI produced the thiol-modified PAEI, which was susceptible to air oxidation to form the networks. These gels based on highly hydrophilic PAEI were stable and swollen in water as a hydrogel. A series of PAEIs having varying amounts of the functional groups were prepared and subjected to cross-linking reactions by reduction-oxidation. The degree of swelling in water increased with a decrease of the degree of substitution in the prepolymer. The disulfide-bridged PAEI gel became soluble to form the linear polymer by the treatment with reducing agents such as sodium hydrosulfite, sodium borohydride, or triphenylphosphine. This solubilization of gel was caused by the reductive cleavage of the disulfide bridge at the cross-linking points. This interconversion from a hydrogel to a soluble polymer can be regarded as a novel redox-reversible hydrogel system by means of reversible conversion between disulfide and thiol groups.
  • Guest-dependent conformations of side chains in cholic acid inclusion compounds
    M. Miyata, K. Sada, K. Hirayama, Y. Yasuda, K. Miki
    Supramolecular Chemistry 2 283 - 288 1993年 [査読有り][通常論文]
  • Y CHUJO, K SADA, T SAEGUSA
    POLYMER JOURNAL 25 6 599 - 608 1993年 [査読有り][通常論文]
     
    Polyoxazoline hydrogel was prepared through the coordination of the metal ions to 2,2'-bipyridyl-branched poly(N-acetylethylenimine) (PAEI), which was synthesized from the partially hydrolyzed PAEI by the reaction with 3-{4-(4'-methyl-2,2'-bipyridyl)}propanoic acid in the presence of dicyclohexylcarbodiimide. Concentrated solution of 2,2'-bipyridyl-branched PAEI gave polyoxazoline gel in a good yield by the treatment with metal salts such as iron(II) sulfate, or ruthenium(III) trichloride. The resulting colored gel was highly swollen in water and stable at ambient temperature for handling. In the case of nickel(II) or cobalt(II) ions, the formed intermolecular cross-linking points via the coordination (gel state) were labile due to the rapid ligand exchange reaction of the cross-linking from intermolecular to intramolecular manner. The nickel(II) and cobalt(II) gels became soluble in a large amount of water within a few hours. A series of PAEIs having varying amounts of the functional groups were prepared and subjected to the cross-linking reaction by the coordination with iron(II). The swelling degree and the stability of the gel in water depended on the content of the functional groups in the prepolymers. Water uptake was up to 56 multiples of its own weight in dry state.
  • Mikiji Miyata, Kazuki Sada, Satoshi Hori, Kunio Miki
    Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals 219 1 71 - 74 1992年08月01日 [査読有り][通常論文]
     
    Cholic acid affords polymorphic crystal forms. The molecular assemblies have a guest-dependent bilayered structure. Insertion and replacement of guest molecules between the layers took place with retention of the crystalline state. The intercalation phenomena give us an opportunity to understand a structure-property relationships in organic solids. © 1992, Taylor & Francis Group, LLC. All rights reserved.
  • Y CHUJO, K SADA, T KAWASAKI, T SAEGUSA
    POLYMER JOURNAL 24 11 1301 - 1306 1992年 [査読有り][通常論文]
  • M MIYATA, K SADA, S HORI, K MIKI
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 219 71 - 74 1992年 [査読有り][通常論文]
  • Y CHUJO, K SADA, T SAEGUSA
    MACROMOLECULES 23 10 2693 - 2697 1990年05月 [査読有り][通常論文]
  • Y CHUJO, K SADA, T SAEGUSA
    MACROMOLECULES 23 10 2636 - 2641 1990年05月 [査読有り][通常論文]
  • Yoshiki Chujo, Kazuki Sada, Kazuaki Matsumoto, Taken Saegusa
    Macromolecules 23 5 1234 - 1237 1990年 [査読有り][通常論文]
     
    As a novel method for the preparation of a hydrogel based on a polyoxazoline, the copolymerization of 2-methyl-2-oxazoline and 2,2’-tetramethylenebis(2-oxazoline) was carried out with methyl triflate initiator. The obtained gel was isolated almost quantitatively after Soxhlet extraction. The resulting hydrogel showed a high swelling degree both in water and in 5% aqueous sodium chloride. The water uptake was up to 45 multiples of the weight of the dry gel. 2-Oxazoline monomers with various 2-alkyl substituents (methyl, ethyl, n-propyl, n-butyl, and n-octyl) were also copolymerized with the above bisoxazoline to produce gels having a wide variety of swelling characteristics, i.e., from hydrogel to lipogel (organogel) depending on the substituents. The gels from 2-n-propyl- or higher alkyl-2-oxazoline showed the characteristic properties of lipogels and were swollen in less polar organic solvents such as toluene or 1,2- dichloroethane. The gel from 2-ethyl-2-oxazoline was a characteristic amphiphilic gel (amphigel), which was swollen both in water and in organic solvents. © 1990, American Chemical Society. All rights reserved.
  • Y CHUJO, K SADA, K MATSUMOTO, T SAEGUSA
    POLYMER BULLETIN 21 4 353 - 356 1989年04月 [査読有り][通常論文]
  • Y CHUJO, Y YOSHIFUJI, K SADA, T SAEGUSA
    MACROMOLECULES 22 3 1074 - 1077 1989年03月 [査読有り][通常論文]
  • Hydrogen Bond'Triple Hooks'in an indusim Crystal of cholanamide with amilni structural differenee of in dusim cryslals of cholie acid and cholamacido with the some guut
    Mol. Cryst. Liq. Cryst 276 121  [査読無し][通常論文]

講演・口頭発表等

  • Toshikazu Ono, Takahiro Sugimoto, Seiji Shinkai, Kazuki Sada
    Polymer Preprints, Japan 2006年12月 
    We previously report development of a new class of ionic polymer gels having lipophilic ion-pairs that consist of a lipophilic tetraphenylborate anion and a quaternary ammonium cation with long alkyl chains. They swelled largely in the less polar solvents as 'super-absorbent' ionic polymer gels. The driving force of the large swelling was osmotic pressure induced by dissociation of lipophilic ion-pairs in these solvents. Here we wish to present discontinuous volume phase transition of 'super-absorbent' ionic polymer gels the by change of solvent polarity even in low dielectric media. Moreover, we investigated the effect of neutral comonomers to swelling behaviours in various organic solvents by changing the length of their alkyl chains. The ionic polymer gels with longer alkyl chain swelled in a large magnitude in the less polar solvents and those with shorter alkyl one did in more polar solvents.
  • Yuta Goto, Kazuki Sada, Seiji Shinkai, Seiji Shinkai
    Polymer Preprints, Japan 2006年12月 
    We previously reported that the mixtures of 1-naphthylmethylammonium (NMA) salts of n-fatty acids with the different lengths of the methylene group form multi-component organic alloys. The d-spacings of the alloys in XRD provided the averages of the metheylene groups. Therefore, this system is the first example of the numericalcalculation based on molecules as inputs of the number. Herein, we report the parallel average calculations performed by mixing four different salts that form the two mixed crystals selectively from two pairs of the salts. For example, the quaternary mixture of [4], [5], [13] and [14] provided two mixed crystals that have the intermediate d-spacings with length of 4.5 and 13.5. They indicate formation of the eutectic mixture of the two pairs of the mixed crystals. High-fidelity control of self and non-self recognitions enables us to control the mixing behaviours of multi-component mixtures in the solid state.
  • Toshikazu Ono, Takahiro Sugimoto, Seiji Shinkai, Kazuki Sada
    Polymer Preprints, Japan 2006年12月 
    Ionic polymer gels with the ability to absorb several hundreds times as much water as their dry weights have been used as 'super-absorbent polymers' in wide range of biomedical and agricultural applications. However, in the low dielectric media (ε < 10), common ions form tightly bound ion-pairs or multiplet aggregates, and incompatibilities between the polymer chain and the solvents greatly diminish the swelling power. Here we report development of a new class of ionic polymer gels having lipophilic ion-pairs that consist of a lipophilic tetraphenylborate anion and a quaternary ammonium cation with long alkyl chains. They swelled largely in the less polar solvents such as tetrahydrofuran and chloroform as 'super-absorbent' ionic polymer gels.
  • Toshikazu Ono, Takahiro Sugimoto, Kazuki Sada, Seiji Shinkai, Seiji Shinkai
    Polymer Preprints, Japan 2006年10月 
    Molecular design of polymer gels with high swelling properties in non polar solvents lays on compatibility of the polymer chain with oil. In this study, we demonstrate new polymer gels based on the hydrophobic ion pairs in the polymer chain. They provided the high swelling degrees in polar solvents. In the mixtures of water and acetonitrile, the polymer gels exhibited volume phase transition.
  • Motoshi Yamanaka, Kazunori Nakano, Kazuki Sada, Mikiji Miyata, Kenji Hanabusa
    Polymer Preprints, Japan 2006年10月 
    Compounds consisting of an alkane and perfluoroalkane can gelate a wide variety of organic solvents at the minimum gel concentration less than 10 g/L. The fibrous aggregates in the organogels can be utilized to produce the Superhydrophobic surface, characterized by water contact angles greater than 150°, due to the appropriate roughness of the aggregates. This method of preparing the Superhydrophobic surfaces using organogels has an advantage of its simplicity compared to other methods.
  • Kazuki Sada, Yuzo Fujiki, Nami Tokunaga, Seiji Shinkai, Seiji Shinkai
    Polymer Preprints, Japan 2006年10月 
    The conjugation of organic molecules to matal nanoparticles has been of much interest due to direct organization into larger supramolecular structures by self-assembly. In this report, we demonstrate formation of composite material from single crystals of L-cystine and Au nanoparticles. Particularly, SEM, AFM, UV-Vis spectroscopy indicated that the (001) surface of L-cystine single crystals was coated selectively by Au nanoparticles. X-ray crystallographic study revealed that the disulfide moieties or amino acid groups are arranged in 2D fashion on (001) face. This provides the selective coating of Au nanoparticles.
  • Takayuki Suzuki, Kazuki Sada, Takahiro Sugimoto, Seiji Shinkai
    Polymer Preprints, Japan 2006年10月 
    We previously reported that 2,6-bis(2-oxazolyl)pyridine (Pybox) forms the complexes with secondary dialkylammonium cations at 1:1 stoichiometries. In this report, we present preparation and complex formation of Bzpybox complexes with poly(trimethylene- iminium) salt (PTMI). The complexation of PTMI with bi-functional BzPybox 1 or 2 provides physically cross-linked gels. Dynamic viscoelastic measurements revealed that the gels prepared from 1 and PTMI in acetonitrile had the network structures cross-linked by complementary hydrogen bonds between the cross-linkers and cationic polymers. supramolecular gel physical gelation hydrogen bond sol-gel phase transition cross-linking.
  • Yuta Goto, Takahiro Tani, Kazuki Sada, Seul Shinkai, Seul Shinkai
    Polymer Preprints, Japan 2006年10月 
    We previously reported that the mixtures of 1-naphthylmethylammonium (NMA) salts of n-fatty acids with different alkyl chain length form multi-component organic alloys. The d-spacing of the alloys in XRD provided the average of the length of the alkyl chains. Therefore, this system is the first example of the numerical arithmetic based on molecules as inputs of the number. Herein, we report the parallel average calculations by mixing four different carboxylic acids that form the mixed crystals selectively from two pairs of the acid. For example, the quaternary mixture of C4s, C5s, C13s and C14s provided two mixed crystals that have the intermediate d-spacings with length of 4.5 and 13.5. They should be eutectic mixtures of the two pairs of the mixed crystals.
  • Takayuki Suzuki, Kazuki Sada, Seiji Shinkai
    Polymer Preprints, Japan 2005年12月 
    Gelation was achieved by physical crosslinking of poly(trimethyleneimine) salt (PTMI). The crosslinker 1 acted as crosslinking molecule between two secondary ammonium cation sites of PTMI. AFM image suggested that PTMI and 1 constructed ladder-like aggregate to form one-dimensional fibers. Trans-cis isomerization of the azobenzene group was induced sol-gel phase transition by UV irradiation. The structural change probably instabilizes the ladder-like aggregates due to inhibition of stacking between 1.
  • Daisuke Kikuno, Yuichi Tateishi, Kazuki Sada, Seiji Shinkai
    Polymer Preprints, Japan 2005年12月 
    We previously reported that cinnamoyl-modified bezpybox undergoes photodimeization in the presence of secondary ammonium cations as a template. Now we prepareed ditopic bezpybox ligand possessing two cinnamoyl moieties (1-a) in the spacer. The dimeric template 2N3C provided the dimmer chiefly. And the trimeric template 3N3C yielded trimer or higher oligomers. The degree of polymerization of 1-a may depend on the number of dialkylammonium moieties in the template.
  • Kazuki Sada, Takayuki Suzuki, Takahiro Sugimoto, Takahiro Tani, Yuzo Fujiki, Daisuke Kikuno, Seiji Shinkai
    Polymer Preprints, Japan 2005年12月 
    Control of number and order in the supramolecular assemblies have been of much interest due to their application for informational technology and mimetic approaches for molecular information of biological polymers such as DNA and proteins. We previously reported that 2,6-bis(2-oxazolyl)pyridine (Pybox) forms the 1:1 complexes with various secondary dialkylammonium cations as a tool for supramolecular assemblies. In this report, we demonstrate formation of ordered supramolecular assembly from two different pybox (P) and bzpybox (B) ligands by complexation with dimeric imminium cation (IA) as a template. The two ammonium sites of IA were differentiated by steric repulsion between the phthalimide moieties of IA and macrocyclic structure of P. 1H-NMR titration indicated that IA form a 1:1:1 complex with P and B.
  • Tsuyoshi Watabe, Kenji Kobayashi, Kazuaki Kato, Mikiji Miyata, Mikiji Miyata, Kazuki Sada
    Molecular Crystals and Liquid Crystals 2005年12月 
    Brucine inclusion crystals with neutral guest molecules exhibit guest-dependent polymorphism due to a hierarchical structure. Chiral brucine molecules are regarded as a primary structure and assemble to form a chiral tape with a 2 1 axis as a common secondary structure. Such tapes meet together in various modes to constitute different bundles as a tertiary structure. The bundle modes are theoretically classified into eight types, which were screened by alteration of guest compounds in the volume range from 39 to 150 Å 3.
  • Takayuki Suzuki, Kazuki Sada, Seiji Shinkai
    Polymer Preprints, Japan 2005年12月 
    We previously reported that 2,6-bis(2-oxazolyl)pyridine (Pybox) forms the complexes with secondary dialkylammonium cations at 1:1 stoichiometries. In this report, we present preparation and complex formation of Bzpybox complexes with poly(trimethylene- iminium) salt (PTMI). Macrocyclic BzPybox 1 was used for immobilization of PTMI on Au or mica surface. AFM observation on mica presented that the polymer complexes only have the linear morphology. The compelxation between PTMI and 1 should arrange 1 into the 1D structure. Moreover, complexation of PTMI with bi-functional BxPybox 2 provides physically cross-linked gels. Trans-cis isomerization of the azobenzene group by photo-irradiation and by heat was induced sol-gel phase transition. The supramolecular structures of PTMI were controlled by the complexation with various BzPybox derivatives.
  • Takanori Kishida, Norifumi Fujita, Kazuki Sada, Seiji Shinkai
    Polymer Preprints, Japan 2005年12月 
    To construct various unique porphyrin assemblies, urea groups bearing-porphyrin gelators 1-H 2, 1-Cu and 1-Zn were newly synthesized. It was revealed by SEM and UV-vis spectra that introduce of Cu(II) into the porphyrin nuclei changes the stacking mode in the gel phases. 2-H 2 and 2-Cu having triethoxysilyl groups at their periphery successfully give organic/inorganic hybrids composed of porphyrin superstructures after sol-gel reaction. On the other hand, 1-Zn is found to gelatinize benzene only in the presence of piperazine. SEM images of the gels showed that increasing the stoichometry of piperazine to 1-Zn varies the morphology of 1-Zn · piperazine complex aggregates: that is, spherical structure(0 eq.), 1-D fibillar structure(0.5 eq.), 2-D sheet structure(1.0 eq.). In addtion, we have studied the viscoelasticity of 1-Zn · piperazine complex gel.
  • Kazuki Sada, Daisuke Kikuno, Seiji Shinkai
    Polymer Preprints, Japan 2005年12月 
    Recently, we reported that pybox or bzpybox ligands form 2:2 ladder-type complexes with oligomeric secondary dialkylammonium salts. In this report, we demonstrate control of photodimerization of cinnamoyl group by introduction to the Bzpybox ligand. Photo-irradiation of the 2:2 ladder complex of cinnamoyl-modified Bzpybox with dimeric secondary dialkylammonium produced efficiently the photodimer under the dilute condition that could not form the dimers without templates. Therefore, this should be supramolecular control of 2 + 2 photodimerization.

その他活動・業績

受賞

  • 2016年05月 高分子学会 高分子学会賞
     低極性溶媒中での解離を利用する機能性高分子の開発 
    受賞者: 佐田 和己
  • 2014年03月 日本化学会 日本化学会学術賞
     非水系媒質中で機能する刺激応答性高分子の創製ならびに配位高分子の架橋を利用した結晶重合系の開発 
    受賞者: 佐田 和己
  • 2008年04月 文部科学省 文部科学大臣表彰 科学技術賞 研究部門
     親油性高分子電解質を用いた有機物質高吸収性ゲルの研究 
    受賞者: 佐田 和己

共同研究・競争的資金等の研究課題

  • エフェクター三成分系による温度応答性の深化と高分子の温度応答性デザインの解明
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2021年04月 -2024年03月 
    代表者 : 佐田 和己
  • 刺激応答性高分子―ナノ多孔性配位高分子ハイブリッドによるオンデマンド触媒の開発
    日本学術振興会:科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2020年04月 -2022年03月 
    代表者 : 佐田 和己
  • 刺激応答性高分子ハイブリッドによるオンデマンド触媒の開発
    日本学術振興会:科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2018年04月 -2020年03月 
    代表者 : 佐田 和己
     
    これまで開発してきたピレン環を繰り返し構造としてもつ温度応答性高分子システムをベースに、共重合反応により、高分子鎖に有機触媒として、DMAP (4-(N,N-dimethylammo)pyridine)を導入した新しい刺激応答性高分子触媒の合成に成功した。この高分子触媒の溶液に適切なエフェクター(電子アクセプター)を加えることにより、高分子の凝集状態が変化することを明らかにした。 さらに、DMAP の触媒活性を調べるために、カルボン酸無水物と第二級アルコールとのエステル化反応について検討した。エフェクターのない場合により、初速で8倍の加速効果があることを明らかにした。さらに温度応答性については、下部臨界共溶型の温度応答性(LCST型温度応答性)を示すエフェクターを用いた場合、高温側で高分子の相分離が生じ、触媒が部分的に遮蔽されるため、高温側での触媒活性の低下が確認された。これに対して、上部臨界共溶型の温度応答性(UCST型温度応答性)を示すエフェクターを用いた場合、低温側で高分子の相分離が生じ、高温側で均一相になるため、高温側で触媒活性が上昇が確認された。 したがって、この高分子触媒が温度やエフェクター(低分子有機化合物)を刺激とした触媒活性の制御が可能なシステムであることが明らかになった。特に添加するエフェクター分子の分子種によって、高温(もしくは低温)での加速と減速が可能になった。 これらは従来の有機触媒とは異なる制御機構を持ち、共存する物質による有機化学反応の制御につながり、自律的な反応系であるフィードバック系などへの応用が可能である。
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2017年04月 -2020年03月 
    代表者 : 佐田 和己, 小門 憲太
     
    本研究では、ナノ多孔性配位高分子を用いて、ジャングルジムのようなフレームワークに固定されたホストモノマーとその間隙を自由に拡散・反応するゲストモノマーとの反応による高分子材料の構築について検討した。固定されたホストモノマーはゲストモノマーと容易に反応して、様々な材料が合成できることがわかった。特にホストモノマーの分子配置を設計することで、1つの方向にのみ膨潤するような異方変形材料が実現できた。また、高分子の合成に応用すると、高分子の重合度の制御にも成功した。また、この手法はサイズの揃った様々な形状の高分子ゲルの製造法として有用であり、機能性材料への応用が期待できる。
  • 低分子の光反応と共役した光応答性高分子システムの開発
    日本学術振興会:科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2015年04月 -2017年03月 
    代表者 : 佐田 和己
     
    光によって高分子の形態が大きく変化する光応答性高分子はこれまで主に温度応答性高分子と光反応性の化合物を直接化学結合することによって設計・合成され、汎用性や多様性に欠けるものであった。新しい光応答性高分子の設計として、本研究では、光反応性の低分子(エフェクターと呼ぶ。)を柔軟な高分子と相互作用させることにより、エフェクターの光反応によって高分子の形態・溶解性を変化させることについて検討を行った。 今年度は光ケージド化合物(o-ニトロフェニルベンジル基)の光分解により、アルコールやカルボン酸を遊離させ、尿素官能基をもつアクリル系高分子のエフェクターとして機能させることで、その溶解性を制御し、可視光照射による温度応答性の発現とそのスイッチングに成功した。また相転移温度についても、光照射により簡便に制御することができた。これらの知見は多様な光応答性・温度応答性高分子の設計指針につながるときたできる。並行して、一連のスピロピラン誘導体を用いて、紫外光の照射によって生成するメロシアニンをエフェクターとする尿素官能基をもつアクリル系高分子の相分離挙動について検討を行った。低極性溶媒中では熱戻り反応が速く、エフェクターとして十分な濃度を光反応によって確保することが困難であることが明らかになった。しかしながら、逆に光を十分照射した後、暗所にすることで、自動的に熱戻りし、相分離が誘起できることを明らかにした。これは時間変化を伴う新しい刺激応答性高分子として期待がもたれる。また、新学術領域内での共同研究として、A01班の玉井グループと配位高分子を原料とする半導体ナノワイヤーの励起電子ダイナミクスを明らかにした。また関連して新しい発光材料についても知見を得た。
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2014年04月 -2017年03月 
    代表者 : 佐田 和己, 小門 憲太
     
    高分子鎖と溶媒だけではなく、両者と相互作用可能な低分子(エフェクターと呼ぶ。)を高分子溶液に第三の成分として加えることで温度応答性高分子を自在に設計できることを明らかにした。また、エフェクターが溶媒和分子となり、高分子を室温で溶解させ、加熱することにより高分子と低分子間の会合が切断され、高分子の自己会合による相分離を引き起こす機構を明らかにした。様々な媒質中で下部臨界共溶温度型相分離を起こすユニバーサルな温度応答性高分子の開発や光学活性なエフェクターによる高分子のキラル認識に連動した相分離の制御に成功した。さらに化学反応と高分子の相分離を共役することで、化学反応応答性高分子の構築にも成功した。
  • 動的秩序形成を利用した化学反応応答システムの開発
    日本学術振興会:科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2014年04月 -2016年03月 
    代表者 : 佐田 和己
     
    高分子と相互作用するエフェクターの濃度を化学反応によって変化させ、高分子の劇的なコンフォーメーション変化とそれに伴う高分子が溶解・凝集を、化学反応の進行に応じて制御するシステムの構築を検討した。尿素官能基を持つアクリル系高分子の水素結合を利用し、すでにエフェクターとして知られている1-デカノールやデカン酸などを用いて、トルエンや1,2-ジクロロエタン中で水酸基およびカルボン酸と反応する試薬(エステル化剤(酸クロリドなど)やシリル化剤(TMSCN,TMSIMなど)、など)を混合することで、高分子の凝集・相分離を評価した。TMSCNを用いたヘキサノールのシリルエーテル化反応を選択することで、エフェクターの化学反応によって高分子のコンフォメーション変化の誘起に成功した。この場合は副生成物がシアン化水素であり、水素結合性が弱いためと思われる。したがって、エフェクターの化学反応を選択する際には副生成物がエフェクターとして機能しない反応を用いることが必要であることを明らかとした。 また、オレフィンメタセシス反応を触媒するグラッブス触媒を上記の尿素官能基を持つアクリル系高分子に導入した。この高分子がエフェクター存在下で閉環メタセシス反応を触媒することを明らかにし、水素結合性のエフェクターの有無によって触媒活性が大きく変化し、触媒活性が制御できることを明らかにした。 また、新学術領域内の共同研究として、親水部に糖を、疎水部にイオン性官能基をもつ両親媒性分子について、溶液中における超分子集合体の構造解析をすすめており、低極性有機溶媒中ではベシクル様の構造を形成することが明らかになった。
  • 日本学術振興会:科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2014年04月 -2016年03月 
    代表者 : 佐田 和己, 小門 憲太
     
    アセチレン誘導体をもつアミノ酸とロイシンを用いてFMOC固相合成によって5-13残基程度のオリゴペプチドを合成し、アジド基をもつ第四級テトラアルキルアンモニウムのテトラフェニルホウ酸塩とのクリック反応により、オリゴペプチドへの親油性イオン対の導入を行った。質量分析から親油性イオン対をもつオリゴペプチドが検出され、生成が確認できた。生成したオリゴペプチドの1,2ジクロロエタン中での溶解度は対応するイオン性導入前のオリゴペプチドより数倍向上することが明らかになった。したがって、親油性イオン対のイオン解離による静電反発および浸透圧がオリゴペプチドの溶解性の向上につながったものと思われる。
  • 配位高分子由来精密ネットワーク高分子を利用した融合マテリアルの構築
    日本学術振興会:科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2013年04月 -2015年03月 
    代表者 : 佐田 和己
     
    様々な金属イオンからなるMOFを原料にして、精密ネットワーク高分子(MTP)を合成し、これらにMTPのナノ空間を利用して無機材料との複合化を検討した。CaCl2 水溶液とNa2CO3 水溶液の交互浸漬や(NH4)2CO3の分解による気相からのCO2と反応させることにより、炭酸カルシウムの結晶成長を検討した。亜鉛イオン由来のMTP からはどちらの方法においても表面に小さな構造体の成長が確認され、SEM-EDXマッピングおよび粉末X線回折の結果より炭酸カルシウムの成長が確認できた。またCaCl2 水溶液とNa2HPO4 水溶液の交互浸漬によるリン酸カルシウムの成長については亜鉛およびジルコニウムイオン由来のMTPからも、表面が均一の微粒子が付着している状態がSEMにより観察された。SEM-EDXマッピングからカルシウムおよびリンが検出され、表面に付着しているリン酸カルシウムであることが示唆された。MOFの結晶由来の外形・サイズの制御された有機無機融合マテリアルの創製に成功した。またγ-シクロデキストリンとKOHをから得られる立方体のMTPに電荷を導入することに成功し、静電相互作用によるMTPの分子集合体の形成が確認できた。さらにカチオン性金ナノキューブとアニオン性MTPによる複合体やアニオン性であるYB(OH)4CO3とカチオン性MTPとの複合体形成が可能であることが明らかになった。この手法は無機立方体結晶と立方体の有機高分子ゲルを相補的に複合化できる手法として大変興味深いものと思われる。
  • 日本学術振興会:科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2012年04月 -2014年03月 
    代表者 : 佐田 和己
     
    有機物の結晶の結晶面を二次元的に分子が配列した界面であると考え、それを基板と接触させることで、固体-固体接触により、その分子配列を基板に転写する技術、「結晶スタンプ法」の開発を行った。走査型トンネル顕微鏡(STM)の観察から、ジスルフィド基をもつ化合物と金基板の接触によって分子膜が形成されることを明らかにした。特に基板に対して平行方向にイオン対を持つジスルフィドを用いた場合は結晶構造を反映した分子パターンが転写できることを明らかにした。結晶スタンプ法を用いることで 簡便に様々な機能性有機化合物を基板へ転写でき、これらを利用した素子の簡便な構築につながると期待できる。
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2011年04月 -2014年03月 
    代表者 : 佐田 和己
     
    媒質に対応したイオン対および高分子鎖から構成される親媒質性高分子電解質を分子設計することにより、様々な媒質で静電反発を利用して、高分子の構造や低分子の溶解性などが制御できることを実証した。さらにこれらの静電反発を利用した機能性材料への展開として、高分子ブラシや刺激応答性ゲルへの応用が可能となった。また本研究の結果より、高分子と低分子の間の分子間相互作用を巧みに利用することで簡便に温度応答性高分子の設計ができることを明らかにした。これらの結果は分子間引力に拮抗して静電反発を様々な媒質で利用することを示しており、新しい機能性材料の開発に貢献すると思われる。
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2008年 -2010年 
    代表者 : 佐田 和己
     
    親油的な官能基で覆われた大きなイオンを持つ高分子 (親油性高分子電解質) が低極性有機溶媒中でイオン間の反発により、その高分子鎖を広げることを世界に先駆けて実証した。この結果により、様々な有機溶媒を高効率に吸収する材料が開発でき、溶液中で温度に応答して高分子鎖が収縮・伸張する新しい材料の合理的な設計指針を得ることができた。また、低温で機能する高吸収材や低極性環境下での交互積によるナノ薄膜の構築が実現した。
  • クリック反応によるナノ多孔質材料の事後修飾
    日本学術振興会:科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2008年 -2009年 
    代表者 : 佐田 和己
     
    多官能性有機配位子をリンカーとして、金属イオンまたは金属イオンクラスターをノードとするMetal-Organic Framework(MOF)は多孔質性配位高分子として、貯蔵材料、分子触媒、分子センサーなどの応用が期待されている。本研究では、溶媒や官能基の影響をほとんど受けることなく広い基質に対して定量的に反応が進行する"クリック反応"を用いて、MOFに代表される多孔質性配位高分子への事後修飾反応を行なった。 クリック反応する有機配位子リンカーとして、ターフェニレン構造をもつアジド修飾有機配位子リンカーを設計し、合成を行った。生成物は^1H-NMR、IR、MASSスペクトルなどで同定を行い、新規リンカーの合成に成功した。次に、このアジド修飾有機配位子リンカーと金属イオンとの塩形成により、アジド基をもつMOFを合成した。まず、亜鉛(II)イオンを用いて、ジエチルアセトアミド中、80℃でMOFの合成を試みたところ、立方体の単結晶が形成された。これをX線回折による分析すると、ターフェニレン構造をもつMOFと同じものであることが明らかになった。多孔質性に関しては合成直後のMOFをDMSO-d_6+DCIに溶解させ、MOFを構成する有機配位子リンカーとゲスト分子の比率より、空孔の収容能力を見積もったところ、同様にターフェニレン構造をもつMOFとほぼ同じような包接挙動を示すことが明らかになり、アジド修飾した多孔質性のMOFの合成ができたものと思われる。 さらに、アジド修飾した多孔質性のMOFと種々のアセチレン誘導体を反応させることにより、"クリック反応"を試みた。銅イオン存在下で反応を行うと、結晶を維持したままで、反応が進行し、アジド基由来の吸収が消失し、クリック反応の進行が確認された。さらに生成したMOFを分解し分析すると、生成物であるトリアゾール環が形成されいた。これにより、クリック反応を利用して様々な材料を修飾したMOFを合成できるものと思われる。さらにチオールを有するアセチレンを用い、事後修飾後、金ナノ微粒子などとの高次複合化に成功した。
  • 回転分子機械を導入したフォトメカニカルネットワークの構築
    日本学術振興会:科学研究費助成事業 特定領域研究
    研究期間 : 2008年 -2008年 
    代表者 : 佐田 和己, 竹内 正之
     
    高分子ネットワーク(ゲル)と回転構造をもつダブルデッカー(DD)ポルフィリンの分子機械の概念を融合させることで、刺激に応答する分子機械の変位を直接ネットワークに反映させ、分子レベルの変位を増幅し、ミリサイズの材料の変位として取り出すことを目標として研究を進めた。回転の自由度をもつ分子として、ダブルデッカー(DD)ポルフィリンを剛直な共役オリゴマーに組み込み、その両端を多官能性架橋剤により架橋することでネットワークを構築することを試みた。回転部位であるCe(IV)DDポルフィリンの光反応を利用して、中性のセリウム(IV)を系中で光還元し、Ce(III)を発生させることのより、中性のネットワークを有機溶媒中でイオン化させ、その浸透圧を利用して、ネットワークの膨張および収縮を行い、フォトメカニカルシステムとしての性質を明らかにし、アクチュエータの素子としての可能性を探った。 まず、回転子としてダブルデッカー(DD)ポルフィリンの2枚のポルフィリンにもつオリゴマーの合成とネットワークの構築の前段階として、直鎖のオリゴマーの合成を行った。特に剛直なリンカーとしてアセチレンやベンゼン環によって、ダブルデッカー(DD)ポルフィリンを結合させる反応を検討した。 特に菌頭カップリング反応などを用いたオリゴマー化を検討し、モノマーの合成まで完了した。しょがしながら、高分子化には成功しなかった。そこで、イミドを用いて高分子鎖の伸長を行ったところ、4量体の生成が確認され、目標であるフォトメカニカルネットワーク構築の第一歩と考えられる。 同時にモデル反応として、低分子のDDポルフィリンの中心金属であるセリウム(IV)イオンをアミン存在下で光還元することで、ネットワーク内に回転子に負電荷を発生させることが可能であることが明らかになった。
  • 核酸塩基対を利用した機能性有機合金及び有機ゲルの分子設計
    日本学術振興会:科学研究費助成事業 特別研究員奨励費
    研究期間 : 2006年 -2008年 
    代表者 : 佐田 和己, TRIVEDI DARSHAK R., DARSHAKR; TRIVEDI, DARSHAK R TRIVEDI
     
    核酸塩基対は塩基対を形成するだけでなく、塩基対間のπ-πスタックによる弱い電荷移動錯体が形成されやすいことに着目し、これらを利用することは新しい材料の開発につながるものと期待できる。そこで、本研究では核酸塩基の誘導体のみならず、核酸塩基対と同じ大きさをもつアクセプター分子を合成し、まず、低分子ゲルの形成について検討を行った。また、これらの分子を利用して、混晶や電荷移動錯体の形成について検討を行った。 様々な有機溶媒中で加熱・冷却することによりのゲル形成能を検討したが、分子が一次元的に配列した低分子ゲルを形成することができなかった。多くの場合。沈殿が生じるか、溶解するするかのどちらかであり、溶液をゲル化することはできなかった。また溶液中での混合による電荷移動錯体形成では一部のペアーでのみ電荷移動錯体が形成された。しかしながら、固体と固体を混合する方法では、多くのペアーで混晶および電荷移動錯体が形成されることが明らかになった。また、それらが結晶中でどのような構造体を形成するかをX線構造解析によって検討し、電荷移動錯体形成と電荷移動吸収帯との関係を明らかにすることができた。多くの電荷移動錯体が大変きれいな色をしていることに着目し、それらの色の変化を利用して、芳香族分子をターゲットにした比色分析としての有用性を検討したところ、様々な芳香族分子を目でみわけるシステムの開発に成功した。この成果は有害物質を簡便に「その場」で調査することができるシステムの構築につながり、社会的にも重要と思われる。
  • ヘリックス構造性高分子をホストとする一次元超構造体の創製
    日本学術振興会:科学研究費助成事業 萌芽研究
    研究期間 : 2006年 -2008年 
    代表者 : 新海 征治, 田丸 俊一, 佐田 和己, 竹内 正之, 藤田 典史, 沼田 宗典
     
    β-1, 3-グルカン構造を基本単位とする天然多糖(シゾフィラン・カードランなど)は、水中で三本鎖からなるヘリックス構造を取るが、DMSO中では一本鎖に解離する。一方、このDMSO溶液を水で希釈すると、水中では三本鎖からなるヘリックスが再生することが知られている。さらに、ヘリックス構造の内側に存在する0.3 nmの疎水性かつキラルな一次元空孔が存在することを見出した。一本鎖と三本鎖間の可逆的な変換を利用することで、この一次元空孔は種々の機能性パーティクルや高分子を一次元配列するためのホストとして機能すると期待される。この作業仮説を出発点として、β-1,3-グルカン類が形成する一次元空孔を、(1)ナノ粒子・導電性高分子などを配列する場として、(2)立体規則性重合を誘起する鋳型として応用することを目的として研究を遂行した。 ベンジルアミンを触媒とし、テトラエトキシシラン(TEOS)を用いたゾルーゲル反応により、その複合体のキラリティを固定化することに成功した。シゾフィランは、キラル誘導の働きだけではなく、複合体表面におけるシリカ粒子の吸着に寄与していることが明らかとなった。さらに、アミノ基を導入したシゾフィランを同様にテンプレートとして用いることで、アミノ基の触媒効果によって、より温和な条件でゾルーゲル反応を進行させることができた。また本手法により、複合体の特性をより効果的に保持することが可能になることを明らかにした。
  • ゾル-ゲル転写システムを活用した機能性有機・無機複合物質群の創製
    日本学術振興会:科学研究費助成事業 基盤研究(S)
    研究期間 : 2003年 -2007年 
    代表者 : 新海 征治, 佐田 和己, 竹内 正之, 藤田 典史, 新森 英之
     
    5年間の研究期間はゾル-ゲル分子転写のための機能性鋳型分子の選定と開発、ゾル-ゲル反応を実行することによる無機-有機複合材料の開発、作製した材料の物性評価、そして得られた物性評価データから材料開発へのフィードバックと、段階的に構成した。具体的には、機能性有機化合物を基体としたゾル-ゲル転写プロセスに適する鋳型子・集合体の開発を目的として、電気化学的・光化学的に興味深いポルフィリンやトリフェニレンなどの芳香族系分子を母核としてアミドやウレアユニットを水素結合部位とした一次元集積構造、ある種のジブロックコポリマーや膜形成化合物が表面・界面で形成する二次元周期構造、金属イオンを取り込むホスト骨格を有するゲル化剤の開発をおこなった。ゲル化剤分子の配列パターンの理解が、ゲル形成時に生成する三次元ネットワーク構造生成に重要な情報を与えるため、各種分光分析やX線を用いて得られる構造情報を手がかりに分子設計を進めた。カーボンナノチューブやフラーレンなどの炭素クラスター類も機能性鋳型分子として取り上げた。その後、上記の有機鋳型に対し、適切なゾル-ゲル反応の条件を探索した。表面選択的に適切な厚みで被覆するため、酸・塩基触媒の選択などの反応条件の選択により慎重に有機物と無機物界面の接合を行い、各次元の有機-無機複合体形成を達成する。これらの確認はTEM、SEM、SPMを用いて行った。DNAなどの生体材料をとりあげ、シリカ中への固定化にも挑戦し生体情報の化石化を実現した。
  • 金属カルボキシレートナノ多孔質結晶を鋳型とした3次元網目状高分子の創製
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2004年 -2005年 
    代表者 : 佐田 和己
     
    従来合成されている金属カルボキシレートナノ多孔質結晶の空孔のサイズの拡大を目指し、分子の長軸の長さが約20Åと見込まれるジフェニレンビニレン骨格を有するジカルボン酸の新規合成を行った。その結果、3ステップの反応で約20%の収率で最終生成物を得ることができた。また、原料を修飾することで、重合性官能基である末端ビニル基をもつジフェニレンビニレンジカルボン酸の合成に成功した。 さらにこれらのカルボン酸と金属イオンを反応させ、多孔質結晶の形成について検討した。その結果、既報の方法により、ジフェニレンビニレン骨格を導入した金属カルボキシレートナノ多孔質結晶の形成が確認できた。熱重量分析からはゲスト分子が多量に包接されていることが明らかになった。またX線粉末回折パターンをみると、他のテレフタル酸誘導体と同様の回折パターンを示しており、同じような3次元格子が形成されているものと思われる。 これらの金属カルボキシレートナノ多孔質結晶の包接挙動を検討した。ジフェニレンビニレン骨格は蛍光色素として機能するため、アクセプターを包接させることで、蛍光の消光が起こると期待できる。そこで、アクセプターであるメチルビオローゲンおよびフラーレン誘導体の溶液に結晶を浸責させ、共焦点蛍光顕微鏡で観察したところ、ゲスト溶液への浸責により、蛍光が消光した。これはアクセプターが結晶内に取り込まれたためと思われる。 このようにゲスト分子の挿入によるホスト格子の発光の制御が可能であることが明らかになった。さらにビニル基をもつ金属カルボキシレートナノ多孔質結晶についてはグラッブス触媒によるオレフィンメタセシス反応による架橋反応を検討した。その結果赤外吸収スペクトルから、十分に反応が進行しているようではなく最終的に3次元網目構造の確認までは至っていない。さらなる反応条件の最適が必要と考えられる。
  • 表面ゾル-ゲル法を利用した多糖系遺伝子診断システムの開発
    日本学術振興会:科学研究費助成事業 萌芽研究
    研究期間 : 2003年 -2005年 
    代表者 : 新海 征治, 佐田 和己, 竹内 正之, 藤田 典史
     
    シゾフィランは溶媒の極性変化に伴い一重鎖【double half arrows】三重鎖の超構造変換を示す。我々は、一重鎖から三重鎖への巻き戻り過程において核酸が共存すると、シゾフィラン三重鎖の一本が核酸に置き換わった新規な生体高分子複合体が生成することを見いだした[J.Am.Chem.Soc.,2000,122,4520]。 本研究は核酸と複合化した多糖の高次構造を表面ゲル-ゾル法を用いて無機物に記憶させ、有機・無機複合型の全く新しい核酸分離システムを開発することが目的である。前年度の成果を受け、本年度は以下の方針で研究を進めた。1)アルギニン、リジン、セリン修飾シゾフィランの核酸に対する相互作用能や選択性の評価を行い、特定核酸分離剤としてのリードシゾフィランのライブラリーを構築する。2)リードシゾフィランの還元末端にエチレングリコールをスペーサーとしてスルフィド基を導入し、酸化処理するこで含ジスルフィドシゾフィラン二量体を得る。3)ジスフィルド基を足がかりとして、リードシゾフィランを金基板上へ結合させ、水晶発振子により担持量に関する詳細な知見を得る。4)さらに、金基板上に担持した修飾シゾフィランに対し、表面ゾル-ゲル反応を施し、基板上への担持に関する最適条件を探索することを行った。その中でも核酸-シゾフィラン複合体へのゾルゲル反応の反応条件を種々探索した結果、アミン:スペーサー:グアニジウム塩を有する化合物がシリカのゾル-ゲル反応の良い触媒になりうることを見出した。これはグアニジウム塩が核酸のリン酸基と水素結合し、残ったアミン部位が表面選択的に核酸のまわりでのゾル-ゲル反応を促進したためと考えられた。またシゾフィラン内部に於いてシリカゲルの伸長反応が進行すること、有機分子の一次元配列およびその重合が可能なことを見いだすことに成功し、一次元ホストとしてのシゾフィランの有効性を示すことに成功した。
  • トポ化学重合を用いた鋳型重合系の開発
    日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2002年 -2003年 
    代表者 : 佐田 和己
     
    新しいトポ化学重合の反応系の構築として、新たにジエン・ジアセチレン・キノジメタンなどの種々のモノマーでの結晶中での重合挙動を検討した。一連のモノマーについて結晶構造解析を行い、結晶中でのモノマーの配向と重合反応性との相関を検討したところ、キノジメタン類においても、その重合反応性の一般化に成功した。特に興味深い点として、モノマー間の距離が約7.3Åが最適な重合距離であり、これは生成するポリマーの繰り返しユニットに相当することが明らかになった。また、酸素との共重合しやすい結晶でのモノマーの配置も明確になり、新しい反応を結晶で設計することができるようになった。ジエン・ジアセチレンにつづく第3のモノマーとして、キノジメタンモノマーのトポ化学重合におけるモノマーの立体的なパラメータを明確にすることができたことは、トポ化学重合の一般化を促すものとして、大変重要である。 さらに生成する高分子を溶液中で鋳型に沿って規則正しく配向させ、重合を行う鋳型重合系の開発の検討も進み、Pybox配位子と第2級アンモニウムオリゴマーの錯体形成を精力的に現在検討している。その結果、3つのPybox配位子を平行に配置することが可能になった。また、第2級アンモニウムオリゴマーの窒素原子間を炭素3個分にすることで、約4.3Åの間隔にモノマーを配置することも明らかになり、溶液中でのトポ化学重合の可能性が高まっている。現在、重合性官能基であるジエン・ジアセチレンの導入法の検討を行なった。現在合成が完了し、ガンマー線による重合を検討し、予備的であるが、重合が固相系で進行することが明らかになった。
  • 有機ゲル超分子構造をマトリックスとするヘリックス状シリカの創製
    日本学術振興会:科学研究費助成事業 萌芽研究
    研究期間 : 2000年 -2002年 
    代表者 : 新海 征治, 藤田 典史, 竹内 正之, 佐田 和己, 池田 篤志, 濱地 格
     
    テトラエトキシシランをゲル化する能力をもつ「有機ゲル化剤」を分子設計しゲル相でテトラエトキシシランのゾルゲル反応を実行し、有機ゲルの超分子構造が表面に刻印されたシリカの創製に挑戦した。特に、「有機ゲル化剤」が分子集合により作り出す多種多様な繊維構造をシリカ表面に分子レベルで「転写」することに主眼を置く。コレステロール骨格を有する分子に加え、あらたに円盤状分子であるポルフィリンおよびトリフェニレンに糖質誘導体を導入した分子を設計した。いずれの分子も有機溶媒をゲル化し、1次元方向にスタックしたゲル構造を与えた。糖を周辺部に有するポルフィリンに関しては,中心金属の種類,価数あるいはゲスト分子の認識によりポルフィリン間のスタッキング距離の制御が可能ことを証明した。さらにこれらの孤立化した分子集合体にゾルゲル反応を行い、絶縁物(シリカ)で被覆化された1次元集合体が得られることを世界に先駆けて発表した。コレステロールにフェナントロリンを修飾した分子は、プロトン化、非プロトン化に伴い有機ゲル中で特異な発光挙動を示すことを見いだした。これは、ゲル中で効率のよいエネルギー移動が起こっていることを示す結果であり、媒体としての「ゲル」の特異性を改めて示すことに成功した。
  • アンモニウムカルボキシレート塩を用いた固相重合系の開発
    日本学術振興会:科学研究費助成事業 奨励研究(A)
    研究期間 : 2000年 -2001年 
    代表者 : 佐田 和己
     
    13年度においても昨年度同様に、1.固相重合系を探索するための多数のモノマーの合成とその酸塩基反応による塩形成、と分子配列の検討、2.モノマーの固相光重合について検討した。 1.モノマーの合成および酸塩碁反応による塩形成とその結晶構造 種々のジエンモノマー、ジアセチレンモノマーを有するカルボン酸の合成を行った。これらをと1-ナフチルアミンを作用させ、塩を形成させた。塩の形成は核磁気共鳴や赤外吸収などで同定した。アミン成分は1-ナフチルアミンに固定して塩の合成を行った単結晶を作成し結晶構造解析を行った。その結果、いずれの塩も2次元に広がる水素結合ネットワークにより同じ集合体を形成していた。特に1-ナフチルアンモニウム基はいずれも同じヘリングボーン型の芳香環のスタックを形成していた。酸成分のアルキル鎖の鎖長によって層構造の面間隔が異なっているだけであった。この結果、1-ナフチルアンモニウムが硬い結晶構造を形成する特別な分子構造であることを明らかにすることができた。 2.光固相重合とモノマー分子配列の関係 光重合を検討したところ、ジエンおよびジアセチレン誘導体では重合が進行することがわかった。トリエン、ビニルモノマーでは重合が全く進行しない。これらのことから、1-ナフチルアンモニウム基はちょうどジエンおよびジアセチレンの重合に適したマトリックスを与えるアミンであることを明らかにした。これらの結果より、ジエンでの結晶重合での原理を明確にすることができただけではな<、結晶中での繰り返し単位の距離と重合によって得られる高分子の単位間の距離をそろえることで様々な結晶重合が可能になることを明らかにした。
  • 炭素鎖定序性情報に基づくらせん状超分子の構築と構造制御
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 1998年 -2000年 
    代表者 : 宮田 幹二, 佐田 和己
     
    申請者は、炭素鎖オリゴマーである胆汁酸ステロイドをホストとして長年包接化合物の研究を続けてきた。この研究過程で、ホスト分子がらせん状超分子を形成する例が見つかった。このらせん構造は、タンパク質や核酸などの生体高分子のらせん構造と何らかの深い関係があるように思われる。そこで本研究は、できるだけ多数のらせん状包接体をつくり、炭素鎖オリゴマーであるステロイドとらせん集合体との相関関係や分子認識機構を解明することを目的とし、次のような研究成果が得られた。 1.キラルな定序性炭素鎖オリゴマーの合成を行った。水素結合基を複数個もつホストを市販品のコール酸、デオキシコール酸、ケノデオキシコール酸などから合成し、これら炭素鎖オリゴマーを各種有機溶媒から結晶化してらせん状超分子体を形成させた。 2.さらに通常の溶媒類を用いて、上記オリゴマーの包接化を探索した。通常一つのオリゴマーについて百種以上のゲスト候補を調べ、らせん状超分子体の有無を探索した。 3.得られた超分子の結晶構造と溶液中の構造を、赤外吸収分光法、核磁気共鳴分光法、X線粉末回折法などにより調べた。数十個以上の超分子の単結晶のX線構造解析により、らせん構造を50種以上見つけた。分子グラフィックスにより分子集合体を解析し、らせん構造や包接空間さらに分子認識機構などを明らかにした。 4.分子構造の変化と水素結合・分子配列の変化との対応関係に基づき、らせん集合体に導く分子構造について考察した結果、らせん集合の普遍的存在を確信するに至った。
  • 定序性に基づく光学活性な高分子包接体の立体構造の制御
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 1996年 -1997年 
    代表者 : 宮田 幹二, 佐田 和己
     
    光学活性な高分子包接体を通して、分子情報が表現されるという概念の立証を目指して、定序性分子情報に基づく包接体の立体構造の制御に関する研究を系統的に行った。次のような成果が得られた。 1.定序性の異なるホストを多数合成した。これらホストの分子集合体形成の有無を通常百種類以上のゲストについて、再結晶法により調べた結果、多種類の包接体の形成を確認した。生成した包接体を用いて、定序性と包接体の立体的関係を詳しく検討した。 2.上記の包接形成の有無をもとに、各ホストの包接境界を求めた。この包接境界とゲストの大きさ・形・極性・キラリティーとの関係により、分子認識の機構解明に必要な基礎データを集積した。各ホストの包接範囲は、全く個性的と言ってもおかしくないほど多様であった。 3.ホスト・ゲスト包接体の単結晶をつくり、まず粉末回折パターンにより、結晶が既知のものと同型か異型かを調べ、次に異型の単結晶についておもに単結晶構造解析を行った。二年間で百個以上の包接単結晶の三次元構造データを集積した。 4.上記のようにして得られた構造解析データに基づいて、分子集合体をパソコン上で組み立て水素結合様式と分子集合様式を解析した。その結果、分子構造の変化と水素結合・分子配列の変化との対応関係が従来以上に鮮明になってきた。例えば、ホスト分子の部分構造と包接空間との関係について、ステロイド骨格と側鎖が包接空間の構築に関わっていく仕組みが明らかになった。 5.さらに分子グラフィックスにて包接空間を解析し、分子認識の機構を考察した。その結果、定序性に基づく光学活性な高分子包接体の立体構造を制御する仕組みが明らかになってきた。
  • 有機結晶-ポリマーハイブリッドの合成
    日本学術振興会:科学研究費助成事業 奨励研究(A)
    研究期間 : 1996年 -1996年 
    代表者 : 佐田 和己
     
    本研究では低分子の形成する結晶格子の中に高分子鎖を閉じこめ、有機結晶と高分子の複合体が形成されるかどうかを検討した。さらに、形成された有機結晶-ポリマーハイブリッドの結晶構造や結晶中での高分子鎖のコンフォーメーションなどをX線結晶構造によって明らかにした。 1.平均分子量400のポリ(エチレンオキシド)をポリマーゲストとして、複合体の合成を検討した。ポリマーから直接再結晶を行う直接法、包接されない有機溶媒を媒介とする溶媒法および、他の有機低分子を包接させた結晶をポリマー溶液中に静置し、ゲスト交換によるインタカレーション法について検討を行った。コール酸は多くの有機小分子を包接することが知られているが、ポリエチレンオキシドからの再結晶ではゲストを含まない結晶のみが形成された。これに対し、ステロイド側鎖をアミドにしたコール酸アミドではポリ(エチレンオキシド)を内包した結晶が形成された。ホスト:ゲスト(高分子鎖のユニットに対して)は1:2であり、ホスト結晶中に二本の高分子鎖が導入できているものと考えられる。 さらに、生成したコール酸アミド-ポリ(エチレンオキシド)の複合体結晶の結晶構造をX線回折により同定した。ホストの格子はテトラヒドロフランやエタノールなどの低分子を包接した場合と同じ構造であり、一次元的なチャンネルを有するものであり、チャンネル空間に高分子鎖がのびていることを示している。 このように胆汁酸ステロイドとポリ(エチレンオキシド)の組合せで有機結晶-ポリマーハイブリッドを形成することおよびその結晶構造を明らかにすることができた。
  • ステロイド包接結晶環境下での分子認識・分子配列・反応
    日本学術振興会:科学研究費助成事業 重点領域研究
    研究期間 : 1994年 -1994年 
    代表者 : 宮田 幹二, 佐田 和己
     
    ステロイドに関する研究の歴史は長いが、その包接化合物の系統的な研究は、デオキシコール酸・アポコール酸を除いて、ほとんどなかった。我々は、既知のステロイドと誘導体の多くが包接化合物形成能力をもつことを世界ではじめて確認しつつある。以下にこの成果を記す。 1.ステロイドホスト分子の合成:ホスト分子として多数のステロイドを合成した。特にステロイド核に水酸基を複数個有する市販のステロイドを出発原料として、その側鎖部分の官能基を変換させ、十数種類の新規ステロイドホスト分子を合成した。 2.ホスト分子の包接化合物の形成:上記ホストの包接結晶形成能を広範囲な有機化合物について調べたところ、予想以上にその能力があった。ほとんどのステロイドホスト化合物が安定な包接体を形成することが明らかとなった。またわずかな側鎖の官能基の違いやステロイド核の水酸基の数や位置などにより、その包接体形成能が大きく変化することも明らかとなった。わずかな官能基の差異が包接体の機能や構造に大きな影響を及ぼすことを示している。 3.ホストーゲスト集合体の構造解析:包接体のX線結晶構造解析を行い、今まで知られているものとの比較を行った。その結果、親水面・親油面を表裏にもつ面状両親媒性化合物に特有な集合様式、すなわち、二重層状構造(二次元の親水層と親油層からなる累積構造)の存在が明確になった。さらに、これらの包接体はこの親水部と親油部が相分離した構造であるため、集合体は動的な側面を持つことが明らかとなった。つまり、ホスト集合体は包接されるゲストの大きさ・形・キラリティを認識してに、親油層での層のずらしなどを行い、多くのゲスト分子を取り込むための種々の空洞を形成していることが明らかとなった。
  • ホスト・ゲスト相互作用による分子操作技術の開発
    日本学術振興会:科学研究費助成事業 試験研究(B)
    研究期間 : 1992年 -1994年 
    代表者 : 宮田 幹二, 田原 秀行, 佐田 和己
     
    ホスト・ゲスト複合化によるナノメートル領域の分子操作技術の開発をめざして、三年間研究を行った。この研究は、水素結合などの弱い結合に基づく、有機分子の自律的な集合能力を生かした自動詞型技術の先駆けとなるものである。ホストとしてステロイドと称されている一群の有機物を用い、次のような研究成果が得られた。 1.市販の胆汁酸ステロイドを出発原料として、既知の方法で側鎖部分の炭素鎖の長さや官能基、骨格の不斉炭素の絶対配置を変えることにより、数百種類以上の有機物ホストを合成することが可能になった。 2.上記ホストの複合体形成能を広範囲な有機化合物について調べた。その結果、ほとんどのステロイド化合物が何らかの有機ゲストと安定にホスト・ゲスト包接体を形成することが明らかとなった。これらの分子は、数千万の異性体を持つことを考えると、この実験結果は有機分子がごく一般的に包接能をもつことを示している。 3.包接体の単結晶や粉末のX線構造解析を大規模に行い、分子配列を詳細に調べた。この配列の比較研究により、親水面・親油面を表裏にもつ面状両親媒性化合物に特有な集合様式として、二重層状構造の一般性が明確になった。さらに、両親媒的な不斉面が累積するときに、多様な方法のあることが初めて明らかになった。 4.コンピュータグラフィクスを用いて、分子間の水素結合を詳細に調べた結果、ステロイドの骨格や側鎖に存在する水酸基の数・位置により、水素結合基の組合せが多様に変化することが明らかになった。三個あるいは四個の組合せについては、理論的な組合せとの対応が可能になった。 5.分子操作技術に必要なホスト・ゲスト複合体の解析システムを、パソコンを用いて構築した。これにより複合体の解析を容易に行え、しかもデータベースを容易に作製できるようになった。
  • コール酸誘導体をホストとした新規包接重合反応系の開発
    日本学術振興会:科学研究費助成事業 奨励研究(A)
    研究期間 : 1992年 -1992年 
    代表者 : 佐田 和己
  • 包接化合物による分子認識に関する研究
  • 有機結晶の分子設計に関する研究
  • Study on Molecular Recognitin Using Indusim Crystals
  • Study on Molecular Design of Organic Crystals

教育活動情報

主要な担当授業

  • 化学特別講義
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 総合化学院
    キーワード : Electron Transfer, Proton Transfer, Respiratory Chain, Cytochromes, Kinetic Analysis
  • 物理化学先端講義
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 総合化学院
    キーワード : 分子構造決定、高分子、分子集合体
  • 物質化学A(ナノ物質化学)
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 総合化学院
    キーワード : 分子集合体・自己組織化・超分子化学・ゲル・結晶・MOF・分子モーター・キネシン・チューブリン・アクチン・ミオシン
  • 先端総合化学特論Ⅱ
    開講年度 : 2021年
    課程区分 : 博士後期課程
    開講学部 : 総合化学院
    キーワード : Electron Transfer, Proton Transfer, Respiratory Chain, Cytochromes, Kinetic Analysis
  • 基礎物理化学
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 理学部
    キーワード : 気体の状態方程式、化学熱力学、エンタルピー、エントロピー、ギブス自由エネルギー、ヘルムホルツ自由エネルギー、化学ポテンシャル
  • 物質電子論
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 理学部
    キーワード : 物質の電子状態、バンド理論、アクティブマター、分子間相互作用、動的自己組織化、ホストゲスト化学、結晶工学、分子認識化学、金属有機構造体(MOF)、X線結晶構造解析、自己組織化
  • 化学実験Ⅳ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 理学部
    キーワード : 物理化学、電気化学、光と物質の相互作用、赤外分光法、蛍光分光法、真空、放電、電子衝撃分光法, エネルギー準位
  • 化学実験C
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 理学部
    キーワード : See the English version
  • 化学実験D
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 理学部
    キーワード : See the English version

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  • 2020年4月1日 - 2022年3月31日 大学院総合化学院副学院長


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