Researcher Database

Kazuki Sada
Faculty of Science Chemistry Physical Chemistry

Researcher Profile and Settings


  • Faculty of Science Chemistry Physical Chemistry

Job Title

  • Professor


  • 1

Research funding number

  • 80225911

J-Global ID

Research Interests

  • Super-Absorbent Polymers   Crosslink   Metal Organic Frameworks   Coordination Polymers   Network Materials   Phase Transition   Thermosensitive Polymers   Nano-Machine   Organic Synthetic Chemistry   Surpamolecular Chemistry   Molecular Assembly   Metal ions   Stereospecific Polymerization   Gold Substarte   Radical Polymerization   Polymer Synthese   Organic Solvents   Photo-Switch   Crystalline-State Polymerization   Polymer Chemistry   Organic Crystals   Nanoporus Materials   Precise Polymerization   Nanomaterials   Stimuli-Sensitive Polymers   Polyelectrolytes   Gels   Ion-pair   結晶構造解析   Environmental Materials   Electrostatic Replusion   Carboxylate   Disulfide   Molecular Recognition   Hyrogen Bond   X-ray Crystallography   Crystal Engineering   Molecular Graphics   Inclusion Compounds   Solid-State Polymerization   Diene   

Research Areas

  • Nanotechnology/Materials / Polymer chemistry
  • Nanotechnology/Materials / Nanostructure physics
  • Nanotechnology/Materials / Nanostructure chemistry
  • Nanotechnology/Materials / Polymer materials
  • Nanotechnology/Materials / Functional solid-state chemistry
  • Nanotechnology/Materials / Biochemistry
  • Nanotechnology/Materials / Composite materials and interfaces
  • Nanotechnology/Materials / Synthetic organic chemistry
  • Nanotechnology/Materials / Synthetic organic chemistry

Academic & Professional Experience

  • 2010/04 - Today Hokkaido University Faculty of Science Professor
  • 2007/04 - 2010/03 Kyushu University Graduate School of Engineering Associate Profesoor
  • 2002/04 - 2007/03 Kyushu University Graduate School of Engineering Associate Profesoor
  • 1998/04 - 2002/04 Osaka University Graduate School of Engineering Assiatant Profesoor
  • 1995/10 - 1998/03 Osaka University Faculty of Engineering Assiatant Profesoor
  • 1990/04 - 1995/09 Gifu University Faculty of Engineering Assiatant Profesoor


  • 1987/04 - 1990/03  Kyoto University  Graduate School of Engineering  Doctor, Department of Synthetic Chemistry
  • 1985/04 - 1987/03  Kyoto University  Graduate School of Engineering  Master, Department of Synthetic Chemistry
  • 1981/04 - 1985/03  Kyoto University  Faculty of Engineering  Department of Synthetic Chemistry

Association Memberships

  • 高分子学会   米国化学会   日本化学会   

Research Activities

Published Papers

  • Sakamoto N, Ohta M, Kokado K, Sada, K
    NEW JOURNAL OF CHEMISTRY 43 (37) 14853 - 14858 2019/10 [Refereed][Not invited]
  • Nasrin SR, Rashedul Kabir AM, Konagaya A, Ishihara T, Sada K, Kakugo A
    Biochemical and biophysical research communications 516 (3) 760 - 764 0006-291X 2019/08 [Refereed][Not invited]
  • Inaba H, Yamamoto T, Iwasaki T, Kabir AMR, Kakugo A, Sada K, Matsuura K
    Chemical communications (Cambridge, England) 55 (62) 9072 - 9075 1359-7345 2019/08 [Refereed][Not invited]
  • Kokado K, Sada K
    Angewandte Chemie (International ed. in English) 58 (26) 8632 - 8639 1433-7851 2019/06 [Refereed][Not invited]
  • Anan S, Mochizuki Y, Kokado K, Sada K
    Angewandte Chemie (International ed. in English) 58 (24) 8018 - 8023 1433-7851 2019/06 [Refereed][Not invited]
  • Matsuda K, Kabir AMR, Akamatsu N, Saito A, Ishikawa S, Matsuyama T, Ditzer O, Islam MS, Ohya Y, Sada K, Konagaya A, Kuzuya A, Kakugo A
    Nano letters 19 (6) 3933 - 3938 1530-6984 2019/06 [Refereed][Not invited]
  • Inaba H, Yamamoto T, Iwasaki T, Kabir AMR, Kakugo A, Sada K, Matsuura K
    ACS omega 4 (6) 11245 - 11250 2019/06 [Refereed][Not invited]
  • Anan Shizuka, Kokado Kenta, Sada Kazuki
    CHEMISTRY LETTERS 48 (3) 285 - 287 0366-7022 2019/03 [Refereed][Not invited]
  • Islam MJ, Matsuo K, Menezes HM, Takahashi M, Nakagawa H, Kakugo A, Sada K, Tamaoki N
    Organic & biomolecular chemistry 17 (1) 53 - 65 1477-0520 2018/12 [Refereed][Not invited]
  • 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) 2041-1723 2018/12/01 [Refereed][Not invited]
    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.
  • Inaba H, Yamamoto T, Kabir AMR, Kakugo A, Sada K, Matsuura K
    Chemistry (Weinheim an der Bergstrasse, Germany) 24 (56) 14958 - 14967 0947-6539 2018/10 [Refereed][Not invited]
  • Keya Jakia Jannat, Kabir Arif, Md. Rashedul, Inoue Daisuke, Sada Kazuki, Hess Henry, Kuzuya Akinori, Kakugo Akira
    SCIENTIFIC REPORTS 8 2045-2322 2018/08/06 [Refereed][Not invited]
  • Sada Kazuki
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 91 (8) 1282 - 1292 0009-2673 2018/08 [Refereed][Invited]
  • Jimbo Takahiro, Tsuji Mikako, Taniguchi Ryosuke, Sada Kazuki, Kokado Kenta
    CRYSTAL GROWTH & DESIGN 18 (7) 3863 - 3869 1528-7483 2018/07 [Refereed][Not invited]
  • Ren Sasaki, Arif Md. Rashedul Kabir, Daisuke Inoue, Shizuka Anan, Atsushi P. Kimura, Akihiko Konagaya, Kazuki Sada, Akira Kakugo
    Nanoscale 10 (14) 6323 - 6332 2040-3372 2018/04/14 [Refereed][Not invited]
    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.
  • Kazuki Sada
    Polymer Journal 50 (4) 285 - 299 1349-0540 2018/04/01 [Refereed][Not invited]
    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.
  • Kazuki Sada
    Polymer Journal 50 (6) 473  1349-0540 2018/04/01 [Refereed][Invited]
    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.
  • Kazuya Iseda, Kenta Kokado, Kazuki Sada
    ChemistryOpen 7 (3) 269 - 274 2191-1363 2018/03/01 [Refereed][Not invited]
    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.
  • Y. Mochizuki, C. Oka, T. Ishiwata, K. Kokado, K. Sada
    Gels 4 (1) 16  2018/02 [Refereed][Not invited]
  • Kenta Kokado, Takashi Machida, Takeshi Iwasa, Tetsuya Taketsugu, Kazuki Sada
    Journal of Physical Chemistry C 122 (1) 245 - 251 1932-7455 2018/01/11 [Refereed][Not invited]
    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.
  • Sokuro Sunaga, Kenta Kokado, Kazuki Sada
    Soft Matter 14 (4) 581 - 585 1744-6848 2018 [Refereed][Not invited]
    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 1364-548X 2018 [Refereed][Not invited]
    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.
  • Mikako Tsuji, Arif Md. Rashedul Kabir, Masaki Ito, Daisuke Inoue, Kenta Kokado, Kazuki Sada, Akira Kakugo
    LANGMUIR 33 (43) 12108 - 12113 0743-7463 2017/10 [Refereed][Not invited]
    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.
  • Kenta Kokado, Takumi Ishiwata, Shizuka Anan, Kazuki Sada
    POLYMER JOURNAL 49 (9) 685 - 689 0032-3896 2017/09 [Refereed][Not invited]
    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.
  • Masami Naya, Yoshimi Hamano, Kenta Kokado, Kazuki Sada
    ACS MACRO LETTERS 6 (9) 898 - 902 2161-1653 2017/09 [Refereed][Not invited]
    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.
  • Md. Sirajul Islam, Kaori Kuribayashi-Shigetomi, Arif Md. Rashedul Kabir, Daisuke Inoue, Kazuki Sada, Akira Kakugo
    SENSORS AND ACTUATORS B-CHEMICAL 247 53 - 60 0925-4005 2017/08 [Refereed][Not invited]
    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 micro-tubule/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. (C) 2017 Elsevier B.V. All rights reserved.
  • Shogo Amemori, Kazuya Iseda, Shizuka Anan, Toshikazu Ono, Kenta Kokado, Kazuki Sada
    POLYMER CHEMISTRY 8 (26) 3921 - 3925 1759-9954 2017/07 [Refereed][Not invited]
    The preparation of the polymers having a self-attractive urea unit via hydrogen bonding and a selfrepulsive 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 1936-0851 2017/06 [Refereed][Not invited]
    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 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 (18) 2444 - 2449 1434-1948 2017/05 [Refereed][Not invited]
    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.
  • K. Hirai, K. Sada
    CHEMICAL COMMUNICATIONS 53 (38) 5275 - 5278 1359-7345 2017/05 [Refereed][Not invited]
    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.
  • Takumi Ishiwata, Kenta Kokado, Kazuki Sada
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 56 (10) 2608 - 2612 1433-7851 2017/03 [Refereed][Not invited]
    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.
  • Taihei Yamada, Kenta Kokado, Kazuki Sada
    LANGMUIR 33 (10) 2610 - 2616 0743-7463 2017/03 [Refereed][Not invited]
    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. zeta 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.
  • Arif Md. Rashedul Kabir, Masaki Ito, Kyohei Uenishi, Shizuka Anan, Akihiko Konagaya, Kazuki Sada, Miwa Sugiura, Akira Kakugo
    CHEMISTRY LETTERS 46 (2) 178 - 180 0366-7022 2017/02 [Refereed][Not invited]
    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 1359-7345 2017/02 [Refereed][Not invited]
    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.
  • Shinya Sudo, Kenta Kokado, Kazuki Sada
    RSC ADVANCES 7 (2) 678 - 683 2046-2069 2017 [Refereed][Not invited]
    We report on the synthesis of nanosized single-crystalline spherical beta-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 crystalline beta-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 (E-g = 4.89 eV) was hypsochromically shifted compared to that of bulk Ga2O3 (E-g(bulk) = 4.56 eV) due to the quantum size effect of beta-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 2046-2069 2017 [Refereed][Not invited]
    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) 2073-4360 2017/01 [Refereed][Not invited]
    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.
  • Tanjina Afrin, Arif Md Rashedul Kabir, Kazuki Sada, Akira Kakugo, Takahiro Nitta
    BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS 480 (1) 132 - 138 0006-291X 2016/11 [Refereed][Not invited]
    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. (C) 2016 Elsevier Inc. All rights reserved.
  • Masaki Ito, Takumi Ishiwata, Shizuka Anan, Kenta Kokado, Daisuke Inoue, Arif M. R. Kabir, Akira Kakugo, Kazuki Sada
    CHEMISTRYSELECT 1 (16) 5358 - 5362 2365-6549 2016/10 [Refereed][Not invited]
    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-triphosphate (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.
  • Daisuke Inoue, Takahiro Nitta, Arif Md. Rashedul Kabir, Kazuki Sada, Jian Ping Gong, Akihiko Konagaya, Akira Kakugo
    NATURE COMMUNICATIONS 7 2041-1723 2016/10 [Refereed][Not invited]
    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.
  • Yusuke Nishikori, Kazuya Iseda, Kenta Kokado, Kazuki Sada
    POLYMERS 8 (4) 2073-4360 2016/04 [Refereed][Not invited]
    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 (epsilon = 7.6) to DMSO (epsilon = 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 (T-NI) on differential scanning calorimetry (DSC) measurement, and the increase of the ionic group content lowered T-NI. The MPEgels absorbing liquid crystalline molecules exhibited differing T-NI, dependent on the compatibility of the mesogenic group on the side chain to the liquid crystalline molecule.
  • Md Sirajul Islam, Arif Md Rashedul Kabir, Daisuke Inoue, Kazuki Sada, Akira Kakugo
    BIOPHYSICAL CHEMISTRY 211 1 - 8 0301-4622 2016/04 [Refereed][Not invited]
    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. (C) 2015 Published by Elsevier B.V.
  • Masahiko Ohta, Toshikazu Ono, Kenta Kokado, Akira Kakugo, Kazuki Sada
    MACROMOLECULAR CHEMISTRY AND PHYSICS 217 (3) 433 - 444 1022-1352 2016/02 [Refereed][Not invited]
    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.
  • 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 2046-2069 2016 [Refereed][Not invited]
    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.
  • Kenji Hirai, Shigehito Isobe, Kazuki Sada
    SCIENTIFIC REPORTS 5 2045-2322 2015/12 [Refereed][Not invited]
    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 2045-2322 2015/11 [Refereed][Not invited]
    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.
  • 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 0024-9297 2015/06 [Refereed][Not invited]
    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.
  • Desi H. Gharib, Shogo Amemori, Masami Naya, Kenta Kokado, Kazuki Sada
    RSC ADVANCES 5 (108) 89319 - 89322 2046-2069 2015 [Refereed][Not invited]
    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 2040-3364 2015 [Refereed][Not invited]
    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 2050-7526 2015 [Refereed][Not invited]
    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 1525-7797 2015/01 [Refereed][Not invited]
    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 1744-683X 2015 [Refereed][Not invited]
    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 1359-7345 2015 [Refereed][Not invited]
    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 0024-9297 2014/09 [Refereed][Not invited]
    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 0366-7022 2014/08 [Refereed][Not invited]
    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 0366-7022 2014/08 [Refereed][Not invited]
    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.
  • Arif Md Rashedul Kabir, Daisuke Inoue, Yoshimi Hamano, Hiroyuki Mayama, Kazuki Sada, Akira Kakugo
    BIOMACROMOLECULES 15 (5) 1797 - 1805 1525-7797 2014/05 [Refereed][Not invited]
    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 0032-3896 2014/04 [Refereed][Not invited]
    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.
  • Kazuki Sada, Kenta Kokado
    Kobunshi 63 225 - 226 2014/01/01 [Not refereed][Not invited]
  • Kazuki Sada, Kenta Kokado
    Kobunshi 63 844 - 846 2014/01/01 [Not refereed][Not invited]
  • Kazuya Iseda, Kenta Kokado, Kazuki Sada
    REACTIVE & FUNCTIONAL POLYMERS 73 (7) 951 - 957 1381-5148 2013/07 [Refereed][Not invited]
    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 0897-4756 2013/07 [Refereed][Not invited]
    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.
  • Shogo Amemori, Kenta Kokado, Kazuki Sada
    Angewandte Chemie - International Edition 52 (15) 4174 - 4178 1433-7851 2013/04/08 [Refereed][Not invited]
    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.
  • Takumi Ishiwata, Yuki Furukawa, Kouta Sugikawa, Kenta Kokado, Kazuki Sada
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 135 (14) 5427 - 5432 0002-7863 2013/04 [Refereed][Not invited]
    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.
  • Daisuke Inoue, Arif Md Rashedul Kabir, Hiroyuki Mayama, Jian Ping Gong, Kazuki Sada, Akira Kakugo
    SOFT MATTER 9 (29) 7061 - 7068 1744-683X 2013 [Refereed][Not invited]
    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 2161-1653 2012/11 [Refereed][Not invited]
    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 0366-7022 2012/07 [Refereed][Not invited]
    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 0032-3896 2012/06 [Refereed][Not invited]
    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 0002-7863 2012/05 [Refereed][Not invited]
    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.
  • Youichi Tsuchiya, Tomohiro Shiraki, Takashi Matsumoto, Kouta Sugikawa, Kazuki Sada, Akihito Yamano, Seiji Shinkai
    CHEMISTRY-A EUROPEAN JOURNAL 18 (2) 456 - 465 0947-6539 2012/01 [Refereed][Not invited]
    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 1744-683X 2012 [Refereed][Not invited]
    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 1466-8033 2012 [Refereed][Not invited]
    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 1744-683X 2012 [Refereed][Not invited]
    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 1433-7851 2012 [Refereed][Not invited]
  • Toshikazu Ono, Kazuki Sada
    JOURNAL OF MATERIALS CHEMISTRY 22 (39) 20962 - 20967 0959-9428 2012 [Refereed][Not invited]
    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 1744-683X 2012 [Refereed][Not invited]
    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 1936-0851 2011/12 [Refereed][Not invited]
    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 0170-0839 2011/09 [Refereed][Not invited]
    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 0897-4756 2011/07 [Refereed][Not invited]
  • Masahiko Ohta, Toshikazu Ono, Kazuki Sada
    CHEMISTRY LETTERS 40 (6) 648 - 650 0366-7022 2011/06 [Refereed][Not invited]
    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 0366-7022 2011/03 [Refereed][Not invited]
    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 1477-0520 2011 [Refereed][Not invited]
    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 1061-0278 2011 [Refereed][Not invited]
    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, Akihito Yamano, Tomohiro Shiraki, Kazuki Sada, Seiji Shinkai
    CHEMISTRY LETTERS 40 (1) 99 - 101 0366-7022 2011/01 [Refereed][Not invited]
    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 1359-7345 2011 [Refereed][Not invited]
    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 1466-8033 2011 [Refereed][Not invited]
    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 1061-0278 2011 [Refereed][Not invited]
    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 1744-683X 2011 [Refereed][Not invited]
    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, Kenji Kaneko, Kazuki Sada, Seiji Shinkai
    LANGMUIR 26 (24) 19100 - 19105 0743-7463 2010/12 [Refereed][Not invited]
    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.
  • Kouta Sugikawa, Munenori Numata, Kazuki Sada, Seiji Shinkai
    CHEMISTRY LETTERS 39 (7) 710 - 711 0366-7022 2010/07 [Refereed][Not invited]
    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 0947-6539 2010 [Refereed][Not invited]
    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 1528-7483 2009/06 [Refereed][Not invited]
    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 0040-4039 2009/04 [Refereed][Not invited]
    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 1528-7483 2009/02 [Refereed][Not invited]
    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 1861-4728 2009 [Refereed][Not invited]
    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 1359-7345 2009 [Refereed][Not invited]
    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 1477-0520 2009 [Refereed][Not invited]
    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 0947-6539 2009 [Refereed][Not invited]
    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 1359-7345 2009 [Refereed][Not invited]
    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
    LANGMUIR 24 (23) 13270 - 13275 0743-7463 2008/12 [Refereed][Not invited]
    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 1616-301X 2008/12 [Refereed][Not invited]
    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 - + 0002-7863 2008/11 [Refereed][Not invited]
    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 0366-7022 2008/05 [Refereed][Not invited]
    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 1528-7483 2008/03 [Refereed][Not invited]
    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 1744-683X 2008 [Refereed][Not invited]
    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 1476-1122 2007/06 [Refereed][Not invited]
    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 0366-7022 2007/05 [Refereed][Not invited]
    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 0366-7022 2007/02 [Refereed][Not invited]
    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.
  • Takahiro Sugimoto, Takayuki Suzuki, Seiji Shinkai, Kazuki Sada
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 129 (2) 270 - 271 0002-7863 2007/01 [Refereed][Not invited]
    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 0306-0012 2007 [Refereed][Not invited]
    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 1468-6996 2006/10 [Refereed][Not invited]
    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 1861-4728 2006/10 [Refereed][Not invited]
    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 0936-5214 2006/09 [Refereed][Not invited]
    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 - + 0935-9648 2006/04 [Refereed][Not invited]
    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 0002-7863 2006/02 [Refereed][Not invited]
    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 0386-2186 2006 [Refereed][Not invited]
    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 1359-7345 2006 [Refereed][Not invited]
    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.
  • K Nakano, K Sada, K Aburaya, K Nakagawa, N Yoswathananont, N Tohnai, M Miyata
    CRYSTENGCOMM 8 (6) 461 - 467 1466-8033 2006 [Refereed][Not invited]
    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 1433-7851 2006 [Refereed][Not invited]
  • Akio Ojida, Hiroshi Nonaka, Yoshifumi Miyahara, Shun-ichi Tamaru, Kazuki Sada, Itaru Hamachi
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 45 (33) 5518 - 5521 1433-7851 2006 [Refereed][Not invited]
  • Nami Tokunaga, Yuzo Fujiki, Seiji Shinkai, Kazuki Sada
    CHEMICAL COMMUNICATIONS (34) 3617 - 3618 1359-7345 2006 [Refereed][Not invited]
    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 1434-193X 2005/12 [Refereed][Not invited]
    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 0743-7463 2005/10 [Refereed][Not invited]
    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 0040-4039 2005/08 [Refereed][Not invited]
    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 0002-7863 2005/05 [Refereed][Not invited]
  • K Nakano, K Sada, K Nakagawa, K Aburaya, N Yoswathananont, N Tohnai, M Miyata
    CHEMISTRY-A EUROPEAN JOURNAL 11 (6) 1725 - 1733 0947-6539 2005/03 [Refereed][Not invited]
    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 1542-1406 2005 [Refereed][Not invited]
    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 1433-7851 2005 [Refereed][Not invited]
  • T Itoh, S Nomura, M Ohtake, T Yoshida, T Uno, M Kubo, A Kajiwara, K Sada, M Miyata
    MACROMOLECULES 37 (22) 8230 - 8238 0024-9297 2004/11 [Refereed][Not invited]
    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 0024-9297 2004/10 [Refereed][Not invited]
    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 0040-4039 2004/10 [Refereed][Not invited]
    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 0366-7022 2004/08 [Refereed][Not invited]
    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 0366-7022 2004/05 [Refereed][Not invited]
    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 1359-7345 2004/05 [Refereed][Not invited]
    Hydrogen bonded supramolecular ladders were constructed by complexation of PYBOX dimers with flexible oligo(sec-dialkyl-ammonium cations).
  • K Nakano, S Akita, N Yoswathananont, K Sada, M Miyata
    JOURNAL OF INCLUSION PHENOMENA AND MACROCYCLIC CHEMISTRY 48 (3-4) 181 - 184 1388-3127 2004/04 [Refereed][Not invited]
    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 1528-7483 2004/03 [Refereed][Not invited]
    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 0002-7863 2004/03 [Refereed][Not invited]
    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 1434-193X 2004/02 [Refereed][Not invited]
    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 0366-7022 2004/02 [Refereed][Not invited]
    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 0366-7022 2004/02 [Refereed][Not invited]
    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 0002-7863 2004/02 [Refereed][Not invited]
    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 0002-7863 2004/02 [Refereed][Not invited]
    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 1476-1122 2004/01 [Refereed][Not invited]
    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 0010-0765 2004 [Refereed][Not invited]
    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 0366-7022 2003/08 [Refereed][Not invited]
    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 1434-193X 2003/07 [Refereed][Not invited]
    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 0022-3263 2003/06 [Refereed][Not invited]
    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 1528-7483 2003/03 [Refereed][Not invited]
    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 0022-3263 2003/02 [Refereed][Not invited]
    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.
  • T Yi, K Sada, K Sugiyasu, T Hatano, S Shinkai
    CHEMICAL COMMUNICATIONS (3) 344 - 345 1359-7345 2003 [Refereed][Not invited]
    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 1359-7345 2003 [Refereed][Not invited]
    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 1477-0520 2003 [Refereed][Not invited]
    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 1058-725X 2003 [Refereed][Not invited]
    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 1433-7851 2003 [Refereed][Not invited]
  • K Kato, Y Aoki, M Sugahara, N Tohnai, K Sada, M Miyata
    CHIRALITY 15 (1) 53 - 59 0899-0042 2003/01 [Refereed][Not invited]
    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 1477-0520 2003/01 [Refereed][Not invited]
    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 0366-7022 2002/12 [Refereed][Not invited]
    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).
  • Matsumoto A, Sada K, Tashiro K, Miyata M, Tsubouchi T, Tanaka T, Odani T, Nagahama S, Tanaka T, Inoue K, Saragai S, Nakamoto S
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 41 (14) 2502 - + 1433-7851 2002 [Refereed][Not invited]
  • T Itoh, S Nomura, T Uno, M Kubo, K Sada, M Miyata
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 41 (22) 4306 - 4309 1433-7851 2002 [Refereed][Not invited]
  • Nakano K, Hishikawa Y, Sada K, Miyata M, Hanabusa K
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 389 11 - 16 1058-725X 2002 [Refereed][Not invited]
  • Yoswathananont N, Sada K, Miyata M
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 389 47 - 51 1058-725X 2002 [Refereed][Not invited]
  • T Odani, A Matsumoto, K Sada, M Miyata
    CHEMICAL COMMUNICATIONS (19) 2004 - 2005 1359-7345 2001/10 [Refereed][Not invited]
    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.
  • J. Am. Chem. Soc. 123 (19) 4386 - 4392 0002-7863 2001 [Not refereed][Not invited]
  • Conformational Polymorphism in Inclusion Crystals of Cholid Acid with Ethyl Acetate
    Cryst. Eng. Comm. 11 (1) 1 - 2 2001 [Not refereed][Not invited]
  • K Nakano, K Sada, M Miyata
    POLYMER JOURNAL 33 (2) 172 - 176 0032-3896 2001 [Not refereed][Not invited]
    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.
  • Conformational polymorphism in inclusion crystals of cholic acid with ethyl acetate
    Nakano K, Katsuta M, Sada K, Miyata M
    CRYSTENGCOMM (11) art. no. - 11 1466-8033 2001 [Refereed][Not invited]
  • M Miyata, K Sada
    SOFT CHEMISTRY LEADING TO NOVEL MATERIALS 191 99 - 123 1012-0386 2001 [Refereed][Not invited]
    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.
  • Sada K, Nakano K, Hirayama K, Miyata M, Sasaki S, Takemoto K, Kasai N, Kato K, Shigesato M, Miki K
    SUPRAMOLECULAR CHEMISTRY 13 (1) 35 - + 1061-0278 2001 [Refereed][Not invited]
  • M Sugahara, J Hirose, K Sada, M Miyata
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 356 155 - 162 1058-725X 2001 [Refereed][Not invited]
    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) 1466-8033 2001 [Refereed][Not invited]
    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 0366-7022 2000/10 [Refereed][Not invited]
    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.
  • Akikazu Matsumoto, Toru Odani, Kazuki Sada, Mikiji Miyata, Kohji Tashiro
    Nature 405 (6784) 328 - 330 0028-0836 2000/05/18 [Not refereed][Not invited]
    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.
  • The design of organic gelators based on a family of bis-ureas
    RE Melendez, AJ Carr, K Sada, AD Hamilton
    MATERIALS OF SMART SYSTEMS III 604 335 - 340 0272-9172 2000 [Refereed][Not invited]
    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.
  • Enantioresolution of aliphatic alcohols by lithocholamide
    Y Aoki, Y Hishikawa, K Sada, M Miyata
    ENANTIOMER 5 (1) 95 - 104 1024-2430 2000 [Refereed][Not invited]
    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.
  • 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  0065-7727 1999/08/22 [Refereed][Not invited]
  • Chem.Commun. (3) 293 - 294 1359-7345 1999 [Not refereed][Not invited]
  • J.Ame.Chem.Soc. 121 (48) 11122 - 11129 0002-7863 1999 [Not refereed][Not invited]
  • M Chikada, K Sada, M Miyata
    POLYMER JOURNAL 31 (11) 1061 - 1064 0032-3896 1999 [Refereed][Not invited]
    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 1061-0278 1999 [Refereed][Not invited]
    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.
  • Hishikawa, Y, Sada, K, Miyata, M
    JOURNAL OF CHEMICAL RESEARCH-S (12) 738 - 739A 1998/12 [Refereed][Not invited]
  • Y Hishikawa, K Sada, R Watanabe, M Miyata, K Hanabusa
    CHEMISTRY LETTERS (8) 795 - 796 0366-7022 1998/08 [Refereed][Not invited]
    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.
  • Yukio Hishikawa, Yuriko Aoki, Kazuki Sada, Mikiji Miyata
    Chemistry Letters (12) 1289 - 1290 0366-7022 1998 [Not refereed][Not invited]
  • Chirality 10 (7) 600 - 618 0899-0042 1998 [Not refereed][Not invited]
  • Bull. Chem. Soc. Jpn. 71 (8) 1931 - 1937 0009-2673 1998 [Not refereed][Not invited]
  • J. Chem Soc. , Chem. Commun. (16) 1763 - 1764 1359-7345 1998 [Not refereed][Not invited]
  • J. Chem Soc. , Chen. Commun (1) 111 - 112 1359-7345 1998 [Not refereed][Not invited]
  • K Sada, M Sugahara, Y Nakahata, Y Yasuda, A Nishio, M Miyata
    CHEMISTRY LETTERS (1) 31 - 32 0366-7022 1998 [Refereed][Not invited]
    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 1061-0278 1998 [Refereed][Not invited]
    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
    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 0386-2186 1997 [Refereed][Not invited]
    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
    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 0366-7022 1997 [Refereed][Not invited]
    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 0108-7681 1996/08 [Refereed][Not invited]
    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 1359-7345 1996/04 [Refereed][Not invited]
    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.
  • Kazuki SADA, Mikiji MIYATA
    J. Synthetic Organic. Chemistry Japan 54 (2) 113 - 121 0037-9980 1996 [Not refereed][Not invited]
  • K Sada, T Maeda, M Miyata
    CHEMISTRY LETTERS (10) 837 - 838 0366-7022 1996 [Refereed][Not invited]
    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
    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
    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.
    CHEMISTRY LETTERS (10) 877 - 878 0366-7022 1995/10 [Refereed][Not invited]
    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.
    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS (9) 953 - 954 0022-4936 1995/05 [Refereed][Not invited]
    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 [Not refereed][Not invited]
    JOURNAL OF MACROMOLECULAR SCIENCE-PURE AND APPLIED CHEMISTRY A32 (6) 1213 - 1223 1060-1325 1995 [Refereed][Not invited]
    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.
    SUPRAMOLECULAR CHEMISTRY 5 (3) 189 - 191 1061-0278 1995 [Refereed][Not invited]
    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.
    CHEMISTRY LETTERS (11) 2113 - 2116 0366-7022 1994/11 [Refereed][Not invited]
    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.
    CHEMISTRY OF MATERIALS 6 (8) 1103 - 1105 0897-4756 1994/08 [Refereed][Not invited]
    CHEMISTRY LETTERS (4) 727 - 730 1348-0715 1994/04 [Refereed][Not invited]
    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS (7) 905 - 907 0022-4936 1994/04 [Refereed][Not invited]
    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.
    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.
    CHEMISTRY LETTERS (1) 137 - 140 0366-7022 1994/01 [Refereed][Not invited]
    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.
    MACROMOLECULES 26 (24) 6320 - 6323 0024-9297 1993/11 [Refereed][Not invited]
    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.
    MACROMOLECULES 26 (24) 6315 - 6319 0024-9297 1993/11 [Refereed][Not invited]
    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.
    MACROMOLECULES 26 (21) 5611 - 5614 0024-9297 1993/10 [Refereed][Not invited]
    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.
    POLYMER BULLETIN 31 (3) 311 - 316 0170-0839 1993/09 [Refereed][Not invited]
    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.
    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS (9) 753 - 755 0022-4936 1993/05 [Refereed][Not invited]
    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.
    MACROMOLECULES 26 (5) 883 - 887 0024-9297 1993/03 [Refereed][Not invited]
    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.
    POLYMER JOURNAL 25 (6) 599 - 608 0032-3896 1993 [Refereed][Not invited]
    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.
    POLYMER JOURNAL 24 (11) 1301 - 1306 0032-3896 1992 [Refereed][Not invited]
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 219 71 - 74 0140-6566 1992 [Refereed][Not invited]
    MACROMOLECULES 23 (10) 2693 - 2697 0024-9297 1990/05 [Refereed][Not invited]
    MACROMOLECULES 23 (10) 2636 - 2641 0024-9297 1990/05 [Refereed][Not invited]
  • Yoshiki Chujo, Kazuki Sada, Kazuaki Matsumoto, Taken Saegusa
    Macromolecules 23 (5) 1234 - 1237 1520-5835 1990 [Refereed][Not invited]
    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.
    POLYMER BULLETIN 21 (4) 353 - 356 0170-0839 1989/04 [Refereed][Not invited]
    MACROMOLECULES 22 (3) 1074 - 1077 0024-9297 1989/03 [Refereed][Not invited]
  • 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  [Not refereed][Not invited]

Conference Activities & Talks

  • Toshikazu Ono, Takahiro Sugimoto, Seiji Shinkai, Kazuki Sada
    Polymer Preprints, Japan  2006/12 
    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  2006/12 
    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  2006/12 
    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  2006/10 
    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  2006/10 
    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  2006/10 
    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  2006/10 
    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  2006/10 
    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  2005/12 
    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  2005/12 
    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  2005/12 
    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  2005/12 
    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  2005/12 
    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  2005/12 
    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  2005/12 
    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.

Awards & Honors

  • 2016/05 高分子学会 高分子学会賞
    受賞者: 佐田 和己
  • 2014/03 日本化学会 日本化学会学術賞
    受賞者: 佐田 和己
  • 2008/04 文部科学省 文部科学大臣表彰 科学技術賞 研究部門
    受賞者: 佐田 和己

Research Grants & Projects

  • 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

Educational Activities

Teaching Experience

  • 化学特別講義
    開講年度 : 2018
    課程区分 : 修士課程
    開講学部 : 総合化学院
  • Advanced Chemistry
    開講年度 : 2018
    課程区分 : 修士課程
    開講学部 : 総合化学院
    キーワード : マイクロ波 / 電磁波 / 電荷移動度 / 化学ドープ / FI-TRMC / 界面 / 有機半導体 / グラフェン / 圧力 / 電荷分離 / 有機太陽電池 / 有機エレクトロニクス
  • 先端総合化学特論Ⅱ
    開講年度 : 2018
    課程区分 : 博士後期課程
    開講学部 : 総合化学院
  • Advanced Chemistry
    開講年度 : 2018
    課程区分 : 修士課程
    開講学部 : 総合化学院
    キーワード : Molecular Machine, Molecular Assembly, Biomolecular Motors, Self-organization, Molecular Networks, Supramolecular Chemistry, Molecular Tectonics, Gel, Nanoporous Materials, Crystals, Kinesin, Myosin, Dynein
  • Inter-Graduate School Classes(General Subject):Natural and Applied Sciences
    開講年度 : 2018
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : Molecular Machine, Molecular Assembly, Biomolecular Motors, Self-organization, Molecular Networks, Supramolecular Chemistry, Molecular Tectonics, Gel, Nanoporous Materials, Crystals, Kinesin, Myosin, Dynein
  • Materials Chemistry A (Mesoscopic Material Chemistry)
    開講年度 : 2018
    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
  • Advanced Lecture of Physical Chemistry
    開講年度 : 2018
    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
  • Modern Trends in Chemical Sciences and Engineering II
    開講年度 : 2018
    課程区分 : 博士後期課程
    開講学部 : 総合化学院
    キーワード : Molecular Machine, Molecular Assembly, Biomolecular Motors, Self-organization, Molecular Networks, Supramolecular Chemistry, Molecular Tectonics, Gel, Nanoporous Materials, Crystals, Kinesin, Myosin, Dynein
  • Fundamental Physical Chemistry
    開講年度 : 2018
    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、熱力学、エンタルピー、エントロピー、自由エネルギー、化学ポテンシャル

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