Research activity information

• Fatty acids as the main energy source in polyps of the jellyfish (Cnidaria: Aurelia aurita) for survival strategy under overpopulation: insights from compound-specific isotope analysis
  Nayeon Park; Hyuntae Choi; Yuko Takizawa; Yoshito Chikaraishi
  Progress in Earth and Planetary Science, 12, 1, Springer Science and Business Media LLC, 16 Oct. 2025
  Scientific journal, Abstract
  
  Jellyfish exhibit an extraordinary survival strategy in high-density populations that exceed the carrying capacity of ecosystems. It is particularly questionable how jellyfish can thrive in habitats where the concentration of toxic nitrogenous waste (i.e., NH₃) in the ambient water could be extremely high caused by high-density populations. However, physiological mechanisms of the survival strategy in jellyfish remain poorly understood, especially at the polyp stage, even though this stage is a key role in jellyfish population dynamics. In the present study, we investigated the trophic isotopic discrimination of amino acids and fatty acids in polyps of the jellyfish Aurelia aurita in controlled feeding experiments, to understand the metabolic flux of these organic substrates in the jellyfish physiology under high-density populations. Contrary to the general trophic isotopic discrimination observed in non-gelatinous organisms, the discrimination in the A. aurita polyps is close to zero for most amino acids (except for glycine and leucine), indicating a little activity of both biosynthesis and degradation of the amino acids. In contrast, the discrimination in the A. aurita polyps is considerably large for fatty acids (ranging from 18.4‰ (for C_18:0) to 50.5‰ (for C_18:2, n-6), indicating a large activity of degradation of fats (and its components, fatty acids). Based on these results, we conclude that A. aurita polyps prioritize the use of fatty acids compared to that of amino acids to produce life energy, for minimizing the production of nitrogenous waste derived from the amino acid degradation (about 0.0 mg/L for NH₃) and maintaining the quality of ambient water, and therefore for allowing them to survive in high-density populations. Moreover, these findings suggest the presence of metabolic plasticity among marine organisms. This plasticity may reflect flexible survival strategies supported by different metabolic pathways. Therefore, integrating the trophic isotopic discrimination of both amino acids and fatty acids can be useful for understanding these physiological mechanisms, as well as for accurately illustrating energy transfer along food chains in ecosystems.
  
  Graphical Abstract
• Fractionation of nitrogen isotopes in the enzymatic deamination of alanine: an insight into the quantitative evaluation of anaerobic metabolism in ecosystems
  Yuko Takizawa; Hyuntae Choi; Mio Shibuya; Nayeon Park; Prarthana S. Dharampal; Shawn A. Steffan; Yoshito Chikaraishi
  Progress in Earth and Planetary Science, 12, 1, Springer Science and Business Media LLC, 30 Sep. 2025
  Scientific journal, Abstract
  
  Nitrogen isotope ratios of amino acids have been employed as a tool for illustrating the resource utilization of organisms and the trophic transfer between organisms in food webs. This tool is proposed based on the empirical observation that a universal trophic enrichment in ¹⁵N is found in glutamic acid from diet to consumer species. Since glutamic acid is deaminated and incorporated into the tricarboxylic acid cycle (aerobic metabolism), the isotope ratios of glutamic acid have been used for evaluating life energy production through aerobic metabolism. However, little is known about the change in the isotope ratio associated with ‘anaerobic’ metabolism such as fermentation in organisms. Therefore, we determined the isotopic fractionation factor (α) for the deamination of alanine, a representative amino acid related to anaerobic metabolism, and conducted laboratory-cultured experiments to see the change in the nitrogen isotope ratio through anaerobic metabolism. Moreover, we compared the trophic enrichment in ¹⁵N between alanine and glutamic acid in natural samples to visualize the contribution of anaerobic metabolism in food webs. In the in vitro enzymatic deamination of alanine, the isotope ratios of alanine are gradually increased, with the α of 0.9923. In the culture of the eukaryote Saccharomyces cerevisiae and the bacterium Lactococcus lactis with organic substrates under hypoxic conditions, the enrichment in ¹⁵N is negligibly small for glutamic acid (by ~ 0‰), but considerably large for alanine (by ~ 5‰) in the culture. These results demonstrate that the activity of anaerobic metabolism is recorded in the isotope ratios of alanine but not glutamic acid in organisms. Moreover, we visualize the contribution of anaerobic metabolism in natural samples: (1) hypoxia within pollen provision for the diet of bee larvae induces a large enrichment in ¹⁵N of alanine; and (2) this ‘anaerobic’ enrichment in ¹⁵N can be identified in the cross-plot of the isotope ratios for alanine and glutamic acid in marine and terrestrial species, dissolved organic nitrogen, and the bees that potentially record of hypoxia within their diets. Thus, we suggest that the comparison of the isotope ratios between alanine and glutamic acid can be useful for evaluating the experience of hypoxia and the activity of anaerobic metabolism in biological and environmental samples.
• A compound-specific method for measuring the stable carbon isotopic composition of amino acids: elimination of the effect of isotopic fractionation during derivatization
  Yoshito Chikaraishi; Hyuntae Choi; Nayeon Park; Yuko Takizawa
  Progress in Earth and Planetary Science, 12, 1, Springer Science and Business Media LLC, 30 Sep. 2025
  Scientific journal, Abstract
  
  Compound-specific isotope analysis (CSIA) of carbon and nitrogen within amino acids by gas chromatography/isotope ratio mass spectrometry (GC/IRMS) has been employed as a powerful tool for estimating the trophic tendency and resource utilization of organisms in food webs, as well as for illustrating the metabolic fate of amino acids and associated energy flux in diverse levels from within a single organism to entire ecosystems. However, the polar functional groups (i.e., carboxyl, amino, and hydroxyl groups) of amino acids should be neutralized by derivatization (i.e., esterification followed by acylation) before injection into a GC/IRMS instrument, which has caused several serious issues. For instance, the toxicity of acylation reagents (e.g., pivaloyl chloride) and the fluorinated derivatives (e.g., derived from trifluoroacetic anhydride) have complicated the use of isotope ratio analysis of amino acids in our studies. Moreover, large isotopic fractionation in ¹³C/¹²C associated with the acylation has considerably reduced the accuracy of the analysis of carbon isotope ratios. In the present study, we therefore developed a new derivatization method to minimize these issues, which can reduce the isotopic fractionation in ¹³C/¹²C by following two sequential reactions for the acylation: the first is acylation, which introduces isotopic fractionation, and the second is replacement of the pivaloyl group with that of pivalic anhydride. Further, the contribution of the ¹³C/¹²C ratios of derivative groups (i.e., isopropyl and pivaloyl groups) can be completely removed by a simultaneous mass balance calculation. Also, the new method is relatively safe, without the use of toxic reagents and the production of fluorinated derivatives. Thus, this derivatization method can be useful for CSIA of amino acids in diverse studies, which promises to provide unprecedented accuracy in understanding the complex physiological, ecological, and geochemical dynamics across aquatic and terrestrial ecosystems.
• Highly effective energy transfer in the autotroph-heterotroph symbiosis: insights from compound-specific isotope analysis of amino acids
  Jincen Li; Mio Shibuya; Yuko Takizawa; Yoshito Chikaraishi
  PROGRESS IN EARTH AND PLANETARY SCIENCE, 12, 1, 10 Feb. 2025
  English, Scientific journal
• A large elevation in ¹⁵N/¹⁴N of collagenous amino acids: an insight from starvation experiments of marine organisms
  Hyuntae Choi; Yuko Takizawa; Nayeon Park; Yoshito Chikaraishi
  PROGRESS IN EARTH AND PLANETARY SCIENCE, 12, 1, 05 Feb. 2025
  English, Scientific journal
• Stable isotope analysis-1: MassWorks on conventional gas chromatograph-mass spectrometer
  力石嘉人; 滝沢侑子; 布浦拓郎
  低温科学, 79, 2021
• Stable isotope analysis-1: gas chromatograph-isotope ratio mass spectrometer
  滝沢侑子; 力石嘉人
  低温科学, 79, 2021
• A new insight into isotopic fractionation associated with decarboxylation in organisms: implications for amino acid isotope approaches in biogeoscience
  Yuko Takizawa; Yoshinori Takano; Bohyung Choi; Prarthana S. Dharampal; Shawn A. Steffan; Nanako O. Ogawa; Naohiko Ohkouchi; Yoshito Chikaraishi
  Progress in Earth and Planetary Science, 7, 1, Springer Science and Business Media LLC, Dec. 2020, [Peer-reviewed]
  Scientific journal,
  Stable nitrogen (¹⁵N/¹⁴N) and carbon (¹³C/¹²C) isotopic compositions of amino acids in organisms have widely been employed as a powerful tool to evaluate resource utilization and trophic connection among organisms in diverse ecosystems. However, little is known about the physiological factors or mechanisms responsible for determining the isotopic discrimination (particularly for carbon) within amino acids of organisms. In the present study, we investigated the inter-trophic discrimination of nitrogen and carbon isotopes within amino acids (Δδ¹⁵N_AA and Δδ¹³C_AA, respectively) using four consumer–diet pairs. Each pairing illustrates a metabolic perspective of isotopic fractionation of amino acids. The Δδ¹⁵N_AA values in these combinations reveal a trend consistent with those observed in many other combinations in previous studies. This further validates a standard scenario: the deamination preferentially removes ¹⁴N amino group from diet-derived amino acids, leaving behind the ¹⁵N-enriched amino acids in consumer biomass. The Δδ¹⁵N_AA values thus mirror the activity of amino acid deamination in consumers. In contrast, the trends in the Δδ¹³C_AA value suggest a different metabolic fate for the amino acid carbon isotope. Based on our results, we predict the following scenario: decarboxylation preferentially removes ¹²C α-carbon (i.e., carbonyl-carbon) from pyruvic acid in glycolysis, and from α-ketoglutaric acid in the tricarboxylic acid cycle, leaving behind the ¹³C-enriched both pyruvic and α-ketoglutaric acids. The ¹³C is then transferred to amino acids that are synthesized from the ¹³C-enriched precursor molecules within consumers. The Δδ¹³C_AA values therefore mirror the pathways of de novo amino acid synthesis in consumers. The proposed link between nitrogen and carbon isotopes can refine our knowledge of the potential processes affecting the isotopic fractionation within diet and consumer compartments, as well as environmental samples.
  
  
  
  Graphical abstract
• Trophic hierarchy of coastal marine fish communities viewed via compound-specific isotope analysis of amino acids
  Daochao Xing; Bohyung Choi; Yuko Takizawa; Rong Fan; Satoshi Sugaya; Masashi Tsuchiya; Naohiko Ohkouchi; Yoshito Chikaraishi
  Marine Ecology Progress Series, 652, 137, 144, Inter-Research, 15 Oct. 2020
  English, Scientific journal
• Trophic response to ecological conditions of habitats: Evidence from trophic variability of freshwater fish
  Bohyung Choi; Changhwa Lee; Yuko Takizawa; Yoshito Chikaraishi; Hye-Ji Oh; Kwang-Hyeon Chang; Min-Ho Jang; Hyun-Woo Kim; Kyung-Lak Lee; Kyung-Hoon Shin
  Ecology and Evolution, 10, 14, 7250, 7260, John Wiley and Sons Ltd, 01 Jul. 2020
  English, Scientific journal
• Quantifying niche partitioning and multichannel feeding among tree squirrels
  Jonathan N. Pauli; Philip J. Manlick; Prarthana S. Dharampal; Yuko Takizawa; Yoshito Chikaraishi; Laura J. Niccolai; Jennifer A. Grauer; Kristina L. Black; Mario Garces Restrepo; Paula L. Perrig; Evan C. Wilson; Marie E. Martin; Mauriel Rodriguez Curras; Tiffany A. Bougie; Kimberly L. Thompson; Matthew M. Smith; Shawn A. Steffan
  Food Webs, 21, Elsevier Inc., 01 Dec. 2019
  English, Scientific journal
• Omnivory in Bees: Elevated Trophic Positions among All Major Bee Families.
  Shawn A Steffan; Prarthana S Dharampal; Bryan N Danforth; Hannah R Gaines-Day; Yuko Takizawa; Yoshito Chikaraishi
  The American naturalist, 194, 3, 414, 421, Sep. 2019, [International Magazine]
  English, Scientific journal, As pollen and nectar foragers, bees have long been considered strictly herbivorous. Their pollen provisions, however, are host to abundant microbial communities, which feed on the pollen before and/or while it is consumed by bee larvae. In the process, microbes convert pollen into a complex of plant and microbial components. Since microbes are analogous to metazoan consumers within trophic hierarchies, the pollen-eating microbes are, functionally, herbivores. When bee larvae consume a microbe-rich pollen complex, they ingest proteins from plant and microbial sources and thus should register as omnivores on the trophic "ladder." We tested this hypothesis by examining the isotopic compositions of amino acids extracted from native bees collected in North America over multiple years. We measured bee trophic position across the six major bee families. Our findings indicate that bee trophic identity was consistently and significantly higher than that of strict herbivores, providing the first evidence that omnivory is ubiquitous among bee fauna. Such omnivory suggests that pollen-borne microbes represent an important protein source for larval bees, which introduces new questions as to the link between floral fungicide residues and bee development.
• What is the parasitic nematode Anisakis doing in host fish?
  菅谷智司; 菅谷智司; 滝沢侑子; 力石嘉人; 力石嘉人
  Researches in Organic Geochemistry, 35, 1/2, 2019
• A new analytical method for determination of the nitrogen isotopic composition of methionine: Its application to aquatic ecosystems with mixed resources
  Ishikawa Naoto F; Chikaraishi Yoshito; Takano Yoshinori; Sasaki Yoko; Takizawa Yuko; Tsuchiya Masashi; Tayasu Ichiro; Nagata Toshi; Ohkouchi Naohiko
  LIMNOLOGY AND OCEANOGRAPHY-METHODS, 16, 9, 607, 620, Sep. 2018, [Peer-reviewed]
  Scientific journal
• Change in the δ15N value of plant amino acids on the phenology of leaf flush and senescence
  Takizawa Yuko; Chikaraishi Yoshito
  Researches in Organic Geochemistry, 33, 1, 1, 6, Dec. 2017, [Peer-reviewed]
  English, Scientific journal
• Comparing compound-specific and bulk stable nitrogen isotope trophic discrimination factors across multiple freshwater fish species and diets
  Chelsey M. Blanke; Yoshito Chikaraishi; Yuko Takizawa; Shawn A. Steffan; Prarthana S. Dharampal; M. Jake Vander Zanden
  CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES, 74, 8, 1291, 1297, Aug. 2017, [Peer-reviewed]
  English, Scientific journal
• Intra-trophic isotopic discrimination of N-15/N-14 for amino acids in autotrophs: Implications for nitrogen dynamics in ecological studies
  Yuko Takizawa; Prarthana S. Dharampal; Shawn A. Steffan; Yoshinori Takano; Naohiko Ohkouchi; Yoshito Chikaraishi
  ECOLOGY AND EVOLUTION, 7, 9, 2916, 2924, May 2017, [Peer-reviewed]
  English, Scientific journal
• Are baby sprouts eating the proteins in the mother sweet potato?
  Takizawa Yuko; Chikaraishi Yoshito
  Researches in organic geochemistry, 30, 1, 29, 32, The Japanese Association of Organic Geochemists, Dec. 2014, [Peer-reviewed]
  English, Scientific journal, Sweet potatoes sometimes sprout the purple color of stems with several small leaves in the house pantry. In the present study, we investigated the trophic hierarchy between a mother sweet potato and its baby sprouts grown without any light in a dark house pantry, based on stable nitrogen isotopic composition (δ^<15>N,‰ vs. AIR) of glutamic acid and phenylalanine. The isotope data reveal that glutamic acid has a significant ^<15>N-enrichment (by 6.9‰) from the mother sweet potato to its baby sprout while phenylalanine has a little ^<15>5N-enrichment (by 0.6‰) between them. Interestingly, the isotopic heterogeneity found within the sweet potato is very similar to the isotopic discrimination generally found in the combination between plants and herbivores during grazing food webs (ca. 8.0‰ for glutamic acid and ca. 0.4‰ for phenylalanine). These results suggest that the proteins in the mother sweet potatoes are major resources for not only proteins in their baby sprouts but also growth energy in the sprouting, when they are grown heterotrophically without any light.

• 環境分析化学特論, 2024年, 修士課程, 環境科学
• 大学院共通授業科目（一般科目）：自然科学・応用科学, 2024年, 修士課程, 大学院共通科目
• 生物地球科学特論, 2024年, 修士課程, 環境科学
• 生態系物質循環学特論, 2024年, 修士課程, 環境科学院
• 生態系環境科学特論, 2024年, 修士課程, 環境科学院
• 一般教育演習(ﾌﾚｯｼｭﾏﾝｾﾐﾅｰ), 2024年, 学士課程, 全学教育

• The quantification of isotopic fractionation on N isotopes during anaerobic metabolism
  Grants-in-Aid for Scientific Research
  01 Apr. 2023 - 31 Mar. 2026
  滝沢 侑子
  本研究の目的は，地球生物圏のあらゆる環境で起きている「嫌気代謝に伴う物質・エネルギー循環」を，定量的に評価するための新しい方法論を開発することである。その第一歩として，本研究課題の達成目標は，代謝における「反応量」を見積もることができる「安定同位体比」を用いて，嫌気代謝の基質として知られる代表的なアミノ酸「アラニン」を対象に（i）異化分解に伴う同位体比変化を明らかにする；（ii）レイリーモデルに基づいて同位体分別係（α），および反応量（F）と同位体比変化（Δ）との関係性を求める；そして（iii）環境試料への展開を見据えた萌芽的研究を実施することである。
  当該年度は，（i）（ii）に相当する「アラニンの異化分解に伴う同位体比変化を明らかにする」を達成することを目標に実験をおこなった。具体的には，アラニンを脱アミノ化酵素（アラニン－アミノトランスフェラーゼ）で分解させ，その「反応量（F）と同位体比変化（Δ）の関係性」について調べ，同位体分別係数（α）を明らかにした。また、その内容について国際学会で発表をおこなった。
  実験方法の詳細については，論文に掲載予定のため，ここでは割愛する。
  Japan Society for the Promotion of Science, Grant-in-Aid for Early-Career Scientists, Hokkaido University, 23K13203
• Development of GC-GC-IRMS
  Grants-in-Aid for Scientific Research
  01 Apr. 2020 - 31 Mar. 2024
  力石 嘉人; 古川 善博; 滝沢 侑子
  本研究では，2次元ガスクロマトグラフ-安定同位体比質量分析計（GC-GC-IRMS）を開発する。その目的は，従来の1次元GC-IRMSを用いた測定において，長年の課題であった「GCでの厳格なピーク分離の要求」を抜本的に解決すること，そして，従来法では測定不可能であった多々の試料に関して，有機化合物の安定同位体比測定を可能にすることである。その達成は，生物から環境試料まで，試料中の全ての有機化合物について5W2H（Who, What, When, Where, Why, How, How many）に関する定性・定量的情報を獲得し，地球惑星科学の多様な研究，とくに (i) 生物の生合成・代謝系の機能の研究，(ii) 地球生物圏における有機物・エネルギー循環の研究，(iii) 宇宙空間や初期地球における有機物生成や生命の起源の研究などで，ブレイクスルーをもたらすと期待できる。
  本年度（繰り越し期間を含む）は，購入したGC-GCモジュール」部を，研究代表者の研究室が現有している「GC-IRMS」と接続し，「GC-GC-IRMS」を組み立てた。また，有機化合物の安定同位体比の測定に向けて，(1) 接続部，ガスライン，キャピラリーラインの再設計や再配置，(2) 様々な条件（導入部の圧力・温度等のプログラム，GC部の温度プログラム，キャリアーガスの流速，溶媒の除去とIRMSへの接続のタイミングなど）に関して，様々な検証・最適化を実施した。これらの大部分は，当初，初年度に行う予定であったが，新型コロナウィルスの感染拡大防止措置のため実施が困難であっため，研究費の繰り越しを申請し，期間を延長して行った。
  検証・最適化を行うなかで，「GC-GCモジュールと燃焼炉の間の温度制御の不安定性」が重要な課題であることがわかり，これを翌年の課題とした。
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 20H00185
• Evaluation of lipid degradation by position-specific carbon isotope analysis
  Grants-in-Aid for Scientific Research
  01 Apr. 2020 - 31 Mar. 2023
  滝沢 侑子
  本研究の目的は、生体内または環境中に存在する脂質が、どのように生産され、その後どのように分解されたかを評価する新規手法である「脂肪酸分子内（カルボニル基）安定炭素同位体比解析法」の実用化を達成することである。具体的には、(i)申請者がこれまでに開発した測定機器（ガスクロマトグラフ－同位体比質量分析計：Gas Chromatograph-Isotope Ratio Mass Spectrometerの改良型）の「測定条件の最適化」、および (ii)その測定法で得られた同位体比から、天然試料に含まれる脂質の生産プロセスと分解量を評価するための「方法論（プロキシ）の確立」をおこなうこと、であった。
  2020年度は、所属研究室既存のGCに、カルボニル基由来の炭素を脂肪酸から分離するために必要不可欠な「熱分解炉」を新たに設置することと、同位体比の解析をおこなうためのソフトウェア（IonOS データ解析ソフトウェア Elementar IonOS-IMDP）を導入した。本年度（2021年度）は、測定条件の最適化、および、今後得られると想定される成果を、有効的に公表するための第一歩である「脂質分解において炭素同位体比に同位体分別が観察される」という観測的事実について、論文執筆をおこない、出版することができた（Takizawa and Chikaraishi, 2021, A large fractionation of 13C/12C ratios for palmitate metabolism in plants. Researches in Organic Geochemistry, 37, 67-72）。
  Japan Society for the Promotion of Science, Grant-in-Aid for Early-Career Scientists, Hokkaido University, 20K14590
• Development of a methodology for measuring the energy transfer along food webs on aquatic-terrestrial mixed resources
  Grants-in-Aid for Scientific Research Challenging Research (Exploratory)
  30 Jun. 2017 - 31 Mar. 2019
  Chikaraishi Yoshito; ISHIKAWA Naoto; SUGAYA Satoshi; TAKIZAWA Yuko; SASAKI Yoko; TAKANO Yoshinori; OGAWA Nanako; OHKOUCHI Naohiko; TSUCHIYA Masashi
  In this study, I developed ‘column-coupling method’ for measuring stable isotopic composition of methionine, a very minor but indispensable amino acid, in natural organisms. Moreover, applying this method developed, we established a compound-specific isotope methodology for estimating ‘resource proportion (aquatic X% vs. terrestrial Y%)’ and ‘trophic position’ of organisms in food webs where both phytoplankton and terrestrial-plants are potentially utilized as primary resources for consumer species along food chains.
  The results including the method and methodology were published as a paper in Limnology and oceanography: Methods, in 2018.
  Japan Society for the Promotion of Science, Challenging Research (Exploratory), Hokkaido University, 17K18796
• 物質循環・環境変遷を正確に解析するための脂肪酸の分子内炭素同位体比測定法の開発
  科学研究費助成事業
  22 Apr. 2016 - 31 Mar. 2018
  滝沢 侑子
  「有機化合物の生産（同化）／分解（異化）のバランス」を区別して定量的に評価するための新規手法確立を目的に研究をおこない，本年度は以下の成果を得た。
  １．分子内安定炭素（C）同位体比測定法の開発：熱分解炉の最適温度の検証
  分解を定量的に評価するための新規手法である「脂肪酸のカルボキシル基のCを対象とした分子内安定同位体比測定法」を開発するために，昨年度に引き続きGC-IRMSの改造と，脂肪酸標準試薬を用いての分析条件の検討を実施した。検討の結果，カルボキシル基由来の二酸化炭素のC同位体比を，最も精度良く測定できる熱分解炉の温度は「1100℃」であることがわかった。
  ２．脂質分解における同位体分別プロセスと反応部位の証明
  脂質分解における同位体分別が，どの元素のどの部位に記録されるか？を証明するために，成長時に体内に貯蔵する脂質を分解・利用することで知られる「植物種子」の発芽実験をおこない，パルミチン酸の分子レベル水素・C同位体比を測定した。その結果，発芽前に対して発芽後の試料に13Cの濃縮（+2.9±1.7‰）が検出され，脂質分解過程にCを反応部位とする同位体分別が存在することが示唆された。分別を与えうるプロセスの候補としては，脂質分解（利用）の初期過程である「酵素による貯蔵性脂質の加水分解反応」が考えられ，もしこの仮説が正しければ，その反応が起こる部位は「貯蔵性脂質中の脂肪酸成分のカルボキシル基のC」となる。これを検証するために，上記1で改良を施したGC-IRMSを用いてカルボキシル基のC同位体比を測定した。その結果，発芽後の試料に含まれる脂肪酸成分中のカルボキシル基のCに，顕著に大きい13C濃縮（+63‰の上昇）が検出された。以上のことから，貯蔵性脂質の「酵素による加水分解」が，カルボキシル基のCに大きな同位体分別を与えるKeyプロセスであることが証明された。
  日本学術振興会, 特別研究員奨励費, 北海道大学, 16J01704