Updated on 2021/10/22

写真a

 
TAKI Masayasu
 
Organization
Institute of Transformative Bio-Molecules Designated associate professor
Graduate School
Graduate School of Science
Title
Designated associate professor

Degree 1

  1. 博士(工学) ( 2002.3   大阪大学 ) 

Research Interests 13

  1. 蛍光プローブ

  2. 蛍光イメージング

  3. 生体金属

  4. 機能性分子

  5. 有機合成

  6. 脂質代謝

  7. 超解像イメージング

  8. Super-resolution imaging

  9. Fluorescence Probes

  10. Fluorescence Imaging

  11. Biometals

  12. Functional Molecules

  13. Chemical Biology

Research Areas 10

  1. Nanotechnology/Materials / Chemical biology

  2. Life Science / Bioorganic chemistry

  3. Nanotechnology/Materials / Organic functional materials

  4. Nanotechnology/Materials / Analytical chemistry

  5. Nanotechnology/Materials / Inorganic/coordination chemistry

  6. Life Science / Bioorganic chemistry

  7. Nanotechnology/Materials / Inorganic/coordination chemistry

  8. Nanotechnology/Materials / Organic functional materials

  9. Nanotechnology/Materials / Analytical chemistry

  10. Nanotechnology/Materials / Chemical biology

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Current Research Project and SDGs 2

  1. 蛍光プローブの創製

  2. 生体イメージング

Research History 16

  1. Nagoya University

    2018.10

  2. Nagoya University   Institute of Innovation for Future Society Nano-Life System

    2018.10

  3. 科学技術振興機構   戦略的創造研究推進事業

    2016.10 - 2020.3

  4. Japan Science and Technology Agency

    2016.10 - 2020.3

  5. Nagoya University   Designated associate professor

    2014.2

  6. Nagoya University   Institute of Transformative Bio-Molecules   Designated associate professor

    2014.2

  7. Kyoto University   Assistant Professor

    2012.4 - 2014.2

  8. Kyoto University   Graduate School of Human and Environmental Studies   Assistant Professor

    2012.4 - 2014.1

  9. Kyoto University   Assistant Professor

    2004.4 - 2012.3

  10. Kyoto University

    2004.4 - 2012.3

  11. Osaka City University

    2003.10 - 2004.3

  12. Osaka City University

    2003.9 - 2004.3

  13. ノースウェスタン大学   特別研究員PD

    2002.4 - 2003.9

  14. Northwestern University   日本学術振興会 特別研究員 PD

    2002.4 - 2003.9

  15. Japan Society for Promotion of Science

    1999.4 - 2002.3

  16. Japan Society for Promotion of Science

    1999.4 - 2002.3

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Education 6

  1. Osaka University

    1999.4 - 2002.3

  2. Osaka University   Graduate School of Engineering

    1999.4 - 2002.3

  3. Osaka University

    1997.4 - 1999.3

  4. Osaka University   Graduate School of Engineering   Department of Material and Life Science

    1997.4 - 1999.3

  5. Doshisha University

    1993.4 - 1997.3

  6. Doshisha University

    1993.4 - 1997.3

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Professional Memberships 10

  1. 日本化学会

  2. 生体関連化学部会

  3. ケミカルバイオロジー学会

  4. 錯体化学会

  5. アメリカ化学会

  6. アメリカ化学会

  7. JAPANESE SOCIETY FOR CHEMICAL BIOLOGY

  8. JAPAN SOCIETY OF COORDINATION CHEMISTRY

  9. 生体機能関連部会

  10. THE CHEMICAL SOCIETY OF JAPAN

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Awards 8

  1. NIKON JOICO AWARD 2019 特別賞

    2020.1  

  2. 科学技術振興機構さきがけ1細胞領域 イノベーション賞

    2020.1  

  3. NIKON JOICO AWARD 2019 特別賞

    2020.1  

  4. イノベーション賞

    2020.1   科学技術振興機構 さきがけ1細胞領域  

  5. とやま賞

    2019.5  

  6. 第36回「とやま賞」

    2019.5   富山県ひとづくり財団  

  7. 日本化学会生体機能関連化学 部会講演賞

    2009.9  

  8. 第24回生体機能関連化学シンポジウム 講演賞

    2009.9   生体機能関連化学部会  

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Papers 63

  1. Pro-tumoral behavior of omental adipocyte-derived fibroblasts in tumor microenvironment at the metastatic site of ovarian cancer

    Iyoshi Shohei, Yoshihara Masato, Nakamura Kae, Sugiyama Mai, Koya Yoshihiro, Kitami Kazuhisa, Uno Kaname, Mogi Kazumasa, Tano Sho, Tomita Hiroyuki, Kajiwara Keiji, Taki Masayasu, Yamaguchi Shigehiro, Nawa Akihiro, Kajiyama Hiroaki

    INTERNATIONAL JOURNAL OF CANCER   Vol. 149 ( 11 ) page: 1961 - 1972   2021.12

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  2. A photostable fluorescent marker for the superresolution live imaging of the dynamic structure of the mitochondrial cristae. Reviewed International journal

    Chenguang Wang, Masayasu Taki, Yoshikatsu Sato, Yasushi Tamura, Hideyuki Yaginuma, Yasushi Okada, Shigehiro Yamaguchi

    Proceedings of the National Academy of Sciences of the United States of America   Vol. 116 ( 32 ) page: 15817 - 15822   2019.8

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Proceedings of the National Academy of Sciences  

    Stimulation emission depletion (STED) microscopy enables ultrastructural imaging of organelle dynamics with a high spatiotemporal resolution in living cells. For the visualization of the mitochondrial membrane dynamics in STED microscopy, rationally designed mitochondrial fluorescent markers with enhanced photostability are required. Herein, we report the development of a superphotostable fluorescent labeling reagent with long fluorescence lifetime, whose design is based on a structurally reinforced naphthophosphole fluorophore that is conjugated with an electron-donating diphenylamino group. The combination of long-lived fluorescence and superphotostable features of the fluorophore allowed us to selectively capture the ultrastructures of the mitochondrial cristae with a resolution of ∼60 nm when depleted at 660 nm. This chemical tool provides morphological information of the cristae, which has so far only been observed in fixed cells using electron microscopy. Moreover, this method gives information about the dynamic ultrastructures such as the intermembrane fusion in different mitochondria as well as the intercristae mergence in a single mitochondrion during the apoptosis-like mitochondrial swelling process.

    DOI: 10.1073/pnas.1905924116

    PubMed

  3. A Highly Photostable Near-Infrared Labeling Agent Based on a Phospha-rhodamine for Long-Term and Deep Imaging Reviewed International journal

    Marek Grzybowski, Masayasu Taki, Kieko Senda, Yoshikatsu Sato, Tetsuro Ariyoshi, Yasushi Okada, Ryosuke Kawakami, Takeshi Imamura, Shigehiro Yamaguchi

    Angewandte Chemie International Edition   Vol. 57 ( 32 ) page: 10137 - 10141   2018.8

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Wiley  

    DOI: 10.1002/anie.201804731

    Web of Science

    PubMed

  4. A far-red fluorescent probe based on a phospha-fluorescein scaffold for cytosolic calcium imaging. Reviewed International journal

    Hiroaki Ogasawara, Marek Grzybowski, Riho Hosokawa, Yoshikatsu Sato, Masayasu Taki, Shigehiro Yamaguchi

    Chemical communications (Cambridge, England)   Vol. 54 ( 3 ) page: 299 - 302   2018.1

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Royal Society of Chemistry ({RSC})  

    The far-red emissive fluorescent probe CaPF-1 based on a phospha-fluorescein scaffold enables the detection of cytosolic calcium ions in living cells. The probe can be excited in the red region (λabs = 636 nm) and exhibits a sufficiently high fluorescence turn-on response in the far-red region (λem = 663 nm) upon complexation with calcium ions. The hydrophilic and anionic characteristics of this phospha-fluorescein fluorophore allowed the cytosolic localization of CaPF-1. Moreover, it was possible to visualize histamine-induced calcium oscillation in HeLa cells using CaPF-1.

    DOI: 10.1039/c7cc07344e

    Web of Science

    Scopus

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  5. A Macrocyclic Fluorophore Dimer with Flexible Linkers: Bright Excimer Emission with a Long Fluorescence Lifetime. Reviewed International journal

    Hiroshi Osaki, Chih-Ming Chou, Masayasu Taki, Kai Welke, Daisuke Yokogawa, Stephan Irle, Yoshikatsu Sato, Tetsuya Higashiyama, Shohei Saito, Aiko Fukazawa, Shigehiro Yamaguchi

    Angewandte Chemie (International ed. in English)   Vol. 55 ( 25 ) page: 7131 - 5   2016.6

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Wiley-Blackwell  

    Bright fluorescent molecules with long fluorescence lifetimes are important for the development of lifetime-based fluorescence imaging techniques. Herein, a molecular design is described for simultaneously attaining long fluorescence lifetime (τ) and high brightness (ΦF ×ɛ) in a system that features macrocyclic dimerization of fluorescent π-conjugated skeletons with flexible linkers. An alkylene-linked macrocyclic dimer of bis(thienylethynyl)anthracene was found to show excimer emission with a long fluorescence lifetime (τ≈19 ns) in solution, while maintaining high brightness. A comparison with various relevant derivatives revealed that the macrocyclic structure and the length of the alkylene chains play crucial roles in attaining these properties. In vitro time-gated imaging experiments were conducted as a proof-of-principle for the superiority of this macrocyclic fluorophore relative to the commercial fluorescent dye Alexa Fluor 488.

    DOI: 10.1002/anie.201602239

    Web of Science

    PubMed

  6. A Phosphole Oxide Based Fluorescent Dye with Exceptional Resistance to Photobleaching: A Practical Tool for Continuous Imaging in STED Microscopy. Reviewed International journal

    Chenguang Wang, Aiko Fukazawa, Masayasu Taki, Yoshikatsu Sato, Tetsuya Higashiyama, Shigehiro Yamaguchi

    Angewandte Chemie (International ed. in English)   Vol. 54 ( 50 ) page: 15213 - 7   2015.12

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:WILEY-V C H VERLAG GMBH  

    The development of stimulated emission depletion (STED) microscopy represented a major breakthrough in cellular and molecular biology. However, the intense laser beams required for both excitation and STED usually provoke rapid photobleaching of fluorescent molecular probes, which significantly limits the performance and practical utility of STED microscopy. We herein developed a photoresistant fluorescent dye C-Naphox as a practical tool for STED imaging. With excitation using either a λ=405 or 488 nm laser in protic solvents, C-Naphox exhibited an intense red/orange fluorescence (quantum yield ΦF >0.7) with a large Stokes shift (circa 5900 cm(-1) ). Even after irradiation with a Xe lamp (300 W, λex =460 nm, full width at half maximum (FWHM)=11 nm) for 12 hours, 99.5 % of C-Naphox remained intact. The high photoresistance of C-Naphox allowed repeated STED imaging of HeLa cells. Even after recording 50 STED images, 83 % of the initial fluorescence intensity persisted.

    DOI: 10.1002/anie.201507939

    Web of Science

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  7. A red-emitting ratiometric fluorescent probe based on a benzophosphole P-oxide scaffold for the detection of intracellular sodium ions. Reviewed International journal

    Masayasu Taki, Hiroaki Ogasawara, Hiroshi Osaki, Aiko Fukazawa, Yoshikatsu Sato, Kimi Ogasawara, Tetsuya Higashiyama, Shigehiro Yamaguchi

    Chemical communications (Cambridge, England)   Vol. 51 ( 59 ) page: 11880 - 3   2015.7

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    We disclose the development of a ratiometric fluorescent probe based on a benzophosphole P-oxide and its application for the detection of intracellular Na(+) ions. Excitation by visible light induced red emission from this probe in water, which was subjected to a hypsochromic shift upon complexation with Na(+). Based on this change, a ratiometric analysis enabled us to visualise changes in the Na(+) concentration in living mammalian cells.

    DOI: 10.1039/c5cc03547c

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  8. Asymmetrical distribution of choline phospholipids revealed by click chemistry and freeze-fracture electron microscopy. Reviewed International journal

    Shohei Iyoshi, Jinglei Cheng, Tsuyako Tatematsu, Sho Takatori, Masayasu Taki, Yukio Yamamoto, Adrian Salic, Toyoshi Fujimoto

    ACS chemical biology   Vol. 9 ( 10 ) page: 2217 - 22   2014.10

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER CHEMICAL SOC  

    Choline-containing phospholipids (Cho-PLs) are major components of all cellular membranes. We developed an electron microscopic technique to investigate the poorly understood problem of how Cho-PLs are distributed between membrane leaflets. Our method relies on generating freeze-fracture replicas of cells metabolically labeled with the choline analog, propargylcholine, followed by "click" reaction to conjugate biotin to propargylcholine head groups, and immunodetection of biotin with colloidal gold. Using this method in budding yeast, we found that, surprisingly, the Golgi and plasma membrane display a cytoplasmic leaflet-dominant asymmetry in Cho-PL distribution; in contrast, Cho-PLs are evenly distributed between the exoplasmic and cytoplasmic leaflets of other organelle membranes. In mammalian culture cells, the plasma membrane shows symmetrical Cho-PL distribution between leaflets, suggesting a fundamental difference between yeast and mammals. Our method should be expandable to other classes of lipids and will be useful for deciphering the mechanism responsible for generating lipid asymmetry in biological membranes.

    DOI: 10.1021/cb500558n

    Web of Science

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  9. A mitochondria-targeted turn-on fluorescent probe based on a rhodol platform for the detection of copper(I). Reviewed International journal

    Masayasu Taki, Kazushi Akaoka, Koji Mitsui, Yukio Yamamoto

    Organic & biomolecular chemistry   Vol. 12 ( 27 ) page: 4999 - 5005   2014.7

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:ROYAL SOC CHEMISTRY  

    A new spirocyclized rhodol-based fluorescent probe has been developed for detecting mitochondrial Cu(+). Alkylation of the hydroxy group of a xanthene moiety with a tris(2-pyridylmethyl)amine-based ligand induced the formation of a non-fluorescent spirocyclic structure. The reaction with Cu(+) in the presence of submillimolar concentrations of glutathione at physiological pH resulted in the elimination of the ligand together with an increase in the fluorescence of the rhodol fluorophore. This probe was used to visualize mitochondrial Cu(+) in copper supplemented cells.

    DOI: 10.1039/c4ob00527a

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  10. Kinetic and structural studies on the catalytic role of the aspartic acid residue conserved in copper amine oxidase.

    Chiu YC, Okajima T, Murakawa T, Uchida M, Taki M, Hirota S, Kim M, Yamaguchi H, Kawano Y, Kamiya N, Kuroda S, Hayashi H, Yamamoto Y, Tanizawa K

    Biochemistry   Vol. 45 ( 13 ) page: 4105 - 20   2006.4

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    DOI: 10.1021/bi052464l

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  11. Oxidation mechanism of phenols by dicopper-dioxygen (Cu(2)/O(2)) complexes.

    Osako T, Ohkubo K, Taki M, Tachi Y, Fukuzumi S, Itoh S

    Journal of the American Chemical Society   Vol. 125 ( 36 ) page: 11027 - 33   2003.9

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    DOI: 10.1021/ja029380+

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  12. C-H bond activation of external substrates with a bis(μ-oxo)dicopper(III) complex [2] Reviewed International journal

    M. Taki, S. Itoh, S. Fukuzumi

    Journal of the American Chemical Society   Vol. 123   page: 6203 - 6204   2001.10

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1021/ja015721s

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  13. Active site models for galactose oxidase containing two different phenol groups Reviewed International journal

    M Taki, H Kumei, S Nagatomo, T Kitagawa, S Itoh, S Fukuzumi

    INORGANICA CHIMICA ACTA   Vol. 300   page: 622 - 632   2000.4

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:ELSEVIER SCIENCE SA  

    Model complexes of the active site of galactose oxidase (GAO) have been developed using a new ligand carrying two different phenol groups, N-[(2-hydroxy-3-methylthio-5-tert-butylphenyl)methyl]-N-[(2-hydroxy-3, 5-di-tert-butylphenyl)methyl]-2-(2-pyridyl)ethylamine (L1H(2)). Deprotonated ligand L1(2-) forms a dimeric Cu(II) complex, [Cu(II)(2)(L1(2-))(2)], in the solid state, the structure of which has been determined by X-ray crystallographic analysis. The dimeric Cu(II)-diphenolate complex can be converted into the monomeric complex, [Cu(II)(L1(2-))(X)] (X = py, AcO, and PhCH2OH), in solution by adding exogenous ligands such as pyridine (py), acetate (AcO-), or benzyl alcohol (PhCH2OH). The structure and physicochemical properties (UV-Vis, ESR, redox potential) of [Cu(II)(L1(2-))(X)] have been explored as a model for the resting state of the enzyme. One-electron oxidation of [Cu(II)(L1(2-))(py)] and [Zn(II)(L1(2-))(py)] by (NH4)(2)[Ce-IV(NO3)(6)] (CAN) yielded the corresponding phenoxyl radical/phenolate complexes, Cu(II)(L1(.-)) and Zn(II)(L1(.-)), respectively, which have also been characterized by UV-Vis, resonance Raman, and ESR. The structure, physicochemical properties and reactivities of the diphenolate and phenoxyl radical/phenolate complexes of L1H(2) are compared to those of the corresponding monophenolate and monophenoxyl radical complexes in order to obtain further insight into the role of Tyr 495 in the native enzyme. (C) 2000 Elsevier Science S.A. All rights reserved.

    DOI: 10.1016/S0020-1693(99)00579-4

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  14. Active site models for galactose oxidase and related enzymes Reviewed International journal

    Shinobu Itoh, Masayasu Taki, Shunichi Fukuzumi

    Coordination Chemistry Reviews   Vol. 198 ( 1 ) page: 3 - 20   2000

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier  

    Redox interaction between a transition-metal ion and a redox active amino acid side chain such as the phenol group of tyrosine in several enzymatic systems has been discovered to play a crucial role in biologically important processes. The tyrosyl radical, which directly coordinates to the copper ion center, has recently been found in the active sites of galactose oxidase (GAO) and glyoxal oxidase (GLO). In this article, model studies on the active site of the enzymes are reviewed by summarizing reported information about the physicochemical properties and the redox functions of the Cu(II) and Zn(II) complexes of the phenolate and phenoxyl radical forms of the cofactor models as well as the organic cofactor models themselves. © 2000 Elsevier Science S.A. All rights reserved.

    DOI: 10.1016/S0010-8545(99)00209-X

    Scopus

  15. Aliphatic hydroxylation by a bis(mu-oxo)dicopper(III) complex Reviewed International journal

    S Itoh, M Taki, H Nakao, PL Holland, WB Tolman, L Que, S Fukuzumi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 39 ( 2 ) page: 398 - +   2000

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:WILEY-V C H VERLAG GMBH  

    By using molecular oxygen bis(μ-oxo)dicopper(III) complexes can be produced from Cu1 complexes with ligand L(X) (L(X) = p-substituted N-ethyl- N-[2-(2-pyridyl)ethyl]-2-phenylethylamine; X = OMe, Me, H, Cl, NO2) in which the benzylic position of the ligand is activated and hydroxylated by the Cu2O2 core (see reaction scheme). Detailed characterization of this new C-H bond activation reaction by the bis(μ-oxo)dicopper(III) core reveals important information on the fundamental chemistry underlying copper monooxygenase reactivity.

    DOI: 10.1002/(SICI)1521-3773(20000117)39:2<398::AID-ANIE398>3.0.CO;2-2

    Web of Science

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  16. Fused Thiophene-S,S-dioxide-Based Super-Photostable Fluorescent Marker for Lipid Droplets

    Masayasu Taki, Keiji Kajiwara, Eriko Yamaguchi, Yoshikatsu Sato, Shigehiro Yamaguchi

    ACS Materials Letters   Vol. 3 ( 1 ) page: 42 - 49   2021.1

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:American Chemical Society (ACS)  

    DOI: 10.1021/acsmaterialslett.0c00451

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  17. Late-stage functionalisation of alkyne-modified phospha-xanthene dyes: lysosomal imaging using an off–on–off type of pH probe Reviewed

    Hiroaki Ogasawara, Yoshiki Tanaka, Masayasu Taki, Shigehiro Yamaguchi

    Chemical Science   Vol. 12 ( 22 ) page: 7902 - 7907   2021

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Royal Society of Chemistry (RSC)  

    <p>A series of NIR-emissive phospha-xanthene dyes bearing an ethynyl group are reported. The late-stage functionalisation of the NIR dyes enables creation of multi-functionalised fluorescent probes that can be designed to target organelles of interest.</p>

    DOI: 10.1039/d1sc01705e

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  18. Donor–acceptor–acceptor-type near-infrared fluorophores that contain dithienophosphole oxide and boryl groups: effect of the boryl group on the nonradiative decay Reviewed

    Yoshiaki Sugihara, Naoto Inai, Masayasu Taki, Thomas Baumgartner, Ryosuke Kawakami, Takashi Saitou, Takeshi Imamura, Takeshi Yanai, Shigehiro Yamaguchi

    Chemical Science   Vol. 12 ( 18 ) page: 6333 - 6341   2021

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Royal Society of Chemistry (RSC)  

    <p>Combination of electron-accepting diarylboryl terminal groups and dithienophosphole oxide spacers with electron-donating triarylamine moieties produces donor–acceptor–acceptor type π-systems, which exhibit emissions in the near-infrared region.</p>

    DOI: 10.1039/d1sc00827g

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  19. Covalent Self-Labeling of Tagged Proteins with Chemical Fluorescent Dyes in BY-2 Cells and Arabidopsis Seedlings. Reviewed International journal

    Ryu J Iwatate, Akira Yoshinari, Noriyoshi Yagi, Marek Grzybowski, Hiroaki Ogasawara, Mako Kamiya, Toru Komatsu, Masayasu Taki, Shigehiro Yamaguchi, Wolf B Frommer, Masayoshi Nakamura

    The Plant cell   Vol. 32 ( 10 ) page: 3081 - 3094   2020.10

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Society of Plant Biologists ({ASPB})  

    Synthetic chemical fluorescent dyes promise to be useful for many applications in biology. Covalent, targeted labeling, such as with a SNAP-tag, uses synthetic dyes to label specific proteins in vivo for studying processes such as endocytosis or for imaging via super-resolution microscopy. Despite its potential, such chemical tagging has not been used effectively in plants. A major drawback has been the limited knowledge regarding cell wall and membrane permeability of the available synthetic dyes. Of 31 synthetic dyes tested here, 23 were taken up into BY-2 cells, while eight were not. This creates sets of dyes that can serve to measure endocytosis. Three of the dyes that were able to enter the cells, SNAP-tag ligands of diethylaminocoumarin, tetramethylrhodamine, and silicon-rhodamine 647, were used to SNAP-tag α-tubulin. Successful tagging was verified by live cell imaging and visualization of microtubule arrays in interphase and during mitosis in Arabidopsis (Arabidopsis thaliana) seedlings. Fluorescence activation-coupled protein labeling with DRBG-488 was used to observe PIN-FORMED2 (PIN2) endocytosis and delivery to the vacuole as well as preferential delivery of newly synthesized PIN2 to the actively forming cell plate during mitosis. Together, the data demonstrate that specific self-labeling of proteins can be used effectively in plants to study a wide variety of cellular and biological processes.

    DOI: 10.1105/tpc.20.00439

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  20. Phosphole-Oxide-Based Fluorescent Probe for Super-resolution Stimulated Emission Depletion Live Imaging of the Lysosome Membrane Reviewed

    Chenguang Wang, Masayasu Taki, Keiji Kajiwara, Junwei Wang, Shigehiro Yamaguchi

    ACS Materials Letters   Vol. 2 ( 7 ) page: 705 - 711   2020.7

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:American Chemical Society ({ACS})  

    DOI: 10.1021/acsmaterialslett.0c00147

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  21. Effects of Amino Group Substitution on the Photophysical Properties and Stability of Near‐Infrared Fluorescent P‐Rhodamines Reviewed

    Marek Grzybowski, Masayasu Taki, Keiji Kajiwara, Shigehiro Yamaguchi

    Chemistry – A European Journal   Vol. 26 ( 35 ) page: 7912 - 7917   2020.6

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Wiley  

    DOI: 10.1002/chem.202000957

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    Other Link: https://onlinelibrary.wiley.com/doi/full-xml/10.1002/chem.202000957

  22. The Effect of Branching on the One‐ and Two‐Photon Absorption, Cell Viability, and Localization of Cationic Triarylborane Chromophores with Dipolar versus Octupolar Charge Distributions for Cellular Imaging Reviewed

    Stefanie Griesbeck, Evripidis Michail, Florian Rauch, Hiroaki Ogasawara, Chenguang Wang, Yoshikatsu Sato, Robert M. Edkins, Zuolun Zhang, Masayasu Taki, Christoph Lambert, Shigehiro Yamaguchi, Todd B. Marder

    Chemistry – A European Journal   Vol. 25 ( 57 ) page: 13164 - 13175   2019.10

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Wiley  

    DOI: 10.1002/chem.201902461

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    Other Link: https://onlinelibrary.wiley.com/doi/full-xml/10.1002/chem.201902461

  23. Optimization of Aqueous Stability versus π‐Conjugation in Tetracationic Bis(triarylborane) Chromophores: Applications in Live‐Cell Fluorescence Imaging Reviewed

    Stefanie Griesbeck, Matthias Ferger, Corinna Czernetzi, Chenguang Wang, Rüdiger Bertermann, Alexandra Friedrich, Martin Haehnel, Daniel Sieh, Masayasu Taki, Shigehiro Yamaguchi, Todd B. Marder

    Chemistry – A European Journal   Vol. 25 ( 32 ) page: 7679 - 7688   2019.6

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Wiley  

    DOI: 10.1002/chem.201900723

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    Other Link: https://onlinelibrary.wiley.com/doi/full-xml/10.1002/chem.201900723

  24. Tuning the π-bridge of quadrupolar triarylborane chromophores for one- and two-photon excited fluorescence imaging of lysosomes in live cells. Reviewed International journal

    Stefanie Griesbeck, Evripidis Michail, Chenguang Wang, Hiroaki Ogasawara, Sabine Lorenzen, Lukas Gerstner, Theresa Zang, Jörn Nitsch, Yoshikatsu Sato, Rüdiger Bertermann, Masayasu Taki, Christoph Lambert, Shigehiro Yamaguchi, Todd B Marder

    Chemical science   Vol. 10 ( 20 ) page: 5405 - 5422   2019.5

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    A series of tetracationic quadrupolar chromophores containing three-coordinate boron π-acceptors linked by different π-bridges, namely 4,4'-biphenyl, 2,7-pyrene, 2,7-fluorene, 3,6-carbazole and 5,5'-di(thien-2-yl)-3,6-diketopyrrolopyrrole, were synthesized. While their neutral precursors 1-5 displayed highly solvatochromic fluorescence, the water-soluble tetracationic target molecules 1M-5M, did not, but their emission colour could be tuned from blue to pink by changing the π-bridge. Compound 5M, containing the diketopyrrolopyrrole bridge, exhibits the most red-shifted absorption and emission maxima and the largest two-photon absorption cross-section (4560 GM at 740 nm in MeCN). Confocal laser scanning fluorescence microscopy studies in live cells confirm localization of the dye at the lysosome. Moreover, the low cytotoxicity, and high photostability of 5M combined with two-photon excited fluorescence imaging studies demonstrate its excellent potential for lysosomal imaging in live cells.

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  25. A far-red emitting fluorescent probe for cytosolic Ca2+ion based on phospha-fluorescein scaffold

    Ogasawara Hiroaki, Taki Masayasu, Sato Yoshikatsu, Yamaguchi Shigehiro

    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY   Vol. 255   2018.3

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  26. Phosphole P-Oxide-Containing pi-Electron Materials: Synthesis and Applications in Fluorescence Imaging

    Yamaguchi Shigehiro, Fukazawa Aiko, Taki Masayasu

    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN   Vol. 75 ( 11 ) page: 1179 - 1187   2017.11

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  27. Selective Conversion of P=O-Bridged Rhodamines into P=O-Rhodols: Solvatochromic Near-Infrared Fluorophores. Reviewed International journal

    Marek Grzybowski, Masayasu Taki, Shigehiro Yamaguchi

    Chemistry (Weinheim an der Bergstrasse, Germany)   Vol. 23 ( 53 ) page: 13028 - 13032   2017.9

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    The substitution of an oxygen atom in rhodols with a phosphine oxide (P=O) moiety affords P=O-bridged rhodols as a new type of near-infrared (NIR) fluorophore. This compound class can be readily accessed upon exposure of the corresponding rhodamines to aqueous basic conditions. The electron-withdrawing effect of the P=O group facilitates the hydrolytic deamination, and, moreover, prolonged exposure to aqueous basic conditions generates P=O-bridged fluoresceins, that is, a series of three P=O-bridged xanthene dyes is available in one simple operation. The P=O-bridged rhodols show significant bathochromic shifts of the longest-wavelength absorption maximum (Δλ=125 nm; >3600 cm-1 ) upon changing the solvent from toluene to water, whereas the emission is shifted less drastically (Δλ=70 nm; 1600 cm-1 ). The hydrogen bonding between the P=O and C=O groups with protic solvents results in substantial stabilization of the LUMO level, which is responsible for the solvatochromism.

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  28. Super-Photostable Phosphole-Based Dye for Multiple-Acquisition Stimulated Emission Depletion Imaging. Reviewed International journal

    Chenguang Wang, Masayasu Taki, Yoshikatsu Sato, Aiko Fukazawa, Tetsuya Higashiyama, Shigehiro Yamaguchi

    Journal of the American Chemical Society   Vol. 139 ( 30 ) page: 10374 - 10381   2017.8

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    As stimulated emission depletion (STED) microscopy can provide structural details of cells with an optical resolution beyond the diffraction limit, it has become an indispensable tool in cell biology. However, the intense STED laser beam usually causes rapid photobleaching of the employed fluorescent dyes, which significantly limits the utility of STED microscopy from a practical perspective. Herein we report a new design of super-photostable dye, PhoxBright 430 (PB430), comprising a fully ring-fused π-conjugated skeleton with an electron-accepting phosphole P-oxide unit. We previously developed a super-photostable dye C-Naphox by combining the phosphole unit with an electron-donating triphenylamine moiety. In PB430, removal of the amino group alters the transition type from intramolecular charge transfer character to π-π* transition character, which gives rise to intense fluorescence insensitive to molecular environment in terms of fluorescence colors and intensity, and bright fluorescence even in aqueous media. PB430 also furnishes high solubility in water, and is capable of labeling proteins with maintaining high fluorescence quantum yields. This dye exhibits outstanding resistance to photoirradiation even under the STED conditions and allows continuous acquisition of STED images. Indeed, using a PB430-conjugated antibody, we succeed in attaining a 3-D reconstruction of super-resolution STED images as well as photostability-based multicolor STED imaging of fluorescently labeled cytoskeletal structures.

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  29. Water-Soluble N-Heterocyclic Carbene-Protected Gold Nanoparticles: Size-Controlled Synthesis, Stability, and Optical Properties. Reviewed International journal

    Kirsi Salorinne, Renee W Y Man, Chien-Hung Li, Masayasu Taki, Masakazu Nambo, Cathleen M Crudden

    Angewandte Chemie (International ed. in English)   Vol. 56 ( 22 ) page: 6198 - 6202   2017.5

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    NHC-AuI complexes were used to prepare stable, water-soluble, NHC-protected gold nanoparticles. The water-soluble, charged nature of the nanoparticles permitted analysis by polyacrylamide gel electrophoresis (PAGE), which showed that the nanoparticles were highly monodisperse, with tunable core diameters between 2.0 and 3.3 nm depending on the synthesis conditions. Temporal, thermal, and chemical stability of the nanoparticles were determined to be high. Treatment with thiols caused etching of the particles after 24 h; however larger plasmonic particles showed greater resistance to thiol treatment. These water-soluble, bio-compatible nanoparticles are promising candidates for use in photoacoustic imaging, with even the smallest nanoparticles giving reliable photoacoustic signals.

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  30. Color-tunable fluorescent nanoparticles encapsulating trialkylsilyl-substituted pyrene liquids Reviewed

    Masayasu Taki, Saki Azeyanagi, Kenzo Hayashi, Shigehiro Yamaguchi

    Journal of Materials Chemistry C   Vol. 5 ( 8 ) page: 2142 - 2148   2017

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    <p>Fluorescent nanoparticles are prepared with fluid trialkylsilylpyrenes, which exhibit intense excimer emission and spontaneously absorb dopant dyes, enabling extensive color tuning without premixing.</p>

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  31. Phospha-fluorescein: a red-emissive fluorescein analogue with high photobleaching resistance. Reviewed International journal

    Aiko Fukazawa, Shinji Suda, Masayasu Taki, Eriko Yamaguchi, Marek Grzybowski, Yoshikatsu Sato, Tetsuya Higashiyama, Shigehiro Yamaguchi

    Chemical communications (Cambridge, England)   Vol. 52 ( 6 ) page: 1120 - 3   2016.1

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    Phospha-fluorescein (POF), a phosphine oxide-containing analogue of fluorescein, was synthesized and its photophysical properties were examined. Compared with fluorescein and sila-fluorescein, POF displayed significantly red-shifted absorption and fluorescence as well as superior photobleaching resistance, while retaining the pH-responsive characteristics of fluorescein dyes.

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  32. Environment-sensitive fluorescent probe: a benzophosphole oxide with an electron-donating substituent. Reviewed International journal

    Eriko Yamaguchi, Chenguang Wang, Aiko Fukazawa, Masayasu Taki, Yoshikatsu Sato, Taeko Sasaki, Minako Ueda, Narie Sasaki, Tetsuya Higashiyama, Shigehiro Yamaguchi

    Angewandte Chemie (International ed. in English)   Vol. 54 ( 15 ) page: 4539 - 43   2015.4

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    Electron-donating aryl groups were attached to electron-accepting benzophosphole skeletons. Among several derivatives thus prepared, one benzophosphole oxide was particularly interesting, as it retained high fluorescence quantum yields even in polar and protic solvents. This phosphole-based compound exhibited a drastic color change of its fluorescence spectrum as a function of the solvent polarity, while the absorption spectra remained virtually unchanged. Capitalizing on these features, this phosphole-based compound was used to stain adipocytes, in which the polarity of subcellular compartments could then be discriminated on the basis of the color change of the fluorescence emission.

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  33. Rosamine-based fluorescent sensor with femtomolar affinity for the reversible detection of a mercury ion. Reviewed International journal

    Masayasu Taki, Kazushi Akaoka, Shohei Iyoshi, Yukio Yamamoto

    Inorganic chemistry   Vol. 51 ( 24 ) page: 13075 - 7   2012.12

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    A Hg(2+)-selective fluorescent sensor, RosHg, has been developed based on a rosamine platform. RosHg exhibited a ∼20-fold increase in fluorescence emission upon binding with Hg(2+), and the enhanced fluorescence was immediately decreased when glutathione was added to a solution of the Hg-RosHg complex. The dissociation constant for the Hg(2+) complex was determined to be 0.10 fM by using a set of Hg(2+)/Mg(2+)/ethylenediaminetetraacetic acid buffer solutions. Confocal microscopy experiments demonstrated that this sensor can monitor changes of the Hg(2+) level in the mitochondria of living cells.

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  34. Development of a dual functional luminescent sensor for zinc ion based on a peptidic architecture. Reviewed International journal

    Tasuku Hirayama, Masayasu Taki, Kazushi Akaoka, Yukio Yamamoto

    Bioorganic & medicinal chemistry letters   Vol. 22 ( 24 ) page: 7410 - 3   2012.12

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    A synthetic peptide bearing a lanthanide complex, TbOTZ exhibits a decrease of chromophore fluorescence and a concomitant luminescence enhancement due to sensitized Tb(3+) upon Zn(2+) binding. Thus, TbOTZ can be a valuable tool for ratiometric sensing of Zn(2+) as well as for time-resolved fluorescence detection with a single molecule.

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  35. Structural insights into the substrate specificity of bacterial copper amine oxidase obtained by using irreversible inhibitors. Reviewed International journal

    Takeshi Murakawa, Hideyuki Hayashi, Masayasu Taki, Yukio Yamamoto, Yoshiaki Kawano, Katsuyuki Tanizawa, Toshihide Okajima

    Journal of biochemistry   Vol. 151 ( 2 ) page: 167 - 78   2012.2

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    Copper amine oxidases (CAOs) catalyse the oxidation of various aliphatic amines to the corresponding aldehydes, ammonia and hydrogen peroxide. Although CAOs from various organisms share a highly conserved active-site structure including a protein-derived cofactor, topa quinone (TPQ), their substrate specificities differ considerably. To obtain structural insights into the substrate specificity of a CAO from Arthrobacter globiformis (AGAO), we have determined the X-ray crystal structures of AGAO complexed with irreversible inhibitors that form covalent adducts with TPQ. Three hydrazine derivatives, benzylhydrazine (BHZ), 4-hydroxybenzylhydrazine (4-OH-BHZ) and phenylhydrazine (PHZ) formed predominantly a hydrazone adduct, which is structurally analogous to the substrate Schiff base of TPQ formed during the catalytic reaction. With BHZ and 4-OH-BHZ, but not with PHZ, the inhibitor aromatic ring is bound to a hydrophobic cavity near the active site in a well-defined conformation. Furthermore, the hydrogen atom on the hydrazone nitrogen is located closer to the catalytic base in the BHZ and 4-OH-BHZ adducts than in the PHZ adduct. These results correlate well with the reactivity of 2-phenylethylamine and tyramine as preferred substrates for AGAO and also explain why benzylamine is a poor substrate with markedly decreased rate constants for the steps of proton abstraction and the following hydrolysis.

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  36. Development of a cholesterol-conjugated fluorescent sensor for site-specific detection of zinc ion at the plasma membrane. Reviewed International journal

    Shohei Iyoshi, Masayasu Taki, Yukio Yamamoto

    Organic letters   Vol. 13 ( 17 ) page: 4558 - 61   2011.9

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    A cholesterol-conjugated fluorescence Zn(2+) sensor based on the fluorescein platform was designed and synthesized. The cholesterol moiety is essential for localizing the Zn(2+) sensor to the cell membrane, allowing the sensor to probe changes in the Zn(2+) concentration in a localized area of the cell.

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  37. Electron microscopic visualization of the filament binding mode of actin-binding proteins. Reviewed International journal

    Takuto Ito, Tasuku Hirayama, Masayasu Taki, Shohei Iyoshi, Shuheng Dai, Shuichi Takeda, Chieko Kimura-Sakiyama, Toshiro Oda, Yukio Yamamoto, Yuichiro Maéda, Akihiro Narita

    Journal of molecular biology   Vol. 408 ( 1 ) page: 26 - 39   2011.4

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    A large number of actin-binding proteins (ABPs) regulate various kinds of cellular events in which the superstructure of the actin cytoskeleton is dynamically changed. Thus, to understand the actin dynamics in the cell, the mechanisms of actin regulation by ABPs must be elucidated. Moreover, it is particularly important to identify the side, barbed-end or pointed-end ABP binding sites on the actin filament. However, a simple, reliable method to determine the ABP binding sites on the actin filament is missing. Here, a novel electron microscopic method for determining the ABP binding sites is presented. This approach uses a gold nanoparticle that recognizes a histidine tag on an ABP and an image analysis procedure that can determine the polarity of the actin filament. This method will facilitate future study of ABPs.

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  38. Human spire interacts with the barbed end of the actin filament. Reviewed International journal

    Takuto Ito, Akihiro Narita, Tasuku Hirayama, Masayasu Taki, Shohei Iyoshi, Yukio Yamamoto, Yuichiro Maéda, Toshiro Oda

    Journal of molecular biology   Vol. 408 ( 1 ) page: 18 - 25   2011.4

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    Spire is an actin nucleator that initiates actin polymerization at a specific place in the cell. Similar to the Arp2/3 complex, spire was initially considered to bind to the pointed end of the actin filament when it generates a new actin filament. Subsequently, spire was reported to be associated with the barbed end (B-end); thus, there is still no consensus regarding the end with which spire interacts. Here, we report direct evidence that spire binds to the B-end of the actin filament, under conditions where spire accelerates actin polymerization. Using electron microscopy, we visualized the location of spire bound to the filament by gold nanoparticle labeling of the histidine-tagged spire, and the polarity of the actin filament was determined by image analysis. In addition, our results suggest that multiple spires, linked through one gold nanoparticle, enhance the acceleration of actin polymerization. The B-end binding of spire provides the basis for understanding its functional mechanism in the cell.

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  39. Design and synthesis of fluorescent probe for polyhistidine tag using macrocyclic nickel(II) complex and fluorescein conjugate Reviewed

    Taki, M., Asahi, F., Hirayama, T., Yamamoto, Y.

    Bulletin of the Chemical Society of Japan   Vol. 84 ( 4 ) page: 386 - 394   2011

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    We report a newly designed polyhistidine tag (His-tag) targeting fluorescent probe, NiL degrees DCF, which we synthesized based on the fluorophore displacement mechanism. A macrocyclic nickel(II) complex (NiL degrees) was employed as a novel binding site for a His-tag motif, and we chose dichlorofluorescein (DCF) (=2',7'-dichloro-3',6'-dihydroxyspiro[iso-benzofuran-1(3H),9'-(9H)xanthen]-3-one) as the fluorophore. A hypochromic shift of NiL degrees DCF from the metal-unbound form (L degrees DCF) in the absorption spectrum suggested that the phenolic oxygen atom of DCF interacted directly with the NiL complex, resulting in efficient fluorescence quenching (Phi = 0.084) in a neutral aqueous solution. When a model peptide having a hexahistidine sequence (H6Y1: YHHHHHH) was added to the solution of NiL degrees DCF, a significant fluorescence enhancement in the emission (Phi = 0.60) was observed. The stoichiometry of the ternary complex between NiL degrees DCF and H6YI was 1:1. The fluorescence intensity increased as the concentration of H6Y1 increased, and the dissociation constant (K-d) was determined to be 24 +/- 1 mu M, consistent with that for the Ni-NTA complex and His(6)-fused proteins (K-d = 1-20 mu M). These results indicate that macrocyclic NiL degrees can serve as a novel binding site for the polyhistidine sequence and that NiL degrees DCF would be applicable to a switchable fluorescent probe for such His-tagged proteins.

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  40. Development of highly sensitive fluorescent probes for detection of intracellular copper(I) in living systems. International journal

    Masayasu Taki, Shohei Iyoshi, Akio Ojida, Itaru Hamachi, Yukio Yamamoto

    Journal of the American Chemical Society   Vol. 132 ( 17 ) page: 5938 - 9   2010.5

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    We describe here the new copper-selective fluorescent probes FluTPA1 and FluTPA2, in which the tetradentate ligand tris[(2-pyridyl)methyl]amine (TPA) is connected to a reduced form of a fluorescein platform through a benzyl ether linkage. These probes selectively react with copper ions in the presence of submillimolar glutathione and emit intense green fluorescence from the reaction product, O-methylfluorescein. Confocal images of live cells further show that FluTPA2 is membrane-permeable and allows visualization of Cu(I) present in living cells.

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  41. Selective labeling of tag-fused protein by tryptophan-sensitized luminescence of a terbium complex. Reviewed International journal

    Tasuku Hirayama, Masayasu Taki, Atsushi Kodan, Hiroaki Kato, Yukio Yamamoto

    Chemical communications (Cambridge, England)   ( 22 ) page: 3196 - 8   2009.6

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    A Tb3+ complex with two di(2-picolyl)amine (DPA) moieties and an oligo-aspartate peptide containing a tryptophan residue have been designed as a new binding pair for use in protein labeling.

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  42. Development of ratiometric fluorescent probe for zinc ion based on indole fluorophore Reviewed

    Taki, M., Watanabe, Y., Yamamoto, Y.

    Tetrahedron Letters   Vol. 50 ( 12 ) page: 1345 - 1347   2009

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    A water-soluble ratiometric fluorescent probe ZID-1 has been developed on the basis of an internal charge transfer (ICT) mechanism. Upon complexation with Zn2+ under physiological conditions, ZID-1 exhibits a significant blue shift of 77 nm in the emission spectrum. The fluorescent behavior of ZID-1 suggests that the pyridyl group incorporated into the fluorophore coordinates the metal ion as the fourth 2 ligand and affords an appropriate binding affinity (K-d = 17.1 nM) for the intracellular imaging of Zn2+. (C) 2009 Elsevier Ltd. All rights reserved.

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  43. Fluorescence imaging of intracellular cadmium using a dual-excitation ratiometric chemosensor. International journal

    Masayasu Taki, Mika Desaki, Akio Ojida, Shohei Iyoshi, Tasuku Hirayama, Itaru Hamachi, Yukio Yamamoto

    Journal of the American Chemical Society   Vol. 130 ( 38 ) page: 12564 - 5   2008.9

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    We described here a coumarin-based dual-excitation ratiometric probe for cadmium, CadMQ. This fluorescence sensor has high quantum yields of 0.59 and 0.70 in the metal-free and Cd2+-bound forms, respectively, and has a dissociation constant of 0.16 nM for Cd2+. CadMQ is cell permeable and locates within the acidic compartments of the cells. We further show that CadMQ is a useful tool to ratiometrically probe the change in the intracellular Cd2+ levels with the use of two excited wavelengths.

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  44. Colorimetric response to mercury-induced abstraction of triethylene glycol ligands from a gold nanoparticle surface. Reviewed International journal

    Tasuku Hirayama, Masayasu Taki, Yukiyasu Kashiwagi, Masami Nakamoto, Atsushi Kunishita, Shinobu Itoh, Yukio Yamamoto

    Dalton transactions (Cambridge, England : 2003)   ( 35 ) page: 4705 - 7   2008.9

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    A simple method for specific colorimetric sensing of aqueous mercury(II) has been developed by using a gold nanoparticle supported by triethylene glycol ligand (Au:S-EG(3)). The unusual kinetic behavior of the sensing process of Hg(2+) and the TEM images of the Au core, as well as the electrospray ionization mass spectroscopic analysis of the analyte solution, have led us to propose a new color changing mechanism that involves ligand abstraction from a gold surface by Hg(2+).

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  45. Further insight into the mechanism of stereoselective proton abstraction by bacterial copper amine oxidase. International journal

    Masayasu Taki, Takeshi Murakawa, Takuya Nakamoto, Mayumi Uchida, Hideyuki Hayashi, Katsuyuki Tanizawa, Yukio Yamamoto, Toshihide Okajima

    Biochemistry   Vol. 47 ( 29 ) page: 7726 - 33   2008.7

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    During the catalytic reaction of copper amine oxidase, one of the two prochiral hydrogen atoms at the C1 position of substrate amine is stereoselectively abstracted by a conserved Asp residue serving as a general base. Using stereospecifically deuterium-labeled enantiomers of 2-phenylethylamine, we previously showed that the pro-S alpha-proton is abstracted by the enzyme from Arthrobacter globiformis (AGAO) [Uchida, M., et al. (2003) Biosci. Biotechnol. Biochem. 67, 2664-2667]. More recently, we have also demonstrated that the pro-S selectivity of alpha-proton abstraction is fully retained even in the reaction of a mutant AGAO lacking the catalytic base [Chiu, Y.-C., et al. (2006) Biochemistry 45, 4105-4120]. On the basis of these findings, we have proposed that the stereoselectivity of alpha-proton abstraction is primarily determined by the conformation of the Schiff base intermediate formed between the substrate and the topa quinone cofactor (TPQ), stabilized by the binding of the distal part of the substrate to a hydrophobic pocket of the enzyme. In this conformation, the pro-S hydrogen atom to be abstracted is nearly perpendicular to the plane of the Schiff base-TPQ conjugate system, achieving the maximum overlap of sigma- and pi-orbitals. To further elucidate the stereochemical details, we have synthesized stereospecifically deuterium-labeled enantiomers of ethylamine, a very poor substrate for AGAO, in addition to those structurally related to the preferred substrate, 2-phenylethylamine. In marked contrast to the nearly complete pro-S selectivity of alpha-proton abstraction for most substrates that have been examined, the stereoselectivity for ethylamine decreased significantly to as little as 88%. The crystal structure of AGAO soaked with ethylamine showed very poor electron densities for the substrate Schiff base intermediate, showing that its conformation is not defined uniquely. Thus, the stereoselectivity of alpha-proton abstraction during the copper amine oxidase reaction is closely associated with the conformational flexibility of the substrate Schiff base intermediate.

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  46. Rosamine-based fluorescent chemosensor for selective detection of silver(I) in an aqueous solution. International journal

    Shohei Iyoshi, Masayasu Taki, Yukio Yamamoto

    Inorganic chemistry   Vol. 47 ( 10 ) page: 3946 - 8   2008.5

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    The synthesis and photophysical properties of a rosamine-based fluorescent chemosensor, RosAg, for detecting Ag ion in an aqueous solution are described. This fluorescent sensor has a negligible quantum yield (<0.005) in the absence of Ag(+), whereas a significant increase in fluorescence is observed upon complexation with Ag(+) under physiological conditions. The crystal structure of the silver complex with the chelator moiety of RosAg reveals a trigonal-planar coordination geometry in which three S atoms occupy the metal center. Although a strong coordinative interaction of Ag-N is not observed in the crystal structure, the (1)H NMR experiments suggest that aniline nitrogen is likely to be associated with the Ag(+) center in the solution state. This may inhibit the photoinduced electron transfer process and result in the enhancement of fluorescence.

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  47. Effects of heteroatom substitution on the structures, physicochemical properties, and redox behavior of nickel(II) complexes with pyridine-containing macrocyclic ligands Reviewed

    Taki, M., Kawashima, Y., Sakai, N., Hirayama, T., Yamamoto, Y.

    Bulletin of the Chemical Society of Japan   Vol. 81 ( 5 ) page: 590 - 597   2008

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    Nickel(II) complexes supported by 14-membered pyridine-containing macrocyclic ligands L-E (E = NH, S, and O), represented as [Ni-II(L-NH)](ClO4)(2) (1a), [Ni-II(L-S)](ClO4)(2) (2a), [Ni-II(L-S)](ClO4)(BPh4) (2b), [Ni-II(L-O)(CH3CN)(2)]-(ClO4)(2) (3a), and [Ni-II(L-O)(CH3CN)(2)](ClO4)(BPh4) (3b), have been synthesized. X-ray crystal structures of complexes la and 2b have square-planar structures in low-spin state, whereas complex 3b exhibits an octahedral high-spin configuration where two solvent molecules occupy the axial positions of the NiN3O1 plane. The absorption spectra of la and 2a in coordinating solvents show interconversion of high-/low-spin states, for which the equilibrium constants and thermodynamic parameters (Delta H-0 and Delta S-0) have been determined. However, in the case of complex 3a in coordinating solvent, the high-spin state dominates at temperatures ranging from -40 to 60 degrees C. Cyclic voltammetry of the complexes la and 2a in CH3CN showed a reversible wave for a Ni-II/Ni-I redox couple. The redox potential for 2a (E-1/2 = -1.20V vs. Ag/AgNO3) is more positive than that for 1a (E-1/2 = -1.48 V). In contrast to these complexes, 3a showed an irreversible redox couple with a significantly large peak separation of 460 mV. This result indicates that the coordination geometries of the nickel complex 3a drastically change between six-coordinate N-II and four-coordinate Ni-I states.

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  48. Synthesis of a new bifunctionalised fluorescent label and physical properties of the bound form on model peptide of troponin C. International journal

    Tasuku Hirayama, Shohei Iyoshi, Masayasu Taki, Yuichiro Maeda, Yukio Yamamoto

    Organic & biomolecular chemistry   Vol. 5 ( 13 ) page: 2040 - 5   2007.7

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    A new bifunctional fluorescent label, BRos, was synthesised in order to monitor protein dynamics using fluorescence microscopy, and the photophysical properties were compared with those of bifunctionalised rhodamine, BRho. In a labelling experiment with a model peptide of troponin C, which regulates muscle contraction and relaxation, it was found that BRos was bound to the peptide through two linkages and provided a homogeneous compound, whereas BRho gave a pair of diastereomers having different physical properties in NMR and HPLC analyses.

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  49. Synthesis of a new water soluble 2,2-bifunctionalized spin label and its application to troponin C

    Tasuku Hirayama, Masayasu Taki, Motoyoshi Nakamura, Toshiaki Arata, Yukio Yamamoto

    CHEMISTRY LETTERS   Vol. 35 ( 8 ) page: 834 - 835   2006.8

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    A new water soluble 2,2-bifunctionalized spin label (2,2E-BSL) having pyrrolidine nitroxide moiety was synthesized starting from a nitro compound with two hydroxymethyl group converted to the linkers of the 2,2E-BSL, and was applied to label troponin C (TnC). Labeled TnC through two linkages were successfully isolated, and 2,2E-BSL was proved to be immobilized on TnC by EPR measurement.

    DOI: 10.1246/cl.2006.834

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  50. Quantum mechanical hydrogen tunneling in bacterial copper amine oxidase reaction. International journal

    Takeshi Murakawa, Toshihide Okajima, Shun'ichi Kuroda, Takuya Nakamoto, Masayasu Taki, Yukio Yamamoto, Hideyuki Hayashi, Katsuyuki Tanizawa

    Biochemical and biophysical research communications   Vol. 342 ( 2 ) page: 414 - 23   2006.4

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    A key step decisively affecting the catalytic efficiency of copper amine oxidase is stereospecific abstraction of substrate alpha-proton by a conserved Asp residue. We analyzed this step by pre-steady-state kinetics using a bacterial enzyme and stereospecifically deuterium-labeled substrates, 2-phenylethylamine and tyramine. A small and temperature-dependent kinetic isotope effect (KIE) was observed with 2-phenylethylamine, whereas a large and temperature-independent KIE was observed with tyramine in the alpha-proton abstraction step, showing that this step is driven by quantum mechanical hydrogen tunneling rather than the classical transition-state mechanism. Furthermore, an Arrhenius-type preexponential factor ratio approaching a transition-state value was obtained in the reaction of a mutant enzyme lacking the critical Asp. These results provide strong evidence for enzyme-enhanced hydrogen tunneling. X-ray crystallographic structures of the reaction intermediates revealed a small difference in the binding mode of distal parts of substrates, which would modulate hydrogen tunneling proceeding through either active or passive dynamics.

    DOI: 10.1016/j.bbrc.2006.01.150

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  51. Kinetic and structural studies on the catalytic role of the aspartic acid residue conserved in copper amine oxidase. International journal

    Yen-Chen Chiu, Toshihide Okajima, Takeshi Murakawa, Mayumi Uchida, Masayasu Taki, Shun Hirota, Misa Kim, Hiroshi Yamaguchi, Yoshiaki Kawano, Nobuo Kamiya, Shun'ichi Kuroda, Hideyuki Hayashi, Yukio Yamamoto, Katsuyuki Tanizawa

    Biochemistry   Vol. 45 ( 13 ) page: 4105 - 20   2006.4

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    Copper amine oxidase contains a post-translationally generated quinone cofactor, topa quinone (TPQ), which mediates electron transfer from the amine substrate to molecular oxygen. The overall catalytic reaction is divided into the former reductive and the latter oxidative half-reactions based on the redox state of TPQ. In the reductive half-reaction, substrate amine reacts with the C5 carbonyl group of the oxidized TPQ, forming the substrate Schiff base (TPQ(ssb)), which is then converted to the product Schiff base (TPQ(psb)). During this step, an invariant Asp residue with an elevated pKa is presumed to serve as a general base accepting the alpha proton of the substrate. When Asp298, the putative active-site base in the recombinant enzyme from Arthrobacter globiformis, was mutated into Ala, the catalytic efficiency dropped to a level of about 10(6) orders of magnitude smaller than the wild-type (WT) enzyme, consistent with the essentiality of Asp298. Global analysis of the slow UV/vis spectral changes observed during the reductive half-reaction of the D298A mutant with 2-phenylethylamine provided apparent rate constants for the formation and decay of TPQ(ssb) (k(obs) = 4.7 and 4.8 x 10(-4) s(-1), respectively), both of which are markedly smaller than those of the WT enzyme determined by rapid-scan stopped-flow analysis (k(obs) = 699 and 411 s(-1), respectively). Thus, Asp298 plays important roles not only in the alpha-proton abstraction from TPQ(ssb) but also in other steps in the reductive half-reaction. X-ray diffraction analyses of D298A crystals soaked with the substrate for 1 h and 1 week revealed the structures of TPQ(ssb) and TPQ(psb), respectively, as pre-assigned by single-crystal microspectrophotometry. Consistent with the stereospecificity of alpha-proton abstraction, the pro-S alpha-proton of TPQ(ssb) to be abstracted is positioned nearly perpendicularly to the plane formed by the Schiff-base imine double bond conjugating with the quinone ring of TPQ, so that the orbitals of sigma and pi electrons maximally overlap in the conjugate system. More intriguingly, the pro-S alpha proton of the substrate is released stereospecifically even in the reaction catalyzed by the base-lacking D298A mutant. On the basis of these results, we propose that the stereospecificity of alpha-proton abstraction is primarily determined by the conformation of TPQ(ssb), rather than the relative geometry of TPQ and the catalytic base.

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  52. Synthesis of C2-chiral bifunctionalised spin labels and their application to troponin C. International journal

    Shunsuke Chatani, Motoyoshi Nakamura, Hidenobu Akahane, Naoki Kohyama, Masayasu Taki, Toshiaki Arata, Yukio Yamamoto

    Chemical communications (Cambridge, England)   ( 14 ) page: 1880 - 2   2005.4

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    An enantiomeric pair of C2-chiral bifunctionalised spin labels having a pyrrolidine nitroxide moiety, whose configurations were determined by X-ray crystal diffraction analysis, was prepared and applied to troponin C whose binding mode of double disulfide linkage was proved by EPR spectroscopy.

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  53. Model complexes of the active site of galactose oxidase. Effects of the metal ion binding sites

    M Taki, H Hattori, T Osako, S Nagatomo, M Shiro, T Kitagawa, S Itoh

    INORGANICA CHIMICA ACTA   Vol. 357 ( 11 ) page: 3369 - 3381   2004.8

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    Model compounds of the active site of galactose oxidase have been developed by using new cofactor model ligands, L1H (2-methylthio-4-tert-butyl-6-[{bis(pyridin-2-ylmethyl)amino}methyl]phenol) and L2H (2-methylthio-4-tert-butyl-6-[{bis(6-methylpyridin-2-ylmethyl)amino)methyl]phenol). Treatment of the ligands with copper(II) and zinc(II) perchlorate in the presence of triethylamine followed by anion exchange reaction with NaPF6 or NaBPh4 provided the corresponding copper(II) and zinc(II) complexes, the crystal structures of which have been determined by X-ray crystallographic analysis. All the copper(II) and zinc(II) complexes have been isolated as a dimeric form in which the phenolate oxygen of each ligand acts as the bridging ligand to form a rhombic M-2(OAr)(2) core (M = Cu or Zn). The dimeric complexes can be converted into the corresponding monomer complexes by the treatment with exogenous ligand such as acetate ion. The redox potential and the spectroscopic features of the monomer complexes have also been examined. Furthermore, the copper(II)- and zinc(II)-complexes of the phenoxyl radical species of the ligands have been generated in situ by the oxidation of the phenolate complexes with (NH4)(2)[Ce-IV(NO3)(6)] (CAN) in CH3CN, and their spectroscopic features have been explored. The structures and physicochemical properties of the phenolate and phenoxyl radical complexes of L1 and L2 have been compared to those of the previously reported copper(II) and zinc(II) complexes of L3 (2-methylthio-4-tert-butyl-6-[{bis(2-pyridin-2-ylethyl)amino}methyl]phenol) in order to get insights into the interaction between the metal ions and the organic cofactor moiety. (C) 2004 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.ica.2004.04.008

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  54. Emission ratiometric imaging of intracellular zinc: design of a benzoxazole fluorescent sensor and its application in two-photon microscopy. International journal

    Masayasu Taki, Janet L Wolford, Thomas V O'Halloran

    Journal of the American Chemical Society   Vol. 126 ( 3 ) page: 712 - 3   2004.1

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    Zinc and calcium are ubiquitous intracellular metals, and while a variety of quantitative probes have been developed for measuring intracellular changes in calcium concentration, the same is not true of zinc. We describe here the design, synthesis, and properties of the benzoxazole-based, ratiometric zinc probe, Zinbo-5. This bright fluorescent reporter has a quantum yield of 0.1 in the zinc-form, exhibits a Kd for Zn2+ in the nanomolar range, and shows significant changes in both excitation and emission maxima upon zinc binding. The utility of this cell permeable probe is demonstrated in fluorescence microscopy emission ratio imaging experiments on mammalian cells. We further show that Zinbo-5 is well suited for two-photon excitation microscopy ratio imaging and can readily reveal changes in intracellular zinc concentration within optical planes of single cells. To the best of our knowledge, this is the first example of two-photon excitation microscopy applied to ratio imaging of zinc. These methods can be applied to real-time emission or excitation ratio imaging studies of zinc physiology in living cells.

    DOI: 10.1021/ja039073j

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  55. Oxidation mechanism of phenols by dicopper-dioxygen (Cu(2)/O(2)) complexes. International journal

    Takao Osako, Kei Ohkubo, Masayasu Taki, Yoshimitsu Tachi, Shunichi Fukuzumi, Shinobu Itoh

    Journal of the American Chemical Society   Vol. 125 ( 36 ) page: 11027 - 33   2003.9

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    The first systematic studies on the oxidation of neutral phenols (ArOH) by the mu-eta(2):eta(2)-peroxo)dicopper(II) complex (A) and the bis(mu-oxo)dicopper(III) complex (B) supported by the 2-(2-pyridyl)ethylamine tridentate and didentate ligands L(Py2) and L(Py1), respectively, have been carried out in order to get insight into the phenolic O-H bond activation mechanism by metal-oxo species. In both cases (A and B), the C-C coupling dimer was obtained as a solely isolable product in approximately 50% yield base on the dicopper-dioxygen (Cu(2)/O(2)) complexes, suggesting that both A and B act as electron-transfer oxidants for the phenol oxidation. The rate-dependence in the oxidation of phenols by the Cu(2)/O(2) complexes on the one-electron oxidation potentials of the phenol substrates as well as the kinetic deuterium isotope effects obtained using ArOD have indicated that the reaction involves a proton-coupled electron transfer (PCET) mechanism. The reactivity of phenols for net hydrogen atom transfer reactions to cumylperoxyl radical (C) has also been investigated to demonstrate that the rate-dependence of the reaction on the one-electron oxidation potentials of the phenols is significantly smaller than that of the reaction with the Cu(2)O(2) complexes, indicative of the direct hydrogen atom transfer mechanism (HAT). Thus, the results unambiguously confirmed that the oxidation of phenols by the Cu(2)O(2) complex proceeds via the PCET mechanism rather than the HAT mechanism involved in the cumylperoxyl radical system. The reactivity difference between A and B has also been discussed by taking account of the existed fast equilibrium between A and B.

    DOI: 10.1021/ja029380

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  56. Fine-tuning of copper(I)-dioxygen reactivity by 2-(2-pyridyl)ethylamine bidentate ligands. International journal

    Masayasu Taki, Shinichi Teramae, Shigenori Nagatomo, Yoshimitsu Tachi, Teizo Kitagawa, Shinobu Itoh, Shunichi Fukuzumi

    Journal of the American Chemical Society   Vol. 124 ( 22 ) page: 6367 - 77   2002.6

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    Copper(I)-dioxygen reactivity has been examined using a series of 2-(2-pyridyl)ethylamine bidentate ligands (R1)Py1(R2,R3). The bidentate ligand with the methyl substituent on the pyridine nucleus (Me)Py1(Et,Bz) (N-benzyl-N-ethyl-2-(6-methylpyridin-2-yl)ethylamine) predominantly provided a (mu-eta(2):eta(2)-peroxo)dicopper(II) complex, while the bidentate ligand without the 6-methyl group (H)Py1(Et,Bz) (N-benzyl-N-ethyl-2-(2-pyridyl)ethylamine) afforded a bis(mu-oxo)dicopper(III) complex under the same experimental conditions. Both Cu(2)O(2) complexes gradually decompose, leading to oxidative N-dealkylation reaction of the benzyl group. Detailed kinetic analysis has revealed that the bis(mu-oxo)dicopper(III) complex is the common reactive intermediate in both cases and that O[bond]O bond homolysis of the peroxo complex is the rate-determining step in the former case with (Me)Py1(Et,Bz). On the other hand, the copper(I) complex supported by the bidentate ligand with the smallest N-alkyl group ((H)Py1(Me,Me), N,N-dimethyl-2-(2-pyridyl)ethylamine) reacts with molecular oxygen in a 3:1 ratio in acetone at a low temperature to give a mixed-valence trinuclear copper(II, II, III) complex with two mu(3)-oxo bridges, the UV-vis spectrum of which is very close to that of an active oxygen intermediate of lacase. Detailed spectroscopic analysis on the oxygenation reaction at different concentrations has indicated that a bis(mu-oxo)dicopper(III) complex is the precursor for the formation of trinuclear copper complex. In the reaction with 2,4-di-tert-butylphenol (DBP), the trinuclear copper(II, II, III) complex acts as a two-electron oxidant to produce an equimolar amount of the C[bond]C coupling dimer of DBP (3,5,3',5'-tetra-tert-butyl-biphenyl-2,2'-diol) and a bis(mu-hydroxo)dicopper(II) complex. Kinetic analysis has shown that the reaction consists of two distinct steps, where the first step involves a binding of DBP to the trinuclear complex to give a certain intermediate that further reacts with the second molecule of DBP to give another intermediate, from which the final products are released. Steric and/or electronic effects of the 6-methyl group and the N-alkyl substituents of the bidentate ligands on the copper(I)-dioxygen reactivity have been discussed.

    DOI: 10.1021/ja026047x

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  57. Oxo-transfer reaction from a bis(mu-oxo)dicopper(III) complex to sulfides. International journal

    Masayasu Taki, Shinobu Itoh, Shunichi Fukuzumi

    Journal of the American Chemical Society   Vol. 124 ( 6 ) page: 998 - 1002   2002.2

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    Oxygenation of sulfides to the corresponding sulfoxides by a distinct bis(mu-oxo)dicopper(III) complex has been accomplished for the first time using 2-(2-pyridyl)ethylamine derivative L(Py1Bz) (N-ethyl-N-[2-(2-pyridyl)ethyl]-alpha,alpha-dideuteriobenzylamine) as the supporting ligand. Detailed kinetic analysis has indicated that the reaction consists of two distinct steps, where the first quick process is association of the substrate to the bis(mu-oxo)dicopper(III) complex (k(1)) and the second slow process is intramolecular oxygen atom transfer from the copper-oxo species to the substrate in the associated complex (k(2)). The rate constant k(2) of the second process is rather insensitive to the oxidation potential of the substrates, suggesting that the oxo-transfer reaction proceeds via a mechanism involving direct oxygen atom transfer rather than a mechanism involving electron transfer.

    DOI: 10.1021/ja016023a

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  58. Modulation of coordination chemistry in copper(I) complexes supported by bis[2-(2-pyridyl)ethyl]amine-based tridentate ligands

    T Osako, Y Tachi, M Taki, S Fukuzumi, S Itoh

    INORGANIC CHEMISTRY   Vol. 40 ( 26 ) page: 6604 - 6609   2001.12

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    Structure and physicochemical properties of copper(I) complexes of the tridentate ligands L-2 (N,N-bis[2-(6-methylpyridin-2-yl)ethyl]phenethylamine) and L-3 (N,N-bis[2-(2-pyridyl)ethyl]-beta -methylphenethylamine) have been examined to obtain deeper insights into modulation of the coordination chemistry of copper(I) complexes. [Cu-I-(L-2)(CH3CN)](ClO4) (2 . CH3CN) has a distorted tetrahedral geometry, which consists of three nitrogen atoms of the ligand and one nitrogen atom of the bound CH3CN. Steric repulsion between the 6-methyl group on the pyridine nucleus of L-2 and the metal ion of the complex prevents the cuprous complex from adaptation to a three-coordinate geometry which must have a shorter Cu-N(pyridine) distance (similar to1.88 Angstrom). Thus, the four-coordinate copper(I) complex (2 . CH3CN) with a longer Cu-N bond (1.98 similar to2.13 Angstrom) becomes favorable, resulting in rather strong binding of CH3CN to the metal ion, In [Cu-I(L-3)] (ClO4) (3), there is a Cu-I-pi interaction between the cuprous ion and the phenyl group of the ligand sidearm. Such a copper(I)-arene interaction is essentially weak, but is significantly stabilized in complex 3. The methyl group at the benzylic position of L-3 reduces the degree of freedom of sidearm rotation to make the phenyl group stick on the cuprous ion, Thus, the reactivity of the copper(I) complexes of L-2 and L-3 toward dioxygen is significantly diminished, showing sharp contrast to the high reactivity of the copper(I) complex supported by a similar tridentate ligand L-1 (N,N-bis[2-(2-pyridiyl)ethyl]phenethylamine).

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  59. Oxygenation of phenols to catechols by a (μ-η2:η2-peroxo)dicopper(II) complex: Mechanistic insight into the phenolase activity of tyrosinase [1]

    S. Itoh, H. Kumei, M. Taki, S. Nagatomo, T. Kitagawa, S. Fukuzumi

    Journal of the American Chemical Society   Vol. 123 ( 27 ) page: 6708 - 6709   2001

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    DOI: 10.1021/ja015702i

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  60. Model complexes for the active form of galactose oxidase. Physicochemical properties of Cu(II)- and Zn(II)-phenoxyl radical complexes

    S Itoh, M Taki, H Kumei, S Takayama, S Nagatomo, T Kitagawa, N Sakurada, R Arakawa, S Fukuzumi

    INORGANIC CHEMISTRY   Vol. 39 ( 16 ) page: 3708 - +   2000.8

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    Physicochemical properties of the Cu(II)- and Zn(II)-phenoxyl radical complexes of ligand 1H and its 2,4-di-tert-butyl derivative 2H have been examined as models for the active form of galactose oxidase to shed light on the role of the thioether group in the novel organic cofactor.
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    DOI: 10.1021/ic9910211

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  61. Resonance Raman spectroscopy as a probe of the bis(mu-oxo)dicopper core

    PL Holland, CJ Cramer, EC Wilkinson, S Mahapatra, KR Rodgers, S Itoh, M Taki, S Fukuzumi, L Que, WB Tolman

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 122 ( 5 ) page: 792 - 802   2000.2

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    Resonance Raman spectra of dicopper complexes [L(2)Cu(2)(mu-O)(2)](2+) contain a number of resonance-enhanced features between 500 and 900 cm(-1), with L = R(3)TACN and various bidentate ligands (TACN = 1,4,7-triazacyclononane). Most importantly, there is a vibration near 600 cm(-1) in all [L(2)Cu(2)(mu-O)(2)](2+) compounds that is polarized, shifts by 19-27 cm(-1) upon (18)O(2) substitution, and gives a new peak with (16)O(18)O substitution, identifying it as a totally symmetric A, vibration of the bis(mu-oxo)dicopper(III) core. Changing the pendant groups on R(3)TACN causes shifts in the frequency of the Cu(2)(mu-O)(2) vibration, but the direction of these shifts depends on the details of the organic fragment. A substantial shift to higher frequency is evident when bidentate ligands are used in place of TACN. Importantly, bidentate ligands with two different types of nitrogen donors show two independent core vibrations; these are assigned as "breathing" and "pairwise" modes through simple group theory considerations as well as by calculations using density functional theory. These calculations are extended to examine systematic trends with ligand variation as well as potential excited-state distortions of the core. Finally, the symmetry and energy of the Cu(2)(mu-O)(2) vibrations are compared with resonance Raman data for other biologically relevant high-valent M(2)(mu-O)(2) cores (M = Fe, Mn) to derive lessons for examining biological and model systems.

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  62. Hydrogen atom abstraction by Cu(II)- and Zn(II)-phenoxyl radical complexes, models for the active form of galactose oxidase

    M Taki, H Kumei, S Itoh, S Fukuzumi

    JOURNAL OF INORGANIC BIOCHEMISTRY   Vol. 78 ( 1 ) page: 1 - 5   2000.1

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    The Cu(II) and Zn(II) complexes of phenoxyl radical species [M-II(L1(.))(NO3)](+) (M = Cu or Zn, L1H: 2-methylthio-4-tert-butyl-6[[bis[2-(2-pyridyl)ethyl] amino] methyl]phenol) and [M-II(L2(.))(NO3)](+) (M = Cu or Zn, L2H: 2,4-di-tert-butyl-6-[[bis[2-(2-pyridyl)ethyl]amino]methyl]phenol) are prepared as model complexes of the active form of galactose oxidase (GAO). Hydrogen atom abstraction of 1,4-cyclohexadiene and tert-butyl substituted phenols by the GAO model complexes proceeds very efficiently to give benzene and the corresponding phenoxyl radical or its C-C coupling dimer as the oxidation products, respectively. Kinetic analyses on the oxidation reactions have shown that the hydrogen atom abstraction of the phenol substrates is significantly enhanced by the coordinative interaction of the OH group to the metal ion center of the complex, providing valuable insight into the enzymatic mechanism of the alcohol oxidation. Details of the substrate-activation process have been discussed based on the activation parameters (Delta H-not equal and Delta S-not equal) of the reactions. (C) 2000 Elsevier Science Inc. All rights reserved.

    DOI: 10.1016/S0162-0134(99)00198-1

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  63. Oxidation of benzyl alcohol with Cu-II and Zn-II complexes of the phenoxyl radical as a model of the reaction of galactose oxidase

    S Itoh, M Taki, S Takayama, S Nagatomo, T Kitagawa, N Sakurada, R Arakawa, S Fukuzumi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 38 ( 18 ) page: 2774 - 2776   1999

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    Profound insights into the catalytic mechanism of galactose oxidase (GO) are offered by new models of the active form of the metalloenzyme. The important role of the Cu(II) center in the oxidation of benzyl alcohol to benzaldehyde by the Cu(II)-phenoxyl radical complex of ligand 1 has been revealed by comparison with the reactivity of the corresponding Zn(II)- phenoxyl radical complex; py = 2-pyridyl.

    DOI: 10.1002/(SICI)1521-3773(19990917)38:18<2774::AID-ANIE2774>3.0.CO;2-E

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Books 3

  1. 錯体化合物事典

    錯体化学会( Role: Contributor ,  Cu3O2)

    朝倉書店  2019.9  ( ISBN:9784254141054

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    Total pages:54, 944p   Language:Japanese

    CiNii Books

  2. Cadmium: From Toxicity to Essentiality, Chapter 5 -Imaging and Sensing of Cadmium in Cells

    Editors: Astrid Sigel, Helmut Sigel, Roland KO Sigel( Role: Sole author)

    Springer Netherlands  2013  ( ISBN:978-94-007-5178-1

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    Language:English Book type:Scholarly book

  3. 基礎化学実験

    京都大学大学院人間・環境学研究科化学部会( Role: Contributor)

    共立出版  2009.3  ( ISBN:9784320043817

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    Total pages:viii, 185p   Language:Japanese

    CiNii Books

MISC 9

  1. Chemistry, latest agricultural biofluorescence molecules group developed by a biological fusion study

    Masayasu Taki, Yoshikatsu Sato

      Vol. 3 ( 2 ) page: 108 - 112   2019.2

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  2. 退色に強い近赤外蛍光色素が招く蛍光イメージング技術

    多喜 正泰, 山口 茂弘

    現代化学   ( 572 ) page: 33 - 37   2018.11

  3. 退色に強い蛍光標識剤と超解像イメージング

    多喜 正泰

    光アライアンス   Vol. 29 ( 5 ) page: 26 - 30   2018.5

  4. 新しいイメージングに対応した新しい蛍光色素

    多喜 正泰, 山口 茂弘

    生体の科学   Vol. 68 ( 5 ) page: 426 - 427   2017.10

  5. Phosphole P-oxide-containing π-electron materials: Synthesis and applications in fluorescence imaging Reviewed

    Shigehiro Yamaguchi, Aiko Fukazawa, Masayasu Taki

    J. Synth. Org. Chem. Jpn.   Vol. 75 ( 11 ) page: 1179 - 1187   2017

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    Phosphole P-oxide is a useful building block for φ-conjugated materials due to its nonaromatic and electron-accepting character. We have synthesized a series of ring-fused derivatives of phosphole P-oxide based on the intramolecular nucleophilic cyclization of appropriate alkyne precursors or radical phosphanylations. Some of the thus obtained compounds exhibited intriguing fluorescence properties and were applied to fluorescence imaging. A donor-acceptor-type benzo[b]phosphole P-oxide with a (diphenylamino)phenyl group exhibited large solvatochromism in its fluorescence spectra, and could hence be used as a staining agent for lipid droplets. C-Naphox and PB430, which consist of fully ring-fused φ - conjugated ladder-type scaffolds, exhibited outstanding photostability and their absorption and emission properties were suitable for super-resolution STED imaging. Moreover, using PB430-conjugated antibodies, we carried out a 3-D reconstruction of the STED images and developed a photostability-based multicolor STED imaging technique.

    DOI: 10.5059/yukigoseikyokaishi.75.1179

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  6. A super photostable fluorescent dye that survives in repeated STED laser irradiation

    Plant Morphology   Vol. 28 ( 1 ) page: 9 - 13   2016

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    DOI: 10.5685/plmorphol.28.9

    J-GLOBAL

  7. Imaging and sensing of cadmium in cells. International journal

    Masayasu Taki

    Metal ions in life sciences   Vol. 11   page: 99 - 115   2013

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    Cadmium is one of the highly toxic transition metals for human beings and is known as a human carcinogen. Once humans are exposed to Cd(2+) on a chronic basis, Cd(2+) primarily accumulates in the liver and kidney where it forms complexes with small peptides and proteins via sulfhydryl groups. Complexed Cd(2+) or the ionic Cd(2+) is then taken up by target cells and tissues and exerts the toxicity. However, the question of how non-essential Cd(2+) crosses the cell membranes remains unanswered. Furthermore, the molecular mechanism of Cd(2+)-induced physiological signaling disruption in cells is still not fully elucidated. Investigations of Cd(2+) uptake kinetics, distributions, and concentrations in cells require chemical tools for its detection. Because of the easy use and high spatiotemporal resolution, optical imaging using fluorescence microscopy is a well-suited method for monitoring Cd(2+) in biological samples. This chapter summarizes design principles of small molecule fluorescent sensors for Cd(2+) detection in aqueous solution and their photophysical and metal-binding properties. Also the applications of probes for fluorescence imaging of Cd(2+) in a variety of cell types are demonstrated.

    DOI: 10.1007/978-94-007-5179-8_5

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  8. Reactivity of bis(mu-oxo)dicopper(III) complex toward external substrates

    M Taki, Y Tachi, S Fukuzumi, S Itoh

    JOURNAL OF INORGANIC BIOCHEMISTRY   Vol. 86 ( 1 ) page: 449 - 449   2001.8

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  9. Important role of Cu(II) in the oxidation of alcohols by galactose oxidase, implication from the model studies

    M., Taki, S., Itoh, S., Takayama, S., Nagatomo, T., Kitagawa, N., Sakurada, R., Arakawa, S., Fukuzumi

    J. Inorg. Biochem.   Vol. 74   page: 309 - 309   1999.1

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Presentations 40

  1. 細胞内銅一価イオンの検出に向けた蛍光プローブの分子設計戦略 Invited

    多喜 正泰

    日本薬学会第141年会  2021.3.29 

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    Event date: 2021.3

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  2. 超耐光性色素で観る細胞動態 Invited

    多喜 正泰

    ABiS Symposium  2021.2.24 

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    Event date: 2021.2

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  3. 近赤外蛍光色素を利用した植物イメージングツールの開発 Invited

    多喜 正泰

    日本植物学会 第84回大会  2020.9.21 

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    Event date: 2020.9

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  4. Molecular tools for super-resolution imaging of sub-organelle structures Invited

    多喜 正泰

    第63回 日本神経化学会大会  2020.9.11 

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    Event date: 2020.9

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  5. Cutting-edge optical imaging techniques enabled by organic fluorescent dyes Invited

    Masayasu Taki

    88th Seminar in OIST Membrane Cooperativity Unit  2020.1.21 

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    Event date: 2020.1

    Language:English   Presentation type:Public lecture, seminar, tutorial, course, or other speech  

  6. Phosphorus-containing fluorescent dyes for optical imaging Invited

    Masayasu Taki

    3rd Asian Conference on Chemosensors & Imaging Probes (Asian-ChIP 2019)  2019.11.7 

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    Event date: 2019.11

    Language:English   Presentation type:Oral presentation (invited, special)  

  7. Molecular tools enable super-resolution imaging of mitochondrial dynamics Invited

    多喜 正泰

    第78回日本癌学会学術総会  2019.9.27 

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    Event date: 2019.9

    Language:English   Presentation type:Oral presentation (invited, special)  

  8. Super-photostable dyes enable detection of ultra-structures of cell organelle Invited

    多喜 正泰

    2019年度化学系学協会東北大会  2019.9.22 

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    Event date: 2019.9

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  9. 有機蛍光色素が導く最先端バイオイメージング技術 Invited

    多喜 正泰

    2019年光化学討論会  2019.9.10 

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    Event date: 2019.9

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  10. Chemical Tools for Fluorescence Imaging Invited

    Masayasu Taki

    15th International Symposium on Applied Bioinorganic Chemistry (ISABC15)  2019.6.4 

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    Event date: 2019.6

    Language:English   Presentation type:Oral presentation (invited, special)  

    Country:Japan  

  11. Visualization of fatty acid metabolism in living cells Invited

    Masayasu Taki

    EMBO Practical Course - Functional live imaging of plants  2019.5.24 

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    Event date: 2019.5

    Language:English   Presentation type:Oral presentation (invited, special)  

    Country:Japan  

  12. 細胞システムを観る分子ツールの創製 Invited

    多喜 正泰

    理研シンポジウム「細胞システムの動態と論理 XI」  2019.3.28 

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    Event date: 2019.3

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  13. リン含有蛍光色素による革新的生体イメージング技術 Invited

    多喜 正泰

    日本化学会第99春季年会化学会  2019.3.19 

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    Event date: 2019.3

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  14. Photostable dyes for super-resolution imaging Invited

    Masayasu Taki

    12th International workshop on approaches to single cell analysis  2019.3.4 

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    Event date: 2019.3

    Language:English   Presentation type:Oral presentation (invited, special)  

    Country:Sweden  

  15. Super-resolution Imaging of Mitochondrial Inner-membrane in Living Cells Invited

    Masayasu Taki

    ABiS International Symposium  2019.2.17 

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    Event date: 2019.2

    Language:English   Presentation type:Oral presentation (invited, special)  

    Country:Japan  

  16. Design of new fluorophores for optical imaging Invited

    Masayasu Taki

    The international symposium on Bioinorganic Chemistry 2018  2018.11.30 

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    Event date: 2018.11 - 2018.12

    Language:English   Presentation type:Oral presentation (invited, special)  

    Country:Japan  

  17. New Imaging Approaches with Phosphorus-containing Dyes Invited

    Masayasu Taki

    The 6th International Symposium on Transformative Bio-Molecules (ISTbM-6)  2018.10.4 

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    Event date: 2018.10

    Language:English   Presentation type:Oral presentation (invited, special)  

    Country:Japan  

  18. 超耐光性蛍光色素が可能にする先端バイオイメージング Invited

    多喜 正泰

    生命科学4プラットフォーム 説明会・成果シンポジウム  2018.6.5 

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    Event date: 2018.6

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  19. 超耐光性蛍光色素による超解像イメージング Invited

    多喜 正泰

    先端イメージング計測 集中セミナー  2018.5.21 

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    Event date: 2018.5

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  20. Phosphorus-containing Dyes: New tools for high-resolution optical imaging Invited

    Masayasu Taki

    4th CSRS-ITbM Joint Workshop  2018.1.7 

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    Event date: 2018.1

    Language:English   Presentation type:Oral presentation (invited, special)  

    Country:Japan  

  21. 不可能を可能にする分子設計戦略~超耐光性色素の創製と応用展開~ Invited

    多喜 正泰

    第2回有機若手ワークショップ  2017.11.29 

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    Event date: 2017.11

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  22. 蛍光プローブ開発と超解像顕微鏡バイオイメージング Invited

    多喜 正泰

    第21回VBLシンポジウム  2017.11.21 

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    Event date: 2017.11

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  23. 細胞内で金属イオンを見る・使う Invited

    多喜 正泰

    第30回生物無機化学夏季セミナー  2017.9.1 

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    Event date: 2017.8 - 2017.9

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  24. 化合物を用いたイメージング

    多喜 正泰

    第1回 異分野融合研究ミーティング  2017.8.22 

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    Event date: 2017.8

    Language:Japanese   Presentation type:Public lecture, seminar, tutorial, course, or other speech  

  25. 超耐光性蛍光色素がもたらすイメージング新技術 Invited

    多喜 正泰

    第69回日本細胞生物学会大会  2017.6.14 

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    Event date: 2017.6

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  26. Fluorescence imaging of fatty acid metabolism by a solvatochromic fluorescent probe Invited

    Masayasu Taki

    IoC-IPMB-ITbM Joint Symposium  2017.6.13 

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    Event date: 2017.6

    Language:English   Presentation type:Oral presentation (invited, special)  

    Country:Taiwan, Province of China  

  27. 細胞イメージングに向けた分子設計戦略 Invited

    多喜 正泰

    私立大学戦略的基盤形成支援事業「細胞自在操作のための分子化学技術の開発拠点形成」2016年度成果報告会 特別講演  2017.4.22 

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    Event date: 2017.4

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  28. 1細胞精密解析を可能にする超耐光性蛍光色素の創製 Invited

    多喜 正泰

    日本化学会第97春季年会化学会  2017.3.16 

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    Event date: 2017.3

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  29. Phospha-xanthene Dyes for Deep Tissue Imaging Invited

    Masayasu Taki

    1st ITbM-IoC Joint Symposium  2016.11.15 

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    Event date: 2016.11

    Language:English   Presentation type:Oral presentation (invited, special)  

    Country:Japan  

  30. ホスホール化合物を基盤としたレシオ型ナトリウム蛍光プローブの創製 Invited

    多喜 正泰

    シンポジウム「ネオ生体機能関連化学」  2016.6.25 

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    Event date: 2016.6

    Language:Japanese   Presentation type:Public lecture, seminar, tutorial, course, or other speech  

  31. 細胞の構造や機能を可視化する分子プローブ設計の新機軸 Invited

    多喜 正泰

    第4回植物イメージングの集い  2016.1.8 

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    Event date: 2016.1

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  32. Design of a red-emitting ratiometric fluorescent probe for the detection of intracellular sodium ion Invited

    Masayasu Taki

    PACIFICHEM 2015  2015.12.19 

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    Event date: 2015.12

    Language:English   Presentation type:Oral presentation (invited, special)  

    Country:United States  

  33. 化学反応を利用した細胞内金属イオン検出プローブの開発 Invited

    多喜 正泰

    第六回 光塾  2014.9.7 

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    Event date: 2014.9

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  34. Fluorescence Imaging of Living Cells with Metal Complexes Invited

    Masayasu Taki

    The 17th Joint Symposium of Core-to-Core  2014.6.12 

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    Event date: 2014.6

    Language:English   Presentation type:Oral presentation (invited, special)  

    Country:Japan  

  35. Lanthanide Complexes for Time-resolved Luminescence Imaging of Metals in Living Cells Invited

    Masayasu Taki

    錯体化学会第63回討論会  2013.11.2 

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    Event date: 2013.11

    Language:English   Presentation type:Oral presentation (invited, special)  

  36. 長残光蛍光体ナノ粒子を用いた光バイオイメージング Invited

    多喜 正泰

    第54回日本組織細胞化学会総会・学術集会  2013.9.27 

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    Event date: 2013.9

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  37. 分子状酸素活性化機構に基づいた銅一価蛍光プローブの開発 Invited

    多喜 正泰

    分子研研究会「生体配位化学の最前線と展望」  2013.2.5 

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    Event date: 2013.2

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

  38. Chemical Labeling of Cellular Compartments with Fluorescent Dye Invited

    Masayasu Taki

    IMS Mini Symposium  2014.12.17 

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    Language:English   Presentation type:Oral presentation (invited, special)  

    Country:Japan  

  39. Super-photostable Fluorophores for Optical Imaging Invited

    Masayasu Taki

    2017.12.7 

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    Language:English   Presentation type:Public lecture, seminar, tutorial, course, or other speech  

    Country:Germany  

  40. 生細胞内オルガネラの超解像イメージングを実現する超耐光性蛍光色素の開発 Invited

    多喜 正泰

    第80回分析化学討論会  2020.5 

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    Language:Japanese  

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Research Project for Joint Research, Competitive Funding, etc. 1

  1. 脂質ダイナミクスの精密解析技術の創出

    2016.10 - 2020.3

    科学技術振興機構  戦略的創造研究推進事業 さきがけ 

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    Authorship:Principal investigator  Grant type:Competitive

KAKENHI (Grants-in-Aid for Scientific Research) 17

  1. Multi-color super-resolution imaging of organelle communications using super-photostable fluorescent dyes

    Grant number:19H02849  2019.4 - 2022.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

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    Authorship:Principal investigator 

    Grant amount:\17290000 ( Direct Cost: \13300000 、 Indirect Cost:\3990000 )

  2. Photo-stable near-infrared fluorescent tools for visualizing pollen tube dynamics

    Grant number:19H04858  2019.4 - 2021.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)  Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

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    Authorship:Principal investigator 

    Grant amount:\13260000 ( Direct Cost: \10200000 、 Indirect Cost:\3060000 )

  3. 受精時の花粉管ライブイメージングを実現する有機蛍光プローブ群の創製

    Grant number:17H05839  2017.4 - 2019.3

    日本学術振興会  科学研究費助成事業 新学術領域研究(研究領域提案型)  新学術領域研究(研究領域提案型)

    多喜 正泰

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    Authorship:Principal investigator 

    Grant amount:\15600000 ( Direct Cost: \12000000 、 Indirect Cost:\3600000 )

    (1) 任意の一本の花粉管を選択的に染色する光ケージド赤色発光色素の開発
    前年度の研究において,花粉管の染色効率が低いため,十分な蛍光強度が得られないことが問題として見つかった。これを解決するためには,光ケージド蛍光色素の細胞膜透過性を高める分子設計が重要である。そこで本年度は,動物細胞でよく知られている細胞膜透過性ペプチド(CPP)が連結した蛍光色素を用い,花粉管染色能のCPP配列依存性について検討した。CPPを含む培地中で花粉管を発芽させ,4時間培養したあと,蛍光顕微鏡で観察した。その結果,リシンを多く含むCPPは花粉管内部からの強い蛍光シグナルが観察されたのに対し,アルギニンを多く含むCPPの場合は,細胞壁に多く補足されていることがわかった。現在,高い花粉管染色能をもつCPP配列の最適化を行っている。
    (2) 植物深部の細胞壁染色を指向した近赤外蛍光性を有する細胞壁染色剤の開発
    近赤外蛍光色素PREX 710は712 nmと740 nmにそれぞれ極大吸収波長と極大蛍光波長を有するため,クロロフィル由来の自家蛍光に影響されずに画像を取得することができる。また,ほぼすべての蛍光タンパク質と併用できるため,最大6色までの多重染色ができることを明らかにした。前年度までに,PREX 710にアルギニンのオリゴマー (R8) を連結したものが細胞壁マーカーとして機能することを見出している。細胞壁マーカーとしての有用性を評価するため,花粉管伸長時における動態をライブで追跡した。その結果,花粉管伸長速度が早いときは細胞壁由来の蛍光強度が低下し,伸長が休止しているときは蛍光強度が増大するという反対の相関が得られた。これは,花粉管伸長におけるペクチンの量やカルシウム濃度に依存しているものと考えられ,詳細な解析を進めている。

  4. 脂質ダイナミクスの精密解析技術の創出

    2016.10 - 2020.3

    科学技術振興機構 (JST)  戦略的創造研究推進事業 さきがけ  統合1細胞解析のための革新的技術基盤

    多喜 正泰

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    Authorship:Principal investigator 

  5. Development of fluorescent organic liquid nanoparticles and its application to cellular imaging

    Grant number:16H04179  2016.4 - 2019.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    TAKI Masaaysu, Yamguchi Shigehiro, Yamguchi Shigehiro

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    Authorship:Principal investigator 

    Grant amount:\17810000 ( Direct Cost: \13700000 、 Indirect Cost:\4110000 )

    Organic fluorescent nanoparticles containing liquid fluorescent dye have been developed. We found that the particle size of fluorescent nanoparticles strongly depends on the viscosity of trialkylsilyl substituted pyrene, and the low viscosity liquid gave the smallest particle size. The fluidity of liquid pyrene is also maintained in the nanoparticle core, and the emission color was successfully tuned based on the new concept of "spontaneous incorporation of the dopant dyes into the nanoparticles". We also synthesized novel liquid fluorescent dyes with outstanding photostability, and examined the effect of the position of the silyl group on the physical properties. Furthermore, we prepared fluorescent nanoparticles containing the liquid dye and found that they are taken up inside the cell by the endocytosis mechanism.

  6. Development of near infrared dyes for photoacoustic imaging

    Grant number:16K13097  2016.4 - 2018.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research  Grant-in-Aid for Challenging Exploratory Research

    TAKI Masayasu

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    Authorship:Principal investigator 

    Grant amount:\3510000 ( Direct Cost: \2700000 、 Indirect Cost:\810000 )

    A series of polymethine NIR dyes containing a cyclic thioester moiety as a molecular probe for photoacoustic imaging. A cationic polymethine dye with dimethylaminophenyl groups on both sides exhibited an absorption maximum at 903 nm in CH2Cl2, whereas a dye substituted with julolidinyl groups showed longer absorption wavelength, indicating that these are promising NIR dyes for photoacoustic imaging. In order to evaluate the photoacoustic properties of these dyes, an optical system was established. In fact, using gold nanoparticles, it was found that the photoacoustic signal intensities increased with increasing the concentration of gold nanoparticles. The comparison of photoacoustic signals between dimethylaminophenyl and julolidinyl derivatives demonstrated that the latter afforded stronger signals when dyes in CH3CN were irradiated with a femto-second pulsed laser at 800 nm.

  7. Persistent luminescence nanoparticles applicable for in vivo imaging of cancer

    Grant number:26560220  2014.4 - 2016.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research  Grant-in-Aid for Challenging Exploratory Research

    Nishi Mayumi, HORII Noriko, TAKI Masayasu, HORII Noriko, TAKI Masayasu

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    Authorship:Collaborating Investigator(s) (not designated on Grant-in-Aid) 

    For developing the innovative probe of persistent luminescence nanoparticles applicable to medicine, we aimed at bioimaging without irradiation to visualize tumor cells in living animals. After transplanting human osteosarcoma (HOS) into subcutaneous of SCID mouse, antibody agaisnt HOS labeled with photactivated persistent luminescence nanoparticles was intravenously injected to this SCID mouse. We successfully peformed in vivo imaging of HOS by using photocouting system, IVIS Imaging System.

  8. 一官能基型金ナノラベル剤の開発およびクライオ電子顕微鏡による生体分子相互作用解析

    Grant number:25390016  2013.4 - 2015.3

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    山本 行男, 多喜 正泰, 多喜 正泰

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    Authorship:Coinvestigator(s) 

    本研究の目標は,高性能の無機・有機複合材料の調製法を確立すれば達成できると考え,平成26年度は,金ナノ粒子とともに無機材料と蛍光色素が併存する複合材料からのアプローチも遂行した.
    第一の課題については,昨年度,ペプチド固相合成によって所期の官能基を保持した金ナノ粒子の調製が確かめられたことに基づき,液相合成によるペプチドの大量合成を実施した.このとき,系統的な構造をもったペプチドを得るため,リンカー長を種々変化させ,また,グリシンを挿入して官能基の方向を揃えることを試みた.その結果,良好な相互作用を得るためには,安定性とともにペプチドの配向性の自由度を制限することが効果的であることが分かった.
    次に,生体適合性の高いナノ粒子を獲得するため,無機セラミックス材料である緑色長残光蛍光体を母体として選択した.実験は緑色長残光蛍光体を粉砕し均一なナノ粒子を得る条件検討から始まった.続いて,その表面に疎水鎖を導入した後,両親媒性ポリマーで被覆することで,必要とされる耐水性および分散性をもったナノ粒子を作成するプロトコールを確立した.次に,被覆する両親媒性ポリマーの両末端に有機蛍光色素を共有結合で連結することを試みたが,得られた試料には有機蛍光色素は残存していなかった.そこで,疎水性相互作用で粒子表面に有機蛍光色素を挿入する手法を検討し,その結果,良好な特性を有する試料を得ることに成功した.続いて,無機材料と蛍光色素との相互作用がスイッチングする工夫として酢酸エステルのエステラーゼによる加水分解を試みた.その結果,長残光蛍光体から蛍光色素へのエネルギー移動が観測され,所期の目的を達成した.

  9. Construction of fluorescence immunochromatography technique using a long persistent phosphor nanoparticles

    Grant number:25620110  2013.4 - 2014.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research  Grant-in-Aid for Challenging Exploratory Research

    TAKI Masayasu

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    Authorship:Principal investigator 

    Grant amount:\4030000 ( Direct Cost: \3100000 、 Indirect Cost:\930000 )

    The immunochromatographic assay is a simple and rapid test, which provides a result without the need for specialized and costly equipment. Although it is known that a fluorescence immunochromatographic assay is high sensitive for detection of the sample as compared with a traditional colorimetric method, this is lacking in convenience of the use because of the necessary of a fluorescence detector. Herein, I focused on a long persistent ceramics (LPC), which shows intense long-lived afterglow luminescence when irradiated with UV-vis light, and addressed the development of new phosphorescence immunochromatographic techniques with the long persistent ceramics. Ball-milling was used to prepare the nanoparticles of ceramics with long persistent property. The synthetic method to introduce biomolecules such as folic acid and antibody on the surface of the nanoparticles has been established.

  10. 長残光蛍光体ナノ粒子を用いた癌細胞および細胞外マトリックスの無励起光型バイオイメージング

    2011.12 - 2013.3

    科学技術振興機構 (JST)  産学共創基礎基盤研究プログラム  ヒト生体イメージングを目指した革新的バイオフォトニクス技術の構築

    多喜 正泰, 田部 勢津久, 石田 昭人, 西 真弓

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    Authorship:Principal investigator 

  11. Development of organelle-targeting fluorescent probes for metal ion and its application to multi-color imaging

    Grant number:23685039  2011.4 - 2014.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (A)  Grant-in-Aid for Young Scientists (A)

    TAKI Masayasu

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    Authorship:Principal investigator 

    Grant amount:\30030000 ( Direct Cost: \23100000 、 Indirect Cost:\6930000 )

    In order to elucidate intracellular signal transduction pathway at the molecular level, it is necessary to detect the temporal and spatial changes of intracellular signaling molecules. For this purpose, we have developed several metal ion fluorescent probes that can specifically localize cell organelle. Attachment of cholesterol or cationic functional groups to the probe skeletons makes it possible to accumulate the probes in the appropriate sites in the cell. By using these probes, I have succeeded in monitoring the local concentration changes of Zn(II) and Cu(I) in fluorescence.

  12. Development of copper(I) fluorescent sensors based on photoinduced electron transfer mechanism and their application to optical imaging of cells

    Grant number:21750168  2009 - 2010

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)  Grant-in-Aid for Young Scientists (B)

    TAKI Masayasu

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    Authorship:Principal investigator 

    Grant amount:\4680000 ( Direct Cost: \3600000 、 Indirect Cost:\1080000 )

    We have developed copper(I)-selective fluorescent probes as a chemical tool for monitoring behavior of copper ions in living cells. We initially synthesized various tioether-containing ligands and prepared the corresponding copper(I) complexes. Spectroscopic measurements and X-ray crystal structure analysis of these copper(I) complexes indicate that the linker chain length of the thioether ligand strongly affect the affinity toward copper(I) ion, binding fashion, and redox potential of copper. We next developed novel copper(I) fluorescent probes based on the oxidative cleavage mechanism. These probes contain a reduced form of fluorescein and TPA tetradentate ligand, those are linked through a benzyl ether group. We found that strong fluorescence is observed when copper(I) is added to the probe solution containing sub mM of gluthatione in water. The same reaction undergoes even in cells. Therefore, this will be useful chemical tool to probe intracellular copper(I) ion behavior.

  13. Development of novel probes for single-molecule imaging of proteihs

    Grant number:19350084  2007 - 2008

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    YAMAMOTO Yukio, TAKI Masayasu, TAKI Masayasu

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    Authorship:Coinvestigator(s) 

  14. Development of fluorescent sensors for intracellular transition metal ions and their applications to ratiometric imaging

    Grant number:19750139  2007 - 2008

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)  Grant-in-Aid for Young Scientists (B)

    TAKI Masayasu

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    Authorship:Principal investigator 

    Grant amount:\3640000 ( Direct Cost: \3400000 、 Indirect Cost:\240000 )

  15. 新規な二波長レシオイメージング型生体機能検出蛍光プローブの開発と応用

    Grant number:17750155  2005 - 2006

    日本学術振興会  科学研究費助成事業 若手研究(B)  若手研究(B)

    多喜 正泰

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    Authorship:Principal investigator 

    Grant amount:\3600000 ( Direct Cost: \3600000 )

    亜鉛イオンに対し特異的な蛍光シフトを示すレシオ型蛍光プローブの設計・合成を行った。2-フェニルインドールを基本骨格として有し、これに金属イオン配位場を導入することにより蛍光プローブIndopyriZinを得た。IndopyriZinは生理的条件下において470nmに蛍光の極大値を示すが、亜鉛イオンの添加に伴い393nmへと約80mmもの大きな短波長シフトが確認された。亜鉛緩衝溶液を用いた滴定からIndopyriZinと亜鉛イオンの解離定数を17nMと決定することができ、亜鉛イオンに対し非常に高感度であることがわかった。亜鉛イオンに対するこのような蛍光の短波長シフトは、高濃度に存在するアルカリおよびアルカリ土類金属イオン存在下においても認められたことから、IndopyriZinは生理的条件下においてもその機能を発揮することがわかった。一方、他の金属イオン選択性についても検討したところ、銅二価およびニッケル二価では蛍光消光が認められ、カドミウムイオンでは亜鉛イオンと同様の蛍光挙動を示すことがわかった。IndopyriZinを用いて細胞イメージングを行った結果、IndopyriZinのアセトキシメチルエステルは細胞膜透過性があり、細胞が生きたままの状態で亜鉛イオンの観測を行うことができることがわかった。
    続いて、アニオンセンサーの開発を行った。蛍光団としてアミノクマリンを有するDPAMQを合成し、その機能評価を行った。様々な金属イオンとの錯形成を行ったところ、DPAMQのカドミウム錯体がアニオンセンサーとして機能することがわかった。様々なアニオン種との反応について検討したところ、リン酸およびその誘導体に対して高い選択性があり、リン酸基のカドミウムイオンへの配位によって励起スペクトルの長波長シフトが誘起されることがわかった。このようなアニオンの配位によるスペクトルの変化は、カドミウム中心のルイス酸性度の低下に起因することが明らかとなった。

  16. ノンヘム遷移金属酵素活性中心の精密モデル化

    Grant number:02J04016  2002 - 2004

    日本学術振興会  科学研究費助成事業 特別研究員奨励費  特別研究員奨励費

    多喜 正泰

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    金属-酸素錯体を用いたフェノールの重合反応は工業化学的立場からも非常に注目を集めている。今回、ピリジルエチルアミン系の2座および3座配位子を用いて調製したペルオキソ錯体とビス-μ-オキソ錯体によるフェノールの二量化反応機構の解明をした。それぞれの酸素錯体に各種フェノールを加えると反応は速やかに進行し、対応するフェノールの二量体を与えることが分かった。速度論的解析から反応は酸素錯体濃度および加えたフェノールの濃度に対しそれぞれ一次で進行することがわかった。各種フェノールとの反応の二次反応速度定数をフェノールの酸化電位に対しプロットすると、いずれの酸素錯体の場合にも直線関係が得られ、その傾きから反応は電子移動に続くプロトン移動で進行していることが判明した。
    さらに、本研究ではガラクトース酸化酵素モデル錯体の物性や酸化還元挙動に及ぼす金属配位場の効果について検討した。ピリジン配位子の電子ドナー性が増大するにつれて金属中心のルイス酸性が減少し、フェノラート部位の酸化電位が負側にシフトすることがわかった。一方、一電子酸化体であるフェノキシルラジカル錯体においては金属配位場の変化による物性や反応性の違いはほとんど認められなかった。これは、ラジカル部位と金属イオンとの間の相互作用はフェノラート錯体に比べてかなり弱いことが原因であることが共鳴ラマンスペクトルの測定により明らかとなった。
    さらに、細胞内における亜鉛イオンの挙動を新規に設計・合成したプローブにより追跡した。合成したプローブはベンゾオキサゾールを骨格として有しており、亜鉛イオン濃度の変化により蛍光の極大波長がシフトするという新しいタイプのものである。蛍光のシフトは亜鉛イオンに特異的であり、その感度はナノMレベルであることがわかった。本プローブは実際に細胞内の亜鉛の濃度変化を感知することが出来、海馬やすい臓のβセル内の亜鉛イオン検出にも成功した。

  17. 銅含有酸化還元酵素活性中心の新しい構造・機能モデルの開発

    Grant number:99J02410  1999 - 2001

    日本学術振興会  科学研究費助成事業 特別研究員奨励費  特別研究員奨励費

    多喜 正泰

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Industrial property rights 8

  1. アザピレン化合物又はその塩

    山口 茂弘, 多喜 正泰, 大崎 博司

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    Applicant:国立大学法人名古屋大学

    Application no:特願2018-037807  Date applied:2018.3

    Announcement no:特開2018-145423  Date announced:2018.9

    J-GLOBAL

  2. 縮環チオフェン化合物及びそれを用いた油滴染色剤

    山口 茂弘, 多喜 正泰, 梶原 啓司

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    Applicant:国立大学法人名古屋大学

    Application no:特願2018-037442  Date applied:2018.3

    Announcement no:特開2018-145422  Date announced:2018.9

    J-GLOBAL

  3. ホスファロドール化合物及びその塩、並びにそれを用いた蛍光色素

    山口 茂弘, 多喜 正泰, マレク, ガージボウスキー, グジャゴッシュ

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    Applicant:国立大学法人名古屋大学

    Application no:特願2017-062190  Date applied:2017.3

    Announcement no:特開2018-165247  Date announced:2018.10

    J-GLOBAL

  4. 油滴染色剤

    山口 茂弘, 多喜 正泰

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    Applicant:国立大学法人名古屋大学

    Application no:特願2016-177122  Date applied:2016.9

    Announcement no:特開2018-039963  Date announced:2018.3

    J-GLOBAL

  5. ホスファフルオレセイン化合物若しくはその塩、又はそれを用いた蛍光色素

    山口 茂弘, 中 愛子, 須田 真司, 多喜 正泰

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    Applicant:国立大学法人名古屋大学

    Application no:JP2016054964  Date applied:2016.2

    Announcement no:WO2016-133218  Date announced:2016.8

    J-GLOBAL

  6. ホスホール化合物及びそれを含有する蛍光色素

    山口 茂弘, 多喜 正泰, 小笠原 宏亮

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    Applicant:国立大学法人名古屋大学

    Application no:特願2015-177520  Date applied:2015.9

    Announcement no:特開2017-052863  Date announced:2017.3

    J-GLOBAL

  7. 二光子吸収材料に使用することができる化合物及びそれを用いた蛍光色素及び二光子吸収材料

    山口 茂弘, 深澤 愛子, 多喜 正泰, 鈴木 直弥

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    Applicant:国立大学法人名古屋大学

    Application no:特願2015-032323  Date applied:2015.2

    Announcement no:特開2016-153385  Date announced:2016.8

    J-GLOBAL

  8. 亜鉛蛍光プローブ

    多喜 正泰, 山本 行男

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    Applicant:国立大学法人京都大学

    Application no:JP2006304749  Date applied:2006.3

    Announcement no:WO2007-013201  Date announced:2007.2

    J-GLOBAL

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Teaching Experience (Off-campus) 6

  1. 有機機器分析

    Nagoya University)

  2. 基礎化学実験

    Kyoto University)

  3. 化学基礎2

    Nagoya University)

  4. フロンティア化学

    Kyoto University)

  5. ケミカルバイオロジー概論

    Nagoya University)

  6. Advanced Organic Chemistry

    Nagoya University)

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Social Contribution 1

  1. 蛍光分子で観る細胞社会

    Role(s):Lecturer

    WPI presents 教育関係者のための研究最前線講座「とどけ!WPIの最新研究」  2020.12