Updated on 2025/04/29

写真a

 
OKUMURA, Taiga
 
Affiliation
Faculty of Education and Integrated Arts and Sciences, School of Education
Job title
Associate Professor
Degree
博士(理学) ( 2014.03 東京大学 )
Mail Address
メールアドレス

Research Experience

  • 2025.04
    -
    Now

    Waseda University   Faculty of Education and Integrated Arts and Sciences   Associate Professor

  • 2020.11
    -
    2025.03

    The University of Tokyo   Graduate School of Science   Assistant Professor

  • 2017.07
    -
    2020.10

    The University of Tokyo   Graduate School of Science

  • 2014.04
    -
    2017.06

    株式会社 日立製作所

Education Background

  • 2009.04
    -
    2014.03

    The University of Tokyo   Graduate School of Science   Department of Earth and Planetary Science  

  • 2007.04
    -
    2009.03

    The University of Tokyo   Faculty of Science   Department of Earth and Planetary Environmental Science  

  • 2005.04
    -
    2007.03

    The University of Tokyo   College of Arts and Sciences  

Research Areas

  • Biogeosciences / Environmental dynamic analysis / Human geosciences

Awards

  • 最優秀口頭発表賞

    2021.10   環境放射能除染学会  

  • 奨励賞

    2021.01   環境放射能除染学会  

  • 最優秀口頭発表賞

    2019.07   環境放射能除染学会  

    Winner: 奥村 大河

  • 優秀口頭発表賞

    2018.07   環境放射能除染学会  

    Winner: 奥村 大河

  • 最優秀口頭発表賞(共同発表者)

    2018.07   環境放射能除染学会  

 

Papers

  • Structural Elucidation of Vaterite by Atomic Imaging and Electron Diffraction

    Taiga OKUMURA

    Nihon Kessho Gakkaishi   66 ( 4 ) 213 - 214  2024.12

    Authorship:Lead author, Corresponding author

    DOI

  • Variations of organic functional chemistry in carbonaceous matter from the asteroid 162173 Ryugu

    Bradley De Gregorio, George D. Cody, Rhonda M. Stroud, A. L. David Kilcoyne, Scott Sandford, Corentin Le Guillou, Larry R. Nittler, Jens Barosch, Hikaru Yabuta, Zita Martins, Yoko Kebukawa, Taiga Okumura, Minako Hashiguchi, Shohei Yamashita, Yasuo Takeichi, Yoshio Takahashi, Daisuke Wakabayashi, Cécile Engrand, Laure Bejach, Lydie Bonal, Eric Quirico, Laurent Remusat, Jean Duprat, Maximilien Verdier-Paoletti, Smail Mostefaoui, Mutsumi Komatsu, Jérémie Mathurin, Alexandre Dazzi, Ariane Deniset-Besseau, Emmanuel Dartois, Yusuke Tamenori, Hiroki Suga, Gilles Montagnac, Kanami Kamide, Miho Shigenaka, Megumi Matsumoto, Yuma Enokido, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Tomohiro Usui, Masanao Abe, Tatsuaki Okada, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Sei-ichiro Watanabe, Yuichi Tsuda

    Nature Communications   15 ( 1 )  2024.08

     View Summary

    Abstract

    Primordial carbon delivered to the early earth by asteroids and meteorites provided a diverse source of extraterrestrial organics from pre-existing simple organic compounds, complex solar-irradiated macromolecules, and macromolecules from extended hydrothermal processing. Surface regolith collected by the Hayabusa2 spacecraft from the carbon-rich asteroid 162173 Ryugu present a unique opportunity to untangle the sources and processing history of carbonaceous matter. Here we show carbonaceous grains in Ryugu can be classified into three main populations defined by spectral shape: Highly aromatic (HA), Alkyl-Aromatic (AA), and IOM-like (IL). These carbon populations may be related to primordial chemistry, since C and N isotopic compositions vary between the three groups. Diffuse carbon is occasionally dominated by molecular carbonate preferentially associated with coarse-grained phyllosilicate minerals. Compared to related carbonaceous meteorites, the greater diversity of organic functional chemistry in Ryugu indicate the pristine condition of these asteroid samples.

    DOI

  • Raman spectroscopy of Ryugu particles and their extracted residues: Fluorescence background characteristics and similarities to CI chondrites

    Mutsumi Komatsu, Hikaru Yabuta, Yoko Kebukawa, Lydie Bonal, Eric Quirico, Timothy J. Fagan, George D. Cody, Jens Barosch, Laure Bejach, Emmanuel Dartois, Alexandre Dazzi, Bradley De Gregorio, Ariane Deniset‐Besseau, Jean Duprat, Cecile Engrand, Minako Hashiguchi, Zita Martins, Jérémie Mathurin, Gilles Montagnac, Smail Mostefaoui, Larry R. Nittler, Takuji Ohigashi, Taiga Okumura, Laurent Rémusat, Scott Sandford, Rhonda Stroud, Hiroki Suga, Yoshio Takahashi, Yasuo Takeichi, Yusuke Tamenori, Maximilien Verdier‐Paoletti, Shohei Yamashita, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hiroshi Naraoka, Kanako Sakamoto, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Tomohiro Usui, Masanao Abe, Tatsuaki Okada, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Shogo Tachibana, Sei‐ichiro Watanabe, Yuichi Tsuda

    Meteoritics & Planetary Science    2024.07

     View Summary

    <jats:title>Abstract</jats:title><jats:p>We present here an investigation of Ryugu particles recovered by the Hayabusa2 space mission and their extracted carbonaceous acid residues using Raman spectroscopy. Raman parameters of Ryugu intact grains and their acid residues are characterized by broad D (defect induced) and G (graphite) band widths, indicating the presence of polyaromatic carbonaceous matter with low thermal maturity. Raman spectra of Ryugu particles and CI (type 1) chondrites exhibit stronger laser‐induced fluorescence backgrounds compared to Type 2 and Type 3 carbonaceous chondrites. The high fluorescence signatures and wide bandwidths of the D and G bands of Ryugu intact grains are similar to the Raman spectra observed in CI chondrites, reflecting the low structural order of their aromatic carbonaceous matter, and strengthening the link between Ryugu particles and CI chondrites. The high fluorescence background intensity of the Ryugu particles is due to multiple causes, but it is likely that the relative abundance of geometry‐bearing macromolecular organic matter in total organic carbon contents makes a large contribution to the fluorescence intensities. Locally observed high fluorescence in the acid‐extracted residues of Ryugu is due to nitrogen‐bearing outlier phase. The high fluorescence signature is one consequence of the low degree of thermal maturity of the organic matter and supports evidence that the Ryugu particles have escaped significant parent body thermal metamorphism.</jats:p>

    DOI

  • Microscale hydrogen, carbon, and nitrogen isotopic diversity of organic matter in asteroid Ryugu

    Larry R Nittler, Jens Barosch, Katherine Burgess, Rhonda M Stroud, Jianhua Wang, Hikaru Yabuta, Yuma Enokido, Megumi Matsumoto, Tomoki Nakamura, Yoko Kebukawa, Shohei Yamashita, Yoshio Takahashi, Laure Bejach, Lydie Bonal, George D Cody, Emmanuel Dartois, Alexandre Dazzi, Bradley De Gregorio, Ariane Deniset-Besseau, Jean Duprat, Cécile Engrand, Minako Hashiguchi, A.L. David Kilcoyne, Mutsumi Komatsu, Zita Martins, Jérémie Mathurin, Gilles Montagnac, Smail Mostefaoui, Taiga Okumura, Eric Quirico, Laurent Remusat, Scott Sandford, Miho Shigenaka, Hiroki Suga, Yasuo Takeichi, Yusuke Tamenori, Maximilien Verdier-Paoletti, Daisuke Wakabayashi, Masanao Abe, Kanami Kamide, Akiko Miyazaki, Aiko Nakato, Satoru Nakazawa, Masahiro Nishimura, Tatsuaki Okada, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Tomohiro Usui, Toru Yada, Kasumi Yogata, Makoto Yoshikawa, Hisayoshi Yurimoto, Takaaki Noguchi, Ryuji Okazaki, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Sei-ichiro Watanabe, Yuichi Tsuda

    Earth and Planetary Science Letters   637   118719 - 118719  2024.07  [Refereed]

    DOI

  • Stacking Structure of Vaterite Revealed by Atomic Imaging and Diffraction Analysis

    Taiga Okumura, Gen Takahashi, Michio Suzuki, Toshihiro Kogure

    Chemistry – A European Journal    2024.06

     View Summary

    Anhydrous calcium carbonate crystals exist as three polymorphs: calcite, aragonite, and vaterite. Although vaterite is a metastable phase rarely found in the geological environment, it is intriguing that various biominerals are composed of vaterite. The processes of stable vaterite formation in biological systems cannot be understood without elucidating the nature of vaterite. The crystal structure of vaterite has been discussed for nearly a century but is still an open question. Here we propose the actual structure of vaterite by combining atomic imaging and diffraction analysis with simulations of disordered stacking sequences. Vaterite basically appears as layers of hexagonal calcium planes and carbonate (CO32−)‐containing sheets stacked with +60°, −60°, or 180° rotations from the underlying layer. However, equivalent carbonate positions in alternating layers are forbidden, and four‐layer stacking in which the fourth layer rotates 180° relative to the first layer are predominant, forming an orthogonal reciprocal lattice in diffraction patterns. These stacking characteristics replicate the intensity distribution in the electron and X‐ray diffraction patterns. This study has almost completely elucidated the crystal structure and stacking sequence of vaterite. Our findings provide insights into the thermodynamic stability of vaterite, which facilitates comprehension of the biomineralization processes and growth dynamics of calcium carbonate.

    DOI

  • AFM-IR nanospectroscopy of nanoglobule-like particles in Ryugu samples returned by the Hayabusa2 mission

    Jérémie Mathurin, Laure Bejach, Emmanuel Dartois, Cécile Engrand, Alexandre Dazzi, Ariane Deniset-Besseau, Jean Duprat, Yoko Kebukawa, Hikaru Yabuta, Lydie Bonal, Eric Quirico, Christophe Sandt, Ferenc Borondics, Jens Barosch, Pierre Beck, D. George Cody, T. Brad De Gregorio, Minako Hashiguchi, A.L. David Kilcoyne, Mutsumi Komatsu, Zita Martins, Megumi Matsumoto, Gilles Montagnac, Smail Mostefaoui, R. Larry Nittler, Takuji Ohigashi, Taiga Okumura, T.H. Van Phan, Laurent Remusat, Scott Sandford, Miho Shigenaka, Rhonda Stroud, Hiroki Suga, Yoshio Takahashi, Yasuo Takeichi, Yusuke Tamenori, Maximilien Verdier-Paoletti, Shohei Yamashita, Tomoki Nakamura, Tomoyo Morita, Mizuha Kikuiri, Kana Amano, Eiichi Kagawa, Takaaki Noguchi, Hiroshi Naraoka, Ryuji Okazaki, Kanako Sakamoto, Hisayoshi Yurimoto, Masanao Abe, Kanami Kamide, Akiko Miyazaki, Aiko Nakato, Satoru Nakazawa, Masahiro Nishimura, Tatsuaki Okada, Takanao Saiki, Shogo Tachibana, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Tomohiro Usui, Sei-ichiro Watanabe, Toru Yada, Kasumi Yogata, Makoto Yoshikawa

    Astronomy & Astrophysics    2024.02  [Refereed]

     View Summary

    The JAXA Hayabusa2 mission returned well-preserved samples collected from the carbonaceous asteroid Ryugu, providing unique non-terrestrially weathered samples from a known parent body. This work aims to provide a better understanding of the formation and evolution of primitive asteroidal matter by studying the fine scale association of organic matter and minerals in Ryugu samples. We characterized the samples by IR nanospectroscopy using the AFM-IR technique. This technique overcomes the diffraction limit (of several microns) of conventional infrared microspectroscopy (µ-FTIR). The samples were mapped in the mid-IR range at a lateral spatial resolution about a hundred times better than with µ-FTIR. This provided us with unique in situ access to the distribution of the different infrared signatures of organic components at the sub-micron scale present in the Ryugu whole-rock samples as well as to the characterization of the compositional variability of Ryugu in the insoluble organic matter (IOM) chemically extracted from the Ryugu samples. The AFM-IR maps of whole-rock particles and IOM residues from Ryugu samples were recorded with a lateral resolution of tens of nanometers. Spectra were recorded in the 1900-900 cm$^−1$ spectral range by AFM-IR (Icon-IR) for all samples, and additional spectra were recorded from 2700 to 4000 cm$^−1$ for one IOM sample by an optical photothermal IR (O-PTIR) technique using a mIRage$^ textregistered $ IR microscope. Organic matter is present in two forms in the whole-rock samples: as a diffuse phase intermixed with the phyllosilicate matrix and as individual organic nanoparticles. We identify the Ryugu organic nanoparticles as nanoglobule-like inclusions texturally resembling nanoglobules present in primitive meteorites. Using AFM-IR, we record for the first time the infrared spectra of Ryugu organic nanoparticles that clearly show enhanced carbonyl (C=O) and CH contributions with respect to the diffuse organic matter in Ryugu whole-rock and IOM residue.

    DOI

  • Electron microscopy observations of the diversity of Ryugu organic matter and its relationship to minerals at the micro‐ to nano‐scale

    Rhonda M. Stroud, Jens Barosch, Lydie Bonal, Katherine Burgess, George D. Cody, Bradley T. De Gregorio, Luke Daly, Emmanuel Dartois, Elena Dobrică, Jean Duprat, Cecile Engrand, Dennis Harries, Minako Hashiguchi, Hope Ishii, Yoko Kebukawa, A. David Kilcoyne, Falko Langenhorst, Martin R. Lee, Larry R. Nittler, Eric Quirico, Taiga Okumura, Laurent Remusat, Scott Sandford, Hikaru Yabuta, Masanao Abe, Neyda M. Abreu, Paul A. J. Bagot, Pierre Beck, Laure Bejach, Phil A. Bland, John C. Bridges, Brittany A. Cymes, Alexandre Dazzi, Francisco de la Peña, Ariane Deniset‐Besseau, Satomi Enju, Yuma Enokido, David R. Frank, Jennifer Gray, Mitsutaka Haruta, Satoshi Hata, Leon Hicks, Yohei Igami, Damien Jacob, Kanami Kamide, Mutsumi Komatsu, Sylvain Laforet, Hugues Leroux, Corentin Le Guillou, Zita Martins, Maya Marinova, James Martinez, Jérémie Mathurin, Megumi Matsumoto, Toru Matsumoto, Junya Matsuno, Samuel McFadzean, Tatsuhiro Michikami, Itaru Mitsukawa, Akira Miyake, Masaaki Miyahara, Akiko Miyazaki, Gilles Montagnac, Smail Mostefaoui, Tomoki Nakamura, Aiko Nakato, Hiroshi Naraoka, Yusuke Nakauchi, Satoru Nakazawa, Masahiro Nishimura, Takaaki Noguchi, Kenta Ohtaki, Takuji Ohigashi, Tatsuaki Okada, Shota Okumura, Ryuji Okazaki, Thi H. V. Phan, Rolando Rebois, Kanako Sakamoto, Takanao Saiki, Hikaru Saito, Yusuke Seto, Miho Shigenaka, William Smith, Hiroki Suga, Mingqi Sun, Shogo Tachibana, Yoshio Takahashi, Yasuo Takeichi, Akihisa Takeuchi, Aki Takigawa, Yusuke Tamenori, Satoshi Tanaka, Fuyuto Terui, Michelle S. Thompson, Naotaka Tomioka, Akira Tsuchiyama, Yuichi Tsuda, Kentaro Uesugi, Masayuki Uesugi, Tomohiro Usui, Maximilien Verdier‐Paoletti, Daisuke Wakabayashi, Sei‐ichiro Watanabe, Toru Yada, Shohei Yamashita, Masahiro Yasutake, Kasumi Yogata, Makoto Yoshikawa, Hisayoshi Yurimoto, Pierre‐M. Zanetta, Thomas Zega, Michael E. Zolensky

    Meteoritics &amp; Planetary Science    2024.01

     View Summary

    Abstract

    Transmission electron microscopy analyses of Hayabusa2 samples show that Ryugu organic matter exhibits a range of morphologies, elemental compositions, and carbon functional chemistries consistent with those of carbonaceous chondrites that have experienced low‐temperature aqueous alteration. Both nanoglobules and diffuse organic matter are abundant. Non‐globular organic particles are also present, and including some that contain nanodiamond clusters. Diffuse organic matter is finely distributed in and around phyllosilicates, forms coatings on other minerals, and is also preserved in vesicles in secondary minerals such as carbonate and pyrrhotite. The average elemental compositions determined by energy‐dispersive spectroscopy of extracted, demineralized insoluble organic matter samples A0107 and C0106 are C100N3O9S1 and C100N3O7S1, respectively, with the difference in O/C slightly outside the difference in the standard error of the mean. The functional chemistry of the nanoglobules varies from mostly aromatic C=C to mixtures of aromatic C=C, ketone C=O, aliphatic (CHn), and carboxyl (COOH) groups. Diffuse organic matter associated with phyllosilicates has variable aromatic C, ketone and carboxyl groups, and some localized aliphatics, but is dominated by molecular carbonate (CO3) absorption, comparable to prior observations of clay‐bound organic matter in CI meteorites.

    DOI

  • Characterization of Submicron‐Thick Layered Structure in Hydrogenetic Ferromanganese Nodule Suggests Short‐Term Redox Fluctuation of Paleo‐Ocean

    Junming Zhou, Toshihiro Kogure, Taiga Okumura, Yoshio Takahashi, Jing Liu, Shengxiong Yang, Peng Yuan

    Journal of Geophysical Research: Oceans   129 ( 1 )  2024.01

     View Summary

    Abstract

    Ferromanganese (Fe‐Mn) nodules are widely considered significant economic potential and paleoenvironmentally significant archives. Generally, submicron‐thick layers (SMLs) are basic units of the Fe‐Mn nodules and record valuable information about the environment of Fe‐Mn nodule formation, but their structural, mineralogical, and chemical features are not well resolved. Here, we investigated a typical hydrogenetic Fe‐Mn nodule from the Penrhyn Basin in the South Pacific Ocean, using various microanalytical techniques. The nodule mainly consists of a micronodule‐dominant region around the core, a crust near the surface with Mn‐ and Fe‐rich layers, and stromatolite‐like textures between them. These textures are composed of distinct and indistinct SMLs parallel to their growth front. Although the distinct and indistinct SMLs have different mineral phases, the transmission electron microscopy revealed that these layered structures are actually interstratification of SMLs with different crystal sizes of foliated phyllomanganates. Large crystals contain higher Mn oxidation states than small crystals. Such variations of Mn oxidation state with different crystal sizes along the growth direction imply the short‐term regular fluctuation in the redox condition of the Lower Circumpolar Deep Water.

    DOI

  • Mineralogical aspects of asteriscus of goldfish (Carassius auratus) consisting of vaterite

    Gen TAKAHASHI, Taiga OKUMURA, Takayoshi NAGAYA, Michio SUZUKI, Toshihiro KOGURE

    Journal of Mineralogical and Petrological Sciences   119 ( 1 ) n/a - n/a  2024

    DOI

  • The thermal history of Ryugu based on Raman characterization of Hayabusa2 samples

    Lydie Bonal, Eric Quirico, Gilles Montagnac, Mutsumi Komatsu, Yoko Kebukawa, Hikaru Yabuta, Kana Amano, Jens Barosch, Laure Bejach, George D. Cody, Emmanuel Dartois, Alexandre Dazzi, Bradley De Gregorio, Ariane Deniset-Besseau, Jean Duprat, Cécile Engrand, Minako Hashiguchi, Kanami Kamide, David Kilcoyne, Zita Martins, Jérémie Mathurin, Smail Mostefaoui, Larry Nittler, Takuji Ohigashi, Taiga Okumura, Laurent Remusat, Scott Sandford, Miho Shigenaka, Rhonda Stroud, Hiroki Suga, Yoshio Takahashi, Yasuo Takeichi, Yusuke Tamenori, Maximilien Verdier-Paoletti, Shohei Yamashita, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Hisayoshi Yurimoto, Shogo Tachibana, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Satoru Nakazawa, Masahiro Nishimura, Tatsuaki Okada, Takanao Saiki, Kanako Sakamoto, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Tomohiro Usui, Sei-ichiro Watanabe, Toru Yada, Kasumi Yogata, Makota Yoshikawa

    Icarus   408   115826 - 115826  2024.01

    DOI

  • Compositional heterogeneity of insoluble organic matter extracted from asteroid Ryugu samples

    Eric Quirico, Lydie Bonal, Yoko Kebukawa, Kana Amano, Hikaru Yabuta, Van T. H. Phan, Pierre Beck, Laurent Rémusat, Emmanuel Dartois, Cecile Engrand, Zita Martins, Laure Bejach, Alexandre Dazzi, Ariane Deniset‐Besseau, Jean Duprat, Jérémie Mathurin, Gilles Montagnac, Jens Barosch, George D. Cody, Bradley De Gregorio, Yuma Enokido, Minako Hashiguchi, Kanami Kamide, David Kilcoyne, Mutsumi Komatsu, Megumi Matsumoto, Smail Mostefaoui, Larry Nittler, Takuji Ohigashi, Taiga Okumura, Scott Sandford, Miho Shigenaka, Rhonda Stroud, Hiroki Suga, Yoshio Takahashi, Yasuo Takeichi, Yusuke Tamenori, Maximilien Verdier‐Paoletti, Daisuke Wakabayashi, Shohei Yamashita, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Hisayoshi Yurimoto, Kanako Sakamoto, Shogo Tachibana, Sei‐Ichiro Watanabe, Yuichi Tsuda, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohitro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa

    Meteoritics & Planetary Science    2023.11

     View Summary

    Abstract

    We report a Fourier transform infrared analysis of functional groups in insoluble organic matter (IOM) extracted from a series of 100–500 μm Ryugu grains collected during the two touchdowns of February 22 and July 11, 2019. IOM extracted from most of the samples is very similar to IOM in primitive CI, CM, and CR chondrites, and shows that the extent of thermal metamorphism in Ryugu regolith was, at best, very limited. One sample displays chemical signatures consistent with a very mild heating, likely due to asteroidal collision impacts. We also report a lower carbonyl abundance in Ryugu IOM samples compared to primitive chondrites, which could reflect the accretion of a less oxygenated precursor by Ryugu. The possible effects of hydrothermal alteration and terrestrial weathering are also discussed. Last, no firm conclusions could be drawn on the origin of the soluble outlier phases, observed along with IOM in this study and in the preliminary analysis of Ryugu samples. However, it is clear that the HF/HCl residues presented in this publication are a mix between IOM and the nitrogen‐rich outlier phase.

    DOI

  • Dispersion Function of a Protein, DP‐1, Identified in Collimonas sp. D‐25, for the Synthesis of Gold Nanoparticles

    Donglin Tang, Yugo Kato, Dingkun Zhang, Lumi Negishi, Hitoshi Kurumizaka, Takafumi Hirata, Makoto Nakakido, Kouhei Tsumoto, Fujisawa Shuji, Saito Tsuguyuki, Taiga Okumura, Koji Nagata, Michio Suzuki

    ChemBioChem   24 ( 14 )  2023.06

    DOI

  • Heme protein identified from scaly-foot gastropod can synthesize pyrite (FeS2) nanoparticles

    Tatsuya Yamashita, Hiroki Matsuda, Kyohei Koizumi, Logu Thirumalaisamy, Myeongok Kim, Lumi Negishi, Hitoshi Kurumizaka, Yoriko Tominaga, Yoshihiro Takagi, Ken Takai, Taiga Okumura, Hidekazu Katayama, Masaki Horitani, Nazmul Ahsan, Yoshitaka Okada, Koji Nagata, Yohey Suzuki, Michio Suzuki

    Acta Biomaterialia   162   110 - 119  2023.05  [Refereed]

    DOI

  • Effect of phosphoproteins on intracellular calcification of bacteria

    Yukihisa Yoshikuni, Mayumi Iijima, Gen Takahashi, Taiga Okumura, Toshihiro Kogure, Michio Suzuki

    European Journal of Oral Sciences   131 ( 3 )  2023.03  [Refereed]

    DOI

  • Dissolution behavior of radiocesium-bearing microparticles as a function of solution compositions

    Taiga Okumura, Noriko Yamaguchi, Toshihiro Kogure

    Scientific Reports   13 ( 1 )  2023.03  [Refereed]

     View Summary

    Abstract

    More than a decade has passed since the Fukushima nuclear accident in 2011 and contamination around the nuclear power plant is primarily caused by 137Cs. One of the materials retaining radiocesium in the environment is radiocesium-bearing silicate glass microparticles (CsMPs), which have not been reported in previous nuclear accidents. Although the prediction of environmental fates of CsMPs is of interest because of their extremely high specific radioactivity, knowledge about their physicochemical properties is still limited. Here we show that the dissolution behavior of CsMPs is comparable to that of silica-rich glass and significantly depends on the surrounding environment. CsMP dissolution experiments were conducted in solutions with various solute components and pH levels at 60 °C. In neutral and basic solutions, the estimated dissolution rate was accelerated by alkali ions such as Na+, which is known to play a catalytic role for the dissolution of silica. In contrast, the dissolution in acid was slow even in the presence of alkali ions. The dissolution under acid conditions was possibly retarded by a thin amorphous silica layer formed on the CsMP surfaces. Such characteristics of the dissolution are consistent with that of silica-rich glass. To infer the dissolution behavior of CsMPs in the human body, the dissolution rate in Ringer’s solution at 37 °C was estimated as 1.00 ± 0.37 μm/year.

    DOI

  • Chemical composition of carbonaceous asteroid Ryugu from synchrotron spectroscopy in the mid- to far-infrared of Hayabusa2-returned samples

    Emmanuel Dartois, Yoko Kebukawa, Hikaru Yabuta, Jérémie Mathurin, Cécile Engrand, Jean Duprat, Laure Bejach, Alexandre Dazzi, Ariane Deniset-Besseau, Lydie BONAL, Eric Quirico, Christophe Sandt, Ferenc Borondics, Jens Barosch, George D. Cody, Bradley De Gregorio, MINAKO HASHIGUCHI, David A. L. Kilcoyne, Mutsumi Komatsu, Zita Martins, Megumi Matsumoto, Gilles Montagnac, Smail Mostefaoui, Larry R. Nittler, Takuji Ohigashi, Taiga Okumura, Laurent Remusat, Scott Sandford, Miho Shigenaka, Rhonda Stroud, Hiroki Suga, Yoshio Takahashi, Yasuo Takeichi, Yusuke Tamenori, Maximilien Verdier-Paoletti, Shohei Yamashita, Tomoki Nakamura, Tomoyo Morita, Mizuha Kikuiri, Kana Amano, Eiichi Kagawa, Takaaki Noguchi, Hiroshi Naraoka, Ryuji Okazaki, Kanako Sakamoto, Hisayoshi Yurimoto, Masanao Abe, Kanami Kamide, Akiko Miyazaki, Aiko Nakato, Satoru Nakazawa

    Astronomy &amp; Astrophysics   671  2023.03

     View Summary

    <jats:p><jats:italic>Context.</jats:italic> The current period is conducive to exploring our Solar System's origins with recent and future space sample return missions, which provide invaluable information from known Solar System asteroids and comets The Hayabusa2 mission of the Japan Aerospace Exploration Agency (JAXA) recently brought back samples from the surface of the Ryugu carbonaceous asteroid.</jats:p>
    <jats:p><jats:italic>Aims.</jats:italic> We aim to identify the different forms of chemical composition of organic matter and minerals that constitute these Solar System primitive objects, to shed light on the Solar System's origins.</jats:p>
    <jats:p><jats:italic>Methods.</jats:italic> In this work, we recorded infrared (IR) hyper-spectral maps of whole-rock Ryugu asteroid samples at the highest achievable spatial resolution with a synchrotron in the mid-IR (MIR). Additional global far-IR (FIR) spectra of each sample were also acquired.</jats:p>
    <jats:p><jats:italic>Results.</jats:italic> The hyper-spectral maps reveal the variability of the functional groups at small scales and the intimate association of phyl-losilicates with the aliphatic components of the organic matter present in Ryugu. The relative proportion of column densities of the identified IR functional groups (aliphatics, hydroxyl + interlayer and/or physisorbed water, carbonyl, carbonates, and silicates) giving access to the composition of the Ryugu samples is estimated from these IR hyper-spectral maps. Phyllosilicate spectra reveal the presence of mixtures of serpentine and saponite. We do not detect anhydrous silicates in the samples analysed, at the scales probed. The carbonates are dominated by dolomite. Aliphatics organics are distributed over the whole samples at the micron scale probed with the synchrotron, and intimately mixed with the phyllosilicates. The aromatic C=C contribution could not be safely deconvolved from OH in most spectra, due to the ubiquitous presence of hydrated minerals. The peak intensity ratios of the organics methylene to methyl (CH<jats:sub>2</jats:sub>/CH<jats:sub>3</jats:sub>) of the Ryugu samples vary between about 1.5 and 2.5, and are compared to the ratios in chondrites from types 1 to 3. Overall, the mineralogical and organic characteristics of the Ryugu samples show similarities with those of CI chondrites, although with a noticeably higher CH<jats:sub>2</jats:sub>/CH<jats:sub>3</jats:sub> in Ryugu than generally measured in C1 chondrites collected on Earth, and possibly a higher carbonate content.</jats:p>

    DOI

  • Macromolecular organic matter in samples of the asteroid (162173) Ryugu

    Hikaru Yabuta, George D. Cody, Cécile Engrand, Yoko Kebukawa, Bradley De Gregorio, Lydie Bonal, Laurent Remusat, Rhonda Stroud, Eric Quirico, Larry Nittler, Minako Hashiguchi, Mutsumi Komatsu, Taiga Okumura, Jérémie Mathurin, Emmanuel Dartois, Jean Duprat, Yoshio Takahashi, Yasuo Takeichi, David Kilcoyne, Shohei Yamashita, Alexandre Dazzi, Ariane Deniset-Besseau, Scott Sandford, Zita Martins, Yusuke Tamenori, Takuji Ohigashi, Hiroki Suga, Daisuke Wakabayashi, Maximilien Verdier-Paoletti, Smail Mostefaoui, Gilles Montagnac, Jens Barosch, Kanami Kamide, Miho Shigenaka, Laure Bejach, Megumi Matsumoto, Yuma Enokido, Takaaki Noguchi, Hisayoshi Yurimoto, Tomoki Nakamura, Ryuji Okazaki, Hiroshi Naraoka, Kanako Sakamoto, Harold C. Connolly, Dante S. Lauretta, Masanao Abe, Tatsuaki Okada, Toru Yada, Masahiro Nishimura, Kasumi Yogata, Aiko Nakato, Miwa Yoshitake, Ayako Iwamae, Shizuho Furuya, Kentaro Hatakeda, Akiko Miyazaki, Hiromichi Soejima, Yuya Hitomi, Kazuya Kumagai, Tomohiro Usui, Tasuku Hayashi, Daiki Yamamoto, Ryota Fukai, Seiji Sugita, Kohei Kitazato, Naru Hirata, Rie Honda, Tomokatsu Morota, Eri Tatsumi, Naoya Sakatani, Noriyuki Namiki, Koji Matsumoto, Rina Noguchi, Koji Wada, Hiroki Senshu, Kazunori Ogawa, Yasuhiro Yokota, Yoshiaki Ishihara, Yuri Shimaki, Manabu Yamada, Chikatoshi Honda, Tatsuhiro Michikami, Moe Matsuoka, Naoyuki Hirata, Masahiko Arakawa, Chisato Okamoto, Masateru Ishiguro, Ralf Jaumann, Jean-Pierre Bibring, Matthias Grott, Stefan Schröder, Katharina Otto, Cedric Pilorget, Nicole Schmitz, Jens Biele, Tra-Mi Ho, Aurélie Moussi-Soffys, Akira Miura, Hirotomo Noda, Tetsuya Yamada, Keisuke Yoshihara, Kosuke Kawahara, Hitoshi Ikeda, Yukio Yamamoto, Kei Shirai, Shota Kikuchi, Naoko Ogawa, Hiroshi Takeuchi, Go Ono, Yuya Mimasu, Kent Yoshikawa, Yuto Takei, Atsushi Fujii, Yu-ichi Iijima, Satoru Nakazawa, Satoshi Hosoda, Takahiro Iwata, Masahiko Hayakawa, Hirotaka Sawada, Hajime Yano, Ryudo Tsukizaki, Masanobu Ozaki, Fuyuto Terui, Satoshi Tanaka, Masaki Fujimoto, Makoto Yoshikawa, Takanao Saiki, Shogo Tachibana, Sei-ichiro Watanabe, Yuichi Tsuda

    Science   379 ( 6634 )  2023.02

     View Summary

    Samples of the carbonaceous asteroid (162173) Ryugu were collected and brought to Earth by the Hayabusa2 spacecraft. We investigated the macromolecular organic matter in Ryugu samples and found that it contains aromatic and aliphatic carbon, ketone, and carboxyl functional groups. The spectroscopic features of the organic matter are consistent with those in chemically primitive carbonaceous chondrite meteorites that experienced parent-body aqueous alteration (reactions with liquid water). The morphology of the organic carbon includes nanoglobules and diffuse carbon associated with phyllosilicate and carbonate minerals. Deuterium and/or nitrogen-15 enrichments indicate that the organic matter formed in a cold molecular cloud or the presolar nebula. The diversity of the organic matter indicates variable levels of aqueous alteration on Ryugu’s parent body.

    DOI

  • Infrared absorption spectra from organic matter in the asteroid Ryugu samples: Some unique properties compared to unheated carbonaceous chondrites

    Yoko Kebukawa, Eric Quirico, Emmanuel Dartois, Hikaru Yabuta, Laure Bejach, Lydie Bonal, Alexandre Dazzi, Ariane Deniset‐Besseau, Jean Duprat, Cecile Engrand, Jérémie Mathurin, Jens Barosch, George D. Cody, Bradley De Gregorio, Minako Hashiguchi, Kanami Kamide, David Kilcoyne, Mutsumi Komatsu, Zita Martins, Gilles Montagnac, Smail Mostefaoui, Larry R. Nittler, Takuji Ohigashi, Taiga Okumura, Laurent Remusat, Scott Sandford, Miho Shigenaka, Rhonda Stroud, Hiroki Suga, Yoshio Takahashi, Yasuo Takeichi, Yusuke Tamenori, Maximilien Verdier‐Paoletti, Daisuke Wakabayashi, Shohei Yamashita, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei‐ichiro Watanabe, Yuichi Tsuda

    Meteoritics &amp; Planetary Science    2023

     View Summary

    Abstract

    The infrared spectral characteristics of organic‐rich acid residues prepared from Ryugu samples returned by the JAXA Hayabusa2 mission generally match those from unheated carbonaceous chondrite meteorites, but the residues from Ryugu are richer in methyl and methylene functional groups and have higher CH2/CH3 ratios. Moreover, two distinct outlier carbonaceous phases are found; one with spectral characteristics of N‐H functional groups, likely amides, and a second phase containing less nitrogen. Such infrared characteristics of Ryugu organic matter might indicate the pristine nature of the freshly collected samples and reflect the near‐surface chemistry in the parent asteroid.

    DOI

  • Presolar Stardust in Asteroid Ryugu

    Jens Barosch, Larry Nittler, Jianhua Wang, Conel M.O'D. Alexander, Bradley De Gregorio, Cecile Engrand, Yoko Kebukawa, Kazuhide Nagashima, R. M. Stroud, Hikaru Yabuta, Yoshinari Abe, Jérôme Aléon, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Laure Bejach, Martin Bizzarro, Lydie Bonal, Audrey Bouvier, Richard Carlson, Marc Chaussidon, Byeon-Gak Choi, George Cody, Emmanuel Dartois, Nicolas Dauphas, Andrew Davis, Alexandre Dazzi, Ariane Deniset-Besseau, Tommaso Di Rocco, Jean Duprat, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Minako Hashiguchi, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Kanami Kamide, Noriyuki Kawasaki, Arthur Kilcoyne, Noriko T. Kita, Kouki Kitajima

    The Astrophysical Journal Letters   935 ( 1 )  2022.08

     View Summary

    We have conducted a NanoSIMS-based search for presolar material in samples recently returned from C-type asteroid Ryugu as part of JAXA's Hayabusa2 mission. We report the detection of all major presolar grain types with O- and C-anomalous isotopic compositions typically identified in carbonaceous chondrite meteorites: 1 silicate, 1 oxide, 1 O-anomalous supernova grain of ambiguous phase, 38 SiC, and 16 carbonaceous grains. At least two of the carbonaceous grains are presolar graphites, whereas several grains with moderate C isotopic anomalies are probably organics. The presolar silicate was located in a clast with a less altered lithology than the typical extensively aqueously altered Ryugu matrix. The matrix- normalized presolar grain abundances in Ryugu are 4.8(-2.6)(+4.7) ppm for O-anomalous grains, 25(-)(5)(+)(6) ppm for SiC grains, and 11(-3)(+5) ppm for carbonaceous grains. Ryugu is isotopically and petrologically similar to carbonaceous Ivuna-type (CI) chondrites. To compare the in situ presolar grain abundances of Ryugu with CI chondrites, we also mapped Ivuna and Orgueil samples and found a total of 15 SiC grains and 6 carbonaceous grains. No O-anomalous grains were detected. The matrix-normalized presolar grain abundances in the CI chondrites are similar to those in Ryugu: 23(-6)(+7) ppm SiC and 9.0 (+5.4)(-3)(.6) ppm carbonaceous grains. Thus, our results provide further evidence in support of the Ryugu-CI connection. They also reveal intriguing hints of small-scale heterogeneities in the Ryugu samples, such as locally distinct degrees of alteration that allowed the preservation of delicate presolar material.

    DOI

  • Microstructure and mineral components of the outer dentin of Chimaera phantasma tooth plates

    Mayumi Iijima, Taiga Okumura, Toshihiro Kogure, Michio Suzuki

    The Anatomical Record   304 ( 12 ) 2865 - 2878  2021  [Refereed]

    DOI

  • Functional analyses of chitinolytic enzymes in the formation of calcite prisms in Pinctada fucata

    Hiroyuki Kintsu, Alberto Pérez-Huerta, Shigeru Ohtsuka, Taiga Okumura, Shinsuke Ifuku, Koji Nagata, Toshihiro Kogure, Michio Suzuki

    Micron   145   103063 - 103063  2021  [Refereed]

    DOI

  • Inner structures and physicochemical properties of radiocesium-bearing microparticles emitted by the FDNPP accident

    Taiga Okumura

    Chikyukagaku   55 ( 1 ) 31 - 40  2021  [Refereed]

    DOI

  • Distinction between Radiocesium (RCs)-bearing Microparticles and RCs-sorbing Minerals Derived from the Fukushima Nuclear Accident Using Acid Treatment

    Taiga Okumura, Noriko Yamaguchi, Toshihiro Kogure

    Chemistry Letters   49 ( 11 ) 1294 - 1297  2020  [Refereed]

    DOI

  • Reactor environment during the Fukushima nuclear accident inferred from radiocaesium-bearing microparticles

    Taiga Okumura, Noriko Yamaguchi, Hiroki Suga, Yoshio Takahashi, Hiroyo Segawa, Toshihiro Kogure

    Scientific Reports   10 ( 1 ) 1352  2020  [Refereed]

    Authorship:Lead author, Corresponding author

     View Summary

    © 2020, The Author(s). Radiocaesium-bearing microparticles (CsMPs), which are substantially silicate glass, were formed inside the damaged reactor and released to the environment by the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011. The present study reports several valuable findings regarding their composition and structure using advanced microanalytical techniques. X-ray absorption near-edge structure of Fe L3-absorption indicated that the oxidation state of the iron dissolved in the glass matrix of the CsMPs was originally nearly divalent, suggesting that the atmosphere in which the CsMPs were formed during the accident was considerably reductive. Another major finding is that sodium, which has not been recognised as a constituent element of CsMPs thus far, is among the major elements in the glass matrix. The atomic percent of Na is higher than that of other alkali elements such as K and Cs. Furthermore, halite (NaCl) was found as an inclusion inside a CsMP. The existence of Na in CsMPs infers that seawater injected for cooling might reach the inside of the reactor before or during the formation of the CsMPs. These results are valuable to infer the environment inside the reactor during the accident and the debris materials to be removed during the decommissioning processes.

    DOI PubMed

  • 下水汚泥等における放射性セシウムの存在形態と挙動に関する調査

    岩﨑宏和, 小暮敏博, 奥村大河, 齊藤進, 江藤隆

    下水道協会誌    2019

    DOI

  • Finding Radiocesium-bearing Microparticles More Minute than Previously Reported, Emitted by the Fukushima Nuclear Accident

    Taiga Okumura, Noriko Yamaguchi, Toshihiro Kogure

    Chemistry Letters   48 ( 11 ) 1336 - 1338  2019  [Refereed]

    DOI

  • Analysis of Radioactive Microparticles Emitted from the Fukushima Nuclear Plant by Using Advanced STEM Techniques

    Taiga Okumura, Toru Hara, Toshihiro Kogure

    Microscopy and Microanalysis   25 ( S2 ) 1582 - 1583  2019  [Refereed]

    DOI

  • A review of Cs-bearing microparticles in the environment emitted by the Fukushima Dai-ichi Nuclear Power Plant accident

    Yasuhito Igarashi, Toshihiro Kogure, Yuichi Kurihara, Hikaru Miura, Taiga Okumura, Yukihiko Satou, Yoshio Takahashi, Noriko Yamaguchi

    Journal of Environmental Radioactivity   205-206   101 - 118  2019  [Refereed]

     View Summary

    Scientists face challenge in identifying the radioactive materials which are found as dotted images on various imaging plate (IP) autoradiographic photos of radioactively contaminated materials by the Fukushima Dai-ichi Nuclear Power Plant (F1NPP, or FDNPP) accident, such as air filter, fugitive dust, surface soil, agricultural materials, and water-shed samples. It has been revealed that they are minute particles with distinct morphology and elemental composition with high specific radioactivity, and different from those of the so-called Chernobyl hot particles. Basically, they are glassy particles once molten, composed of Si, O, Fe, Zn etc. with highly concentrated radiocaesium, which can be called as radiocaesium-bearing microparticles (CsMP). At present, CsMP can be classified into two types, Types-A and-B, which are characterized by different specific radioactivity, Cs-134/Cs-137 ratio, size and morphology, and geographic distribution around F1NPP. Such studies on the CsMP from various aspects have provided valuable information about what happened in the nuclear reactors during the F1NPP accident and fates of the CsMP in the environment. This review first provides a retrospective view on the research history of the CsMP, which is helpful to understand the unique character of the CsMP. Subsequently, more details about the current understanding of the natures of these hot particles, such as origin, morphology, chemical compositions, thermal properties, water-solubility, and secondary migration of CsMP in river and ocean systems are described with future prospects.

    DOI

  • Inner structure and inclusions in radiocesium-bearing microparticles emitted in the Fukushima Daiichi Nuclear Power Plant accident

    Taiga Okumura, Noriko Yamaguchi, Terumi Dohi, Kazuki Iijima, Toshihiro Kogure

    Microscopy   68 ( 3 ) 234 - 242  2019  [Refereed]

    DOI

  • Dissolution behaviour of radiocaesium-bearing microparticles released from the Fukushima nuclear plant

    Taiga Okumura, Noriko Yamaguchi, Terumi Dohi, Kazuki Iijima, Toshihiro Kogure

    Scientific Reports   9   3520  2019  [Refereed]

    DOI

  • Soil decontamination by heat treatments with chlorides under low-pressure conditions

    Shimoyama Iwao, Kogure Toshihiro, Okumura Taiga, Baba Yuji

    Abstracts of Annual Meeting of the Geochemical Society of Japan   65 ( 0 ) 244 - 244  2018  [Refereed]

     View Summary

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    DOI CiNii

  • Chitin degraded by chitinolytic enzymes induces crystal defects of calcites

    Hiroyuki Kintsu, Taiga Okumura, Lumi Negishi, Shinsuke Ifuku, Toshihiro Kogure, Shohei Sakuda, Michio Suzuki

    Biomineralization     375 - 381  2018  [Refereed]

    DOI

  • On the transition temperature to calcite and cell lengths for various biogenic aragonites

    Taiga Okumura, Masahiro Yoshimura, Toshihiro Kogure

    Biomineralization     3 - 10  2018  [Refereed]

    DOI

  • Sulfate-containing calcite: crystallographic characterization of natural and synthetic materials

    Taiga Okumura, Hye-jin Kim, Jin-wook Kim, Toshihiro Kogure

    European Journal of Mineralogy   30 ( 5 ) 929 - 937  2018  [Refereed]

    DOI

  • Secondary radiocesium contamination of agricultural products by resuspended matter

    Nihei, N, Yoshimura, K, Okumura, T, Tanoi, K, Iijima, K, Kogure, T, Nakanishi, T

    Journal of Radioanalytical and Nuclear Chemistry   318 ( 1 ) 341 - 346  2018  [Refereed]

    DOI

  • Electron tomography of whole cultured cells using novel transmission electron imaging technique

    Taiga Okumura, Minami Shoji, Akiko Hisada, Yusuke Ominami, Sukehiro Ito, Tatsuo Ushiki, Masato Nakajima, Takashi Ohshima

    Micron   104   21 - 25  2018.01  [Refereed]

     View Summary

    Since a three-dimensional (3D) cellular ultrastructure is significant for biological functions, it has been investigated using various electron microscopic techniques. Although transmission electron microscopy (TEM)-based techniques are traditionally used, cells must be embedded in resin and sliced into ultrathin sections in sample preparation processes. Block-face observation using a scanning electron microscope (SEM) has also been recently applied to 3D observation of cellular components, but this is a destructive inspection and does not allow re-examination. Therefore, we developed electron tomography using a transmission electron imaging technique called Plate-TEM. With Plate-TEM, the cells cultured directly on a scintillator plate are inserted into a conventional SEM equipped with a Plate-TEM observation system, and their internal structures are observed by detecting scintillation light produced by electrons passing through the cells. This technology has the following four advantages. First, the cells cultured on the plate can be observed at electron-microscopic resolution since they remain on the plate. Second, both surface and internal information can be obtained simultaneously by using electron- and photo-detectors, respectively, because a Plate-TEM detector is installed in an SEM. Third, the cells on the scintillator plate can also be inspected using light microscopy because the plate has transparent features. Finally, correlative observation with other techniques, such as conventional TEM, is possible after Plate-TEM observation because Plate-TEM is a non-destructive analysis technique. We also designed a sample stage to tilt the samples for tomography with Plate-TEM, by which 3D organization of cellular structures can be visualized as a whole cell. In the present study, Mm2T cells were investigated using our tomography system, resulting in 3D visualization of cell organelles such as mitochondria, lipid droplets, and microvilli. Correlative observations with various imaging techniques were also conducted by successive observations with light microscopy, SEM, Plate-TEM, and conventional TEM. Consequently, the Plate-TEM tomography technique encourages understanding of cellular structures at high resolution, which can contribute to cellular biological research.

    DOI

  • Loss of radioactivity in radiocesium-bearing microparticles emitted from the Fukushima Dai-ichi nuclear power plant by heating

    Taiga Okumura, Noriko Yamaguchi, Terumi Dohi, Kazuki Iijima, Toshihiro Kogure

    Scientific Reports   8   9707  2018  [Refereed]

    DOI

  • Crystal defects induced by chitin and chitinolytic enzymes in the prismatic layer of Pinctada fucata

    Hiroyuki Kintsu, Taiga Okumura, Lumi Negishi, Shinsuke Ifuku, Toshihiro Kogure, Shohei Sakuda, Michio Suzuki

    BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS   489 ( 2 ) 89 - 95  2017.07  [Refereed]

     View Summary

    Biomineralization, in which organisms create biogenic hard tissues, with hardness or flexibility enhanced by organic inorganic interaction is an interesting and attractive focus for application of biomimetic functional materials. Calcites in the prismatic layer of Pinctada fucata are tougher than abiotic calcites due to small crystal defects. However, the molecular mechanism of the defect formation remains unclear. Here, chitin and two chitinolytic enzymes, chitinase and chitobiase, were identified as organic matrices related to for the formation of small crystal defects in the prismatic layer. Experiments with a chitinase inhibitor in vivo showed chitinase is necessary to form the prismatic layer. Analysis of calcite crystals, which were synthesized in a chitin hydrogel treated with chitinolytic enzymes, by electron microscopy and X-ray diffraction showed that crystal defects became larger as chitin was more degraded. These results suggest that interactions between chitin and calcium carbonate increase as chitin is thinner. (C) 2017 Published by Elsevier Inc.

    DOI

  • Whole-cell tomography using a conventional scanning electron microscope

    Taiga Okumura, Minami Shoji, Akiko Hisada, Yusuke Ominami, Tatsuo Ushiki, Masato Nakajima, Takashi Ohshima

    Microscopy and Microanalysis   21 ( S3 ) 907 - 908  2015  [Refereed]

    DOI

  • Direct observation of cesium at the interlayer region in phlogopite mica

    Taiga Okumura, Kenji Tamura, Eiko Fujii, Hirohisa Yamada, Toshihiro Kogure

    MICROSCOPY   63 ( 1 ) 65 - 72  2014.02  [Refereed]

     View Summary

    To investigate the sorption mechanism of cesium (Cs) into clay minerals, high-resolution (scanning) transmission electron microscopy (TEM/STEM) imaging of Cs in mica (phlogopite) has been conducted. Platy phlogopite powders were immersed in a cesium chloride (CsCl) solution to achieve Cs+-K+ ion-exchange at the interlayer regions in phlogopite. To observe many phlogopite particles with the incident electron beam parallel to the mica layers, cross-sectional thin specimens were prepared from sedimented particles using a focused ion beam. High-angle annular dark-field imaging with STEM is superior to conventional high-resolution TEM (HRTEM) for visualizing Cs at interlayer sites even in thicker crystal regions and/or at lower magnification due to the intense Z-contrast of Cs. However, HRTEM is also practical for estimating the concentration of Cs at the interlayer site from the thickness dependence of the contrast at the interlayer region. Cs sorption of micas was previously thought to be localized mainly at the frayed-edge sites of mica crystals. However, the present observations indicate that Cs substitution of K occurs not around crystal edges but deep inside the crystals along specific interlayer regions.

    DOI

  • Microstructural control of calcite via incorporation of intracrystalline organic molecules in shells

    Taiga Okumura, Michio Suzuki, Hiromichi Nagasawa, Toshihiro Kogure

    JOURNAL OF CRYSTAL GROWTH   381   114 - 120  2013.10  [Refereed]

     View Summary

    It is widely accepted that organic substances regulate or influence the structure of biominerals, but its direct evidences are not plenty. Here we show that the crystallographic microstructures in biotic calcites arise from incorporated intracrystalline organic molecules (IOMs), through a comparison between biotic calcites in shells and synthetic ones with the IOMs extracted from the shells. Although the prismatic layers of a pearl oyster (Pinctada fucata) and a pen shell (Atrina pectinata) morphologically resemble eact other, the crystallographic features of constituent calcites are considerably differnet; in Pinctada, the IOMs are distributed inhomogeneously to form small-angle grain boundaries and associated crystal defects, whereas in Atrina, the IOMs are distributed almost homogeneously and defects are rare in the calcite crystals. We conducted in vitro calcite syntheses in the presence of the IOMs in EDTA-soluble extracts from the prisms. The IOMs in the extracts from Pinctada and Atrina were incorporated into synthetic calcites in a different manner, exhibiting defect-rich/free features as observed in the nature shells. With regard to amino acid compositions of the IOMs. the extract from Atrina has a higher proportion of acidic amino acids than that from Pinctada, implying that acidic proteins do not correlate directly to their affinity for aclcium carbonate crystals. (C) 2013 Elsevier B.V. All rights reserved.

    DOI

  • Distribution and role of intracrystalline organic macromolecules in the pearl oyster, Pinctada fucata

    Toshihiro Kogure, Michio Suzuki, Naoki Yokoo, Taiga Okumura, Hiromichi Nagasawa

    Recent Advances in Pearl Research     125 - 135  2013  [Refereed]

  • Microstructural Variation of Biogenic Calcite with Intracrystalline Organic Macromolecules

    Taiga Okumura, Michio Suzuki, Hiromichi Nagasawa, Toshihiro Kogure

    CRYSTAL GROWTH & DESIGN   12 ( 1 ) 224 - 230  2012.01  [Refereed]

     View Summary

    The influence of intracrystalline organic macromolecules on the microstructure and properties of host crystals has been investigated by micro- and macroscopic analyses for several biogenic calcites: prisms in the outer layers of pearl oysters (Pinctada fucata), oysters (Crassostrea nippona), and pen shells (Atrina pectinata); folia in the inner layers of C. nippona and scallops (Patinopecten yessoensis); and coccoliths of Pleurochrysis carterae. Thermogravimetric analysis showed that the three prisms contain more intracrystalline organic matter than the folia and coccolith. Transmission electron microscopy (TEM) revealed that Fresnel contrasts, which probably correspond to the intracrystalline organic macromolecules, are distributed inhomogeneously and partition the calcite crystals into subgrains with small misorientations in the prisms of P. fucata and C. nippona. From peak broadening in powder X-ray diffraction (XRD), we found a large variance of lattice spacing (Delta d/d) in the two prisms. On the other hand, intracrystalline macromolecules in the prisms of A. pectinata are distributed rather homogeneously and do not influence the crystal structure, as revealed by diffraction contrast in TEM. XRD of the prisms in A. pectinata indicates significantly smaller Delta d/d than that for the other two prisms. In the folia and coccolith, intracrystalline macromolecules were scarcely observed in TEM, and the estimated Delta d/d is small.

    DOI

  • Localization of intracrystalline organic macromolecules in mollusk shells

    Michio Suzuki, Taiga Okumura, Hiromichi Nagasawa, Toshihiro Kogure

    JOURNAL OF CRYSTAL GROWTH   337 ( 1 ) 24 - 29  2011.12  [Refereed]

     View Summary

    As a crucial first step for understanding the organic-inorganic interaction in biomineralization of mollscan shells, localization of the intracrystalline organic macromolecules in biogenic calcium carbonate crystals of the nacreous, prismatic (Pinctada fucata) and foliated (Cellana toreuma) microstructures were investigated using Fresnel contrast analysis in a transmission electron microscope. Spherular Fresnel contrasts in the crystals correspond to organic substances, which was confirmed by the detection of 1s -&gt; m* (C=C) transition peak at 284 eV in electron energy loss spectroscopy. Nanosized (5-10 nm) spherules in the aragonite tablets constituting the nacreous layer of P. fucata specifically concentrate in the vicinity of the interlamellar membrane between the aragonite tablets. The dominant sizes of the organic macromolecules extracted by dissolving the aragonite tablets in the nacreous layer of P. fucata were estimated using the gel-filtration analysis to be roughly 10 and 4 nm, which dimensionally corresponds to the sizes observed by Fresnel contrast imaging in the tablets. These results will serve for understanding the functions of intracrystalline organic macromolecules in mollusk shells. (C) 2011 Elsevier B.V. All rights reserved.

    DOI

  • Characteristics of biogenic calcite in the prismatic layer of a pearl oyster, Pinctada fucata

    Taiga Okumura, Michio Suzuki, Hiromichi Nagasawa, Toshihiro Kogure

    MICRON   41 ( 7 ) 821 - 826  2010.10  [Refereed]

     View Summary

    The fine structure of the calcite prism in the outer layer of a pearl oyster, Pinctada fucata, has been investigated using various electron beam techniques, in order to understand its characteristics and growth mechanism including the role of intracrystalline organic substances. As the calcite prismatic layer grows thicker, sinuous boundaries develop to divide the prism into a number of domains. The crystal misorientation between the adjacent domains is several to more than ten degrees. The component of the misorientation is mainly the rotation about the c-axis. There is no continuous organic membrane at the boundaries. Furthermore, the crystal orientation inside the domains changes gradually, as indicated by the electron back-scattered diffraction (EBSD) in a scanning electron microscope (SEM). Transmission electron microscopy (TEM) examination revealed that the domain consists of sub-grains of a few hundred nanometers divided by small-angle grain boundaries, which are probably the origin of the gradual change of the crystal orientation inside the domains. Spherular Fresnel contrasts were often observed at the small-angle grain boundaries, in defocused TEM images. Electron energy-loss spectroscopy (EELS) indicated the spherules are organic macromolecules, suggesting that incorporation of organic macromolecules during the crystal growth forms the sub-grain structure of the calcite prism. (c) 2010 Elsevier Ltd. All rights reserved.

    DOI

  • Some reference data for the JCSS clay specimens

    Ritsuro Miyawaki, Takashi Sano, Fumihiko Ohashi, Masaya Suzuki, Toshihiro Kogure, Taiga Okumura, Jun Kameda, Takuya Umezome, Tsutomu Sato, Daisuke Chino, Kaori Hiroyama, Hirohisa Yamada, Kenji Tamura, Kazuya Morimoto, Seiichiro Uehara, Tamao Hatta

    Journal of the Clay Science Society of Japan   48 ( 4 ) 158 - 198  2010  [Refereed]

    DOI CiNii

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Presentations

  • 微細構造解析によって明らかになった放射性セシウム含有微粒子(CsMP)の正体

    奥村大河, 山口紀子, 小暮敏博  [Invited]

    第82回分析化学討論会 

    Presentation date: 2022.05

  • 福島原発事故により発生した放射性微粒子の環境動態:加熱および溶解特性について

    奥村大河, 山口紀子, 土肥輝美, 藤原健壮, 飯島和毅, 小暮敏博  [Invited]

    日本地球惑星科学連合2019年大会 

    Presentation date: 2019.05

  • 結晶内に存在する有機高分子によるバイオミネラル結晶の構造制御

    奥村大河, 鈴木道生, 長澤寛道, Buseck P.R, 小暮敏博  [Invited]

    日本地球惑星科学連合2013年大会 

    Presentation date: 2013.05

Research Projects

  • バイオミネラリゼーションにおける有機・無機相互作用の分子レベルでの理解

    日本学術振興会  科学研究費助成事業

    Project Year :

    2024.06
    -
    2026.03
     

    奥村 大河

  • OBF-STEM法を用いたファーテライトの結晶構造解明

    三菱財団  第55回 自然科学研究助成(一般助成)

    Project Year :

    2024.10
    -
    2025.09
     

  • レアアースのイオン吸着型鉱床の分子地球化学:その形成機構・探査・抽出法・モデル化

    日本学術振興会  科学研究費助成事業

    Project Year :

    2022.04
    -
    2025.03
     

    高橋 嘉夫, 柏原 輝彦, 奥村 大河

  • バイオミネラル中の微量元素と有機分子の可視化によるvital effect精緻化

    日本学術振興会  科学研究費助成事業

    Project Year :

    2022.04
    -
    2025.03
     

    奥村 大河, 鈴木 道生

  • バイオミネラリゼーションにおけるアラゴナイトの双晶密度制御機構の解明

    日本学術振興会  科学研究費助成事業

    Project Year :

    2021.07
    -
    2023.03
     

    鈴木 道生, 奥村 大河

     View Summary

    炭酸カルシウムのアラゴナイト結晶は双晶と呼ばれる、結晶内のカルシウムと炭酸の原子配置が反転した現象が起こり易いことが知られている。この双晶の密度が貝殻の種類によって厳密に制御されていることから、貝殻に含まれる何らかの有機分子が双晶の密度や方向の制御に重要であると考えられた。そこで、双晶の密度の高い貝殻および双晶の密度の低い貝殻から有機分子を抽出し、in vitroのアラゴナイト結晶形成実験を行うことで、双晶の形成に重要な因子を特定する研究を行う。
    2021年度はコロナの影響もあり、研究のスタートアップのみを行った。まずはアラゴナイト結晶を形成するための基盤の作製を試みた。鉱物試料として販売されているモロッコ産のアラゴナイト結晶を購入し、柱状構造を樹脂に包埋した。包埋した柱に対して、精密切断機を用いて、完全に垂直に切断した。このように切断することで{001}の面を表出させた基盤を作成することができる。この基盤に対してアラゴナイト結晶を合成することが重要となる。
    また合成したアラゴナイト結晶を基盤から剥がし、XRDにて双晶の密度を定量化するために、まずはXRDの測定の条件の検討を行った。2021年度に新たに購入したXRDで装置のセッティングから行う予定だったが、半導体不足の影響により装置が5月に納入されたため、2022年度にセッティングを開始する予定である。

  • バイオミネラルにおける双晶形成とアラゴナイト結晶内基質タンパク質の関係

    日本学術振興会  二国間交流事業

    Project Year :

    2021.04
    -
    2023.03
     

  • Evaluation of dissolution characteristics of radiocesium-bearing microparticles released by the Fukushima nuclear accident for the elucidation of their environmental dynamics

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Early-Career Scientists

    Project Year :

    2020.04
    -
    2022.03
     

    Okumura Taiga

     View Summary

    During the Fukushima nuclear accident in March 2011, radiocesium-bearing microparticles (CsMPs) were released into the environment from the damaged reactor. In this study, we succeeded in artificially synthesizing a glass that simulates CsMPs, and evaluated the dissolution characteristics of CsMPs using this glass. As a result, it was found that the glass dissolved much faster in seawater than in pure water, which supports the previous study.

  • Modeling re-distribution of radioactive cesium deposited by the accident of Fukushima Dai-ichi nuclear power station and predicting influences of the cesium in livelihood area

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

    Project Year :

    2015.04
    -
    2018.03
     

    Nishimura Taku, Renschler Chris, Hamamoto Shoichiro, Yamasaki Takuhei, Nihei Naoto, Yoshida Shuichiro, Kogure Toshihiro, Okumura Taiga, Hadano Satoshi

     View Summary

    In this study, we confirmed discharge of radioactive Cs (RCs) is small and was correlated with sediment discharge. However, the relationship between RCs and sediment discharges has changed by a flooding during large typhoon at summer of 2015. From an examination of a smaller forested watershed by a combination of numerical simulation, monitoring of river discharge and ground truth revealed that quite limited area in the forest floor contributed sediment and RCs discharges from the forest. This suggested low annual RCs discharge rates from forests.
    Observation and analysis by transmission and scanning electron microscopy and energy dispersive X-ray spectrometry suggested cesium-bearing particle in river water samples had a role on radioactivity of the water samples, especially the sample contained less suspended solids.

  • バイオミネラリゼーションにおける生体高分子が関与した炭酸カルシウムの結晶成長機構

    日本学術振興会  科学研究費助成事業 特別研究員奨励費

    Project Year :

    2011
    -
    2013
     

    奥村 大河

     View Summary

    生物が関与して形成される固体無機物質はバイオミネラルと呼ばれ、それを構成する結晶の結晶相や方位、形態、機械的性質などは高度に制御されている。この要因として、結晶内部に含有されている有機高分子が重要な役割を果たしていると考えられている。そこで私は軟体動物の貝殻を研究対象とし、結晶内に存在する有機高分子の機能を解明することを目指した。
    本研究では、炭酸カルシウムの多形の一つである方解石で構成された貝殻に着目した。まず、アコヤガイ(Pinctada fucata)、タイラギ(Atrina pectinata)、イワガキ(Crassostrea nippona)のという三種の二枚貝貝殻の稜柱層を調べた。EDTA(エチレンジアミン四酢酸)で結晶を溶解し、残渣として残った有機高分子を走査型電子顕微鏡(SEM)で観察すると、アコヤガイとイワガキにはネットワーク状の、タイラギには細い繊維状の有機高分子が見られた。次に走査透過電子顕微鏡(STEM)により得られるZコントラスト像の電子線トモグラフィーを用いて、有機高分子の3次元分布を可視化した。その結果、やはりアコヤガイやイワガキではネットワーク状の有機高分子が存在していることが確かめられた。ネットワーク状の有機高分子は結晶に小角粒界を伴ったsub-grain構造を導入することが透過型電子顕微鏡(TEM)観察により分かり、結晶成長の物理的障害となっていることが考えられた。ネットワーク状の有機高分子がsub-grain構造を導入している様子は、二枚貝のみならず、巻貝のエゾアワビ(Haliotis discus hannai)やカモガイ(Collisella dorsuosa)の方解石結晶でも観察され、多種に渡って見られた。sub-grain構造は方解石結晶の機械的性質を向上させることが示唆されており、貝が生き残るための戦略としてこのように微細構造を制御していることが考えられた。またこのようなバイオミネラルにおける有機・無機相互作用は、新規の有機・無機複合ナノ材料の創製や、炭酸塩バイオミネラルの二酸化炭素固定による環境科学への応用が期待される。

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Misc

  • Structure, Composition, and Physicochemical Properties of Radiocesium-Bearing Microparticles Emitted by the Fukushima Daiichi Nuclear Power Plant Accident

    Taiga Okumura, Noriko Yamaguchi, Toshihiro Kogure

    Agricultural Implications of Fukushima Nuclear Accident (IV)     63 - 78  2023

    Authorship:Lead author, Corresponding author

     View Summary

    Abstract

    During the accident at TEPCO’s Fukushima Daiichi Nuclear Power Plant, radiocesium-bearing microparticles (CsMPs) were released from damaged reactors into the environment. These micron-sized spherical particles with high specific radioactivity have not been reported in previous nuclear accidents. Herein, the current understanding of the structure, composition, and physicochemical properties of CsMPs is summarized. Electron microscopy revealed that the CsMP matrix is composed of silicate glass containing Na, Cl, K, Fe, Zn, Rb, Sn, and Cs as major constituents. These elements are often inhomogeneously distributed, depending on the particle radius, and Cs was concentrated around the outer side of the particles. In addition, nanocrystals including Cr-rich oxides and chalcogenides were frequently found inside CsMPs. The average valence state of Fe in the CsMP glass matrix was almost Fe2+, indicating formation under a reducing atmosphere through condensation from the gas phase. Radiocesium diffused away from the CsMPs when heated to &gt;600 °C. Accordingly, CsMPs may lose their high specific radioactivity when related radiation-contaminated waste is incinerated at sufficiently high temperatures. Although CsMP solubility is low, they cannot be regarded as “insoluble” materials owing to their small size. CsMP dissolution rates depend on the pH and dissolved species in the solution, and their dissolution behavior is comparable to that of silica-rich glass. Based on these dissolution properties, a method for estimating CsMP abundance and spatial distribution in the environment was proposed. The findings detailed herein contribute to the comprehensive elucidation of CsMP environmental dynamics.

    DOI

  • 福島原発事故によって放出された放射性セシウム含有微粒子

    奥村大河, 小暮敏博

    令和3年度 低温科学研究センター年報   13   12 - 17  2022

    Authorship:Lead author, Corresponding author

  • 二枚貝の貝殻稜柱層内に存在するキチン繊維の形成機構の比較

    近都浩之, 奥村大河, 根岸瑠美, 中西啓仁, 永田宏次, 鈴木道生

    日本農芸化学会大会講演要旨集(Web)   2019  2019

    J-GLOBAL

  • Analysis of iron oxidation state and light elements in radiocesium-bearing microparticles emitted by the Fukushima nuclear accident

    Okumura Taiga, Suga Hiroki, Takahashi Yoshio, Kogure Toshihiro

    Abstracts of Annual Meeting of the Geochemical Society of Japan   66 ( 0 ) 194 - 194  2019

     View Summary

    <p></p>

    DOI CiNii

  • 二枚貝稜柱層における結晶欠陥形成因子の比較

    近都浩之, 奥村大河, 根岸瑠美, 永田宏次, 小暮敏博, 作田庄平, 鈴木道生

    日本農芸化学会大会講演要旨集(Web)   2018  2018

    J-GLOBAL

  • Functional analyses of organic network in the calcite crystal of the prismatic layer of Pinctada fucata

    SUZUKI Michio, KINTSU Hiroyuki, OKUMURA Taiga, NEGISHI Lumi, IFUKU Shinsuke, KOGURE Toshihiro, SAKUDA Shohei

    日本水産学会大会講演要旨集   2017 (CD-ROM)  2017

    J-GLOBAL

  • アコヤガイ稜柱層カルサイト結晶形成に関与するキチナーゼの働き

    近都浩之, 奥村大河, 根岸瑠美, 小暮敏博, 作田庄平, 鈴木道生

    日本農芸化学会大会講演要旨集(Web)   2017  2017

    J-GLOBAL

  • A role of the chitinolytic enzymes in calcite crystals of the prismatic layer in Pinctada fucata.

    近都浩之, 奥村大河, 根岸瑠美, 伊福伸介, 小暮敏博, 作田庄平, 鈴木道生

    キチン・キトサン研究   23 ( 2 )  2017

    J-GLOBAL

  • Relation between the organic network and the crystal defects in the calcite of the prismatic layer of Pinctada fucata

    KINTSU Hiroyuki, OKUMURA Taiga, NEGISHI Lumi, KOGURE Toshihiro, SAKUDA Shohei, SUZUKI Michio

    日本地球惑星科学連合大会予稿集(Web)   2016  2016

    J-GLOBAL

  • アコヤガイ貝殻稜柱層の炭酸カルシウム結晶形成を制御する有機基質に関する研究

    近都浩之, 奥村大河, 根岸瑠美, 小暮敏博, 作田庄平, 鈴木道生

    日本農芸化学会大会講演要旨集(Web)   2016  2016

    J-GLOBAL

  • バイオミネラル写真館

    小暮敏博, 向井広樹, 横尾直樹, 奥村大河, 藤井英子

    生物の科学 遺伝 7月号     2 - 8  2010

    Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)  

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Industrial Property Rights

  • 荷電粒子線装置

    特許6383650

    奥村大河, 大嶋卓, 大南祐介, 庄子美南, 久田明子, 米山明男

    Patent

 

Syllabus

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Social Activities

  • 電子顕微鏡で見るバイオミネラルの世界

    文京区教育センター  バイオミネラル展 

    2024.02
    -
     

Sub-affiliation

  • Faculty of Science and Engineering   Graduate School of Creative Science and Engineering