光合成マンガンクラスターに酸素発生機能をもたらす基本原理の抽出と検証

• Project Area: Creation of novel light energy conversion system through elucidation of the molecular mechanism of photosynthesis and its artificial design in terms of time and space
• Project/Area Number: 18H05167
• Research Category: Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
• Allocation Type: Single-year Grants
• Research Institution: Okayama University
• Principal Investigator: 磯部 寛 岡山大学, 異分野基礎科学研究所, 特任准教授 (00379281)
• Project Period (FY): 2018-04-01 – 2020-03-31
• Project Status: Completed (Fiscal Year 2019)
• Budget Amount: ¥6,500,000 (Direct Cost: ¥5,000,000、Indirect Cost: ¥1,500,000); Fiscal Year 2019: ¥3,250,000 (Direct Cost: ¥2,500,000、Indirect Cost: ¥750,000); Fiscal Year 2018: ¥3,250,000 (Direct Cost: ¥2,500,000、Indirect Cost: ¥750,000)
• Keywords: 光合成 / 光化学系II / マンガンクラスター / 水分解反応 / 機能発現

Outline of Annual Research Achievements

水を分解し生物の生存に必要な酸素を作り出す触媒であるMn4CaO5クラスターは、電子の授受に伴ってその構造を巧妙に変化させることで触媒活性を示す。本研究では、機能を発現する上で本質的に重要だと考えられる概念や原理・法則を見出すため、電子の属性である「電荷」と「スピン」に着目して、触媒がどのように化学反応を進めているのかを調べた。その結果、Mnクラスターが外部刺激に応答してその物理化学的挙動を変化させるスイッチング機能をもっていることが判明した。スイッチングは、基質水分子が高い酸化状態にあるクラスターの配位不飽和金属サイトに結合することでトポロジカル構造が異なる構造異性体と金属の電荷状態の間の対応関係が反転する現象を利用して、分子レベルで起こる。この機構において重要な役割を果たしているのが、基本構成原子であるMnイオンの電荷とスピンの可変性である。特に、Mn3+はヤーン・テラー（JT）効果によりeg軌道から生じる極めて強い方向性をもち、配位子の原子軌道と効果的な重なりを形成する。基質が捕捉されてスイッチがONになると、各MnイオンのJT歪みに起因する局所配位構造変化と電荷状態変化が協応し、ある特定の全体構造変化が誘起されることで、JT軸が１つに集まるクラスター内部の疎水空間において金属と基質間の共有結合性が高まる。この協同効果により、基質の結合により引き起こされる金属の電荷状態変化を金属と基質間の多電子移動として効率よく取り出せるようになる。つまり、スイッチ機能により、非常に困難な水の酸化反応を、適切なタイミングで、高い収率で、限りなく低い過電圧で触媒することができるようになると同時に、電荷担体の流れに整流性が発現する。このような触媒・整流器としての作動が分子レベルで可能になるのは、JT効果を鍵要素とする構成原子が「歪んだ椅子」を形成するように配置されているからに他ならない。

Research Progress Status

令和元年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

令和元年度が最終年度であるため、記入しない。

Research Products

• [Journal Article] UNO(ULO) active space for multireference calculations on classical and quantum computers. Revisit to the iron-sulfur complexes (2020)
  • Author(s): Miyagawa Koichi、Shoji Mitsuo、Isobe Hiroshi、Yamanaka Shusuke、Kawakami Takashi、Okumura Mitsutaka、Yamaguchi Kizashi
  • Journal Title: Chemical Physics Letters Volume: 746 Pages: 137252-137252
  • DOI: 10.1016/j.cplett.2020.137252
  • Peer Reviewed
• [Journal Article] Theory of chemical bonds in metalloenzymes XXIII fundamental principles for the photo-induced water oxidation in oxygen evolving complex of photosystem II (2020)
  • Author(s): Yamaguchi K.、Yamanaka S.、Isobe H.、Shoji M.、Miyagawa K.、Kawakami T.
  • Journal Title: Molecular Physics Volume: 印刷中 Issue: 21-22 Pages: 1725168-1725168
  • DOI: 10.1080/00268976.2020.1725168
  • Peer Reviewed
• [Journal Article] Theoretical and computational investigations of geometrical, electronic and spin structures of the CaMn4OX (X=5, 6) cluster in the Kok cycle Si (i=0-3) of oxygen evolving complex of photosystem II (2019)
  • Author(s): Yamaguchi Kizashi、Yamanaka Shusuke、Isobe Hiroshi、Shoji Mitsuo、Miyagawa Kouichi、Nakajima Takahito、Kawakami Takashi、Okumura Mitsutaka
  • Journal Title: Physiologia Plantarum Volume: 166 Issue: 1 Pages: 44-59
  • DOI: 10.1111/ppl.12960
  • Peer Reviewed
• [Journal Article] Elucidation of the entire Kok cycle for photosynthetic water oxidation by the large-scale quantum mechanics/molecular mechanics calculations: Comparison with the experimental results by the recent serial femtosecond crystallography (2019)
  • Author(s): Shoji Mitsuo、Isobe Hiroshi、Shen Jian-Ren、Suga Michihiro、Akita Fusamichi、Miyagawa Koichi、Shigeta Yasuteru、Yamaguchi Kizashi
  • Journal Title: Chemical Physics Letters Volume: 730 Pages: 416-425
  • DOI: 10.1016/j.cplett.2019.06.026
  • Peer Reviewed
• [Journal Article] Domain-based local pair natural orbital CCSD(T) calculations of six different S1 structures of oxygen evolving complex of photosystem II. Proposal of multi-intermediate models for the S1 state (2019)
  • Author(s): Miyagawa K.、Kawakami T.、Isobe H.、Shoji M.、Yamanaka S.、Nakatani K.、Okumura M.、Nakajima T.、Yamaguchi K.
  • Journal Title: Chemical Physics Letters Volume: 732 Pages: 136660-136660
  • DOI: 10.1016/j.cplett.2019.136660
  • Peer Reviewed
• [Journal Article] Domain-based local pair natural orbital CCSD(T) calculations of fourteen different S2 intermediates for water oxidation in the Kok cycle of OEC of PSII. Re-visit to one LS-two HS model for the S2 state (2019)
  • Author(s): Miyagawa K.、Isobe H.、Kawakami T.、Shoji M.、Yamanaka S.、Okumura M.、Nakajima T.、Yamaguchi K.
  • Journal Title: Chemical Physics Letters Volume: 734 Pages: 136731-136731
  • DOI: 10.1016/j.cplett.2019.136731
  • Peer Reviewed
• [Journal Article] An oxyl/oxo mechanism for oxygen-oxygen coupling in PSII revealed by an x-ray free-electron laser (2019)
  • Author(s): Suga M、Akita F、Yamashita K、Nakajima Y、Ueno G、Li H、Yamane T、Hirata K、Umena Y、Yonekura S、Yu L-J、Murakami H、Nomura T、Kimura T、Kubo M、Baba S、Kumasaka T、Tono K、Yabashi M、Isobe H、Yamaguchi K、Yamamoto M、Ago H、Shen J-R
  • Journal Title: Science Volume: 366 Issue: 6463 Pages: 334-338
  • DOI: 10.1126/science.aax6998
  • Peer Reviewed / Open Access
• [Journal Article] Domain-based local pair natural orbital CCSD (T) calculations of strongly correlated electron systems: Examination of dynamic equilibrium models based on multiple intermediates in S1 state of photosystem II (2019)
  • Author(s): K Miyagawa, H Isobe, T Kawakami, M Shoji, S Yamanaka, M Okumura, T Nakajima, K Yamaguchi
  • Journal Title: Molecular Physics Volume: - Issue: 12 Pages: 1666171-1666171
  • DOI: 10.1080/00268976.2019.1666171
  • Peer Reviewed
• [Journal Article] Concerted bond switching mechanism coupled with one-electron transfer for the oxygen-oxygen bond formation in the oxygen-evolving complex of photosystem II (2019)
  • Author(s): Shoji Mitsuo、Isobe Hiroshi、Yamaguchi Kizashi
  • Journal Title: Chemical Physics Letters Volume: 714 Pages: 219-226
  • DOI: 10.1016/j.cplett.2018.10.041
  • Peer Reviewed
• [Journal Article] Possibility of the right-opened Mn-oxo intermediate (R-oxo(4444)) among all nine intermediates in the S3 state of the oxygen-evolving complex of photosystem II revealed by large-scale QM/MM calculations (2019)
  • Author(s): Shoji Mitsuo、Isobe Hiroshi、Miyagawa Koichi、Yamaguchi Kizashi
  • Journal Title: Chemical Physics Volume: 518 Pages: 81-90
  • DOI: 10.1016/j.chemphys.2018.11.003
  • Peer Reviewed
• [Journal Article] Spin, Valence, and Structural Isomerism in the S3 State of the Oxygen-Evolving Complex of Photosystem II as a Manifestation of Multimetallic Cooperativity (2019)
  • Author(s): Isobe Hiroshi、Shoji Mitsuo、Suzuki Takayoshi、Shen Jian-Ren、Yamaguchi Kizashi
  • Journal Title: Journal of Chemical Theory and Computation Volume: 15 Issue: 4 Pages: 2375-2391
  • DOI: 10.1021/acs.jctc.8b01055
  • Peer Reviewed
• [Journal Article] Theory of chemical bonds in metalloenzymes XXI. Possible mechanisms of water oxidation in oxygen evolving complex of photosystem II (2018)
  • Author(s): K. Yamaguchi, M. Shoji, H. Isobe, S. Yamanaka, T. Kawakami, S. Yamada, M. Katouda, T. Nakajima
  • Journal Title: Molecular Physics Volume: 116 Issue: 5-6 Pages: 717-745
  • DOI: 10.1080/00268976.2018.1428375
  • Peer Reviewed
• [Journal Article] Nonadiabatic one-electron transfer mechanism for the O-O bond formation in the oxygen-evolving complex of photosystem II (2018)
  • Author(s): Mitsuo Shoji, Hiroshi Isobe, Yasuteru Shigeta, Takahito Nakajima, Kizashi Yamaguchi
  • Journal Title: Chemical Physics Letters Volume: 698 Pages: 138-146
  • DOI: 10.1016/j.cplett.2018.02.056
  • Peer Reviewed
• [Journal Article] Relative stability between the manganese hydroxide- and oxo-models for water oxidation by CCSD, DMRG CASCI, CASSCF, CASPT2 and CASDFT methods; Importance of static and dynamical electron correlation effects for OEC of PSII (2018)
  • Author(s): Kawakami T.、Miyagawa K.、Isobe H.、Shoji M.、Yamanaka S.、Katouda M.、Nakajima T.、Nakatani K.、Okumura M.、Yamaguchi K.
  • Journal Title: Chemical Physics Letters Volume: 705 Pages: 85-91
  • DOI: 10.1016/j.cplett.2018.05.046
  • Peer Reviewed
• [Journal Article] Concerted Mechanism of Water Insertion and O2 Release during the S4 to S0 Transition of the Oxygen-Evolving Complex in Photosystem II (2018)
  • Author(s): Shoji Mitsuo、Isobe Hiroshi、Shigeta Yasuteru、Nakajima Takahito、Yamaguchi Kizashi
  • Journal Title: The Journal of Physical Chemistry B Volume: 122 Issue: 25 Pages: 6491-6502
  • DOI: 10.1021/acs.jpcb.8b03465
  • Peer Reviewed
• [Journal Article] Theory of chemical bonds in metalloenzymes XXII: a concerted bond-switching mechanism for the oxygenーoxygen bond formation coupled with one electron transfer for water oxidation in the oxygen-evolving complex of photosystem II (2018)
  • Author(s): K Yamaguchi, M Shoji, Hiroshi Isobe, K Miyagawa, K Nakatani
  • Journal Title: Molecular Physics Volume: 2018 Issue: 17 Pages: 1-35
  • DOI: 10.1080/00268976.2018.1552799
  • Peer Reviewed
• [Presentation] 光化学系IIマンガンクラスターの電子スピン状態解析 (2019)
  • Author(s): 磯部寛、鈴木孝義、沈建仁、庄司光男、山口兆
  • Organizer: 新学術領域「光合成分子機構の学理解明と時空間制御による革新的光―物質変換系の創製」第2回合同班会議
• [Presentation] Theoretical Analysis of the Electronic and Spin Structures of the Oxygen-Evolving Complex (2019)
  • Author(s): Hiroshi Isobe, Misuto Shoji, Takayoshi Suzuki, Jian-Ren Shen, Kizashi Yamaguchi
  • Organizer: International Conference on Artificial Photosynthesis-2019 (ICARP2019)
  • Int'l Joint Research
• [Presentation] 光合成Mnクラスターの構造変化とスピン転移の相関および基質活性化に関する理論的研究 (2019)
  • Author(s): 磯部寛
  • Organizer: 新学術領域「光合成分子機構の学理解明と時空間制御による革新的光―物質変換系の創製」第2回公開シンポジウム
• [Presentation] Density Functional Study on Chemical Equilibria in the S3 State of the Oxygen-Evolving Complex of Photosystem II (2018)
  • Author(s): Hiroshi Isobe, Misuto Shoji, Takayoshi Suzuki, Jian-Ren Shen, Kizashi Yamaguchi
  • Organizer: 5th International Workshop on Solar Energy for Sustainability
  • Int'l Joint Research
• [Presentation] 量子化学計算による光合成水分解反応機構解析 (2018)
  • Author(s): 磯部寛
  • Organizer: 新学術領域「光合成分子機構の学理解明と時空間制御による革新的光―物質変換系の創製」第1回合同班会議