Large-scale QM/MM calculations of the CaMn4O5 cluster in the S3 state of the oxygen evolving complex of photosystem II. Comparison between water-inserted and no water-inserted structures

Mitsuo Shoji, Hiroshi Isobe, Takahito Nakajima, Yasuteru Shigeta, Michihiro Suga, Fusamichi Akita, Jian-Ren Shen, Kizashi Yamaguchi

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Large-scale QM/MM calculations were performed to elucidate an optimized geometrical structure of a CaMn4O5 cluster with and without water insertion in the S3 state of the oxygen evolving complex (OEC) of photosystem II (PSII). The left (L)-opened structure was found to be stable under the assumption of no hydroxide anion insertion in the S3 state, whereas the right (R)-opened structure became more stable if one water molecule is inserted to the Mn4Ca cluster. The optimized Mna(4)-Mnd(1) distance determined by QM/MM was about 5.0 Å for the S3 structure without an inserted hydroxide anion, but this is elongated by 0.2-0.3 Å after insertion. These computational results are discussed in relation to the possible mechanisms of O-O bond formation in water oxidation by the OEC of PSII.

Original languageEnglish
Pages (from-to)83-106
Number of pages24
JournalFaraday Discussions
Early online dateMar 9 2017
Publication statusPublished - 2017
Externally publishedYes



  • Journal Article

ASJC Scopus subject areas

  • Medicine(all)
  • Physical and Theoretical Chemistry

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