title: Large-scale QM/MM calculations of the CaMn4O5cluster in the S3state of the oxygen evolving complex of photosystem II. Comparison between water-inserted and no water-inserted structures.
abstract: Large-scale QM/MM calculations were performed to elucidate an optimized geometrical structure of a CaMn4O5cluster with and without water insertion in the S3state 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 S3state, 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 S3structure 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.
authors.affiliation: Center for Computational Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8577, Japan. mshoji@ccs.tsukuba.ac.jp.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Shoji
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Isobe
authors.forename: Takahito
authors.initials: T
authors.lastname: Nakajima
authors.forename: Yasuteru
authors.initials: Y
authors.lastname: Shigeta
authors.forename: Michihiro
authors.initials: M
authors.lastname: Suga
authors.forename: Fusamichi
authors.initials: F
authors.lastname: Akita
authors.forename: Jian-Ren
authors.initials: JR
authors.lastname: Shen
authors.forename: Kizashi
authors.initials: K
authors.lastname: Yamaguchi