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Issue 12, 2005
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The mechanism for dioxygen formation in PSII studied by quantum chemical methods

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Abstract

The availability of an X-ray structure for PSII including the water-oxidizing cluster, where the metal atoms and the amino acids are assigned, has opened up new possibilities to study the mechanism for dioxygen formation. In the present paper the main results of an ongoing hybrid DFT study are presented. The model used follows the structure suggested by the X-ray analysis as closely as possible. After nearly one thousand optimizations of different structures, each one with about 70 atoms, the main features of a water oxidizing mechanism start to emerge. The key intermediate is an oxyl radical state in S3, stabilized by a weak trans effect to a bridging oxo in the cube. To reach this radical state a structural rearrangement appears necessary, in which one additional bridging oxo is formed between the dangling manganese and a manganese in the cube. The calculated energetics is reasonable but still not fully consistent with a correct mechanism. It is suggested that some part of the structure is not correct, probably the presence of the bicarbonate.

Graphical abstract: The mechanism for dioxygen formation in PSII studied by quantum chemical methods

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Publication details

The article was received on 12 May 2005, accepted on 13 Sep 2005 and first published on 04 Oct 2005


Article type: Paper
DOI: 10.1039/B506746B
Citation: Photochem. Photobiol. Sci., 2005,4, 1035-1043
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    The mechanism for dioxygen formation in PSII studied by quantum chemical methods

    P. E. M. Siegbahn and M. Lundberg, Photochem. Photobiol. Sci., 2005, 4, 1035
    DOI: 10.1039/B506746B

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