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The S2 to S3 transition for water oxidation in PSII, revisited.

Abstract

The formation of O$_2$ from water requires four transitions, each one after the absorption of one light flash. The mechanism for one of these transitions, the one from S$_2$ to S$_3$, has been under considerable debate the past five years. There has since long been a concensus that one water molecule becomes inserted into the OEC in this transition, but the mechanism for this insertion is not clear. A major conclusion obtained in the recent studies has been that a so called closed cubane structure of the oxygen evolving complex (OEC) is a key factor in this transition. Leading suggestions for the water insertion have been the so called pivot and carousel mechanisms. In the present study, inspired by recent experiments, it is found that the closed cubane structure never enters into the mechanism for this transition, nor do the different suggestions mentioned above for water insertion. In the experiments, a high spin S$_2$ (HS-S$_2$) intermediate has been detected. It is here suggested that this state has an open structure of the OEC.

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Publication details

The article was received on 12 Jun 2018, accepted on 09 Aug 2018 and first published on 09 Aug 2018


Article type: Paper
DOI: 10.1039/C8CP03720E
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    The S2 to S3 transition for water oxidation in PSII, revisited.

    P. Siegbahn, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C8CP03720E

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