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Alternative mechanisms for O-2 release and O-O bond formation in the oxygen evolving complex of photosystem II
Stockholm University, Faculty of Science, Department of Organic Chemistry. Beijing Normal University, People's Republic of China.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
2015 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, no 18, 12168-12174 p.Article in journal (Refereed) Published
Abstract [en]

In a previous detailed study of all the steps of water oxidation in photosystem II, it was surprisingly found that O-2 release is as critical for the rate as O-O bond formation. A new mechanism for O-2 release has now been found, which can be described as an opening followed by a closing of the interior of the oxygen evolving complex. A transition state for peroxide rotation forming a superoxide radical, missed in the previous study, and a structural change around the outside manganese are two key steps in the new mechanism. However, O-2 release may still remain rate-limiting. Additionally, for the step forming the O-O bond, an alternative, experimentally suggested, mechanism was investigated. The new model calculations can rule out the precise use of that mechanism. However, a variant with a rotation of the ligands around the outer manganese by about 301 will give a low barrier, competitive with the old DFT mechanism. Both these mechanisms use an oxyl-oxo mechanism for O-O bond formation involving the same two manganese atoms and the central oxo group (O5).

Place, publisher, year, edition, pages
Owner Societies 2015 , 2015. Vol. 17, no 18, 12168-12174 p.
National Category
Chemical Sciences Physical Sciences
URN: urn:nbn:se:su:diva-117748DOI: 10.1039/c5cp00138bISI: 000353767500025OAI: diva2:817455
Knut and Alice Wallenberg Foundation
Available from: 2015-06-05 Created: 2015-06-01 Last updated: 2016-10-05Bibliographically approved

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Siegbahn, Per E. M.
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