Alternative mechanisms for O-2 release and O-O bond formation in the oxygen evolving complex of photosystem II
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
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.
Chemical Sciences Physical Sciences
IdentifiersURN: urn:nbn:se:su:diva-117748DOI: 10.1039/c5cp00138bISI: 000353767500025OAI: oai:DiVA.org:su-117748DiVA: diva2:817455
FunderKnut and Alice Wallenberg Foundation