Water oxidation mechanism in photosystem II, including oxidations, proton release pathways, O-O bond formation and O2 release

Biochim Biophys Acta. Aug-Sep 2013;1827(8-9):1003-19. doi: 10.1016/j.bbabio.2012.10.006. Epub 2012 Oct 24.


The present status of DFT studies on water oxidation in photosystem II is described. It is argued that a full understanding of all steps is close. In each S-transition, the manganese that is oxidized and the proton released are strongly implicated, and structures of all intermediates have been determined. For the S2-state, recent important experimental findings support key elements of the structure and the mechanism. In this mechanism, the O-O bond is formed between an oxyl radical in the center of the cluster and an Mn-bridging μ-oxo ligand, which was suggested already in 2006. The DFT structure of the oxygen evolving complex, suggested in 2008, is very similar to the recent high-resolution X-ray structure. Some new aspects of the interaction between P680 and the OEC are suggested. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems.

Keywords: Density functional theory; Energy diagrams; Oxygen evolving complex; O―O bond formation; Photosystem II; Transition states.

MeSH terms

  • Models, Molecular
  • Oxidation-Reduction
  • Oxygen / chemistry*
  • Photosystem II Protein Complex / chemistry*
  • Protons
  • Water / chemistry*


  • Photosystem II Protein Complex
  • Protons
  • Water
  • Oxygen