The water oxidation mechanism in photosystem II is now nearlysettled. The O-O bond formation mechanism was obtained in model DFTstudies in 2006 and the structure of the active complex in 2008. Threevery important recent experiments have confirmed the DFT resultsalmost in detail. First, a high resolution X-ray structure wasobtained in 2011 in very close agreement with the DFTstructure. Second, in 2011, from EPR and ENDOR studies the details ofthe intermediate S2 state were determined. The oxidation states ofthe metals and the protonation states of the ligands are the same asin the DFT model. Third, in 2012, in isotope labeled water exchangeexperiments using W-band 17-O ELDOR detected NMR spectroscopy theoxo-oxyl coupling mechanism for O2 formation suggested by DFT wasconfirmed. Some important conclusions concerning models and methodscan be drawn, specifically concerning the DFT functionals.

Mechanisms for water oxidation in photosystem II

248th National Meeting (2014)

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