The S0 state of the water oxidizing complex in photosystem II : pH dependence of the EPR split signal induction and mechanistic implications
Water oxidation in photosystem II is catalyzed by the CaMn4 cluster. The electrons extracted from the CaMn4 cluster are transferred to P680+ via the redox-active tyrosine residue D1-Tyr161 (YZ). The oxidation of YZ is coupled to a deprotonation creating the neutral radical YZ•. Light-induced oxidation of YZ is possible down to extreme temperatures. This can be observed as a split EPR signal from Y