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Updated: Apr 1, 2026

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Published on: October 5, 2019
Photosynthetic water oxidation: binding and activation of substrate waters for O-O bond formation
David J Vinyard1, Sahr Khan1, Gary W Brudvig1
1Department of Chemistry, Yale University, New Haven, CT, United States. gary.brudvig@yale.edu.
Abstract:
Photosynthetic water oxidation occurs at the oxygen-evolving complex (OEC) of Photosystem II (PSII). The OEC, which contains a Mn4CaO5 inorganic cluster ligated by oxides, waters and amino-acid residues, cycles through five redox intermediates known as S(i) states (i = 0-4). The electronic and structural properties of the transient S4 intermediate that forms the O-O bond are not well understood. In order to gain insight into how water is activated for O-O bond formation in the S4 intermediate, we have performed a detailed analysis of S-state dependent substrate water binding kinetics taking into consideration data from Mn coordination complexes. This analysis supports a model in which the substrate waters are both bound as terminal ligands and react via a water-nucleophile attack mechanism.
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