Cox, NickPantazis, Dimitrios A.Lubitz, Wolfgang2022-07-200066-4154http://hdl.handle.net/1885/269811The investigation of water oxidation in photosynthesis has remained a central topic in biochemical research for the last few decades due to the importance of this catalytic process for technological applications. Significant progress has been made following the 2011 report of a high-resolution X-ray crystallographic structure resolving the site of catalysis, a protein-bound Mn4CaOx complex, which passes through ≥5 intermediate states in the water-splitting cycle. Spectroscopic techniques complemented by quantum chemical calculations aided in understanding the electronic structure of the cofactor in all (detectable) states of the enzymatic process. Together with isotope labeling, these techniques also revealed the binding of the two substrate water molecules to the cluster. These results are described in the context of recent progress using X-ray crystallography with free-electron lasers on these intermediates. The data are instrumental for developing a model for the biological water oxidation cycle.This work has been supported by the Max Planck Society and the Australian Research Council (FT140100834)application/pdfen-AUCopyright © 2020 by Annual Reviews.oxygen-evolving complex in PS IIspectroscopyX-ray crystallographyX-ray free-electron laserXFELquantum chemical calculationswater oxidation mechanism202010.1146/annurev-biochem-011520-1048012021-08-01