The structure of the oxygen evolving complex (OEC) of photosystem II (PSII) was recently analyzed by crystallography at 1.95 Å resolution using X-ray free electron laser (XFEL), but the positions of hydrogen atoms were not determined. We have examined the XFEL structure theoretically under the assumption of four protonation cases. The spin densities obtained by the high-spin UB3LYP revealed that a partial internal reduction of the high-valent Mn ions in the CaMn4O4X(H2O)3Y cluster occurs for the O(5)(=X) = O2- case, entailing its protonation (X = OH-) in the XFEL structure.
ASJC Scopus subject areas
- General Physics and Astronomy
- Physical and Theoretical Chemistry