What does the Sr-substituted 2.1 Å resolution crystal structure of photosystem II reveal about the water oxidation mechanism?

@article{Terrett2014WhatDT,
  title={What does the Sr-substituted 2.1 {\AA} resolution crystal structure of photosystem II reveal about the water oxidation mechanism?},
  author={Richard N L Terrett and Simon Petrie and Ron J. Pace and Robert Stranger},
  journal={Chemical communications},
  year={2014},
  volume={50 24},
  pages={3187-90}
}
A density functional study of the Sr-substituted photosystem II water oxidising complex demonstrates that its recent X-ray crystal structure is consistent with a (Mn(III))4 oxidation state pattern, and with a Sr-bound hydroxide ion. The Sr-water-hydroxide interactions rationalize differences in the exchange rates of substrate water and kinetics of dioxygen bond formation relative to the Ca-containing structure.