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Published on: August 18, 2012
A Reappraisal of the S2 State of Nature's Water Oxidizing Complex in Its Low and High Spin Forms
Maxim Barchenko1, Patrick J O'Malley1
1Department of Chemistry, School of Natural Sciences, The University of Manchester, Manchester M13 9PL, United Kingdom.
Abstract:
Density functional theory calculated 14N hyperfine couplings are obtained for the Mn1 ligated π-N of residue His332 of the photosystem 2 water oxidizing complex. An open cubane, O4H, model closely matches the experimental coupling obtained for the high spin S = 5/2 form of the S2 state, supporting an open cubane structure for this state. We also investigate the unusual geometric features for the S2 state obtained by X-ray free electron laser structure determinations and rationalize it as an equilibrium occurring at room temperature between W1/O4 deprotonated and protonated forms of the open cubane structure.
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