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Cited by 289

The DOI matches its Crossref record; 86 of the 86 references it cites were found in a registry or an index.

Theoretical Evaluation of Structural Models of the S2 State in the Oxygen Evolving Complex of Photosystem II: Protonation States and Magnetic Interactions

Ames, William, Pantazis, Dimitrios A., Krewald, Vera, Cox, Nicholas, Messinger, Johannes, Lubitz, Wolfgang, Neese, Frank·2011·Journal of the American Chemical Society
DOI 10.1021/ja2041805
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Abstract

Protonation states of water ligands and oxo bridges are intimately involved in tuning the electronic structures and oxidation potentials of the oxygen evolving complex (OEC) in Photosystem II, steering the mechanistic pathway, which involves at least five redox state intermediates S(n) (n = 0-4) resulting in the oxidation of water to molecular oxygen. Although protons are practically invisible in protein crystallography, their effects on the electronic structure and magnetic properties of metal active sites can be probed using spectroscopy. With the twin purpose of aiding the interpretation of the complex electron paramagnetic resonance (EPR) spectroscopic data of the OEC and of improving the view of the cluster at the atomic level, a complete set of protonation configurations for the S(2) state of the OEC were investigated, and their distinctive effects on magnetic properties of the cluster were evaluated. The most recent X-ray structure of Photosystem II at 1.9 Å resolution was used and refined to obtain the optimum structure for the Mn(4)O(5)Ca core within the protein pocket. Employing this model, a set of 26 structures was constructed that tested various protonation scenarios of the water ligands and oxo bridges. Our results suggest that one of the two water molecules that are proposed to coordinate the outer Mn ion (Mn(A)) of the cluster is deprotonated in the S(2) state, as this leads to optimal experimental agreement, reproducing the correct ground state spin multiplicity (S = 1/2), spin expectation values, and EXAFS-derived metal-metal distances. Deprotonation of Ca(2+)-bound water molecules is strongly disfavored in the S(2) state, but dissociation of one of the two water ligands appears to be facile. The computed isotropic hyperfine couplings presented here allow distinctions between models to be made and call into question the assumption that the largest coupling is always attributable to Mn(III). The present results impose limits for the total charge and the proton configuration of the OEC in the S(2) state, with implications for the cascade of events in the Kok cycle and for the water splitting mechanism.

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Metadata

Authors
Ames, W., Pantazis, D. A., Krewald, V., Cox, N., Messinger, J., Lubitz, W., & Neese, F.
Venue
Journal of the American Chemical Society
Publisher
American Chemical Society (ACS)
Published
2011-11-17
Volume
133
Issue
49
Pages
19743-19757
ISSN
  • 0002-7863 (ISSN-L)
  • 1520-5126
DOI
10.1021/ja2041805
OpenAlex
W1977055255
Cited by
289
References
86
FWCI
11.40
Type
journal article
Language
en
Open access
closed

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