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Science. 2014 Aug 15;345(6198):804-8. doi: 10.1126/science.1254910. Epub 2014 Aug 14.

Photosynthesis. Electronic structure of the oxygen-evolving complex in photosystem II prior to O-O bond formation.

Author information

1
Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany. nicholas.cox@cec.mpg.de wolfgang.lubitz@cec.mpg.de.
2
Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany.
3
Institut de Biologie et de Technologies de Saclay, CNRS UMR 8221, Commissariat à l'Énergie Atomique (CEA) Saclay, 91191 Gif-sur-Yvette, France.

Abstract

The photosynthetic protein complex photosystem II oxidizes water to molecular oxygen at an embedded tetramanganese-calcium cluster. Resolving the geometric and electronic structure of this cluster in its highest metastable catalytic state (designated S3) is a prerequisite for understanding the mechanism of O-O bond formation. Here, multifrequency, multidimensional magnetic resonance spectroscopy reveals that all four manganese ions of the catalyst are structurally and electronically similar immediately before the final oxygen evolution step; they all exhibit a 4+ formal oxidation state and octahedral local geometry. Only one structural model derived from quantum chemical modeling is consistent with all magnetic resonance data; its formation requires the binding of an additional water molecule. O-O bond formation would then proceed by the coupling of two proximal manganese-bound oxygens in the transition state of the cofactor.

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PMID:
25124437
DOI:
10.1126/science.1254910
[Indexed for MEDLINE]
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