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Science 11 November 2005:
Vol. 310. no. 5750, pp. 1019 - 1021
DOI: 10.1126/science.1117551
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Reports

Photosynthetic O2 Formation Tracked by Time-Resolved X-ray Experiments

M. Haumann,* P. Liebisch, C. Müller, M. Barra, M. Grabolle, H. Dau*

Plants and cyanobacteria produce atmospheric dioxygen from water, powered by sunlight and catalyzed by a manganese complex in photosystem II. A classic S-cycle model for oxygen evolution involves five states, but only four have been identified. The missing S4 state is particularly important because it is directly involved in dioxygen formation. Now progress comes from an x-ray technique that can monitor redox and structural changes in metal centers in real time with 10-microsecond resolution. We show that in the O2-formation step, an intermediate is formed—the enigmatic S4 state. Its creation is identified with a deprotonation process rather than the expected electron-transfer mechanism. Subsequent electron transfer would give an additional S4' state, thus extending the fundamental S-state cycle of dioxygen formation.

Freie Universität Berlin, FB Physik, Arnimallee 14, D-14195 Berlin, Germany

* To whom correspondence should be addressed. E-mail: haumann{at}physik.fu-berlin.de (M.H.); holger.dau{at}physik.fu-berlin.de (H.D.)

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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Multifrequency electron spin-echo envelope modulation studies of nitrogen ligation to the manganese cluster of photosystem II.
G. J Yeagle, M. L. Gilchrist Jr, L. M Walker, R. J Debus, and R. D. Britt (2008)
Phil Trans R Soc B 363, 1157-1166
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Water oxidation chemistry of photosystem II.
G. W Brudvig (2008)
Phil Trans R Soc B 363, 1211-1219
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Investigation of substrate water interactions at the high-affinity Mn site in the photosystem II oxygen-evolving complex.
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Phil Trans R Soc B 363, 1229-1235
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A ligand field chemistry of oxygen generation by the oxygen-evolving complex and synthetic active sites.
T. A Betley, Y. Surendranath, M. V Childress, G. E Alliger, R. Fu, C. C Cummins, and D. G Nocera (2008)
Phil Trans R Soc B 363, 1293-1303
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Deletion of PsbM in Tobacco Alters the QB Site Properties and the Electron Flow within Photosystem II.
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J. Biol. Chem. 282, 9758-9767
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PsbI Affects the Stability, Function, and Phosphorylation Patterns of Photosystem II Assemblies in Tobacco.
S. Schwenkert, P. Umate, C. D. Bosco, S. Volz, L. Mlcochova, M. Zoryan, L. A. Eichacker, I. Ohad, R. G. Herrmann, and J. Meurer (2006)
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Time-resolved vibrational spectroscopy detects protein-based intermediates in the photosynthetic oxygen-evolving cycle.
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