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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 inphotosystem II. A classic S-cycle model for oxygen evolutioninvolves five states, but only four have been identified. Themissing S4 state is particularly important because it is directlyinvolved in dioxygen formation. Now progress comes from an x-raytechnique that can monitor redox and structural changes in metalcenters in real time with 10-microsecond resolution. We showthat in the O2-formation step, an intermediate is formedtheenigmatic S4 state. Its creation is identified with a deprotonationprocess 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.)
Deletion of PsbM in Tobacco Alters the QB Site Properties and the Electron Flow within Photosystem II.
P. Umate, S. Schwenkert, I. Karbat, C. D. Bosco, L. Mlcochova, S. Volz, H. Zer, R. G. Herrmann, I. Ohad, and J. Meurer (2007)
J. Biol. Chem.
282, 9758-9767
|Abstract »|Full Text »|PDF »
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)
J. Biol. Chem.
281, 34227-34238
|Abstract »|Full Text »|PDF »
Calcium Exchange and Structural Changes during the Photosynthetic Oxygen Evolving Cycle.
A. De Riso, D. L. Jenson, and B. A. Barry (2006)
Biophys. J.
91, 1999-2008
|Abstract »|Full Text »|PDF »
Time-resolved vibrational spectroscopy detects protein-based intermediates in the photosynthetic oxygen-evolving cycle.
B. A. Barry, I. B. Cooper, A. De Riso, S. H. Brewer, D. M. Vu, and R. B. Dyer (2006)
PNAS
103, 7288-7291
|Abstract »|Full Text »|PDF »
A time-resolved vibrational spectroscopy glimpse into the oxygen-evolving complex of photosynthesis.