Oxidation states of the manganese cluster during the flash-induced S-state cycle of the photosynthetic oxygen-evolving complex
Journal Article
·
· Proceedings of the National Academy of Sciences of the United States of America
- Lawrence Berkeley National Laboratory, CA (United States); and others
The Mn K-edge x-ray absorption spectra for the pure S states of the tetranuclear Mn cluster of the oxygen-evolving complex of photosystem II during flash-induced S-state cycling have been determined. The relative S-state populations in samples given 0, 1,2,3,4, or 5 flashes were determined from fitting the flash-induced electron paramagnetic resonance (EPR) multiline signal oscillation pattern to the Kok model. The edge spectra of samples given 0,1,2, or 3 flashes were combined with EPR information to calculate the pure S-state edge spectra. The edge positions (defined as the zero-crossing of the second derivatives) are 6550.1, 6551.7, 6553.5, and 6553.8 eV for S{sub 0}, S{sub 1}, S{sub 2}, and S{sub 3}, respectively In addition to the shift in edge position, the S{sub 0} {r_arrow} S{sub 1} and S{sub 1} {r_arrow} S{sub 2} transitions are accompanied by characteristic changes in the shape of the edge, both indicative of Mn oxidation. The edge position shifts very little (0.3 eV) for the S{sub 2} {r_arrow} S{sub 3} transition, and the edge shape shows only subtle changes. We conclude that probably no direct Mn oxidation is involved in this transition. The proposed Mn oxidation state assignments are as follows: S{sub 0}(II,III,IV,IV) or (III,III,III,IV), S{sub 1} (III, III, IV, IV), S{sub 2} (III,IV,IV,IV), S{sub 3} (III,IV,IV,IV). 28 refs., 4 figs., 1 tab.
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 258598
- Journal Information:
- Proceedings of the National Academy of Sciences of the United States of America, Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Issue: 8 Vol. 93; ISSN PNASA6; ISSN 0027-8424
- Country of Publication:
- United States
- Language:
- English
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