The Mn Cluster in the S0 State of the Oxygen-Evolving Complex of Photosystem II Studied by EXAFS Spectroscopy: Are There Three Di-
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- 作者：John H. Robblee ; Johannes Messinger ; Roehl M. Cinco ; Karen L. McFarlane ; Carmen Fernandez ; Shelly A. Pizarro ; Kenneth Sauer ; and Vittal K. Yachandra
- 刊名：Journal of the American Chemical Society
- 出版年：2002
- 出版时间：June 26, 2002
- 年：2002
- 卷：124
- 期：25
- 页码：7459 - 7471
- 全文大小：304K
- 年卷期：v.124,no.25(June 26, 2002)
- ISSN：1520-5126
文摘
A key component required for an understanding of the mechanism of the evolution of molecularoxygen by the photosynthetic oxygen-evolving complex (OEC) in photosystem II (PS II) is the knowledgeof the structures of the Mn cluster in the OEC in each of its intermediate redox states, or S-states. In thispaper, we report the first detailed structural characterization using Mn extended X-ray absorption finestructure (EXAFS) spectroscopy of the Mn cluster of the OEC in the S0 state, which exists immediatelyafter the release of molecular oxygen. On the basis of the EXAFS spectroscopic results, the most likelyinterpretation is that one of the di-
-oxo-bridged Mn-Mn moieties in the OEC has increased in distancefrom 2.7 Å in the dark-stable S1 state to 2.85 Å in the S0 state. Furthermore, curve fitting of the distanceheterogeneity present in the EXAFS data from the S0 state leads to the intriguing possibility that threedi--oxo-bridged Mn-Mn moieties may exist in the OEC instead of the two di--oxo-bridged Mn-Mn moietiesthat are widely used in proposed structural models for the OEC. This possibility is developed using novelstructural models for the Mn cluster in the OEC which are consistent with the structural information availablefrom EXAFS and the recent X-ray crystallographic structure of PS II at 3.8 Å resolution.
-oxo-bridged Mn-Mn moieties in the OEC has increased in distancefrom 2.7 Å in the dark-stable S1 state to 2.85 Å in the S0 state. Furthermore, curve fitting of the distanceheterogeneity present in the EXAFS data from the S0 state leads to the intriguing possibility that threedi--oxo-bridged Mn-Mn moieties may exist in the OEC instead of the two di--oxo-bridged Mn-Mn moietiesthat are widely used in proposed structural models for the OEC. This possibility is developed using novelstructural models for the Mn cluster in the OEC which are consistent with the structural information availablefrom EXAFS and the recent X-ray crystallographic structure of PS II at 3.8 Å resolution.