High-Resolution Structure of the Photosynthetic Mn4Ca Catalyst From X-Ray Spectroscopy
The application of high-resolution X-ray spectroscopy methods to study the photosynthetic water oxidizing complex, which contains a unique hetero-nuclear catalytic Mn{sub 4}Ca cluster, is described. Issues of X-ray damage, especially at the metal sites in the Mn{sub 4}Ca cluster, are discussed. The structure of the Mn{sub 4}Ca catalyst at high resolution, which has so far eluded attempts of determination by X-ray diffraction, X-ray absorption fine structure (EXAFS) and other spectroscopic techniques, has been addressed using polarized EXAFS techniques applied to oriented photosystem II (PSII) membrane preparations and PSII single crystals. A review of how the resolution of traditional EXAFS techniques can be improved, using methods such as range-extended EXAFS, is presented, and the changes that occur in the structure of the cluster as it advances through the catalytic cycle are described. X-ray absorption and emission techniques (XANES and K{beta} emission) have been used earlier to determine the oxidation states of the Mn{sub 4}Ca cluster, and in this report we review the use of X-ray resonant Raman spectroscopy to understand the electronic structure of the Mn{sub 4}Ca cluster as it cycles through the intermediate S-states.
- Research Organization:
- Stanford Linear Accelerator Center (SLAC)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-76SF00515
- OSTI ID:
- 959361
- Report Number(s):
- SLAC-REPRINT-2009-035
- Journal Information:
- Phil.Trans.Roy.Soc.Lond.B 363:1139-1147,2008, Journal Name: Phil.Trans.Roy.Soc.Lond.B 363:1139-1147,2008 Journal Issue: 1494 Vol. 363
- Country of Publication:
- United States
- Language:
- English
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