| Literature DB >> 16248606 |
Junko Yano1, Yulia Pushkar, Pieter Glatzel, Azul Lewis, Kenneth Sauer, Johannes Messinger, Uwe Bergmann, Vittal Yachandra.
Abstract
The biological generation of oxygen by the oxygen-evolving complex in photosystem II (PS II) is one of nature's most important reactions. The recent X-ray crystal structures, while limited by resolutions of 3.2-3.5 A, have located the electron density associated with the Mn4Ca cluster within the multiprotein PS II complex. Detailed structures critically depend on input from spectroscopic techniques, such as EXAFS and EPR/ENDOR, as the XRD resolution does not allow for accurate determination of the position of Mn/Ca or the bridging and terminal ligand atoms. The number and distances of Mn-Mn/Ca/ligand interactions determined from EXAFS provide important constraints for the structure of the Mn4Ca cluster. Here, we present data from a high-resolution EXAFS method using a novel multicrystal monochromator that show three short Mn-Mn distances between 2.7 and 2.8 A and, hence, the presence of three di-mu-oxo-bridged units in the Mn4Ca cluster. This result imposes clear limitations on the proposed structures based on spectroscopic and diffraction data and provides input for refining such structures.Entities:
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Year: 2005 PMID： 16248606 PMCID： PMC3981608 DOI： 10.1021/ja054873a
Source DB: PubMed Journal: J Am Chem Soc ISSN： 0002-7863 Impact factor: 15.419