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Title: Where Water Is Oxidized to Dioxygen: Structure of the Photosynthetic Mn4Ca Cluster

Abstract

No abstract prepared.

Authors:
; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Stanford Linear Accelerator Center (SLAC)
Sponsoring Org.:
USDOE
OSTI Identifier:
897444
Report Number(s):
SLAC-REPRINT-2006-173
TRN: US200705%%244
DOE Contract Number:
AC02-76SF00515
Resource Type:
Journal Article
Resource Relation:
Journal Name: Science 314:821-825,2006
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; WATER; OXIDATION; MANGANESE ALLOYS; CALCIUM ALLOYS; INTERMETALLIC COMPOUNDS; PHOTOSYNTHESIS; MORPHOLOGY; Other,OTHER

Citation Formats

Yano, J., Kern, J., Sauer, K., Latimer, M.J., Pushkar, Y., Biesiadka, J., Loll, B., Saenger, W., Messinger, J., Zouni, A., Yachandra, V.K., and /LBL, Berkeley /UC, Berkeley /Berlin, Tech. U. /SLAC, SSRL /Freie U., Berlin /Max Planck Inst., Mulheim. Where Water Is Oxidized to Dioxygen: Structure of the Photosynthetic Mn4Ca Cluster. United States: N. p., 2007. Web.
Yano, J., Kern, J., Sauer, K., Latimer, M.J., Pushkar, Y., Biesiadka, J., Loll, B., Saenger, W., Messinger, J., Zouni, A., Yachandra, V.K., & /LBL, Berkeley /UC, Berkeley /Berlin, Tech. U. /SLAC, SSRL /Freie U., Berlin /Max Planck Inst., Mulheim. Where Water Is Oxidized to Dioxygen: Structure of the Photosynthetic Mn4Ca Cluster. United States.
Yano, J., Kern, J., Sauer, K., Latimer, M.J., Pushkar, Y., Biesiadka, J., Loll, B., Saenger, W., Messinger, J., Zouni, A., Yachandra, V.K., and /LBL, Berkeley /UC, Berkeley /Berlin, Tech. U. /SLAC, SSRL /Freie U., Berlin /Max Planck Inst., Mulheim. Fri . "Where Water Is Oxidized to Dioxygen: Structure of the Photosynthetic Mn4Ca Cluster". United States. doi:.
@article{osti_897444,
title = {Where Water Is Oxidized to Dioxygen: Structure of the Photosynthetic Mn4Ca Cluster},
author = {Yano, J. and Kern, J. and Sauer, K. and Latimer, M.J. and Pushkar, Y. and Biesiadka, J. and Loll, B. and Saenger, W. and Messinger, J. and Zouni, A. and Yachandra, V.K. and /LBL, Berkeley /UC, Berkeley /Berlin, Tech. U. /SLAC, SSRL /Freie U., Berlin /Max Planck Inst., Mulheim},
abstractNote = {No abstract prepared.},
doi = {},
journal = {Science 314:821-825,2006},
number = ,
volume = ,
place = {United States},
year = {Fri Jan 12 00:00:00 EST 2007},
month = {Fri Jan 12 00:00:00 EST 2007}
}
  • Light-driven oxidation of water to dioxygen in plants, algae and cyanobacteria iscatalyzed within photosystem II (PS II) by a Mn4Ca cluster. Although the cluster has been studied by many different methods, the structure and the mechanism have remained elusive. X-ray absorption and emission spectroscopy and EXAFS studies have been particularly useful in probing the electronic and geometric structure, and the mechanism of the water oxidation reaction. Recent progress, reviewed here, includes polarized X-ray absorption spectroscopy measurements of PS II single crystals. Analysis of those results has constrained the Mn4Ca cluster geometry to a setof three similar high-resolution structures. The structuremore » of the cluster from the present study is unlike either the 3.0 or 3.5 Angstrom-resolution X-ray structures or other previously proposed models. The differences between the models derived from X-rayspectroscopy and crystallography are predominantly because of damage to the Mn4Ca cluster by X-rays under the conditions used for structure determination by X-ray crystallography. X-ray spectroscopy studies are also used for studying the changes in the structure of the Mn4Ca catalytic center as it cycles through the five intermediate states known as the Si-states (i=0-4). The electronic structure of the Mn4Ca cluster has been studied more recently using resonant inelastic X-ray scattering spectroscopy (RIXS), in addition to the earlier X-ray absorption and emission spectroscopy methods. These studies are revealing that the assignment of formaloxidation states is overly simplistic. A more accurate description should consider the charge density on the Mn atoms that includes the covalency of the bonds and delocalization of the charge over the cluster. The geometric and electronic structure of the Mn4Ca cluster in the S-states derived from X-ray spectroscopy are leading to a detailed understanding of the mechanism of the O-O bond formation during the photosynthetic water splitting process.« less
  • Oxidation of water to dioxygen is catalyzed withinphotosystem II (PSII) by a Mn4Ca cluster, the structure of which remainselusive. Polarized extended X-ray absorption fine structure (EXAFS)measurements on PSII single crystals constrain the Mn4Ca cluster geometryto a set of three similar high-resolution structures. Combining polarizedEXAFS and X-ray diffraction data, the cluster was placed within PSIItaking into account the overall trend of the electron density of themetal site and the putative ligands. The structure of the cluster fromthe present study is unlike either the 3.0 or 3.5 Angstrom resolutionX-ray structures, and other previously proposed models.
  • Light-driven oxidation of water to dioxygen in plants, algae, and cyanobacteria is catalyzed within photosystem II (PS II) by a Mn{sub 4}Ca cluster. Although the cluster has been studied by many different methods, its structure and mechanism have remained elusive. X-ray absorption and emission spectroscopy and extended X-ray absorption fine structure studies have been particularly useful in probing the electronic and geometric structures and the mechanism of the water oxidation reaction. Recent progress, reviewed here, includes polarized X-ray absorption spectroscopy measurements of PS II single crystals. Analysis of those results has constrained the Mn{sub 4}Ca cluster geometry to a setmore » of three similar high-resolution structures. The structure of the cluster from the present study is unlike either the 3.0- or 3.5-{angstrom}-resolution X-ray structures or other previously proposed models. The differences between the models derived from X-ray spectroscopy and crystallography are predominantly because of damage to the Mn{sub 4}Ca cluster by X-rays under conditions used for the structure determination by X-ray crystallography. X-ray spectroscopy studies are also used for studying the changes in the structure of the Mn{sub 4}Ca catalytic center as it cycles through the five intermediate states known as the S{sub i} states (i = 0--4). The electronic structure of the Mn{sub 4}Ca cluster has been studied more recently using resonant inelastic X-ray scattering spectroscopy (RIXS), in addition to the earlier X-ray absorption and emission spectroscopy methods. These studies are revealing that the assignment of formal oxidation states is overly simplistic. A more accurate description should consider the charge density on the Mn atoms, which includes the covalency of the bonds and delocalization of the charge over the cluster. The geometric and electronic structures of the Mn{sub 4}Ca cluster in the S states derived from X-ray spectroscopy are leading to a detailed understanding of the mechanism of O-O bond formation during the photosynthetic water-splitting process.« less
  • Photosynthetic water oxidation, where water is oxidized to dioxygen, is a fundamental chemical reaction that sustains the biosphere. This reaction is catalyzed by a Mn4Ca complex in the photosystem II (PS II) oxygen-evolving complex (OEC): a multiproteinassembly embedded in the thylakoid membranes of green plants, cyanobacteria, and algae. The mechanism of photosynthetic water oxidation by the Mn4Ca cluster in photosystem II is the subject of much debate, although lacking structural characterization of the catalytic intermediates. Biosynthetically exchanged Ca/Sr-PS II preparations and x-ray spectroscopy, including extended x-ray absorption fine structure (EXAFS), allowed us to monitor Mn-Mn and Ca(Sr)-Mn distances in themore » four intermediate S states, S0 through S3, of the catalytic cycle that couples the one-electron photochemistry occurring at the PS II reaction center with the four-electron water-oxidation chemistry taking place at the Mn4Ca(Sr) cluster. We have detected significant changes in the structure of the complex, especially in the Mn-Mn and Ca(Sr)-Mn distances, on the S2-to-S3 and S3-to-S0 transitions. These results implicate the involvement of at least one common bridging oxygen atom between the Mn-Mn and Mn-Ca(Sr) atoms in the O-O bond formation. Because PS II cannot advance beyond the S2 state in preparations that lack Ca(Sr), these results show that Ca(Sr) is one of the critical components in the mechanism of the enzyme. The results also show that Ca is not just a spectator atom involved in providing a structural framework, but is actively involved in the mechanism of water oxidation and represents a rare example of a catalytically active Ca cofactor.« less
  • No abstract prepared.