Publication Date:
2005-11-15
Description:
Plants and cyanobacteria produce atmospheric dioxygen from water, powered by sunlight and catalyzed by a manganese complex in photosystem II. A classic S-cycle model for oxygen evolution involves five states, but only four have been identified. The missing S4 state is particularly important because it is directly involved in dioxygen formation. Now progress comes from an x-ray technique that can monitor redox and structural changes in metal centers in real time with 10-microsecond resolution. We show that in the O2-formation step, an intermediate is formed--the enigmatic S4 state. Its creation is identified with a deprotonation process rather than the expected electron-transfer mechanism. Subsequent electron transfer would give an additional S4' state, thus extending the fundamental S-state cycle of dioxygen formation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Haumann, M -- Liebisch, P -- Muller, C -- Barra, M -- Grabolle, M -- Dau, H -- New York, N.Y. -- Science. 2005 Nov 11;310(5750):1019-21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Freie Universitat Berlin, FB Physik, Arnimallee 14, D-14195 Berlin, Germany. haumann@physik.fu-berlin.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16284178" target="_blank"〉PubMed〈/a〉
Keywords:
Chemistry, Physical
;
Electrons
;
Entropy
;
Kinetics
;
Lasers
;
Manganese/chemistry
;
Models, Biological
;
Models, Chemical
;
Oxidation-Reduction
;
Oxygen/chemistry/*metabolism
;
*Photosynthesis
;
Photosystem II Protein Complex/chemistry/*metabolism
;
Physicochemical Phenomena
;
Protons
;
Spectrum Analysis
;
Spinacia oleracea
;
Water/metabolism
;
X-Rays
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
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