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Metalloradical EPR Signals from the Y-Z center dot S-State Intermediates in Photosystem II
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
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2010 (English)In: Applied Magnetic Resonance, ISSN 0937-9347, E-ISSN 1613-7507, Vol. 37, no 1-4, 151-176 p.Article, review/survey (Refereed) Published
Abstract [en]

The redox-active tyrosine residue (Y-Z) plays a crucial role in the mechanism of the water oxidation. Metalloradical electron paramagnetic resonance (EPR) signals reflecting the light-induced Y-Z center dot in magnetic interaction with the CaMn4-cluster in the particular S-state, Y-Z center dot S-X intermediates, have been found in intact photosystem II. These so-called split EPR signals are induced by illumination at cryogenic temperatures and provide means to both study the otherwise transient Y-Z center dot and to probe the S-states with EPR spectroscopy. The illumination used for signal induction grouped the observed split EPR signals in two categories: (i) Y-Z in the lower S-states was oxidized by P680(+) formed via charge separation, while (ii) Y-Z in the higher S-states was oxidized by an excited, highly oxidizing Mn species. Applied mechanistic studies of the Y-Z center dot S-X intermediates in the different S-states are reviewed and compared to investigations in photosystem II at physiological temperature. Addition of methanol induced S-state characteristic changes in the split signals' formation which reflect changes in the magnetic coupling within the CaMn4-cluster due to methanol binding. The pH titration of the split EPR signals, on the other hand, could probe the proton-coupled electron transfer properties of the Y-Z oxidation. The apparent pK (a)s found for decreased split signal induction were interpreted in the fate of the phenol proton.

Place, publisher, year, edition, pages
2010. Vol. 37, no 1-4, 151-176 p.
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Chemical Sciences
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URN: urn:nbn:se:uu:diva-140640DOI: 10.1007/s00723-009-0045-zISI: 000272173500012OAI: oai:DiVA.org:uu-140640DiVA: diva2:384144
Available from: 2011-01-07 Created: 2011-01-07 Last updated: 2017-12-11Bibliographically approved

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Ho, Felix M.Mamedov, FikretStyring, Stenbjörn

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