Electron donation in Photosystem II |
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Authors: | Jonathan H. A. Nugent Christalla Demetriou Christopher J. Lockett |
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Affiliation: | Department of Botany and Microbiology, University College London, London, U.K. |
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Abstract: | The electron transfer resulting from illumination and dark storage of PS II has been studied using EPR signals from several electron carriers. The recombination of D+ (Signal II) and Q−A formed by illumination occurred during dark storage at 77 K and was used to deplete reaction centres of D+. The donor D was then shown to be oxidized in the dark by the S2 state of the oxygen-evolving complex. A slow change which occurred during dark storage of PS II samples was detected using the power saturation characteristics of D. We interpret this effect on D to be an indirect result of a rearrangement of the manganese complex during long-term dark adaptation. A role for D in the stability, protection and perhaps initial manganese binding of the oxygen-evolving complex is suggested. |
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Keywords: | Photosystem II Oxygen evolution EPR Signal II Cytochrome b-559 Iron-quinone |
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