EPR properties of a g=2 broad signal trapped in an S1 state in Ca2+-depleted Photosystem II |
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Authors: | Mino Hiroyuki Itoh Shigeru |
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Institution: | Division of Material Science (Physics), Graduate School of Science, Nagoya University, Furocyo, Chikusa, Nagoya 464-8602, Japan. mino@bio.phys.nagoya-u.ac.jp |
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Abstract: | We investigated a new EPR signal that gives a broad line shape around g=2 in Ca(2+)-depleted Photosystem (PS) II. The signal was trapped by illumination at 243 K in parallel with the formation of Y(Z)*. The ratio of the intensities between the g=2 broad signal and the Y(Z)* signal was 1:3, assuming a Gaussian line shape for the former. The g=2 broad signal and the Y(Z)* signal decayed together in parallel with the appearance of the S(2) state multiline at 243 K. The g=2 broad signal was assigned to be an intermediate S(1)X* state in the transition from the S(1) to the S(2) state, where X* represents an amino acid radical nearby manganese cluster, such as D1-His337. The signal is in thermal equilibrium with Y(Z)*. Possible reactions in the S state transitions in Ca(2+)-depleted PS II were discussed. |
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