X-ray Detection of the Period-Four Cycling of the Manganese Cluster in Photosynthetic Water Oxidizing Enzyme

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Science  20 Nov 1992:
Vol. 258, Issue 5086, pp. 1335-1337
DOI: 10.1126/science.258.5086.1335


X-ray absorption near-edge structure spectra of the manganese (Mn) cluster in physiologically native intermediate states of photosynthetic water oxidation induced by short laser flash were measured with a compact heat-insulated chamber equipped with an x-ray detector near the sample surface. The half-height energy of the Mn Kedge showed a period-four oscillation dependent on cycling of the Joliot-Kok's oxygen clock. The flash number-dependent shift in the Mn K-edge suggests that the Mn cluster is oxidized by one electron upon the S0-to-S1, S1-to-S2, and S2-to-S3 transitions and then reduced upon the S3-to-S0 transition that releases molecular oxygen.

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