The Photosynthesis "Oxygen Clock" Gets a New Number

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Science  11 Nov 2005:
Vol. 310, Issue 5750, pp. 982-983
DOI: 10.1126/science.1120919

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The oxygen clock refers to a cycle of reactions by which photosynthesis converts water to oxygen. Manganese atoms of a multipolypeptide complex called photosystem II are key players in this reaction. In their Perspective, Penner-Hahn and Yocum discuss the report by Haumann et al. that reveals how x-ray absorption spectroscopy was used to examine photosystem II and the manganese atoms. The powerful approach has uncovered a new chemical intermediate in the final step of water oxidation and oxygen formation.