A quantum chemical study of tyrosyl reduction and O—O bond formation in photosystem II |
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| Authors: | MARGARETA R A BLOMBERG PER E M SIEGBAHN |
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| Institution: | Department of Physics, Stockholm Center for Physics , Astronomy and Biotechnology, Stockholm University , S-106 91, Stockholm, Sweden |
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| Abstract: | Density functional theory has been used to study two of the main topics of oxygen evolution in photosystem II. The first concerns the reduction of the tyrosyl radical that occurs in every S-state transition. The two leading models, hydrogen atom transfer and electron transfer, have been investigated. In the present study, hydrogen atom transfer has the lower barrier. The second topic addressed is O—O bond formation in the S3 to S0 transition, where a Mn3 complex including calcium and chloride cofactors was used as a model. The reaction is suggested to proceed from a bridging oxyl group to a radical hydroxyl, which combines to form the O—O bond with a hydroxide ligand of the Mn complex. |
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