Biomimetic Model Studies Reveal the Role of the Ca Ion in Photosystem II Redox-inactive metal ions play crucial roles in tuning the reactivity of oxygen-containing metal complexes and metalloenzymes such as the oxygen-evolving complex (OEC) in photosystem II (PSII)
نویسنده
چکیده
Redox-inactive metal ions play crucial roles in tuning the reactivity of oxygen-containing metal complexes and metalloenzymes such as the oxygen-evolving complex (OEC) in photosystem II (PSII) and its small-molecule mimics. In PSII, a Ca ion is part of the tetrameric Mn cluster, Mn4CaO5, and is integral to the water oxidation catalysis and evolution of oxygen by the OEC. Several different functional roles have been proposed for this Ca cofactor based on intense enzymatic and model studies, such as modulation of the reduction potential of the manganese center, and enhancement of the nucleophilic reactivity of water or hydroxide bound to the Ca ion. Interestingly, the only other redox-inactive metal ion capable of replacing the Ca center and maintaining O2 evolution is Sr.
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