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Mishra N.,Gangadhar Meher College College | Raval M.K.,Gangadhar Meher College College | Biswal B.,Sambalpur University | Biswal U.C.,Sambalpur University
Indian Journal of Geo-Marine Sciences | Year: 2012

The redox active component of oxygenic photosynthetic reaction center II contains metal cluster Mn4-Ca, where two H2O are oxidized to O2 and four H+ ions are liberated. A binuclear Mn-Ca metal center binding one substrate H2O on each ion is proposed to be the minimal unit of the redox center. A model for the water oxidizing metal cluster is built with molecular modeling software (HyperChem 8.0 Pro). Mn, being a transitional metal with variable valency is redox active, while Ca is redox inert. Formation and deprotonation of H2O˙+ on MnIII may be favorable compared to Ca. Deprotonation of H2O˙+ yields a stable species HO­ on MnIV by transfer of one electron from MnIII as a consequence of first photoact. Similarly, during second photoact, it may lead to formation of MnV = O. The O-O bond may be formed in the third photoact between O on Mn and H2O on Ca. Subsequently, HO2˙- may be formed, leading to formation of O2. Molecular models are built for each transition states. © 2012, National Institute of Science Communication and Information Resources (NISCAIR). All rights reserved.


PubMed | Gangadhar Meher College College
Type: Journal Article | Journal: Indian journal of biochemistry & biophysics | Year: 2012

The redox active component of oxygenic photosynthetic reaction center II contains metal cluster Mn4-Ca, where two H2O are oxidized to O2 and four H+ ions are liberated. A binuclear Mn-Ca metal center binding one substrate H2O on each ion is proposed to be the minimal unit of the redox center. A model for the water oxidizing metal cluster is built with molecular modeling software (HyperChem 8.0 Pro). Mn, being a transitional metal with variable valency is redox active, while Ca is redox inert. Formation and deprotonation of H2O+ on MnIII may be favorable compared to Ca. Deprotonation of H2O+ yields a stable species HO(-) on MnIV by transfer of one electron from MnIII as a consequence of first photoact. Similarly, during second photoact, it may lead to formation of MnV = O. The O-O bond may be formed in the third photoact between O on Mn and H2O on Ca. Subsequently, HO2*(-) may be formed, leading to formation of O2. Molecular models are built for each transition states.

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