A molecular model of artificial photosynthesis: Mn-Ca binuclear complex for photosynthetic oxidation of water

作者：Mishra Nibedita; Mohapatra Pranab Kishor; Raval Mukesh Kumar^*; Biswal Basanti; Biswal Uday Chand

来源：Indian Journal of Biochemistry & Biophysics, 2012, 49(4): 246-249.

• Molecular modeling
• Photosynthetic water oxidation
• Photosystem II
• Quantum mechanical calculations
• Oxygen evolving complex
• Mn-Ca binuclear complex

The redox active component of oxygenic photosynthetic reaction center II contains metal cluster Mn-4-Ca, where two H2O are oxidized to O-2 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 Mn-III may be favorable compared to Ca. Deprotonation of H2O+ yields a stable species HO- on Mn-IV by transfer of one electron from Mn-III as a consequence of first photoact. Similarly, during second photoact, it may lead to formation of Mn-V = 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 O-2. Molecular models are built for each transition states.

• 出版日期2012-8