Abstract
The formation of oxygen during photosynthesis results from the photooxidation of intracellular water molecules and is one of the most important and least decipherable processes in animate nature. The O2 formation has been ascertained to take place in the oxygen-evolving complex (OEC) of chloroplast membranes at the expense of effective transformation of absorbed light energy into chemical energy of oxidative equivalents localized on Mn cations of the water-oxidizing center of the OEC. Based on the study of the molecular composition, photochemical properties, and structural organization of the isolated oxygen-evolving complex, it has been ascertained that the OEC represents the dimer of the pigment-lipoprotein complexes of photosystem 2 (PLPC PS-2) associated according to the dissymmetry rule into the integral structure on the basis of hydrophobic bonds. The studies on the regularities of the functioning of the OEC has permitted us to develop a mechanism of photosynthetic water oxidation and oxygen formation that is based on the concept of the formation of the two-anode reactor in the water-oxidizing center, which is determined by the symmetry in the location of structural D1-proteins and unidentant ligands (Tyrz) that are coordinated with Mn cations that perform water molecule oxidation, as well as in the structure of the hydrophobic boiler. Taking into consideration these data, we have conducted the quantum-chemical modeling of the reaction process, which confirms the developed mechanism. It has been shown that this mechanism is also possible in the monomeric complex of PS-2, the structure of which is determined by homologous D1/D2 proteins.
Published Version
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