Chemical bonding and quadrupole splittings of (57)Fe Mossbauer spectrum in active sites of oxyhemoglobin as calculated by X(alpha)-discrete variation method

Abstract

Results of quantum-chemical X(alpha)-discrete variation method (X(alpha)-DVM) calculations of interaction parameters between iron (II) and oxygen molecule in active sites of alpha- and beta-subunits of oxyhemoglobin are presented within three models: without extra electron and in spin-unrestricted mode (model I); without extra electron and in spin-restricted mode (model II); with extra electrons in spin-unrestricted mode (model III). The electronic structure and (57)Fe quadrupole splitting Delta E(Q) for the active site of alpha- and beta-subunits (within model I) and only of the alpha-subunit (within models II and III) of oxyhemoglobin are calculated. The differences in Delta E(Q) values for these three models are discussed.