[Electron factors in peroxidase properties and the mechanism of activation of oxygen with heme-containing proteins].

A quantum-chemical calculation was carried out for the electronic structure of coordination compounds of general formula FeP (L1) (L2) (P-porphine; L1-imidazole or imidazolate; L2-CO, O2 or is absent), modelling the active sites of number of hemoproteins. The elucidation of electronic structures of the complexes under consideration explains the similar shapes and band positions of optical absorption and magnetic circular dichroism spectra of oxy- and carboxycomplexes of myoglobin, hemoglobin, and peroxidase. It is shown that the Coulomb repulsion between electrons of the lone pair of the imidazolate distal nitrogen leads to the transfer of the electronic density from this ligand to the dioxygen.

[Electron factors in the properties of cytochrome P-450 and mechanism of activation of molecular oxygen].

A quantum-chemical calculation was carried out for the electronic structures of coordination compounds of general formula: FeP(L1)(L2) (P--porphin; L1 = SHCH3, [SCH3]-, [SC6F4H]-; L2 = CO, NO, O2), modeling the active site of cytochrome P450. It was shown that Coulomb repulsion between the electrons of the sulfur lone pair leads to the transfer of the electronic density from the ligands L1 = [SCH3]- or [SC6F4H]- to the porphyrin of/and to the L2 ligand. This explains the origin of the band at 450 nm in the absorption spectra of the complexes of cytochrome P450 with CO, the absence of such a band in those with O2, and the strong activation of dioxygen by cytochrome P450.