X-alpha-DVM Investigation of Double Water Molecule Interactions with Active Sites of alpha- and beta-Subunits of Hemoglobin

Abstract

In this work, the results of X-alpha-discrete variation method calculations of the electronic structure and interatomic parameters of chemical bonding between iron (H) and oxygen molecule with and without extra electrons and protons in active site (AS) of alpha- and beta-subunits of oxyhemoglobin are presented. The Skulachev model [Skulachev, Sorosovskii obrazovatel'nyi zhurnal, 1998, 8, 2] of O-2 molecule existing in respiration medium in the 2H(2)O form was used. The introduction of extra electrons does not change considerably the interaction of the iron atom with the O-2 oxygen molecule, but strengthens the repulsion in the Fe-N bonds. In this case, the estimated effective charge of the iron atom is +1.8/1.5e for AS of alpha-/beta-subunits of oxyhemoglobin, and the magnetic moment of iron atoms becomes zero. The deoxygenation effect of the AS of the alpha- and beta-subunits of oxyhemoglobin is due to the ability of extra protons to break down covalent attraction between the iron atom and the nearest oxygen atom and also to weakening of the repulsive component of the covalent Fe-N interactions. (C) 2008 Wiley Periodicals, Inc. Int J Quantum Chem 108: 2648-2656, 2008