Heitler-London Calculation on the Bonding of Oxygen to Hemoglobin. : I. Singlet States in the Case of O-O Axis Parallel to Heme Plane

概要

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Bonding of O_2 to heme is studied by Heitler-London calculation with three ionic structures (Fe^<2+>-O_2, Fe^<2+>-O_2, and Fe^<2+>-O_2^+). The basic configurations are constructed from the low-lying terms of Fe-<2+>, Fe^<3+> and Fe^+ in the heme, and those O_2, O_2^- and O_2^+. Hamiltonian matrix elements are evaluated with the method of "Atoms in Molecule." The empirically determined term energies of O_2 are used and the electronic structure of Fe atom in the heme is estimated with the ligand field theory. The molecular integrals necessary for the evaluation of interaction part are computed with the Gaussian type SCF atomic orbitals. As O_2 approaches to the heme, one of the ^1A_2 states, which is the combination of the excited ^3E term of the heme and the ground ^3Σ_g^- term of O_2, becomes the ground state. In this state the negative exchange interaction between O_2 and Fe atom is effective in lowering the energy.
社団法人日本物理学会の論文
1972-12-05