First Principles Electronic Structure Investigation of Singlet and Triplet States of Oxyhemoglobin by Hartree-Fock Procedure Combined with Many-Body Perturbation Theory

Interest in the possibility of magnetic character of oxyhemoglobin has been recently stimulated by spin-lattice relaxation effects studied [1] by the muon-spin rotation technique. In view of this, we have carried out first-principles electronic structure investigations involving Hartree-Fock theory combined with many body perturbation effects on the singlet and triplet states of oxyhemoglobin. Our results indicates using two recent x-ray structural data [2,3] for oxyhemoglobin that, using only Hartree-Fock theory without correlation effects included, the singlet state lies above the triplet state by about 0.08a.u.[2] and 0.13a.u.[3]. Incorporation of many body effects by perturbation methods reverses the order with the triplet state located 0.18a.u.[2] and 0.14a.u.[3] respectively above the singlet state. Physical reasons for these relative orderings of the singlet and triplet states will be discussed.\\[4pt] [1] K. Nagamine etal. Proc. Acad.Ser.B 83,120(2007).\\[0pt] [2] Massimo Paoli etal. J.Mol. Biol. 256,775(1996).\\[0pt] [3] Sam-Yong Park etal. J.Mol. Biol. 360,690(2006)