First-Principles Hartree-Fock Investigation of Electronic Structure and Hyperfine Properties of Deoxyhemoglobin

The electronic structure of Deoxyhemoglobin is studied using the Unrestricted Hartree--Fock Cluster Procedure considering as representative the entity involving the porphyrin ring, the Fe$^{2+}$ ion and the proximal histidine. The positions of the atoms are taken from X-ray data. The calculated electronic structure of the spin S=2 system is used to derive the magnetic hyperfine fields, nuclear quadrupole interaction parameters and the Mossbauer isomer shifts for the $^{57m}$Fe. The results are in good agreement with experiment, providing support for the accuracy of the calculated isotropic and anisotropic components of the spin density and electronic charge density near the $^{57m}$Fe nucleus. Results for the hyperfine properties of $^{14}$N, $^{13}$C, $^{1}$H and $^{2}$H nuclei will also be discussed. (*) Present Address: Dept. of Physics, Uppsala University, Sweden (**) Present Address: M. D. Anderson Center, Houston, Texas (***) Also: Dept. of Physics, University of Central Florida, Orlando, Florida