Influence of heme periphery upon electronic structúre and Mössbauer spectra parameters of hemoglobin

Quantum-chemical analysis of electronic structure peculiarities and mossbauer spectra parameters was performed for penta-coordinated complex of ferro-protoporphyrin with imidazole (Fe(+2)PPIm). Peripheral substitutes (−CH3, −C2H3, −C2H4COOH) introduced in the porphyrin macrocycle simulated real chemical structure of protoporphyrin (PP) in heme group of Hb. Calculations displayed that doubly occupied molecular orbitals (MO) of the peripheral substitutes (−CH=CH2 and −CH2−CH2−COOH) always appeared near the occupat ion border. The orientation of vinyl fragment have the essential influence upon Fe5 dorbital populations and quadrupole splittingAEQ for5B1 and5B2 terms. The values of isomer shift were insensitive to that modification of fragment orientation.