INFLUENCE OF HEME PERIPHERY ON THE ELECTRONIC-STRUCTURE AND MOSSBAUERPARAMETERS OF HEMOGLOBIN

For the five-coordinated complexes of ferroprotoporphyrin with imidazo le, a quantum-chemical analysis of the electronic structure and Mossba uer spectral parameters has been carried out. Peripheral substituents (-CH3, -C2H3, -C2H4COOH) were introduced into the porphyrin macrocycle to model the real chemical structure of protoporphyrin in the heme gr oup of desoxyhemoglobin. The calculations have shown that near the occ upation border in the complexes there are MO which are due to the pi-s ystems of the -CH=CH2 and -CH2-CH2-COOH substituents. The orientation of the vinyl fragments has a considerable effect on the populations of the Fe d-orbitals and the quadrupole splitting DELTAEQ for the B-5(1) and B-5(2) terms.