The relationship of the heme iron electronic structure and hemoglobin functions is of interest in order to understand the molecular nature of biological function. Previous Mossbauer study of various human hemoglobins demonstrated small variations of the Mossbauer hyperfine parameters (quadrupole splitting △EQ and isomer shift δ) for normal adult and fetal as well as for normal and leukemic oxyhemoglobins [1]. This fact indicates small variations of the heme iron electronic structure and stereochemistry in these hemoglobins. Moreover, it was shown that some features of the Mossbauer spectra related with the iron electronic structure nonequivalence in nonidentical subunits of tetrameric hemoglobins. Further study of human oxyhemoglobin modified by lyophilization demonstrated some changes of the heme iron electronic structure and stereochemistry [2]. On the other hand, some modified hemoglobins appeared useful as blood substitutes. Mossbauer study of hemoglobin modified by glutaraldehyde showed that cross-linking of hemoglobin by this reagent modified the heme iron stereochemistry [3]. In the present work we discuss the results of comparative study of human oxyhemoglobin modified by both pyridoxal-5 ′-phosphate which binds to the NH3-terminal groups of the β-chains and glutaraldehyde which mainly (70 %) cross-linked α- and β-subunits in each hemoglobin molecule.
