*Biochemistry Department, National Research Centre, Cairo, Egypt
**Faculty of Medicine, Cairo University, Egypt

The fractions and concentrations of the inactive Hb pigments (such as MetHb, carboxyhemoglobin, HbCO, and sulfohemoglobin, SHb) and the active Hb (in the oxyhemoglobin form) as well as the total blood Hb concentration were determined in human and mice blood, using a newly developed multi-component spectrophotometric method. The conformational stability of mice and human oxyhemoglobins was investigated by measuring the auto-oxidation kinetics of oxyhemoglobin, bioenergetics of this reaction and intrinsic viscosity. The results obtained by using the new method of multi-component spectrophotometric analysis revealed higher concentrations of all inactive Hb derivatives in mice blood, when compared to human blood. To determine whether the increase in methemoglobin (MetHb) is attributed to changes in conformational stability against auto-oxidation, the auto-oxidation kinetics, bioenergetics and intrinsic viscosity were determined. The results revealed difference in conformation between mice and human blood accompanied by changes in intermolecular interactions represented by the slope of the ηsp/C = F(C) lines and Huggins’ constant K’, while no measurable change in intrinsic viscosity [η] of Hb was observed. These results indicate a lack of changes in the dimensions and shape of the Hb molecule. Study of the kinetics of oxyhemoglobin (HbO2) auto-oxidation revealed an increase in the auto-oxidation raction rate of mice HbO2 by 58%, when compared to human HbO2. This increase in auto-oxidation reaction rate was attributed to the decrease in the conformational stability as indicated by the smaller values of Eact (137.522 kJ/mole), ( ) (134.047 kJ/mole) and hence the smaller value of (105.098 kJ/mole) for mice HbO2, compared with those values for native human HbO2 (Eact = 139.118 kJ/mole, = 136.640 kJ/mole and = 106.155 kJ/mole). Therefore, it can be concluded that human HbO2 is more conformationally stable against auto-oxidation than mice HbO2.

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