INFLUENCE OF FREEZING-THAWING ON THE HEMOGLOBIN TEMPERATURE BEHAVIOR

The use of blood preservation at low temperatures methods in medical practice makes it necessary to study the temperature effect on hemoglobin. The effect of freezing-thawing to a liquid nitrogen temperature of -196C and subsequent thawing on hemoglobin A was studied, using the methods of temperature-perturbation differential spectrophotometry and analysis of absorption spectra first derivatives. After the hemoglobin A solution freezing-thawing, a smoothing of the breaks in the S-shaped temperature intensity dependence at the maximum of the temperature-perturbation differential spectra at 286 nm is noted. This probably means that temperature-dependent conformational changes in the hemoglobin A molecule are smoothed out and become less noticeable. It should be noted that after freezing-thawing, this dependence S-shaped form is preserved, i.e. conformational changes take place, but they are less pronounced than before freezing-thawing. Thus, on the one hand, freezing the hemoglobin A solution leads to conformational changes in the hemoglobin A molecule affecting the polar regions, namely, to an increase in the polar regions availability to the solvent, which is consistent with the data on the protein globule partial unfolding, accompanied by the globin aromatic amino acids exposure to the solvent, and with the data that the freezing-thawing process leads in most cases to conformational changes in the protein, which consist in the molecule weakening and increasing the protein active sites accessibility. On the other hand, freezing of hemoglobin A solutions leads to compaction of the hemoglobin A molecule subunits. This can probably be explained by the fact that, presumably, an increase in the availability of the hemoglobin A molecule absorbing chromophores located in the polar regions to the solvent leads to the compaction of the hemoglobin molecule A other parts, not involved in increasing the amino acid residues availability to the solvent. That is, some parts of the hemoglobin A molecule become more accessible to the solvent, while others become compact.