Govorova Y. Low Temperature and Molecular Invironment Influence on Phase Transitions of Hemoglobin-containing Systems

The research aim: to determine the influence of low temperatures and the molecular environment on phase transitions in hemoglobin-containing systems. The research object: the influence of physical and chemical factors of cryopreservation on phase transitions in protein-containing systems. Research methods: differential scanning microcalorimetry, low temperature scanning calorimetry, spectrophotometry. Phase transitions in hemoglobin-containing systems caused by low temperature exposure and molecular environment changes were studied in this thesis. Such systems included isolated hemoglobin, hemoglobin within erythrocyte ghosts, hemoglobin of fractions of human placenta extracts and suspensions of red blood cells. The study of thermodynamic and kinetic parameters of hemoglobin thermal denaturation showed that the presence of cryoprotective agents of different concentrations in protein solution had stabilizing or destabilizing effect on conformational stability of macromolecules. By the caused decrease in thermal stability of human hemoglobin the studied cryoprotectants could be arranged in the following row: glycerol < oxyethylated glycerol with polimerization degree n=25 < oxyethylated glycerol with polimerization degree n=5 < dimethylsulphoxide < 1.2-propanediol. It is shown that freezing of hemoglobin solutions with 40 and 50% concentration of studied cryoprotectants increased thermal stability of frozen-thawed protein if compared with the protein that not subjected to low-temperature effect. It was shown that the changes of phase transitions in systems containing erythrocytes ghosts and placenta extract fraction were reversible. Freezing placenta down to -196°C did not cause any changes in values and character of phase transitions in the studied systems.