Stabilizing effect of organic solvents on oxyhemoglobin.

The role of hemoglobin solutions as oxygen carriers in biotechnology are numerous, such as in the oxygen supply to biocatalysts or in the preparation of blood substitutes. However, the major barrier to the successful use of hemoglobin in biological and medical engineering is the autoxidation of heme iron during preparation, storage, and utilization. Fifty-six solvents, chosen among the group of Parker's classification, were studied with regard to the autoxidation kinetics of oxyhemoglobin under nondenaturant conditions. Among these solvents 27 present a concentration range in which the autoxidation rates were reduced compared to autoxidation in water. Three groups of solvent have been observed: one exhibiting only a destabilizing effect regardless of the solvent proportion, a second showing a strong stabilizing effect (k(H2O)/k(solvent) greater than 20) and a third showing a low stabilization (k(H2O)/k(solvent) less than 20). The most effective stabilizing solvents were glycerol, glycols, and alcohols. The effect of hydroorganic solvents could be explained by taking into account the globin solvation by water molecules. The solvents that enhance the structure of the water and form few hydrophobic interactions with globin prevent oxyhemoglobin autoxidation.