ENHANCEMENT OF THE STABILITY OF THROMBIN BY POLYOLS - MICROCALORIMETRIC STUDIES

Glycerol increased the transition temperature (T(m)) of thrombin in a concentration-dependent fashion up to a concentration of 50% glycerol in aqueous buffer solution. Glycerol showed a comparable effect on T(m) of trypsin. This effect on T(m) of thrombin was not seen in the presence of excess sodium chloride (1.2 M) in aqueous buffer solution. The stabilizing effect of glycerol may be due to increased energy demand to unfold the protein molecule, as reflected by an increase in T(m). This stabilizing effect, as measured by T(m), was seen for other polyols, including sucrose, and was also dependent on the concentration of the stabilizing agent. Microcalorimetry may be used as an effective tool to screen for the protective action of compounds in enzyme stabilization studies before conducting the time-consuming and expensive stability studies of proteins in the presence of additives under different storage conditions.