DSC STUDIES ON THE DENATURATION AND AGGREGATION OF SERUM ALBUMINS

Denaturation temperatures and enthalpies of bovine serum albumin (BSA) and human serum albumin (HSA) measured by DSC at different pH values and protein concentrations are compared with the literature data on BSA, or SH-blocked BSA. Both parameters display a trend in the region of pH 6.0-8.5 with a maximum at pH 7.1-7.2, in agreement with the literature data. An exothermic peak related to protein aggregation and precipitation was found at higher temperatures. For BSA, at lower pH values, this peak moves towards lower temperatures and overlaps the denaturation endothermic peak at pH < 5.5. The maximum temperature of aggregation, however, depends markedly on the protein concentration: therefore a separation of the two peaks was attempted. At pH 4.0, a shoulder appears at a temperature lower than that of denaturation. A gelification phenomenon also occurs and partially interferes with the other thermal processes.