Impact of glycerol on thermostability and heat-induced gelation of bovine serum albumin

The influence of glycerol (0-40 wt%) on the thermal denaturation and gelation of bovine serum albumin (BSA) in aqueous solution has been studied. The effect of glycerol on heat denaturation of 0.5 wt% BSA solutions (pH 7.0) was measured using ultrasensitive differential scanning calorimetry. The unfolding process was irreversible and was characterized by a denaturation temperature (T-m). There was no significant change in T. as the glycerol concentration was increased from 0 to 40 wt%, suggesting that glycerol interacted similarly with the native and heat-denatured forms of the protein. The dynamic shear theology of 4 wt% BSA solutions containing 200 mM NaCl was monitored as they were heated from 30 to 90 degreesC at 1.5 degreesC min(-1), held at 90 degreesC for 70 min, and then cooled back to 30 degreesC at - 1.5 degreesC min(-1). The turbidity of the same solutions was monitored as they were heated from 30 to 90 degreesC at 1.5 degreesC min(-1) or held isothermally at 90 degreesC for 10 min. Glycerol increased the protein gelation temperature (DeltaT(gel) similar to +3 degreesC for 40 wt% glycerol) and decreased the gelation rate, which was attributed primarily to its ability to decrease the protein-protein collision frequency by increasing solution viscosity. The presence of glycerol either increased or decreased the shear modulus of the gels depending on its concentration and temperature, which was attributed to its ability to alter protein aggregation kinetics during gelation and its ability to increase the attractive forces between proteins at lower temperatures. (C) 2003 Elsevier Ltd. All rights reserved.