DIFFERENTIAL SCANNING CALORIMETRY - A USEFUL TOOL FOR STUDYING PROTEIN DENATURATION

Power-compensated differential scanning calorimetry is applied to the determination of the thermodynamic parameters of protein denaturation. The heating of relatively high mass samples (approximate to 40 mg) is programmed at relatively high scan rates (10 degrees C min(-1)). For these dynamic thermal measurements, attention is paid to the problems of sample thermal lag and to the construction of the baseline under the calorimetric curve. Simplified mathematical models are applied to the case of the denaturation transition of beta-lactoglobulin and alpha-lactalbumin dispersed in distilled water at relatively high concentration (approximate to 5% w/w). The effects of Na+ and Ca2+ addition on the conformational stability of the proteins upon thermal treatment are compared at pH 3.5 and 7, where these two major whey proteins display different thermal behaviours.