ELECTROCHEMICAL STUDIES OF THE INTERFACIAL BEHAVIOR OF ALPHA-LACTALBUMIN AND BOVINE SERUM-ALBUMIN

Knowledge of the conformational behaviour of proteins as a function of temperature is important in the thermal processing of foods. Equally important is their interfacial behaviour with surfaces under these sam e processing conditions. This paper describes electrochemical techniqu es developed to study these structurally related properties of protein s. The interfacial behaviour of alpha-lactalbumin and bovine serum alb umin was studied on a platinum electrode using cyclic voltammetry over a temperature range from 273 to 363 K. It was found that both protein s adsorbed strongly on the metal surface. As the temperature was incre ased up to the denaturation temperature of the protein, the surface ch arge density for protein adsorption also increased due to the conforma tional unfolding. Above the temperature for denaturation, the surface charge density continued to increase. Mixtures of the two proteins res ulted in a substantial increase in surface charge density above the de naturation temperatures. A comparison of surface concentrations (Gamma ) of cyclic voltammetric measurements with those for ellipsometric mea surements reported in the literature showed a similar behaviour with i ncreasing adsorption with temperature. A value of 17 +/- 4 carboxylate groups for the alpha-lactalbumin protein was determined from an analy sis of the surface coverage which is consistent with the number of aci dic residues on the protein. (C) 1997 Published by Elsevier Science Lt d on behalf of the Canadian Institute of Food Science and Technology.