Kinetics of adsorption of denatured protein at alumina-water interface

The kinetics of adsorption of soluble denatured protein, gelatin has been studied at the alumina-water interface as a function of protein concentration, pH, temperature and ionic strength. The rate of adsorption of gelatin has been compared with rate of adsorption of BSA denatured by 8 M urea or 0.05 M SDS. The initial stage for the adsorption process is diffusion-controlled and the surface diffusion coefficients evaluated from equations of Ward and Tordai and by Bull for globular and denatured proteins are found to be widely different from each other. The kinetic data for gelatin fit into a first order rate equation with two rate constants, k(1)(a) and k(2)(a). Using Arrhenius equation, the activation energies Delta E(1)* and Delta E(2)* have been evaluated from the values ai k(1)(a) and k(2)(a) respectively. The corresponding changes in values of enthalpy of activation (Delta H*), entropy of activation (Delta S*) and free energy of activation (Delta G*) have been evaluated using Eyring's equation for absolute reaction rate. It has been found that for both gelatin and denatured BSA, in the first kinetic step Delta H-1* > T Delta S-1* and for the second step T Delta S-2* > Delta H-2.