THE MODEL OF CONTINUOUS HETEROGENEITY OF PROTEIN SURFACE INTERACTIONS FOR HUMAN SERUM-ALBUMIN AND HUMAN IMMUNOGLOBULIN-G ADSORPTION ONTO QUARTZ

A theoretical model is developed for the reversible and irreversible protein adsorption in a kinetic regime by assuming the continuous energetic heterogeneity for protein-surface interaction and the possibility of structural alterations of adsorbed molecules. The mathematical approach is based on the approximation of the "controlling band," which holds true for wide monotonous distributions of the energetic characteristics of protein-surface interactions. The simplest rectangular distributions of adsorption centers in terms of activation energy are used to explain the logarithmic kinetics of IgG and HSA adsorption onto a quartz surface. The main difference in the HSA and IgG adsorption can be due to the ability of IgG to change significantly the "effective adsorption area" by reorientation of the adsorbed IgG molecules. To explain the Freundlich character of HSA adsorption onto a precoated surface the exponential distributions of adsorption centers in terms of activation energy are used. The irreversibility of HSA and IgG adsorption is compared. The competitive analysis of some approaches allowed for energetic heterogeneity of protein-surface interaction is performed. The possibility of lateral electrostatic repulsion forming the logarithmic kinetics of HSA adsorption is checked experimentally. It was found that the "long time" logarithmic adsorptional dependence corresponds mainly to the heterogeneity of protein-surface interactions, rather than to electrostatic repulsion. © 1991.