Theoretical analysis of the forward reaction of antibody binding to surface-immobilized antigen

Abstract

The binding of monoclonal antibodies to surface-adsorbed antigen was measured by ellipsometry. Mouse IgG-antibodies directed against dinitrophenyl were used. The different binding affinities to free hapten in solution had previously been determined. — The experimental findings indicate that the mechanism of heterogeneous antibody-antigen reactions is more complex than the corresponding reaction mechanism in solution. The initial binding of antibodies easily becomes diffusion-rate-limited. The progressive, forward-reaction rate is continuously retarded. The reverse reaction is slow enough to make the total reaction practically irreversible. Experimental data were considered, especially in order to analyze the decreasing forward reaction rate. — It was found that the forward rate constant has a dependence on time, such that k(t) ∝ k ₁ t ^−h, where 0<h<1. This scaling property of the binding reaction can be used in calculation of intrinsic reaction rate coefficients. The analysis reveals a concentration-independent, intrinsic, forward-rate constant. The magnitudes of the calculated initial reaction rates are comparable to reaction rates measured in homogeneous antibody-antigen reactions.