[Ellipsometric study of immunologic reactions on the surface of silicon]

Adsorption of human serum albumin (HSA), egg albumin (EA), immunoglobulin G (IgG) and immunologic reactions occurring between them on silicon surface were studied by ellipsometry. Adsorption of HSA, IgG and antibodies on the monolayer of antigen is monomolecular in their isoelectric points and can be depicted by Langmuir's equation. Adsorption of EA is polymolecular apparently because of great tendency of the protein to aggregation in aqueous solutions. Comparison of the magnitudes of the protein monolayer thickness and areas per adsorbed molecule with their linear dimensions indicate that they preserve their native conformation. This allows an evaluation of the maximum number of the active sites (as approximately four) on the antigen surface accessible for antibodies and the adsorption constants for specific and nonspecific adsorption of IgG.