DIFFERENTIAL SURFACE BINDING OF ALBUMIN, IMMUNOGLOBULIN-G AND FIBRINOGEN

Protein-protein interactions, as well as the nature of the surface, si gnificantly affect the activity of a specific protein towards a define d surface. Indications are that protein-protein associations may affec t antibody detectability, but in some cases this is the result of alte red antigenic accessibility rather than physical removal of the molecu le. The antibody binding patterns are also quite variable over an enti re methyl-silanol wettability gradient on silicon, suggesting that the surface itself is affecting protein-protein and protein-protein-surfa ce associations. Ellipsometric studies were carried out on the gradien ts which were incubated in single, binary and tertiary physiological c oncentration solutions of human albumin, immunoglobulin G (IgG) and fi brinogen. The ellipsometric-antibody detectability of the proteins on such surfaces were found to be variable, depending upon the location o n the gradient and the order and combination in which the proteins wer e presented to the surface. Radiolabelled proteins were studied on dis crete regions of these gradients. Competitive effects of albumin were found to be inhibitory (negative) with respect to IgG adsorption on hy drophobic surfaces, while enhancing IgG deposition on hydrophilic surf aces (positive). Scanning force microscopy in the so-called tapping mo de indicates that proteins, particularly IgG, organize themselves diff erently with respect to surfaces, depending upon the nature of the sur face and the presence of other proteins.