ADSORPTION COMPETITION BETWEEN ALBUMIN AND MONOCLONAL IMMUNOGAMMAGLOBULINS ON POLYSTYRENE LATTICES

Adsorption competition between bovine serum albumin (BSA) and monoclonal immuno-gamma-globulins (IgG's) has been studied by sequential and simultaneous addition of the proteins to differently charged polystyrene (PS) latices as the adsorbates. Electrostatic interactions were systematically studied by using (i) IgG's of different isoelectric points, (ii) positively and negatively charged latices, and (iii) by performing experiments at various pH-values. In sequential adsorption experiments the displacement of the preadsorbed protein by the secondly added protein was studied. Preadsorbed IgG is more easily displaced by BSA than the converse. Electrostatic interactions do not play a major role; under certain conditions their effect is absent. Displacement of the first protein is not always a prerequisite for the adsorption of the second protein. In simultaneous adsorption experiments from binary and ternary mixtures of BSA and four different monoclonal IgG's the enrichment of one of the proteins at the expense of the other(s) was studied as a function of the supply from the solution and the electrostatic interaction between the proteins and the latex. Under electrostatically repulsive conditions the adsorption competition is strongly influenced by the electrostatic interaction between the adsorbent surface and the respective proteins. The preference becomes less pronounced with increasing adsorption time. When the proteins are electrostatically attracted to the adsorbent the influence of electrostatics on preferential adsorption is hardly discernable. Both with sequential and simultaneous addition of the proteins the results indicate that conformational rearrangements in adsorbates of BSA are faster than in those of the IgG's. © 1992.