ADSORPTION OF BETA-LACTOGLOBULIN ONTO SILICA, METHYLATED SILICA, AND POLYSULFONE

The adsorption of β-lactoglobulin onto silica, methylated silica, and polysulfone was studied by in situ ellipsometry for concentrations of 0.1, 1.0, and 12% β-lactoglobulin in phosphate buffer, pH 7. The amount adsorbed after 1 h decreased in the order polysulfone, methylated silica, and silica for all concentrations. The largest difference in the amounts adsorbed was found between polysulfone and silica at a bulk concentration of 1% β-lactoglobulin. The β-lactoglobulin adsorbed to polysulfone and methylated silica showed no tendency to desorb upon buffer rinsing whereas protein adsorbed to silica partially desorbed. The latter was taken as an indication of multiple states of adsorption at the silica surface. The influence of preadsorption was investigated and the adsorbed amounts from a 12% β-lactoglobulin solution were reduced if the surfaces were pretreated with 0.1% β-lactoglobulin. Polysulfone and methylated silica showed the largest effect having amounts adsorbed in the same range as for adsorption from 0.1% β-lactoglobulin alone. Silica surfaces were less influenced by preadsorption, indicating only minor conformational changes upon adsorption and/or exchange between adsorbed molecules and molecules in solution. © 1990.