ADSORPTION OF PROTEIN-FRACTIONS FROM WHEAT ONTO METHYLATED SILICA

The kinetics of the sequential adsorption of gliadins and water-solubl e fraction (WSF) from the wheat variety Kosack onto hydrophobic silica (methylated silica) surfaces were studied by in situ ellipsometry. Th e measurements were made in water and in 0.01M acetate buffer, pH 4.0 and 5.0, with and without 0.1M NaCl. The concentration of gliadins and WSF was 1.7 mu g/ml. The adsorption of gliadins in water was investig ated at three different protein concentrations (0.17, 1.7, and 17 mu g /ml), and the adsorption was found to be very high with regard to the low concentrations of protein in solution. The results of the sequenti al adsorption in water indicated that the WSF adsorbed to preadsorbed gliadins. When proteins of the WSF were adsorbed first, they blocked f urther adsorption of gliadins. Measurements in acetate buffer at diffe rent pH values showed that the effect of pH was larger in the experime nts where the gliadins were adsorbed first, both for the initial adsor ption and for the sequential addition of WSF. An increase in ionic str ength also increased the amount of WSF adsorbed to preadsorbed gliadin s. These results indicate that the sequential adsorption of WSF to gli adins is strongly affected by electrostatic interactions.