Desorption of lysine modified and unmodified proteins from solid surfaces -: Elution of β-lactoglobulin adsorbed on alumina and silica

The strength of attachment of adsorbed bovine beta-lactoglobulin (beta lg) and acetylated beta-lactoglobulin (Ac-beta lg) has been studied by comparing the elution profiles of the adsorbed proteins. beta lg binds very loosely to alumina at pH 4.2 and both beta lg and Ac-beta lg bind very tightly to alumina at pH 5.1 where the proteins showed highest adsorption at alumina/water interface [Bhaduri, A & Das, K. P., J. Disp. Sci. Technol., 15, 165-188 (1994)]. Adsorbed protein can only be eluted out if the pH of the elution buffer is raised to 7.6. beta lg elutes as a single peak whereas Ac-beta lg as two peaks indicating the later is adsorbed to alumina with different affinities. Elution profile of adsorbed beta lg at pH 6.3 shows that adsorbed beta lg population consists of partly folded elutable fraction and partly unfolded resistant one. The interaction of first layer of protein with the silica surface at pH 5.1 is primarily hydrophobic for beta lg and electrostatic for Ac-beta lg.