Adsorption Kinetics and Elutability of α-Lactalbumin, β-Casein, β-Lactoglobulin, and Bovine Serum Albumin at Hydrophobic and Hydrophilic Interfaces

Abstract

Adsorption kinetic data recorded for α-lactalbumin, β-casein, βlactoglobulin, and bovine serum albumin at silanized silica surfaces of low and high hydrophobicity, along with the surfactant-mediated elutability of each from hydrophobic silica, were interpreted with reference to a simple kinetic model for protein adsorption. The model includes an initial, reversible adsorption step, followed by a surface-induced conformational change yielding an irreversibly adsorbed form. The single-component adsorption kinetic data enabled estimation of the product of rate constants defining protein arrival, and conversion to an irreversibly adsorbed state, thus providing an index of relative adsorption affinity from single-component solutions. Elutability of each protein from hydrophobic silica with sodium dodecylsulfate, interpreted with reference to the same model, allowed further resolution of the single-component affinity data. In particular, the rate constants defining surface-induced unfolding for these proteins could be ranked in order of magnitude. The relative magnitudes of rate constants defining initial arrival and unfolding were found to be consistent with molecular properties shown to affect the surface activity of each protein.