Self-consistent-field modelling of casein adsorption Comparison of results for αs1-casein and β-casein

Abstract

The theoretical adsorption behaviour of the milk proteins, α _s1 - and β-casein, has been studied using a self-consistent-field (SCF) model. Previously published results for β-casein on the effects of ionic strength and pH on protein conformation are compared with those for α _s1 -casein. We find a lower adsorbed amount for α _s1 -casein, and a more complex adsorbed conformation because of its more heterogeneous primary structure. The predominant conformation appears to involve a substantial loop for α _s1 -casein, producing a thinner adsorbed layer than is predicted for β-casein, which has, predominantly, a long tail extending away from the surface into the aqueous region. The overall layer structure for both proteins is shown to consist of a combination of many coexisting protein conformations. The relative proportion of the different conformations controls the overall layer properties and their variation with pH and ionic strength.