Adsorption of milk proteins (β-casein and β-lactoglobulin) and BSA onto hydrophobic surfaces

Abstract

Here, we study films of proteins over planar surfaces and protein-coated microspheres obtained from the adsorption of three different proteins (β-casein, β-lactoglobulin and bovine serum albumin (BSA)). The investigation of protein films in planar surfaces is performed by combining quartz crystal microbalance (QCM) and atomic force microscopy (AFM) measurements with all-atomic molecular dynamics (MD) simulations. We found that BSA and β-lactoglobulin form compact monolayers, almost without interstices between the proteins. However, β-casein adsorbs forming multilayers. The study of the electrokinetic mobility of protein-coated latex microspheres shows substantial condensation of ions from the buffer over the complexes, as predicted from ion condensation theories. The electrokinetic behavior of the latex-protein complexes is dominated by the charge of the proteins and the phenomenon of ion condensation, whereas the charge of the latex colloids plays only a minor role.