Binding of Surfactants onto Preadsorbed Layers of Bovine Serum Albumin at the Silica−Water Interface

Abstract

The binding of nonionic and anionic surfactants from bulk solutions onto preadsorbed layers of bovine serum albumin (BSA) at the hydrophilic silicon oxide/water interface has been studied using specular neutron reflection. The distributions of surfactant, protein, and water at the solid/aqueous interface were separately determined by using deuterium labeling of the surfactant and water. The preadsorbed BSA layers were formed by equilibrating the hydrophilic oxide surface with a 0.15 g dm-3 BSA solution, which produced a densely packed uniform BSA layer of thickness 35 ± 3 A. The possible association of nonionic surfactant pentaethylene glycol monododecyl ether (C12 E5) with BSA at the interface was examined by following the change in neutron reflectivity before and after surfactant addition. That no measurable difference between these reflectivity profiles was observed suggests that the nonionic surfactant did not bind to the adsorbed BSA. The binding of sodium dodecyl sulfate (SDS) onto the BSA layer was...