Dynamics of proteins at air-water and oil-water interfaces using novel Langmuir trough methods

Abstract

Spread monolayers of β-lactoglobulin and bovine serum albumin and adsorbed films of lysozyme and β-lactoglobulin were studied at the oil (n-tetradecane) -water (O-W) and air-water (A-W) interfaces. In general, spread monolayers were more expanded at the O-W interface than at the A-W interface. Desorption rates from monolayers increased greatly with increasing interfacial pressure, π, but were still quite low until typical equilibrium adsorption π were exceeded. Desorption rates as a function of the energy barrier to desorption were similar at both types of interface. Adsorption kinetics of lysozyme at the A-W interface were in agreement with measurements obtained via ellipsometry. Spread and adsorbed films of β-lactoglobulin were subjected to dilatational expansion. The dynamics of the change in π were slower at the O-W interface, but for both interfaces the dynamics of the in-film relaxation processes were quite fast, diffusion from the bulk aqueous phase accounting for the long time-scale of the relaxation back to the equilibrium π for adsorbed films. A new type of Langmuir trough was used for these measurements.