Thermal denaturation of interfacial protein layers

We report for the first time the structural measurements at nanometre resolution of the denaturation of β-lactoglobulin and lysozyme at an air-water interface using the technique of neutron reflectivity. The incipient denaturation shown previously for myogloblin is also studied for these molecules at room temperature, and denaturation is provoked by increasing the temperature of the solutions progressively to 75°C. The change in the adsorbed protein layer thickness, its scattering length density and density distribution perpendicular to the surface as a function of increased temperature are reported and the data analysed in terms of a two-state model for the denaturation process. These measurements are relevant to an understanding of the way in which proteins at interfaces act as templates, for example, in biomineralization.