Dynamics of adsorption and desorption of proteins at an air/water interface

Adsorption and desorption dynamics of lysozyme and β-casein at the air/water interface were investigated through stress relaxation experiments. The resulting surface tension changes due to a step-type surface area disturbance, as a function of time, were measured through a capillary wave probe. The adsorption data, obtained after a surface area expansion, can be well fitted to a diffusion-controlled adsorption model. However, desorption relaxation following a surface compression is much slower and cannot be modeled by the diffusion theory. Characteristic diffusion frequency and high-frequency dilational elasticity for protein layers were also obtained and found to be consistent with data reported in the literature.