RELAXATION BEHAVIOR OF HUMAN ALBUMIN ADSORBED AT THE SOLUTION AIR INTERFACE

The adsorption kinetics of human albumin (HA) at the aqueous solution/air interface and the surface relaxation behaviour of HA adsorption layers after transient area disturbances are studied using an axisymmetric drop shape technique (ADSA). Transient relaxation measurements were performed with the ADSA technique by changing the volume of the pendent drop by definite increments. In the concentration interval studied, the relaxation behaviour of HA is not diffusion controlled. Relaxation phenomena observed during the induction time show the presence of structured adsorption layers. The relaxation behaviour of a quasi-equilibrium HA adsorption layer is independent of the HA concentration. The calculated apparent diffusion coefficients represent the order of magnitude of the rate constant of the real mechanism. A comparison of results calculated from adsorption kinetics and relaxation data shows good agreement with an apparent diffusion coefficient in the order of 0.001 cm2 s-1.