Interactions of spread lecithin monolayers with bovine serum albumin in aqueous solution

The dynamics of surface pressure (Pi) and of surface concentration (Gamma) of C-14 radiolabeled bovine serum albumin (BSA) adsorbed onto spread lecithin monolayers at the air-water interface were measured. The adsorption of BSA onto spread lecithin monolayers of 107 and 64 Angstrom(2)/molecule was enhanced at short times (within a few seconds), indicating synergism due to possible dissolution of BSA molecules into loosely or moderately packed lecithin layers. The surface concentration of BSA increased to 2-2.5 mg/m(2) from about 1 mg/m(2) and the surface pressure to 20-35 mN/m from about 10 mN/m in the presence of spread lecithin monolayer. At long times, monolayer composition was found, however, to be dominated by lecithin. BSA was expelled from the interface by close-packed lecithin monolayers, possibly because of the surface pressure and steric exclusion effects.