RHEOKINETIC ANALYSIS OF PROTEIN FILMS AT THE AIR-AQUEOUS PHASE INTERFACE .1. BOVINE SERUM-ALBUMIN ADSORPTION ON ETHANOL AQUEOUS-SOLUTIONS

The dilational rheological properties and surface tension of bovine se rum albumin (BSA) adsorbed at the air-aqueous phase interface were mea sured as a function of time, protein concentration (1 x 10(-1)-3 x 10( -3)% w/w), and subphase composition (aqueous ethanol solutions from 0 to 2 M). The temperature was maintained at 20 degrees C. Adsorbed BSA films on water and aqueous ethanol solutions exhibited rheological pro perties that were mainly elastic and not very frequency dependent. The time dependence of surface tension and surface rheological properties was related with the rate of protein adsorption and the influence of ethanol on competitive adsorption. This phenomenon as well as protein- ethanol interactions could be supported by a significant reduction of the surface dilational modulus as either ethanol concentration increas ed (at constant BSA content) or BSA concentration decreased (at consta nt ethanol content). Circular dichroism measurements showed no signifi cant change in the secondary structure of BSA in the presence of ethan ol, at the concentrations used in these experiments.