An Ellipsometric Study of Protein Adsorption at the Saliva-Air Interface

At the liquid-air interface of human saliva a protein layer is adsorbed. From ellipsometric measurements it was found that the thickness of the surface layer ranged from 400 to 3600 A and the amount of protein material adsorbed was 9-340 mg/m 2. Based on the concentration of protein in the layer the samples could be classified into two groups: a low concentration (ca. 0.15 g/ml) and a high concentration (0.7l.l g/ml). In the low concentration group the surface layers appeared to be thin (500-600 ,~) while those in the high concentration group appeared to be much thicker (1000-3500 ~,). A correlation between the bulk pH and the thickness of the surface layer could be established. © 1989 Academic Press, Inc.