EFFECT OF IONIZATION ON THE MONOLAYERS OF BOVINE SERUM-ALBUMIN, HEMOGLOBIN, AND INSULIN AT THE AIR-WATER-INTERFACE

The spread monolayers of the proteins insulin, bovine serum albumin, and hemoglobin were studied at the air-water interface in the low surface pressure region (by using the Wilhelmy plate method). The effect of subphase pH was investigated, which was analyzed with the help of the Davies' equation of state for the charged monolayers. The molecular weights were estimated for these different proteins, which were found to agree with the values reported in the literature from bulk studies, only in the case where the subphase pH was approximately equal to the isoelectric point (as found from bulk studies). The number of charges per molecule on the spread protein molecule was estimated as a function of subphase pH, by using the Davies' equation. This analysis showed that the zero net charge in the bovine serum albumin monolayer was at the same pH as the isoelectric point reported from bulk studies. © 1979 American Chemical Society.