Interaction of soluble proteins with protein monolayers

The direction and strength of intermolecular forces at an air-water or oil-water interface is such that many proteins in the interface are distorted in structure. This involves substantial changes in solubility and cross-sectional area. Many of the changes can be accounted for by rupture of the secondary and tertiary bonds and are often irreversible. The hydrophilic groups of the protein will be concentrated in the aqueous phase and participate in interactions with normal proteins in the supporting solution. It can be shown that certain types of interaction between these hydrophilic groups of a protein monofilm and a soluble protein are dependent on the interfacial pressure, that they are sensitive to a small (one or more amino acid) change in structure of the protein. Evidence is given that they are related to certain antigen-antibody type reactions between molecules in three-dimensional systems. Since many proteins in vivo are exposed to oilwater and air-water interfaces, this laboratory model may have physiologic as well as chemical significance.