The structural organization of polypeptides at the air-water interface

The surface pressure-area isotherms generated by compressing monolayers formed by five polypeptide hormones at the air-water interface were studied. The results indicate that amphiphilic alpha-helical structures occupy the interfacial area, in agreement with predictions based only on the arrangements of the hydrophilic and hydrophobic amino-acid residues in the linear sequences of these polypeptides. The variety of such arrangements which result in the formation of stable helical structure, and their low degree of self-association, suggest that the induction of amphiphilic alpha-helical structure at suitable phase boundaries is likely to represent the earliest form of structural organization in polypeptides.