The Roles of Prolyl Residue in Polypeptide Monolayers. III. Surface Films of Gelatin

Abstract

Abstract Surface films of gelatin, which is very rich in l-prolyl and l-hydroxyprolyl residues, were examined on salt-free and 1 m potassium chloride solutions at three different pH’s by the measurements of surface pressure, potential and viscosity. They were found to spread incompletely but to be of expanded types. The incomplete spreading and the other properties of the films were regarded as a manifestation of the specific configuration of gelatin in films. The expanded nature of the films was attributed to the roles of prolyl residue in gelatin such as observed in polypeptides. The extent of expansion of the films appeared to give evidence to support the results from chemical analysis that a gelatin molecule is composed of a large amount of l-prolyl-l-hydroxyprolyl bonds. The behavior of gelatin films was adequately explained by assuming that the parts of cis l-prolyl-l-hydroxyprolyl bond form the film and the parts of trans bond dissolve in aqueous subphase.