Structural, topographical, and rheological characteristics of beta-casein-dioleoyl phosphatidylcholine (DOPC) mixed monolayers.

The surface pressure (pi)-area (A) isotherms and Brewster angle microscopy (BAM) images of beta-casein-dioleoyl phosphatidylcholine (DOPC) mixed films spread on buffered water at pH 7 and 9 and at 20 degrees C were determined as a function of the mass fraction of DOPC in the mixture (X(DOPC)). The structural characteristics, miscibility, and topography (morphology and reflectivity) of DOPC-beta-casein mixed films were very dependent on surface pressure and monolayer composition. The structure in DOPC-beta-casein mixed monolayers was liquid-expanded-like, as for pure components.

Memory effects on the interfacial characteristics of dioctadecyldimethylammonium bromide monolayers at the air-water interface.

The structural and dynamic characteristics of dioctadecyldimethylammonium bromide (DODAB) monolayers on a pure water subphase were investigated by surface film balance, Brewster angle microscopy, and relaxation in area and surface pressure at constant surface pressure and area, respectively. The first compression-expansion cycle of the monolayer is not reversible and the second pi-A compression isotherm deviates to larger molecular areas relative to the first one. At a microscopic level this hysteresis may be assigned to an irreversible hydration of the ammonium groups of DODAB.