Abstract
Molecualr interactions between saturated and unsaturated phospholipids in a mixed monolayer and a mixed bilayar were investigated in terms of surface pressure, surface viscosity, micropolarity, and ζ-potential.
The DSPC single monolayer formed a condensed monolayer, while the DOPC or DLPC single monolayer formed an expanded layer. Collapse pressure for the single monolayer decreased with an increase in the degree of unsaturation in the unsaturated phsopholipid. Each phospholipid mixed monolayer formed an expanded monolayer collaspe pressure for the mixed monolayer of phospholipids was independent of the molar ratio of the unsaturated phospholipid. The surface viscosity of the single and mixed monolayer increased with a decrease in area per molecule of phospholipid. The micropolarity and surface change density of the mixed (liposomes) decreased with increase in the concentration and/or degree of unsaturation of the unsaturated phospholipid. The miscibility of the saturated phospholipid with the one unsaturated was shown to be low in the monolayer and bilayer.
