Rheologic hysteresis curve shape specificity of mixed lipid films

Abstract

1. 1. The surface tension (γ)-area ( A) hysteresis loops of mixed lipid films were studied to discern if such a procedure might be suitable to investigate lipid domains and the effects of molar composition. 2. 2. Using cyclic film compression and the Wilhelmy measurement of surface tension, it was shown that there is an evolution of both γ— A hysteresis curve shape and loop size. 3. 3. With film composition being the only variant in the experimental system, the γ- A shape often was distinctive. 4. 4. Specific zones of one hysteresis trace were interpreted as representing phospholipid ionic interaction. 5. 5. Differential, sequential entry of the phospholipid acyl chains and polar groups in the hysterectic process indicated the separate importance of the forces governing the two parts of the film. 6. 6. Controlled ionic concentration, pH, and temperature could effect an equalization of magnitude between the “strong” ionic forces of the polar groups and the “weak” dipole forces of the hydrocarbon chains. 7. 7. With balanced forces functional significance of molar composition could be expressed through grouping of the lipids into interacting domains.