Mixed Monolayers Containing Phosphatidylcholine, Cholesterol, Oleic Acid, and Mono- and Triolein.

Abstract

The properties of egg phosphatidylcholine, cholesterol, monoolein, oleic acid, and triolein in mixed monolayers at the air-water interface were studied. Phosphatidylcholine, monoolein, and oleic acid generate miscible 2- and 3-component systems in all combinations and proportions. Triolein forms partially miscible films with all the other lipids studied. The partial molar area and the limiting solubility of triolein in the mixed monolayers were calculated. Triolein has a relatively high 2-dimensional miscibility in mixed monolayers with monoolein and oleic acid. Cholesterol generates miscible monolayers with phosphatidylcholine, monoolein and oleic acid in all proportions in both 2, 3 and 4-component systems. Cholesterol has a condensing effect on the liquid expanded monolayers, which is at maximum when the ratio between cholesterol and fatty acid chains reaches 1:1. Cholesterol forms partially miscible films with triolein. The systems studied may provide a model for studying the molecular organization of the lipids in, e.g., intestine emulsion particles, and serum lipoproteins, and the enzymatic attack on these.