Monolayer interactions of phospholipids and cholesterol

1. 1.|The force-area characteristics of monolayers of saturated and unsaturated phospholipids have been studied. 2. 2.|Interaction in phospholipid monolayers depends on the nature of the fatty acid constituents of the phospholipid, and on the temperature. 3. 3.|The mean area per molecule in mixed films of cholesterol with (1,2-disteroyl)-3-lecithin and (1,2-didecanoyl)-3-lecithin at 22° practically followed the simple additivity rule. 4. 4.|A condensing effect of cholesterol was evident with films of (1-steaoyl-2-lauroyl)-3-lecithin; (1,2-ditetradecanoyl)-3-lecithin, (1-stearoyl-2-oleoyl)-3-lecithin and the corresponding ethanolamine analogue, as well as with (1,2-dioleoyl)-3-lecithin at 22°. At 5° the condensation effect with (1,2-ditetradecanoyl)-3-lecithin was much reduced. 5. 5.|The very expanded films of synthetic lecithins and phosphatidyl ethanolamines containing linoleic and linolenic acid showed no appreciable condensation effects with cholesterol. 6. 6.|The behaviour of the mixed cholesterol-phospholipid films is governed by a number of factors, including Van der Waals' interactions, configurational entropy effects and alterations in the structure of water adjacent to the monolayers. These factors depend on chain length and degree of unsaturation