The linoleic acid influence on molecular interactions in the model of biological membrane.

The present work explores the properties for binary (LA/DPPC), (cholesterol/DPPC) and also ternary (LA/cholesterol/DPPC) mixed Langmuir monolayers, at the air-water interface, treated as the simplest models of a half of the biological membranes. In ternary monolayers both cholesterol and DPPC were mixed at constant molar ratios that correspond to the proportions occuring in different natural membranes, among which fibroblast membrane (where the amount of phospholipid predominates) and also erythrocyte membrane (where the amount of sterol predominates) were taken into consideration. Our researches were conducted by using the Langmuir film balance, by means of which we registered the surface pressure (pi) as a function of the area of water surface available to each molecule (A). It was found that LA and DPPC also cholesterol and DPPC are miscible in binary as well as LA, cholesterol and DPPC in ternary mixed monolayers, however in ternary mixed monolayers, at higher content of fatty acid (for molar fraction X(LA)=0.6, 0.8) these components were miscible only at the surface pressure below approximately 27 mN/m. Furthermore the results of our measurements show that LA reveals very strong influence on the membrane composition. Depending on various amounts of this fatty acid within the models of biological membranes it seems to affect different stability of natural bilayer.