MIXED MONOLAYERS OF PHOSPHOLIPIDS AND CHOLESTEROL

1. 1. The force-area characteristics of mixed monolayers of cholesterol with synthetic lecithins and phosphatidylethanolamines are presented. 2. 2. The nature of the fatty acid constituent of the phospholipid and the temperature are important since the action of cholesterol is related to the physical state of the pure phospholipid monolayer. 3. 3. Generally an expanded monolayer is condensed by the addition of cholesterol and this is associated with an effect upon the hydrocarbon chain mobility. This is greatest when the phospholipid is close to the transition temperature for the change from condensed to expanded monolayer. In condensed monolayers the hydrocarbon chain fluidity is reduced and cholesterol does not have a large effect. 4. 4. Cholesterol effectively reduces the transition temperture by disrupting the cooperative movements of the hydrocarbon chains. 5. 5. The position of cis double bonds in unsaturated phospholipids is not important for condensation effects with cholesterol; furthermore the presence of a double bond is not a necessary condition for such effects. 6. 6. Specific molecular structures are not necessary for a condensation with cholesterol and a complex is not formed. © 1969.