Study of the interaction of cholesterol with potentially hypocholesterolemic substances in a monolayer form

The behaviour of mixed monolayers of cholesterol (chol) and stigmastanil ph osporylcholine (SPC) at the air-water interface was studied and compared wi th that of the cholesterol-arachidonic acid (Ara) system in order to examin e the molecular interactions between the film components. The structural ch aracteristics of the mixed films was determined from the pi-A isotherms rec orded on an automated Langmuir-type film balance. The studies confirm that the mixed films are homogeneous and their components exhibit negative devia tions from ideality as the result of mutual interactions at the interface. The magnitude of these interactions depends on the surface pressure region, temperature, as well as the system composition. Values of the thermodynami c parameters such as Delta G(exc), Delta S-exc and Delta H-exc provide evid ence for the presence of interactions, which are stronger in the chol-SPC s ystem than in the chol-Ara mixed films. (C) 2000 Elsevier Science B.V. All rights reserved.