The interaction energies of cholesterol and lecithin in spread mixed monolayers at the air-water interface

Abstract

1. 1. The interaction between dilauroyl lecithin, diundecyloyl lecithin, didecanoyl lecithin and dinonanoyl lecithin with cholesterol was investigated using the Goodrich method. No interaction with cholesterol was found for dinonanoyl lecithin, while with didecanoyl lecithin small effects could be detected only at high surface pressure. Strong condensation effects occurred with diundecyloyl lecithin and dilauroyl lecithin. The pressure-area curves of these lecithins are given. 2. 2. Assuming a regular surface mixture, a theory was derived which allows one to describe the collapse pressure of a mixed monolayer with miscible components. 3. 3. The interaction between distearoyl lecithin, dipalmitoyl lecithin, dimyristoyl lecithin, dilauroyl lecithin, diundecyloyl lecithin, didecanoyl lecithin, dinonanoyl lecithin, oleoyl-stearoyl lecithin, dioleoyl lecithin and dilinoleoyl lecithin with cholesterol was investigated by measuring the collapse pressure of the mixed monolayers. An interaction parameter and interaction energies were calculated. 4. 4. According to this method distearoyl lecithin, dipalmitoyl lecithin, dinonanoyl lecithin and dilinoleoyl lecithin showed no interaction with cholesterol; while dimyristoyl lecithin, dilauroyl lecithin, diundecyloyl lecithin, oleoyl-stearoyl lecithin and dioleoyl lecithin interacted markedly with cholesterol. A small effect was observed for didecanoyl lecithin.The most pronounced effect was observed for dilauroyl lecithin and oleoyl-stearoyl lecithin. 5. 5. The results obtained using the Goodrich and collapse pressure methods are in good agreement.