Thermodynamic studies of bovine lung surfactant extract mixing with cholesterol and its palmitate derivative

Langmuir film behavior of bovine lipid extract surfactant (BLES), mixed with cholesterol (CHOL) and cholesterol palmitate (CHOLP), has been studied by surface pressure (π)–area (A) measurements. Associative interactions, observed for both systems, were less favored at lower BLES content. The presence of unsaturated phospholipids and surfactant proteins in BLES favored the association. Miscibility of BLES was better with CHOLP than with CHOL at all compositions, indicating more compact packing of the BLES–CHOLP than of the BLES–CHOL system. The most stable mixtures were found at 30–40 mol% CHOL and at low π and at 20–25 mol% CHOLP but at higher π. These results suggest that BLES–CHOL miscibility is better at low π and low CHOL concentrations, while BLES–CHOLP miscibility is better at high π and high CHOLP concentrations.

Aex/AidAex/Aid as a function of composition for mixed monolayers of BLES/CHOL and BLES/CHOLP at 296 K.Figure optionsDownload as PowerPoint slide