Physicochemical studies on goat pulmonary surfactant

The large aggregate (LA) fraction of goat pulmonary surfactant (GPS) was isolated and characterized. Goat lung surfactant extract (GLSE) was obtained by chloroform-methanol extraction of the saline suspended LA fraction. Total phospholipid (PL), cholesterol (CHOL), and protein were biochemically estimated. It was composed of approximately 83% (w/w) PL, approximately 0.6% (w/w) CHOL and approximately 16% (w/w) protein. CHOL content was found to be lower while the protein content was found to be higher than other mammalian pulmonary surfactants. Electrospray Ionization Mass Spectrometry (ESIMS) of GLSE confirmed dipalmitoylphosphatidylcholine (DPPC) as the major phospholipid species, with significant amounts of palmitoyl-oleoyl phosphatidylcholine (POPC), palmitoyl-myristoyl phosphatidylcholine (PMPC) and dioleoylphosphatidylcholine (DOPC). Functionality of the solvent spread GLSE film was carried out in a Langmuir surface balance by way of surface pressure (pi)-area (A) measurements. A high value of pi (approximately 65 mN m(-1)) could be attained with a lift-off area of approximately 1.2 nm(2) molecule(-1). A relatively large hysteresis was observed during compression-expansion cycles. Monolayer deposits at different pi, transferred onto freshly cleaved mica by Langmuir-Blodgett (LB) technique, were imaged by atomic force microscopy. DPPC-enriched domains (evident from height analyses) showed dimensions of 2.5 microm and underwent changes in shapes after 30 mN m(-1). Functionality and structure of the surfactant films were proposed to be controlled by the relative abundances of protein and cholesterol.