Pulmonary surfactant proteins SP-B and SP-C in spread monolayers at the air-water interface: II. Monolayers of pulmonary surfactant protein SP-C and phospholipids.
The interaction of the hydrophobic pulmonary surfactant protein SP-C with dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylglycerol (DPPG) and DPPC:DPPG (7:3, mol:mol) in spread monolayers at the air-water interface has been studied. At low concentrations of SP-C (about 0.5 mol% or 3 weight%protein) the protein-lipid films collapsed at surface pressures of about 70 mN.m-1, comparable to those of the lipids alone. At initial protein concentrations higher than 0.8 mol%, or 4 weight%, the isotherms displayed kinks at surface pressures of about 50 mN.m-1 in addition to the collapse plateaux at the higher pressures. The presence of less than 6 mol%, or 27 weight%, of SP-C in the protein-lipid monolayers gave a positive deviation from ideal behavior of the mean areas in the films. Analyses of the mean areas in the protein-lipid films as functions of the monolayer composition and surface pressure showed that SP-C, associated with some phospholipid (about 8-10 lipid molecules per molecule of SP-C), was squeezed out from the monolayers at surface pressures of about 55 mN.m-1. The results suggest a potential role for SP-C to modify the composition of the monolayer at the air-water interface in the alveoli.
Taneva
S
S
Department of Biochemistry, Memorial University of Newfoundland, St. John's, Canada.
Keough
K M
KM
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D000388:Air; D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D004548:Elasticity; D066298:In Vitro Techniques; D008567:Membranes, Artificial; D010715:Phosphatidylglycerols / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry*; D011312:Pressure; D011510:Proteolipids / Q000737:chemistry*; D011650:Pulmonary Alveoli / Q000737:chemistry; D011663:Pulmonary Surfactants / Q000737:chemistry*; D013499:Surface Properties; D013552:Swine; D014867:Water
D008567:Membranes, Artificial; D010715:Phosphatidylglycerols; D010743:Phospholipids; D011510:Proteolipids; D011663:Pulmonary Surfactants; D014867:Water; D015060:1,2-Dipalmitoylphosphatidylcholine; C030345:1,2-dipalmitoylphosphatidylglycerol