Pulmonary surfactant proteins SP-B and SP-C in spread monolayers at the air-water interface: I. Monolayers of pulmonary surfactant protein SP-B and phospholipids.
The effects of pulmonary surfactant protein SP-B on the properties of monolayers of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG), and a mixture of DPPC:DPPG (7:3, mol:mol) were studied using spread films at the air-water interface. The addition of SP-B to the phospholipid monolayers gave positive deviations from additivity of the mean areas in the films. At low protein concentrations (less than 45% amino acid residues which corresponds to 0.5 mol% or 10 weight% SP-B) monolayers of SP-B/DPPC, SP-B/DPPG and SP-B/(DPPC:DPPG) collapsed at surface pressures of about 70 mN.m-1, comparable to those of the lipids alone. At higher concentrations of SP-B in the protein-lipid monolayers, kink points appeared in the isotherms at about 40-45 mN.m-1, implying possible exclusion of material from the films, hence, changes in the original monolayer compositions. Calculated analyses of the monolayer compositions as a function of surface pressure indicated that nearly pure SP-B, associated with small amounts of phospholipid (2-3 lipid molecules per SP-B dimer), was lost from SP-B/DPPC, SP-B/DPPG, and SP-B/(DPPC:DPPG) films at surface pressures higher than 40-45 mN.m-1. The results are consistent with a low effectiveness of SP-B in removing saturated phospholipids, DPPC or DPPG, from the spread SP-B/phospholipid films.
Department of Biochemistry, Memorial University of Newfoundland, St. John's, Canada.
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Taneva
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Keough
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D000388:Air; D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; 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*; D011817:Rabbits; 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