title: Interactions between lipopolysaccharide and phosphatidylethanolamine in molecular monolayers.
abstract: Lipopolysaccharide and phosphatidylethanolamine are the two major lipid constituents of the membrane of Salmonella typhimurium. Interactions between the purified lipopolysaccharide and phosphatidylethanolamine were studied in molecular monolayers at air-water interfaces. The equilibrium surface pressures of mixed films of lipopolysaccharide and phosphatidylethanolamine were determined as a function of the film composition. The plot of the equilibrium surface pressrue vs. the area occupied by phosphatidylethanolamine molecules exhibited two distinct regions. Below a phosphatidylethanolamine surface concentration at which 55% of the surface was occupied by phosphatidylethanolamine molecules, the equilibrium pressure was invariant and had the value of a pure lipopolysaccharide monolayer at maximum compression. At phosphatidylethanolamine surface concentrations in excess of 55% surface area occupation (phosphatidylethanolamine/lipopolysaccharide (mol/mol) greater than 16), the equilibrium surface pressure was a function of the surface concentration of phosphatidylethanolamine. The results suggest a simple model in which lipopolysaccharide and phosphatidylethanolamine form a complex in which each lipopolysaccharide molecule is surrounded ("lipidated") by a shell of approx. 16 phosphatidylethanolamine molecules.
mesh_terms: D008070:Lipopolysaccharides / Q000302:isolation & purification; D008433:Mathematics; D008563:Membrane Lipids; D008567:Membranes, Artificial; D008968:Molecular Conformation; D010714:Phosphatidylethanolamines; D012486:Salmonella typhimurium
chemical_list: D008070:Lipopolysaccharides; D008563:Membrane Lipids; D008567:Membranes, Artificial; D010714:Phosphatidylethanolamines