Multilayer structures in lipid monolayer films containing surfactant protein C: effects of cholesterol and POPE.
The influence of cholesterol and POPE on lung surfactant model systems consisting of DPPC/DPPG (80:20) and DPPC/DPPG/surfactant protein C (80:20:0.4) has been investigated. Cholesterol leads to a condensation of the monolayers, whereas the isotherms of model lung surfactant films containing POPE exhibit a slight expansion combined with an increased compressibility at medium surface pressure (10-30 mN/m). An increasing amount of liquid-expanded domains can be visualized by means of fluorescence light microscopy in lung surfactant monolayers after addition of either cholesterol or POPE. At surface pressures of 50 mN/m, protrusions are formed which differ in size and shape as a function of the content of cholesterol or POPE, but only if SP-C is present. Low amounts of cholesterol (10 mol %) lead to an increasing number of protrusions, which also grow in size. This is interpreted as a stabilizing effect of cholesterol on bilayers formed underneath the monolayer. Extreme amounts of cholesterol (30 mol %), however, cause an increased monolayer rigidity, thus preventing reversible multilayer formation. In contrast, POPE, as a nonbilayer lipid thought to stabilize the edges of protrusions, leads to more narrow protrusions. The lateral extension of the protrusions is thereby more influenced than their height.
Malcharek
Stefan
S
Institut für Biochemie, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany.
Hinz
Andreas
A
Hilterhaus
Lutz
L
Galla
Hans-Joachim
HJ
D000818:Animals; D001703:Biophysics / Q000379:methods*; D002784:Cholesterol / Q000737:chemistry*; D008055:Lipids / Q000737:chemistry; D008168:Lung / Q000378:metabolism; D046911:Macromolecular Substances / Q000737:chemistry; D008563:Membrane Lipids / Q000737:chemistry*; D018625:Microscopy, Atomic Force / Q000379:methods*; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D015233:Models, Statistical; D010169:Palmitic Acids / Q000737:chemistry; D010714:Phosphatidylethanolamines / Q000737:chemistry*; D011510:Proteolipids / Q000737:chemistry; D037701:Pulmonary Surfactant-Associated Protein B / Q000737:chemistry; D037721:Pulmonary Surfactant-Associated Protein C / Q000737:chemistry*; D011663:Pulmonary Surfactants / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry; D013552:Swine
D008055:Lipids; D046911:Macromolecular Substances; D008563:Membrane Lipids; D010169:Palmitic Acids; D010714:Phosphatidylethanolamines; D011510:Proteolipids; D037701:Pulmonary Surfactant-Associated Protein B; D037721:Pulmonary Surfactant-Associated Protein C; D011663:Pulmonary Surfactants; D013501:Surface-Active Agents; C057561:1-palmitoyl-2-oleoylphosphatidylethanolamine; D002784:Cholesterol