Cholesterol rules: direct observation of the coexistence of two fluid phases in native pulmonary surfactant membranes at physiological temperatures.

J. BERNARDINO DE LA SERNA; J. PEREZ-GIL; A.C. SIMONSEN; LUIS A. BAGATOLLI

JOURNAL OF BIOLOGICAL CHEMISTRY

AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Lugar: Bethesda, Maryland; Año: 2004 vol. 279 p. 40715 - 40715

0021-9258

ulmonary surfactant, the lipid-protein material that stabilizes the respiratory surface of the lungs, contains approximately equimolar amounts of saturated and unsaturated phospholipid species and significant proportions of cholesterol. Such lipid composition suggests that the membranes taking part in the surfactant structures could be organized heterogeneously in the form of inplane domains, originating from particular distributions of specific proteins and lipids. Here we report novel results concerning the lateral organization of bilayer membranes made of native pulmonary surfactant where the coexistence of two distinct micrometer sized fluid phases (fluid ordered and fluid disordered-like phases) is observed at physiological temperatures by using fluorescence microscopy and atomic force microscopy. Additional experiments using fluorescent-labeled proteins SP-B and SP-C show that at physiological temperatures these hydrophobic proteins are located exclusively in the fluid disordere