COLL 87 |
| Horia I. Petrache, Laboratory of Physical and Structural Biology, Laboratory of Physical and Structural Biology, National Institutes of Health, Bldg 9, Rm 1E116, Bethesda, MD 20892 |
| Cholesterol and its metabolic and evolutionary precursors have been shown to affect physical properties of lipid bilayers mainly through modification of interactions within the hydrophobic core. These effects are customarily interpreted in terms of material properties such as lateral (areal) compressibility and bending elasticity. Here we present X-ray measurements of bending parameters obtained by the dual-solvent stress method (Rand et al. 1990, Biochemistry, 29). In this method, nonpolar solvents such as tetradecane are used to induce a phase transition into a reverse hexagonal phase through relaxation of acyl chain packing. Curvature energies are then measured by osmotic stress. While monolayer (intrinsic) curvature is not manifest in the lamellar geometry, measurements of interlamellar spacings and interactions give indirect information on bilayer elasticity. Additional information is obtained by 2H NMR spectroscopy through the functional relationship between acyl chain order and relaxation parameters. Results on both lamellar and inverted hexagonal phases of disaturated and monounsaturated phosphatidylcholines will be discussed in terms of modification of bilayer elasticity and lipid interactions by cholesterol and its precursors. |
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Bio-Colloids
8:30 AM-11:30 AM, Monday, March 29, 2004 Marriott -- Grand Ballroom K, Oral
Division of Colloid and Surface Chemistry |