title: Orientation and vertical fluctuations of spin-labeled analogues of cholesterol and androstanol in phospholipid bilayers.
abstract: We have used ESR and NMR linewidth broadening by spin-labels to determine the overall orientation of spin-labeled analogues of cholesterol and androstanol in egg lecithin bilayers. While the cholesterol analogues were found to have a single orientation in each monolayer, with the acyl chain pointing towards the center of the bilayer, the androstanol analogue appeared, at least in sonicated vesicles, to experience two opposite orientations in the same monolayer, very likely with a rapid reorientation. The possibility of rapid vertical fluctuations of the sterol molecules within the phospholipid bilayer is also discussed.
mesh_terms: D000732:Androstanols; D002784:Cholesterol; D004578:Electron Spin Resonance Spectroscopy; D008051:Lipid Bilayers; D009682:Magnetic Resonance Spectroscopy; D008433:Mathematics; D013113:Spin Labels / Q000378:metabolism
chemical_list: D000732:Androstanols; D008051:Lipid Bilayers; D013113:Spin Labels; D002784:Cholesterol