title: Effect of cholesterol on the molecular motion in the hydrocarbon region of lecithin bilayers studied by nanosecond fluorescence techniques.
abstract: Effects of cholesterol on the dynamic structure of the hydrocarbon region of dipalmitoyllecithin vesicles were examined. Decays of the emission anisotropy and the fluorescence intensity of 1,6-diphenyl-1,3,5-hexatriene embedded in lecithin-cholesterol vesicles were measured over a temperature range of 10--60 degrees C. The emission anisotropy decreased rapidly with time and then leveled off. The rotational motion of the probe was analyzed by a model of wobbling diffusion confined in a cone. Cholesterol (10--50 mol%) decreased the cone angle in the liquid-crystalline phase and increased it in the gel phase. In the presence of 33 mol% cholesterol, the wobbling diffusion constant increased in the gel phase and changed little in the liquid-crystalline phase. The viscosity in the cone decreased in the gel phase and remained almost unchanged in the liquid-crystalline phase in the presence of 33 mol% cholesterol. The total fluorescence intensity followed a singel exponential decay independently of the cholesterol content 0--50 mol%.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D002784:Cholesterol; D007700:Kinetics; D008433:Mathematics; D008567:Membranes, Artificial; D008968:Molecular Conformation; D010713:Phosphatidylcholines; D013050:Spectrometry, Fluorescence; D013696:Temperature
chemical_list: D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D002784:Cholesterol