Effect of cholesterol on the molecular motion in the hydrocarbon region of lecithin bilayers studied by nanosecond fluorescence techniques

• Published in: Biochemistry (Easton) Vol. 17; no. 23; pp. 5026 - 5031
• Main Authors: Kawato, Suguru, Kinosita, Kazuhiko, Ikegami, Akira
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 14-11-1978
• Subjects: Chemical Phenomena; Chemistry; Cholesterol; Kinetics; Mathematics; Membranes, Artificial; Molecular Conformation; Phosphatidylcholines; Spectrometry, Fluorescence; Temperature
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00616a026

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%.