Carbon-13 nuclear magnetic resonance studies of cerebroside derivatives and their properties in lecithin bilayers (1) |
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Authors: | P Tkaczuk E R Thornton |
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Affiliation: | Department of Chemistry University of Pennsylvania Philadelphia, Pennsylvania 19104 USA |
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Abstract: | The 13C NMR chemical shifts and spin-lattice relaxation times of D-galactosylsphingosine derivatives in CDCl3-CD3OD and in egg-yolk lecithin vesicles in D2O, and of N-acetylpsychosine micelles, are reported. Results with sonicated, unilamellar vesicles containing cerebroside and EYLa show that (1) cerebrosides decrease the fluidity of the lecithin bilayer membrane and have the greatest effect on the glycerol backbone and choline methyl carbons. (2) N-acetylpsychosine experiences a greater freedom of motion in the galactose region than does cerebroside and does not reduce the fluidity of the lecithin as much as cerebroside. (3) Ac-Psy/EYL vesicles formed are permeable to Yb3+ but cerebroside/lecithin vesicles are not. (4) The choline groups on the inner bilayer surface are less mobile than those on the outer surface according to preliminary T1 measurements of the Yb3+-separated resonances. (5) Yb3+-induced chemical shifts of choline methyl and choline OP peaks in mixed cerebroside-lecithin vesicle systems indicate a small preference for cerebroside in the outside monolayer. The data show that these molecules have significant effects on bilayer conformational mobilities, particularly near the surface, and thus demonstrate one mechanism for modulation of cell surface properties by glycosphingolipids. |
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