| Abstract: | Solid-state high resolution 13C NMR spectra of bovine brain sulfatide, egg sphingomyelin, egg phosphatidylcholine, and cholesterol/phosphatidylcholine dispersions were obtained by the cross-polarization/magic angle spinning (CP/MAS) method as functions of contact time, temperature and composition. Quantitative analysis of the chemical shift and linewidth data indicate that in the liquid-crystalline state the hydrocarbon chains of sulfatide are packed less orderly than those of sphingomyelin, and that there are two or more conformers for the ceramide residues of natural sphingolipids. The fatty acid double bond showed higher mobility than that of sphingosine as monitored by the signal intensity profiles as a function of contact time. The same approach was used to study the coexisting Lα (liquid-crystalline phase) and β (cholesterol-rich characterized phase) two-phase region of cholesterol/phosphatidylcholine mixtures. Without isotope enrichment, structural and phase properties of natural lipid dispersions can be obtained easily by monitoring the chemical shift, the signal intensity and the linewidth of l3C NMR spectra. |
