Solid State NMR experiments will be employed to elucidate the dynamic structure of pure and mixed lipid bilayers. The research focuses on four different areas: (1) C13, H2, N14 and P31 NMR will be used to examine the phase behavior and dynamic structure of several pure lipids including sphingomyelins (SM's), ether phosphatidylcholine (PC's), and ethanolamines (PE's), phosphatidylserines (PS's) and glycolipids (GL's). Quadrupole echo lineshapes and their Tau-dependence and T1 anisotropies will be the main sources of H2 spectral information and sn-2 C=O powder patterns will be studied with C13 spectroscopy. PO4-31 and N14 NMR spectra and differential scanning calorimetry will be employed where appropriate. (2) Using similar techniques the interaction of cholesterol (CHOL) with several lipids--SM's, Ether lipids, PS's and GL's with unsaturated chains--will be investigated to determine if these lipids manifest the """"""""liquid-gelatin"""""""" species found in PE/CHOL, PC/CHOL, and in GL/CHOL mixtures. (3) Binary and ternarv mixtures of well-defined lipids which mimic those found in biological membranes will also be examined. (4) The changes in phase behavior and dynamic structure induced by ions such as Li+, Ca+2 and Mg+2--isothermal phase transitions--in charged lipids like PA and PS will be studied in part with magic angle spinning spectra. Finally, it has recently been demonstrated that trehalose, a disaccharide found in anhydrobiotic organisms induces Lalpha-like behavior in dry DPPC. We plan to investigate the mechanism of this effect and to determine if trehalose produces similar effects in other lipids.
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