High-field, high-resolution proton "magic-angle" sample-spinning nuclear magnetic resonance spectroscopic studies of gel and liquid crystalline lipid bilayers and the effects of cholesterol

We have obtained proton ( super(1)H) "magic-angle" sample-spinning (MASS) nuclear magnetic resonance (NMR) spectra of a variety of smectic liquid crystalline phases, including sodium decanoate (30.1 wt%)-decanol (38.9 wt%)-water, potassium oleate (72 wt %)-water, and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (lecithin) (50 wt %)-water, in addition to investigating the effect of temperature and cholesterol (CHOL) addition on the lecithin spectrum. Our results indicate that even relatively slow MASS causes averaging of the dipolar interactions causing line broadening in the static NMR spectra, at least for the non-CHOL species. All the of the major proton-containing groups are well resolved, the resolution being at least as good as obtained in previous studies of oriented samples or sonicated systems. Taken together, our results indicate a very promising future for high-field super(1)H MASS NMR studies of other lipid and membrane systems because of the extremely high sensitivity of the super(1)H nucleus and the unique ability to obtain chemical shift, T sub(1), and 2-D information for a single sample, without recourse to isotopic labeling, macroscopic sample orientation, or ultrasonic irradiation.