A solvent system for the high-resolution proton nuclear magnetic resonance spectroscopy of membrane lipids

NMR spectroscopy has tremendous potential as an analytical tool for studying the compositions and structural details of complex mixtures of lipids. Unfortunately, because of aggregate formation, lipids generally give poorly resolved NMR spectra and there is no general solvent system which gives good spectra of all classes of lipids. A simple solvent system for the high-resolution NMR spectroscopy of membrane lipids has been developed. This solvent system is composed of a mixture of pyridine-d5, deuterium chloride in deuterium oxide, methanol-d4, and chloroform-d in a volume ratio of 1:1:2:10, respectively. The use of this solvent system gives uniformly well-resolved 1H-NMR spectra over a wide selection of lipid classes including the lipid A region of bacterial lipopolysaccharides, phospholipids, and large gangliosides. Phosphorous spectra obtained with this solvent system do not show the typical undesirable distortions due to anisotropic effects. The use of this solvent system makes the undesirable practice of methylation of the phosphate groups in lipid A and other molecules, in order to acquire high-resolution spectra, unnecessary. It also increases the general utility and potential for NMR studies on bacterial adaptation, serum lipid composition, and membrane lipid alterations in cancer cells.