Analysis of mixed lipid extracts using 1H NMR spectra.

A method has been developed for rapid analysis of lipid proton NMR spectra. Identification of lipid content is possible because of the presence of unique peaks or ratios of peaks for individual lipids. Spectra can be subdivided into regions where peaks represent certain chemical groups held in common, or uniquely by the various lipids. Vectors (B) are made up of the areas of these subdivisions of peaks from spectra of unknown components. A new FORTRAN algorithm, LIPICK, tests for the presence of unique peaks or combinations of peaks to determine which lipids may be present. The spectra vectors of known identified lipids are then placed in the (A) matrix of possible solution candidates. Quantitation of lipids in an 1H NMR spectrum (B) of an unknown mixture then proceeds by solving the equation AX = B for X (the concentrations of the individual lipids present) by singular value analysis. At this time, it is possible to test 1 mg of total lipid for the presence and relative concentration of 15 common lipids: cholesterol and its esters; phosphatidyl-ethanolamine, -choline, -serine, -inositol, -glycerol; tri- or di-glycerides; fatty acid; lysophosphatidylcholine; sphingomyelin; cerebrosides and sulfatides; dolichol and dolichol P; and phosphatidic acid. This procedure is suitable for membrane lipid analysis and has been evaluated using known mixtures of purified standard lipids.