The application of mass spectrometry in the structural elucidation of glycosphingolipids

Mass spectrometry has been successfully applied to the analysis of permethylated glycosphingolipids, with and without reduction, as well as of permethylated gangliosides after reduction and silylation. The results obtained by several groups of workers are reviewed. From the data available it can be stated that, with the aid of mass spectrometry, conclusive evidence may be obtained concerning the carbohydrate sequence as far as the typo of sugar is concerned such as hexose, deoxyhexose, hexosamine, and neuraminic acid residues. Branching points can be recognized, and specific fragmentation products allow the differentiation between 1,3 and 1,4-substituted hexosamines of blood-group-active glycosphingolipids (type 1 and type 2 chains). The ceramide residue is documented by several characteristic ions that allow determination not only of sphingosine bases and fatty acid components but also of individual ceramide molecular species. Valuable structural information can thus be obtained to a certain extent also for mixtures of glycosphingolipids composed of different carbohydrate chains or different ceramide residues.