Mass spectrometry of neutral, mono- and disialoglycosphingolipids

Microgram quantities of complex glycosphingolipids were fully trimethylsilylated and analyzed by mass spectrometry. Reproducible ratios of the intensities of certain sugar fragment ions to the total intensity of ions characteristic of the sphingolipid bases were used to determine the number of monosaccharides in the glycosyl moiety and how many of them were unsubstituted at C-3. N-Acetylated hexosamine residues were readily detected and further characteristic fragment ions appeared if they were the terminal residues of the oligosac-charide chain. It was also possible to distinguish between the N-glycolyl and N-acetyl forms of neuraminic acid and to determine the number of sialic acid residues present in the lipid. Considerable information about the fatty acid and long-chain base composition was obtained from the same mass spectral analysis. It has been concluded that reliable structural information can be obtained from small amounts (less than 50 micro g) of a purified glycosphingolipid.