ELECTRON-IMPACT IONIZATION TANDEM MASS-SPECTROMETRY OF GLYCOSPHINGOLIPIDS .3. STUDY OF THE FRAGMENTATION MODES OF SELECTED GLYCOSPHINGOLIPIDS

Results are presented from a systematic study of the high-energy tandem mass spectra (fragment ion spectra) of derivitized (permethylation followed by LiAlH4 reduction) porcine glycosphingolipids (GSLs) using a four-sector mass spectrometer. The ions studied were the ammonium ions of the GSLs formed on loss of the sphingosine side-chain following electron impact ionization. Fragment ion spectra are shown to provide structural data useful in identifying carbohydrate sequence, the location of hexosamine residues and the identification of fatty acid chain length. Differences between the fragment ion spectra of isomers differing in carbohydrate linkage position and stereochemistry were observed, but not easily predicted.