FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRIC ANALYSIS OF GLYCOSPHINGOLIPIDS BY DIRECT DESORPTION FROM THIN-LAYER CHROMATOGRAPHY PLATES - APPLICATION OF THE METHOD TO A RECEPTOR-ACTIVE 8-SUGAR GLYCOLIPID

Glycosphingolipids separated on thin layer chromatograms were analyzed by direct negative-ion fast atom bombardment mass spectrometry (FAB-M S). The thin-layer plates were moved within the ion source with a moto r-driven sample probe. The technique was optimized using glycosphingol ipids containing 5- and 7-sugar residues; the Forssman glycolipid (Gal NAc alpha 3Gal-NAc beta 3Gal alpha 4Gal beta 4Glc beta Cer) and A-7 (G alNAc alpha 3(Fuc alpha 2)Gal beta 3(Fuc alpha 4) GlcNAc beta 3Gal bet a 4Glc beta Cer). Spectra containing pseudo-molecular ions and fragmen t ions caused by cleavage at the glycosidic bonds were successfully ob tained and due to the chromatographic separation it was also possible to record spectra of glycolipids with different ceramide compositions. This separation was maintained after blotting onto a hydrophobic memb rane which also was analyzed by direct-desorption FAB-MS. The thin lay er chromatography (TLC)/FAB-MS method was used to analyze a receptor-a ctive glycosphingolipid from female C3H/HeN mice kidneys with eight su gar residues: Gal beta 4(Fuc alpha 3) GlcNAc beta 6(Gal beta 3)GalNAc beta 3Gal alpha 4Gal-beta 4Glc beta Cer. Although the analysis was mad e on a complex mixture of glycosphingolipids without purification, the pseudo-molecular ion and fragment ions obtained were of high abundanc e and allowed sequence determination of this glycolipid that is recogn ized by uropathogenic P-fimbriated Escherichia coli.