STRUCTURE OF UNDERIVATIZED BRANCHED OLIGOSACCHARIDES BY NEGATIVE-ION FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRY

We report here a study by negative-ion fast-atom bombardment (FAB) mass spectrometry of branched oligosaccharides containing a 3-O glycosidic linkage. Our results show that discrimination of the monosaccharide unit linked in the 3-O position is made possible by the analysis of the negative-ion FAB mass spectra. In the mass spectrum of A-trisaccharide (alpha-Fuc1-2-(alpha-GalNAc1-3)-Gal) the peak at m/z 307 can be explained as elimination of a neutral molecule of GaINAc (221 u) from the molecular ion. Also in the mass spectrum of 3-fucosyllactose (alpha-Fuc1-3-(beta-Gal1-4)-Glc) an intense peak at m/z 323, corresponding to the elimination of the fucose linked at the 3 position of glucose is present. To investigate further the fragmentations of the 3-O-linked sugars, the negative-ion FAB mass spectra of disaccharides have also been studied.