Negative ion fast-atom bombardment tandem mass spectrometry to determine sulfate and linkage position in glycosaminoglycan-derived disaccharides

Negative ion fast-atom bombardment tandem mass spectrometry has been used in the analysis of monosulfated disaccharides. These commercially obtained disaccharides have been enzymatically prepared from glycosaminoglycans using polysaccharide lyases. Three disaccharides from chondroitin sulfate and dermatan sulfate and two disaccharides from heparan sulfate and chemically derivatized heparin were analyzed. All five disaccharides were isomeric, with differences in sulfate position and linkage position. The full-scan mass spectra are useful in differentiating isomers when the sulfate group resides on different saccharide units. This structural information was obtained from fragment ions produced through cleavage at the glycosidic linkage. the full-scan mass spectra of each monosulfated disaccharide also produced intense molecular anions having long lifetimes. Collisional activation of these resulted in tandem mass spectra rich in significant product ions. Some of these fragment ions were formed through ring cleavage and were useful in the determination of both sulfate and linkage position.