Evidence for linkage position determination in cobalt coordinated pentasaccharides using ion trap mass spectrometry.

A methodology to determine the linkage position of oligosaccharides is presented. In order to illustrate this technique, several oligosaccharides and disaccharides were ionized by electrospray and analyzed in a Paul trap mass spectrometer. Multiple stage tandem mass spectrometry experiments were used to determine linkage and structural information for the following four cobalt coordinated and singly charged ([M + Co-H]+) pentasaccharides: Lacto-N-fucopentaose I, II, III, and V. In order to differentiate between linkage positions, multiple low energy collision induced experiments with mass selected C type ions have been carried out in an ion trap mass spectrometer. Because of the coordination with cobalt, which directs the dissociation pathways, these C type ions undergo specific fragmentation reactions upon low energy collision induced dissociation. These dissociation pathways are unambiguously dependent on their linkage position, thus allowing differentiation between 1-->2, 1-->3, 1-->4, and 1-->6 linkage positions throughout the oligomers. Studies on various linked disaccharides and N-acetyl-disaccharides, which are smaller constituents of the pentasaccharides, were used to verify and confirm the results obtained from the pentasaccharides.