Tandem Mass Spectrometry of Alkali Cationized Polysaccharides in a Quadrupole Ion Trap

Abstract

Quadrupole ion trap mass spectrometry is used to study the linkage type dependent dissociation pathways of alkali-cationized disaccharides, mostly of the type glucosyl(1 → X)glucose ( X = 1, 2, 3, 4, or 6). The reaction mechanisms of a set of disaccharides containing all possible α anomeric linkage types and some β anomers are probed with tandem mass spectrometry, MS n , and double resonance experiments. Tandem mass spectrometry experiments on an 18O-labeled disaccharide show that the dissociation paths for Li and Na cationized species are the same. Experiments on three trisaccharides (isomaltotriose, maltotriose, and panose), a tetrasaccharide (isomaltotetraose), and a pentasaccharide (maltopentaose) show that tandem mass spectrometry provides all available linkage information and MS n can provide selected linkage information. The mode of alkali binding is examined via semiempirical calculations and by measuring alkali-carbohydrate relative cation affinities.