Sequence Ion Structures and Dissociation Chemistry of Deprotonated Sucrose Anions.

We investigate the tandem mass spectrometry of regiospecifically labeled, deprotonated sucrose analytes. We utilize density functional theory calculations to model the pertinent gas-phase fragmentation chemistry of the prevalent glycosidic bond cleavages (B-Y and C-Z reactions) and compare these predictions to infrared spectroscopy experiments on the resulting B and C product anions. For the C anions, barriers to interconversion of the pyranose [α-glucose-H], C anions to entropically favorable ring-open aldehyde-terminated forms were modest (41 kJ mol) consistent with the observation of a band assigned to a carbonyl stretch at ~ 1680-1720 cm.

Cationized Carbohydrate Gas-Phase Fragmentation Chemistry.

We investigate the fragmentation chemistry of cationized carbohydrates using a combination of tandem mass spectrometry, regioselective labeling, and computational methods. Our model system is D-lactose. Barriers to the fundamental glyosidic bond cleavage reactions, neutral loss pathways, and structurally informative cross-ring cleavages are investigated.