Sodium-cationized carbohydrate gas-phase fragmentation chemistry: influence of glycosidic linkage positionElectronic supplementary information (ESI) available. See DOI: 10.1039/c7cp04738j

• Main Authors: Rabus, Jordan M, Abutokaikah, Maha T, Ross, Reginald T, Bythell, Benjamin J
• Format: Article
• Language: English
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c7cp04738j

We investigate the gas-phase structures and fragmentation chemistry of two isomeric sodium-cationized carbohydrates using combined tandem mass spectrometry, hydrogen/deuterium exchange experiments, and computational methods. Our model systems are the glucose-based disaccharide analytes cellobiose (β- d -glucopyranosyl-(1 → 4)- d -glucose) and gentiobiose (β- d -glucopyranosyl-(1 → 6)- d -glucose). These analytes show substantially different tandem mass spectra. We characterize the rate-determining barriers to both the glycosidic and structurally-informative cross-ring bond cleavages. Sodiated cellobiose produces abundant Y 1 and B 1 peaks. Our deuterium labelling and computational chemistry approach provides evidence for 1,6-anhydroglucose B 1 ion structures rather than the 1,2-anhydroglucose and oxacarbenium ion structures proposed elsewhere. Unlike those earlier proposals, this finding is consistent with the experimentally observed B n /Y m branching ratios. In contrast to cellobiose, sodiated gentiobiose primarily fragments by cross-ring cleavage to form various A 2 ion types. Fragmentation is facilitated by ring-opening at the reducing end which enables losses of C n H 2 n O n oligomers. Deuterium labelling and theory enables rationalization of these processes. Theory and experiment also support the importance of consecutive fragmentation processes at higher collision energies. Gas-phase structure and fragmentation chemistries of isomeric sodium-cationized sugars.