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Sodium-cationized carbohydrate gas-phase fragmentation chemistry: influence of glycosidic linkage position

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Abstract

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 Y1 and B1 peaks. Our deuterium labelling and computational chemistry approach provides evidence for 1,6-anhydroglucose B1 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 Bn/Ym branching ratios. In contrast to cellobiose, sodiated gentiobiose primarily fragments by cross-ring cleavage to form various A2 ion types. Fragmentation is facilitated by ring-opening at the reducing end which enables losses of CnH2nOn 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.

Graphical abstract: Sodium-cationized carbohydrate gas-phase fragmentation chemistry: influence of glycosidic linkage position

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Publication details

The article was received on 13 Jul 2017, accepted on 07 Sep 2017 and first published on 08 Sep 2017


Article type: Paper
DOI: 10.1039/C7CP04738J
Citation: Phys. Chem. Chem. Phys., 2017, Advance Article
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    Sodium-cationized carbohydrate gas-phase fragmentation chemistry: influence of glycosidic linkage position

    J. M. Rabus, M. T. Abutokaikah, R. T. Ross and B. J. Bythell, Phys. Chem. Chem. Phys., 2017, Advance Article , DOI: 10.1039/C7CP04738J

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