Abstract
RATIONALEIon mobility mass spectrometry (IMMS) has previously been shown to resolve small isobaric oligosaccharides, but larger alpha-oligoglucans are also abundant in biology and are of industrial importance. If conformational differences between such isomers are retained in the gas phase, IMMS could be used to address questions in biology and industry.METHODSNegative mode electrospray ionization (ESI) travelling-wave IMMS was used to resolve large isobaric α-glucan ions on the basis of their different gas-phase conformations. α,ω-Dicarboxy-terminated polystyrene was used to calibrate the instrument allowing the collision cross-sections (CCSs) of ions to be determined.RESULTSα-1,4-Linked maltooligosaccharides with a degree of polymerisation of up to 35 could be discriminated from α-1,6-linked dextran and α-1,4/1,6-linked pullulan using IMMS. Fragmentation spectra of ions separated by IMMS could also distinguish isomers. Two conformational isomers of maltohexaose were resolvable by IMMS, likely reflecting extended and V6 helical conformations. IMMS was also able to identify a product within a mixture of maltooligosaccharides treated with the potential anti-tuberculosis drug target Mycobacterium tuberculosis GlgB branching enzyme.CONCLUSIONSBiological samples of complex isobaric oligosaccharides can be analysed using IMMS in the negative mode providing facile analyses and high sensitivity without the need for either derivatisation or chromatographic separation. © 2013 The Authors. Rapid Communications in Mass Spectrometry published by John Wiley & Sons Ltd.
Highlights
Recent examples of Ion mobility mass spectrometry (IMMS) being able to differentiate isobaric oligosaccharides include N-linked glycans associated with proteins,[8,9,10,11,12] glycosaminoglycans[18] and other small oligosaccharides[14] including a few glucans with a degrees of polymerisation (DP) of up to 5.[13,15,16,17] It has been possible to resolve isobaric carbohydrates with different primary structures, branching patterns and anomeric/
The separation of ions with DP ≥16 and up to 35 was readily observed in the triply charged state (Table 4 and Fig. 2). The sensitivity of this approach is exemplified by the limited solubility of maltooligosaccharides with a DP of >18.[32] it was possible to discriminate between the conformations of maltooligosaccharides and dextrans with a wide range of DP and high sensitivity using IMMS
The increased conformational freedom of α-1,6 over α-1,4 linkages observed in solution was retained in the gas phase, allowing large linear oligosaccharides to be distinguished
Summary
Several new approaches have been developed to tackle isobaric carbohydrates such as ion mobility mass spectrometry (IMMS) and energy-resolved collision-induced dissociation.[6] IMMS provides a two-dimensional (2D). More recent advances included combining IMMS with tandem mass spectrometry[14,17,19] and the development of tandem IMMS.[13] there are no reports of a systematic analysis of larger linear homoand hetero-oligomeric α-glucans using IMMS establishing whether conformational differences in aqueous solution are retained with such large molecules in the gas phase. We show that linear homo- and hetero-oligomeric α-glucans with a DP of up to 35, which differ in only their content of α-1,4- and α-1,6-linkages, can be resolved using
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
