Session: Advances in Mass Spectrometry:

Carbohydrates have important biological functions such as signaling and intermolecular recognition. Sequencing of carbohydrates is crucial to identifying their biological functions because they modulate the biological activity of proteins through specific interactions. However, the sequencing of carbohydrate oligosaccharides has been challenging due to their polydispersity and structural complexity. Moreover, unidentified isomeric fragment ions produced by fragmentation methods often lead to ambiguities in the sequence of carbohydrates.

Here, we apply our recently-developed tandem trapped ion mobility spectrometer-mass spectrometer (tTIMS/MS) to carbohydrate sequencing. Specifically, we discuss the ability of tTIMS/MS to sequence several carbohydrates including trisaccharides (raffinose, melezitose, and maltotriose), pentasaccharide (arixtra) to octasaccharide of dermatan sulfate. tTIMS/MS has the unique ability to mobility-separate, mobility-select, and collisionally-dissociate (CID) precursor ions in a first CID stage, which is followed by a secondary CID stage in which the fragment ions are mobility-separated, mass-selected, and subsequently collisonally-dissociated followed by TOF-mass analysis.

Various fragments obtained by CID show fragmentation patterns corresponding to glycosidic cleavages labeled as B/Z or Y/C ions and cross-ring cleavages labeled as A/X ions. Y/C and/or B/Y fragment ions produced provide the sequence information of carbohydrate oligosaccharides, and A/X fragment ions provide structural information of those. In addition, fragmentation patterns, measured mobilities, and cross sections of fragments generated by CID offer the ability of distinguishing isomeric and isobaric fragment ions. Identified isomeric and isobaric fragment ions provide an accurate sequence of carbohydrates. Hence, our data demonstrate that tTIMS/MS is useful for carbohydrate sequencing.

Christian Bleiholder

Appearances