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Glycans and Glycoconjugates

Glycans, or carbohydrates, densely decorate cell surfaces and form the glycocalyx (Figure a), where they modulate recognition, adhesion, and signalling. Attached to proteins and lipids, these glycoconjugates exhibit extraordinary structural complexity arising from their non-template-driven biosynthesis. Monosaccharides occur as closely related isomers that may differ at a single stereocenter, and they can be linked at multiple positions, extended into branched architectures, and exist in both α- and β-anomeric forms (Figure b). This combinatorial diversity produces numerous isomeric structures with identical masses, rendering unambiguous structural elucidation exceptionally challenging. Our research group develops advanced mass-spectrometry methods to decode this structural complexity.

By integrating high-resolution MS/MS, ion mobility-MS and cryogenic infrared spectroscopy we study glycan and glycoconjugate structure with molecular precision. Using these platforms, we probe conformations and reactivity of glycan structures including glycosyl cation intermediates and other isomeric species. Another central focus of our work is elucidating gas-phase rearrangements, including fucose migration and our recently discovered sulfate migration, to ensure accurate structural assignments.

The group also investigates mucus proteins, which are heavily modified with complex O-glycans. Within the DFG-funded CRC 1449 Dynamic Hydrogels at Biointerfaces, we have established strategies to analyse this mucosal glycosylation and extended this to the analysis of glycosaminoglycans. Combined, these efforts to resolve glycan structures are essential for understanding how protein glycoforms differ, how mucus protects against pathogenic infection, and how glycosylation is modulated during disease and recovery.

Figure: a) the glycocalyx b) the isomerism present in glycan species c) developing high-throughput IM-MS methods

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