Complex carbohydrates (’glycans’) or polysaccharides are arguably the most structurally complex and heterogeneous family of biomacromolecules. They are typically built of different types of monomers (monosaccharides or “sugars”) linked to each other through a great variety of glycosidic linkages with rich stereochemistry. Glycans are often substituted and exhibit branched structures, which result in an extremely complex macromolecular architecture. The complete structural determination of the ’primary structure’ of glycans is far from being implemented as it is routinely done for nucleic acids and proteins through common genomic, transcriptomic, and proteomic sequencing techniques. Determining the constituent sugars and substitution/branching patterns in glycans is fundamental to decipher the biological functions and their physico-chemical properties.<br/><br/>In this tutorial we will discuss different mass spectrometric strategies for a comprehensive understanding of the molecular structure of complex glycans, focusing on their constituent sugars, glycosidic linkages and patterns of substitution. These mass-spectrometric based strategies (’glycomics’) require the integration of biochemical approaches (e.g. selective enzymatic deconstruction and/or chemical derivatization) and hyphenation with different chromatographic separation modes (e.g. gas chromatography, hydrophilic interaction liquid chromatography, anion-exchange chromatography). Traditional GC-EI-MS has been used for decades to detemine the average monosaccharides and linkages in complex glycans. The introduction of soft ionization mass spectrometric techniques (e.g. MALDI, ESI), alone or in combination with LC, has enabled the mass profiling of complex mixtures and the full sequencing of oligosaccharide structures in some successful cases by sequential fragmentation (MS<sup>n</sup>). Recent advances in ion mobility mass spectrometry (IMS) for high throughput glycan analysis will be as well presented. These different glycomic strategies need however to be adapted to the rich variety of glycan structures and the specific molecular information that is aimed at. The tutorial will be illustrated with several examples, focusing on the elucidation of the substitution patterns of heterogeneous native plant polysaccharides and chemically-modified polysaccharide derivatives.

MS techniques in structure analysis of complex glycans

253rd National Meeting (2017)

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