The fucosylation of glycans leads to diverse structures and is associated with many biological and disease processes. The exact determination of fucoside positions by tandem mass spectrometry (MS/MS) is complicated because rearrangements in the gas phase lead to erroneous structural assignments. Here, we demonstrate that the combined use of ion-mobility MS and well-defined synthetic glycan standards can prevent misinterpretation of MS/MS spectra and incorrect structural assignments of fucosylated glycans. We show that fucosyl residues do not migrate to hydroxyl groups but to acetamido moieties of N-acetylneuraminic acid as well as N-acetylglucosamine residues and nucleophilic sites of an anomeric tag, yielding specific isomeric fragment ions. This mechanistic insight enables the characterization of unique IMS arrival-time distributions of the isomers which can be used to accurately determine fucosyl positions in glycans.
Keywords: carbohydrates; fucose; ion-mobility spectrometry; mass spectrometry; rearrangement.
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