A combined strategy for glycan profiling: a model study with pyridylaminated oligosaccharides

Structural glycomics plays a fundamental role in glycoscience and glycotechnology. In this paper, a novel strategy for the structural characterization of glycans is described, in which MS2 analysis involving a LIFT-TOF/TOF procedure is combined with frontal affinity chromatography (FAC). As model compounds, 20 neutral pyridylaminated (PA) oligosaccharides were chosen, which included four groups of structural isomers differing in sequence, linkage, position, or branching features. By depicting significant diagnostic ions on MS2, most of the analyzed oligosaccharides were successfully differentiated, while two pairs of linkage isomers, i.e., LNT/LNnT, and LNH/LNnH were not. For subsequent analysis by FAC, 14 lectins showing significant affinity to either LNT (type 1) or LNnT (type 2) were screened, and a galectin from the marine sponge Geodia cydonium (GC1) and a plant seed lectin from Ricinus communis (RCA-I) were used for determination of type 1 and 2 chains, respectively. With these specific probes, both of the isomeric pairs were unambiguously differentiated. Furthermore, a pair of triantennary, asparagine-linked oligosaccharide isomers could also be successfully differentiated. Thus, the combination of MS2 and FAC is a practical alternative for the structural characterization of complex glycans.