Breaking the Limits in Analyzing Carbohydrate Recognition by NMR Spectroscopy: Resolving Branch‐Selective Interaction of a Tetra‐Antennary N‐Glycan with Lectins

The biological recognition of complex‐type N‐glycans is part of many key physiological and pathological events. Despite their importance, the structural characterization of these events remains unsolved. The inherent flexibility of N‐glycans hampers crystallization and the chemical equivalence of individual branches precludes their NMR characterization. By using a chemoenzymatically synthesized tetra‐antennary N‐glycan conjugated to a lanthanide binding tag, the NMR signals under paramagnetic conditions discriminated all four N‐acetyl lactosamine antennae with unprecedented resolution. The NMR data revealed the conformation of the N‐glycan and permitted for the first time the direct identification of individual branches involved in the recognition by two N‐acetyllactosamine‐binding lectins, Datura stramonium seed lectin (DSL) and Ricinus Communis agglutinin (RCA120).