The development of new chemical methods using synthetic probes for affinity-directed protein labeling is one of the most important research interests in the group. First, a traceless strategy in labeling of glycoproteins with synthetic boronic acid (BA)-tosyl probes was successfully developed. Due to the reversible formation of boronate ring, a competition reaction can recover the native glycan of the tagged glycoprotein, conserving its biological significance. To extend the concept to a chip-based study of glycoprotein-protein interactions, a BA-tosyl–functionalized glass slide was used to fabricate glycoprotein microarrays with highly conserved glycans. By interacting with various lectins (carbohydrate-binding proteins), such as Concanavalin A (Con A) and wheat germ agglutinin (WGA), the types of carbohydrates could be systematically monitored. It is believed that the newly developed method will greatly accelerate the understanding of glycoproteins. Very recently, the labeling efficiency and specificity of glycoproteins was found to be considerably improved by modifying the structures and electronic properties of the benzenesulfonyl reactive center.

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To further improve the sensitivity as well as the specificity, a two-step activation strategy has been successfully developed very recently. The synthetic probes are composed of affinity ligands for protein recognition and a benzensulfonyl azide as a reactive group to trigger a denitrogenative coupling reaction for further tag modification. While affinity ligand recognizes the corresponding protein, in the presence of Cu (I) and reducing agent, the benzensulfonyl azide would react with alkynes to furnish benzenesulfonyl triazole, which immediately transforms to a highly reactive ketenimine intermediate. The ketenimine intermediate functions as an electrophile to react with the nucleophilic residues of labeled proteins by nucleophilic addition. We hope this bioorthogonal method can be used in protein-protein interaction and therefore accelerate the understanding of glycobiology.