Facile and Selective Enrichment of Intact Sialoglycopeptides Using Graphitic Carbon Nitride

Combining powerful selectivity, high stability, convenient operation, mild condition, and eco-friendliness, a novel graphitic carbon nitride (g-C₃N₄)-based enrichment method of intact sialoglycopeptides (SGs) was developed. The intact SGs could be simply enriched and separated from protein tryptic digests by hydrogen bonding without damage of glycan structures due to the specific structure of g-C₃N₄. By optimizing the enrichment and elution conditions, 45 and 38 SGs were detected from the tryptic digests of bovine fetuin and transferrin, respectively. Under the synergistic effect of hydrogen bonding and electrostatic adsorption, the SGs could be enriched simply in less than 2 h with a detection limit of 50 fmol. The method is repeatable due to the high stability of g-C₃N₄ and the simple protocol of the method, indicating the potential application of g-C₃N₄ in efficient and selective enrichment of intact SGs.