A2G2 glycan (G2), procainamide labelled (A2G2 N-linked oligosaccharide, procainamide labelled; A2G(4)2 glycan, procainamide labelled) is a N-polysaccharide protein and a multifunctional fluorescent linker. The resulting conjugates exhibit high sensitivity and specificity by mimicking the antennal elements of N-glycans.