FA2G2S1 glycan (G2FS1), procainamide labelled (FA2G2S1 N-linked oligosaccharide, procainamide labelled; α(2,6)/FA2G2S(6)1 glycan, procainamide labelled; F(6)A2G(4)2S(6)1 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.