FA2B glycan (G0B), 2-AA labelled (FA2B N-linked oligosaccharide, 2-AA labelled; G0F with bisecting GlcNAc, 2-AA 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.