FA2BG1 & FA2BG1 glycan (G1B), 2-AB labelled (FA2BG1 & FA2BG1 glycan N-linked oligosaccharide, 2-AB labelled; G1F with bisecting GlcNAc, 2-AB 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.