M3 glycan (Man3), 2-AA labelled (Mannose-3 N-linked oligosaccharide, 2-AA labelled; Oligomannose 3 glycan, 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.