M8 glycan (Man8), 2-AB labelled (Mannose-8 N-linked oligosaccharide, 2-AB labelled; Oligomannose 8 glycan, 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.