Ac4GlcNAz (N-azidoacetylglucosamine-tetraacylated) is a cell-permeable azide-functionalized marker of which natural monosaccharide counterpart is GlcNAc, that can observe glycan splicing by the introduction of a fluorescent moiety via click chemistry.

Ac4GlcNAz is a chemical probe for metabolic O-GlcNAc labeling. In mammalian cells (e.g., PC-3, HeLa, HEK293), Ac4GlcNAz efficiently taken up and converted into UDP-GlcNAz, which is incorporated into proteins by OGT. At 100 μM for 24 hours, labeling is efficient and time- and dose-dependent, as shown by CuAAC detection. However, due to its per-O-acetylated structure, Ac4GlcNAz also causes undesired S-glyco modification on cysteine residues[1].