Patent ID: 8785212

Claim:
A method of labeling a protein by labeling an oligosaccharide attached to said protein, comprising: incubating a protein-producing cell in the presence of an unnatural sugar, wherein the unnatural sugar comprises an azide group, to provide a modified protein, wherein the modified protein produced by the protein-producing cell is attached to an oligosaccharide that comprises the unnatural sugar, wherein the unnatural sugar comprises GalNAz, GlcNAz, Ac 4 GalNAz, or Ac 4 GlcNAz; and attaching the modified protein to a label that comprises an alkyne group or an activated alkyne group by contacting the modified protein with the label under a condition such that a covalent bond is formed between the alkyne or the activated alkyne group of the label and the azide group of the unnatural sugar, thereby labeling the protein.