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. Author manuscript; available in PMC: 2019 Oct 9.
Published in final edited form as: Biochemistry. 2018 Sep 24;57(40):5769–5774. doi: 10.1021/acs.biochem.8b00648

Figure 1.

Figure 1.

Quantification of O-GlcNAc stoichiometry by chemoenzymatic mass tagging. (A) Endogenous O-GlcNAc modifications are first enzymatically modified by 2-keto-galactose before installation of a PEG mass tag via oxime chemistry. The O-GlcNAcylated fraction of any given protein can then be measured by visualizing the slower-migrating “mass-tagged” species by Western blotting. (B) Here, we optimize the conditions for a similar procedure that utilizes strain-promoted cycloaddition (SPAAC) chemistry.