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Updated: Jan 23, 2026

Selective Labelling of Cell-surface Proteins using CyDye DIGE Fluor Minimal Dyes
Published on: November 26, 2008
Inducible, Selective Labeling of Proteins via Enzymatic Oxidation of Tyrosine
Jorick J Bruins1, Criss van de Wouw1, Jordi F Keijzer1
1Laboratory of Organic Chemistry, Wageningen University & Research, Wageningen, The Netherlands.
Abstract:
Proteins can be labeled site-specifically and in inducible fashion by exposing a small peptide tag (G4Y) on any of its termini and activating the newly exposed tyrosine residue with the enzyme mushroom tyrosinase. The enzyme generates a quinone by oxidizing the tyrosine, which in turn can perform strain-promoted oxidation-controlled ortho-quinone cycloaddition (SPOCQ) with strained alkynes and alkenes, generating a stable conjugation product. Here, we describe a protocol to perform SPOCQ reaction on proteins, along with notes to optimize yield and reaction rates. Conjugation efficiencies of over 95% to antibodies have been reported using this protocol.
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