Modification of Protein Scaffolds via Copper-Catalyzed Azide-Alkyne Cycloaddition.

The copper-catalyzed azide-alkyne cycloaddition (CuAAC) has proven to be a reliable, high-efficiency method for modification of protein scaffolds. This "click" reaction offers specificity and nearly quantitative yields even at low reagent concentrations. While robust, CuAAC still requires proper setup to achieve the high efficiency characteristic of this reaction, as well as to avoid degradation of sensitive substrates. Detailed herein is a generic CuAAC protocol for protein modification. Key features include the use of DMSO and triazole-based accelerating ligands for protection against reactive oxygen species, as well as aminoguanidine for intercepting deleterious ascorbate by-products formed during the bioconjugation.