Synthesis and Application of Azide-Incorporated Copper-Chelating Peptides for Efficient Click Conjugation Reaction

Bioorthogonal reactions that rapidly generate stable products in water are powerful tools for the functionalization and analysis of biomolecules of interest. Here, we developed a series of water-soluble copper-chelating azides for rapid copper-catalyzed azide-alkyne [3+2] cycloaddition (CuAAC) reactions. The integrated accelerating ligand, in which introduced an azido group via a linker to a histidine- and methionine-containing peptide, rapidly and quantitatively afford the triazole product. In the application to protein labeling, the apparent rate constant was approximately three orders of magnitude higher than that of tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine (TBTA) by changing the trimolecular reaction to a bimolecular reaction, and also by performing it entirely in aqueous solution. The excellent biocompatibility allowed the reaction to proceed almost completely with trace proteins.