α-Vinyl azide–cysteine click coupling reaction enabled bioorthogonal peptide/protein modification

Abstract

α-Alkyl and α-aryl vinyl azides were found to be able to couple with cysteine-derived alkyl thiols chemoselectively under mild conditions, providing the corresponding β-ketosulfides with simultaneous extrusion of N₂ and ammonia. This reaction was developed into an effective chemical platform for peptide and protein modification, which is completely cysteine selective and highly bioorthogonal, that avoids the interference from other native residues. The in situ formed ketone group can react specifically with alkoxyamines or hydrazines and therefore can serve as a versatile handle for a second modification. The modification of bovine serum albumin (BSA) with a dansyl fluorescent probe and the labeling of the genetically encoded fluorescent protein YPet-ECFP with biotin have been accomplished successfully through this platform.