Chemoselective Copper-Mediated Radical Modification of Selenocysteines in Peptides and Proteins

Highly valuable bioconjugated molecules must be synthesized through efficient, chemoselective chemical modifications of peptides and proteins. Herein we report the chemoselective modification of peptides and proteins via a reaction between selenocysteine residues and aryl/alkyl radicals. In situ radical generation from hydrazine substrates and copper ions proceeds rapidly in neat aqueous buffer at near neutral pH (5-8), providing a variety of Se-modified linear and cyclic peptides and proteins conjugated to aryl and alkyl molecules, as well as to affinity label tag (biotin). This chemistry opens a new avenue for chemical protein modifications.