Ligand-directed selective protein modification based on local single-electron-transfer catalysis

A photocatalyst ([Ru(bpy)₃]²⁺) bound to a protein ligand was essential for the title method. Local single-electron transfer from the catalyst resulted in the formation of tyrosyl radicals. N′-Acetyl-N,N- dimethyl-1,4-phenylenediamine was used as the tyrosyl radical trapping agent and used in a radical addition to afford selective modification of the target protein.