Update publication information. we develop a series of arginine selective bifunctional aromatic glyoxal cross-linkers (ArGOs) and demonstrate their ability to cross-link model proteins and a protein complex. We also introduce the first arginine-lysine heterobifunctional cross-linker (KArGO), which provides significantly greater surface coverage than the corresponding homobifunctional reagents (e.g. ArGOs and BS3), due to access to the combined abundances of lysine and arginine residues.