GHK Cu Copper peptide GHK Cu Tripeptide Proteasome Bortezomib, angle, white png PNGEgg Your copper peptide product should be this exact blue. If it isn't, you already have your answer. GHK Cu is blue because of coordination chemistry, not dye. The Cu ion at the center The copper(II) binding tripeptide GHK, a valuable crystallization and phasing tag for macromolecular crystallography inorganic chemistry Why do copper (II) complexes contain so many valence electrons? Chemistry Stack Exchange