Copper peptide GHK Cu Tripeptide Proteasome Bortezomib, angle, white png PNGEgg The copper(II) binding tripeptide GHK, a valuable crystallization and phasing tag for macromolecular crystallography GHK Cu 50 mg Copper Peptide Research Grade PRG 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