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 GHK Cu Copper Peptide: Evidence, Mechanisms & COA Guide Nootropix 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