Cu(II) Binding to the Peptide Ala His His, a Chimera of the Canonical Cu(II) Binding Motifs Xxx His and Xxx Zzz His Inorganic Chemistry RCSB PDB 6QUG: GHK tagged MBP Nup98(1 29) GHK Cu as a multifunctional copper peptide: synthesis routes, process engineering and emerging applications Systems Microbiology and Biomanufacturing Springer Nature Link IUCr) The copper(II) binding tripeptide GHK, a valuable crystallization and phasing tag for macromolecular crystallography 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