GHK Cu vs AHK Cu: Which Copper Peptide Is More Effective? Defy GHK Cu (glycyl L histidyl L lysine) is a naturally occurring copper binding peptide found in human plasma. As levels decline with age, so may its support of the biological processes involved in collagen production, skin Molecular crystal structure of the tripeptide GHK Cu. In solution, Download Scientific Diagram Copper Peptides Elmhurst IL Chicago Accelerated Aesthetics