Molecular crystal structure of the tripeptide GHK Cu. In solution, Download Scientific Diagram Essential GHK Cu Serum: What It Is, How It Works, and Why It Matters f Bacteriostaticwater.com 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 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