GHK Cu Copper Peptide Neck & Face Serum GHK Cu Topical Gel Transparent Peptides 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 GHK Cu Copper Peptide Collagen Boost & Skin Regeneration Calibrate Hydration GHK Cu Copper Peptide 0.5% (topical foam)