PDF) The Effect of the Human Plasma Molecule GHK Cu on Stem Cell Actions and Expression of Relevant Genes GHK Cu vs AHK Cu: Which Copper Peptide Is More Effective? Revitalize Your Skin: The Benefits of Copper Peptide for Youthful Glow Resetting Skin Genome Back to Health Naturally with GHK Springer Nature Link 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