Copper Peptide Regenerating Serum for Glowing Skin and Hair GHK Cu (Copper Peptide) is a naturally occurring peptide in the body that binds with copper to support cell repair and renewal. As we age, our levels decrease and thats where supplementation or GHK Cu vs AHK Cu: Which Copper Peptide Is More Effective? We're often asked what the difference is between our two Buffet serums. Do they target different concerns? Is one for more mature skin? Is one better suited to dry skin? As we're