AHK-Cu is a short peptide that is complexed with (chemically linked to) a copper molecule. In the case of AHK, the copper atom is linked between the alanine and histidine residues of the alanine-histidine-lysine peptide. The copper atom is bound to three of the nitrogen atoms in the tripeptide. AHK-Cu has been heavily researched as a skin conditioning agent and has recently gained interest as a potential treatment for hair loss after promising bench-top experiments.