GHK vs GHK-Cu
GHK is the tripeptide glycyl-L-histidyl-L-lysine; GHK-Cu is the same peptide bound to a copper(II) ion. This page explains how the free peptide and the copper complex differ in structure, research use, analysis and handling.
GHK (Gly-His-Lys) is a tripeptide first identified in human plasma, and it binds copper(II) ions with high affinity. When supplied as a copper complex it is called GHK-Cu, or copper tripeptide-1 in cosmetic ingredient naming. The free peptide is sometimes listed as tripeptide-1.
Much of the biological activity reported for GHK is linked to its copper complex, and in biological fluids the free peptide can pick up copper that is already present. In the laboratory, however, the free peptide and the preformed complex are different materials, with different appearance, expected mass, analytical requirements and stability. Most published research, both in vitro and in cosmetic science, has used the copper complex.
Side-by-side
| Attribute | GHK (free tripeptide) | GHK-Cu (copper complex) |
|---|---|---|
| Composition | Gly-His-Lys peptide only | Gly-His-Lys coordinated to a copper(II) ion |
| Appearance | White to off-white powder | Blue to blue-violet powder or solution |
| Copper binding | Binds available copper(II) with high affinity | Copper already bound; histidine imidazole, glycine amine and backbone nitrogen act as ligands |
| Research areas | Comparison control in copper-dependence studies; cosmetic formulations | In-vitro studies of collagen and extracellular matrix, wound models in animals, cosmetic research |
| Evidence level | Preclinical and cosmetic | Preclinical and cosmetic; no approved drug use |
| Regulatory status | Not approved by the FDA as a drug; used as a cosmetic ingredient | Not approved by the FDA as a drug; used as a cosmetic ingredient (copper tripeptide-1) |
| Identity testing | MS shows the free peptide mass | MS may show both complexed and free peptide ions; copper content needs separate measurement |
| Analytical pitfalls | Counter-ion and salt form affect net content | Copper-to-peptide ratio, free copper excess, other metal contamination |
| Storage | Lyophilized at -20 °C, protected from moisture | Lyophilized at -20 °C, protected from light and moisture; avoid strong chelators and reducing agents in solution |
Same peptide, different material
Free GHK and GHK-Cu share an amino acid sequence, but the complex includes a coordinated copper(II) ion that changes its color, charge and solution behavior. The copper sits in a site formed by the histidine side chain, the N-terminal amine of glycine and a backbone amide nitrogen. Because GHK takes up copper readily, adding free GHK to copper-containing media can form the complex in situ, which complicates studies meant to separate the effects of peptide and metal.
Analytical requirements
For free GHK, a standard certificate showing mass spectrometry identity and HPLC purity is enough. For GHK-Cu, the certificate should also report copper content and, ideally, the molar ratio of copper to peptide, since too much unbound copper or too little complexation changes the material's properties. Mass spectra of the complex can show free peptide ions, because copper can dissociate during ionization or chromatography, so the peptide mass alone does not confirm complexation. See how to read a COA.
Research context
Reported findings for GHK-Cu include stimulation of collagen and glycosaminoglycan synthesis in fibroblast cultures and effects in animal wound models. Gene-expression analyses have also linked GHK to many genes, but these are computational and in-vitro observations. Controlled human evidence is limited mostly to cosmetic studies of topical formulations, which are not evidence of therapeutic effect. Experiments comparing the free peptide, the complex and copper salt alone help separate peptide-specific effects from copper effects.
Frequently asked questions
Is GHK the same as GHK-Cu?
They share the same tripeptide sequence, Gly-His-Lys, but GHK-Cu has a copper(II) ion bound to it. The complex is blue and needs copper content testing, while the free peptide is white. In copper-containing biological fluids, free GHK can form the complex on its own.
Why is GHK-Cu blue?
The blue color comes from the copper(II) ion coordinated by the peptide's nitrogen ligands. Copper(II) complexes of this type absorb light in the red-orange part of the visible spectrum and so look blue. A marked change in color can indicate loss of copper or a change in the complex, and is worth investigating.
How do you verify GHK-Cu identity?
Mass spectrometry confirms the peptide sequence, but because copper may dissociate during analysis it does not prove complexation on its own. A good certificate also reports copper content, for example by elemental analysis, and the copper-to-peptide ratio, together with HPLC purity of the peptide component.
Full entries
- GHK-Cu
GHK-Cu is the copper(II) complex of GHK (glycyl-histidyl-lysine), a tripeptide found in human plasma. It is widely used as a cosmetic ingredient and studied in cell, animal and small human skin studies.
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