What the molecule is
GHK is a tripeptide, glycyl histidyl lysine, with the sequence GHK and a free peptide mass of 340.4 daltons. Supplied as the copper complex, it carries a bound copper two ion and shows the characteristic deep blue colour of that complex.
It was isolated from human plasma by Loren Pickart, working with Max Thaler, and reported in 1973. The isolation came out of work comparing plasma fractions from donors of different ages in a liver cell culture system, and the active fraction narrowed down to this tripeptide.
The copper binding is the point of the molecule. The imidazole nitrogen of the histidine side chain, the amino terminal nitrogen and the adjacent amide nitrogen together form a strong chelating site for copper two. The resulting complex has an affinity that sits in a useful range, tight enough to hold copper in transport but not so tight that the metal is permanently sequestered.
Published research context
Published research on GHK and its copper complex spans more than fifty years and covers copper transport and coordination chemistry, gene expression profiling in cultured fibroblasts, and extracellular matrix biology in cell culture systems. Reviews by Pickart and colleagues collect much of this work.
For laboratory planning, the copper complex raises considerations that peptide only preparations do not. Copper two is redox active, and in the presence of reducing agents and oxygen it can drive Fenton type chemistry generating reactive oxygen species. Buffer composition, the presence of chelators such as EDTA, and the presence of reducing agents in the medium all affect what the complex does in a given system.
A further practical matter is the distinction between the copper complex and the free peptide, which are different materials and are not interchangeable in an experiment. Some published work uses the free tripeptide, some uses the copper complex, and results from one do not transfer automatically to the other. Reading the methods section carefully to establish which was used is worth the time.
The published work describes cell culture and animal model systems. This material is supplied for laboratory research only.
How each lot is characterised
A tripeptide is small and simple to synthesise, so the analytical questions differ from those for a long chain peptide. Purity by reversed phase high performance liquid chromatography at 214 nanometres remains the headline figure, but for a metal complex the copper content and the stoichiometry matter just as much as the purity of the organic component.
Identity is confirmed by mass spectrometry. The free peptide mass of 340.4 daltons and the copper adduct both provide identification points, and the isotope pattern of copper, which has two stable isotopes at mass sixty three and sixty five in roughly a seventy to thirty ratio, gives a distinctive signature in the spectrum that confirms the metal is present.
The certificate records appearance, which for this material includes the blue colour, purity, identity, net content, water content and counter ion.
Handling on the bench
Store the unopened vial at minus twenty degrees, dark and desiccated. Keep it dark in particular, since copper complexes are generally more light sensitive than the free peptide.
Bring the vial to room temperature before opening, then reconstitute with bacteriostatic water added slowly against the wall of the vial and swirled to dissolve. Do not shake.
Refrigerate and aliquot for single use. Two points are specific to the copper complex. First, avoid buffers containing strong chelators unless the experiment intends to strip the copper, because EDTA and similar agents will compete for the metal. Second, be aware that the complex is pH sensitive, and that the coordination geometry and the colour both change as the pH moves away from neutral, which is a useful visual check that the material is still in the state expected.
Specification
| Form | Lyophilised powder, copper complex |
|---|---|
| Sequence | GHK, glycyl histidyl lysine |
| Residues | 3 |
| Free peptide mass | 340.4 Da |
| Fill size | 50 mg |
| Storage | Minus 20 degrees, dark and desiccated |
References
- Pickart L, Thaler MM (1973). Tripeptide in human serum which prolongs survival of normal liver cells and stimulates growth in neoplastic liver. Nature New Biology, volume 243.
- Pickart L, Margolina A (2018). Regenerative and protective actions of the GHK-Cu peptide in the light of the new gene data. International Journal of Molecular Sciences, volume 19.
For research use only
Products are supplied for laboratory research by qualified researchers and institutions. They are not for human or veterinary use, not for diagnostic or therapeutic use, and are not drugs, foods or cosmetics.