What Is GHK-Cu? The Copper Peptide Explained

What is GHK-Cu, in the terms a laboratory uses? It is a small peptide and a metal complex at the same time, and most confusion about it comes from treating it as only one of the two. This profile covers the sequence, how the copper binds, where the peptide was first described, how the published research is made up, and what changes when the material reaches an instrument. How a purity figure is produced is covered in our explainer on what an RP-HPLC purity number actually measures.

Scope: this article summarizes published chemistry and laboratory research. It does not describe or recommend use in people or animals, and the research use policy sets out how materials on this site are supplied.

What is GHK-Cu, chemically?

The peptide is three amino acids long: glycine, histidine, lysine. PubChem’s record for glycyl-histidyl-lysine gives its formula as C14H24N6O4 and its molecular weight as 340.38 daltons.

• Gly
• His
• Lys

The copper sits at the front of the chain. A 2011 structural study by Hureau and colleagues, using X-ray crystallography and several spectroscopies, describes the complex in solution as monomeric, with copper held by three nitrogen atoms: the free amine of glycine, a deprotonated amide nitrogen from the backbone, and a nitrogen of the histidine ring. In the crystal the complex is a dimer, and the fourth position around the copper is taken by a loosely bound carboxylate oxygen. Lysine, the third residue, is not part of that binding site.

Where GHK came from

The peptide was found in blood before anyone knew it bound copper. In 1973, Pickart and Thaler reported a tripeptide in human serum, and in 1977 Schlesinger, Pickart and Thaler identified it as glycyl-histidyl-lysine. The 2011 structural study cited above describes GHK as a naturally occurring, high affinity copper chelator found in blood plasma.

“High affinity” is meant literally. A 2020 potentiometric and spectroscopic study by Bossak-Ahmad and colleagues calculated a conditional dissociation constant of 0.24 picomolar for the equimolar copper and GHK complex at pH 7.4. The same work identified six copper species in copper and GHK solutions, including free aqueous copper, protonated and deprotonated one to one complexes, and a species with two peptides per copper. The authors followed complex formation by absorbance at 605 nanometers, in the visible range, which is where the complex’s blue color comes from.

How the published GHK-Cu literature is made up

A large share of the GHK-Cu literature is chemistry and formulation work rather than biology. Structure and binding papers, like the two above, measure the complex itself. Formulation papers measure how it behaves in a model system.

• Coordination chemistry. X-ray structures, spectroscopy and binding constants describe the molecule and its copper. They make no biological claim.
• Model membranes. A 2007 in vitro study by Mazurowska and Mojski used ESI-MS and a diffusion cell with a liposome membrane as a model of the outer skin layer. A model membrane is a laboratory system, not tissue.
• Preformulation and stability. A preformulation study by Badenhorst, Svirskis and Wu measured solubility, partitioning and degradation of GHK-Cu under stressed laboratory conditions.
• Biological activity reviews. A 2018 review co-written by Pickart, who first described the peptide, draws on cell culture experiments, rodent wound models and computational analysis of gene expression data.

This article deliberately does not summarize reported biological effects. Results from cells, rodents or gene expression databases describe those systems under their own conditions, and they do not establish any effect in people.

Where the evidence stops

The chemistry of GHK-Cu is well characterized. The human record is not, and several analytical points are less settled than a single label suggests.

• Human data are limited. On its page of bulk drug substances that may present significant safety risks, in the version current as of April 22, 2026, FDA lists GHK-Cu for injectable routes among substances whose nominations were withdrawn. The entry notes possible immunogenicity due to aggregation, peptide-related impurities, and limited data in humans to inform safety considerations.
• The structure depends on the state. The complex is a dimer in the crystal and a monomer in solution, so a solid state result does not describe a solution.
• The species depend on pH. With six copper species identified across conditions, the composition of a solution is a function of how it was made.
• The peptide can break down. Badenhorst and colleagues found the peptide susceptible to hydrolytic cleavage under basic and oxidative stress, and to a lesser extent acidic stress. It was stable in water and in pH 4.5 to 7.4 buffers for at least two weeks at 60 degrees Celsius. HPLC with mass spectrometry identified three degradation products, one of them free histidine.

FDA revises its page, so check the current version. Handling after testing matters too, which is covered in our article on cold chain and why the storage temperature is on the label.

How the copper changes HPLC and mass spectrometry readouts

For most peptides, identity comes down to one expected mass and one main peak. GHK-Cu adds a metal, and two points are often missed.

First, an HPLC purity figure describes peaks, not copper. Badenhorst and colleagues quantified GHK with a validated stability-indicating RP-HPLC method. Because the copper species present depend on pH, the conditions of a method decide what its trace reflects. A purity number on its own does not state the copper content or the ratio of copper to peptide. A certificate that reports copper should say how copper was measured.

Second, the expected mass depends on which formula the laboratory uses. PubChem holds more than one record under these names. Its prezatide copper record lists C14H23CuN6O4 as a positive ion at 402.92, while its GHK-Cu record lists C14H21CuN6O4 as a negative ion at 400.90. The differences are hydrogen count and charge, not a different molecule. The free peptide has a monoisotopic mass of 340.186, so its protonated ion appears near m/z 341.19.

Species	Formula as listed	Molecular weight	Where to look in a spectrum
Free GHK	C14H24N6O4	340.38	Protonated ion near m/z 341.19
GHK-Cu, positive ion form	C14H23CuN6O4, charge plus one	402.92	Near m/z 402.11, with a partner near 404.11
GHK-Cu, negative ion form	C14H21CuN6O4, charge minus one	400.90	Negative mode, near m/z 400.09

Copper also leaves a fingerprint. NIST lists the isotopic composition of copper as 69.15 percent copper-63 and 30.85 percent copper-65. An ion that carries copper therefore shows a second peak about two mass units higher, at a little under half the height of the first. The free peptide does not. Mazurowska and Mojski used ESI-MS to tell apart GHK, GHK-Cu and the two to one complex in solutions of different pH, so one sample can show several of these signals at once.

What a GHK-Cu certificate should show

A certificate of analysis links one lot to one set of results. For GHK-Cu, these are the fields to read against the chemistry above.

• Sequence stated as Gly-His-Lys
• Formula and charge used for the expected mass
• Measured mass reported next to the expected value
• Copper isotope pattern visible or the spectrum attached
• HPLC method, column and detection wavelength named
• Copper content and its method stated if copper is claimed
• Purity figure tied to a specific lot number
• Lot number on the certificate matches the vial label
• Testing laboratory and test date identified

Our guide on how to read a certificate of analysis walks through a full certificate section by section. Iron Rack Labs lists the material on its GHK-Cu 50mg page, in the modified peptides category, and publishes lot matched certificates in the certificate of analysis library. The quality and testing page explains which tests are run on each lot. Pick a GHK-Cu lot record there and read it against the list above.

Frequently asked questions