What GHK-Cu peptide is, and what the research examines

GHK-Cu is a small coordination compound: the tripeptide glycyl-L-histidyl-L-lysine (Gly-His-Lys, or GHK) with one copper(II) ion bound to it. You will see it spelled GHK Cu, GHKCu or simply "the copper peptide"; cosmetic ingredient lists use copper tripeptide-1; and papers from around 1980 abbreviate the peptide GHL. All of these point at the same complex. This guide treats it as what it is chemically, a peptide carrying a metal, and works through how the copper is held, how tightly, why the solution is blue, what pulls the copper off, how to confirm identity, and how it is supplied in the United States. We sell it as GHK-Cu.

Research use only. GHK-Cu is supplied strictly for in-vitro laboratory research. It is not for human or veterinary use, is not supplied for cosmetic or personal use, and has not been evaluated by the FDA.

GHK-Cu at a glance

Peptide and complex are two different things

GHK on its own is a colorless tripeptide. GHK-Cu is that peptide with a copper(II) ion bound, and the difference shows even in the formula: the complex carries two fewer hydrogen atoms than the free peptide (C₁₄H₂₂ against C₁₄H₂₄), because two protons are released when the doubly charged metal binds and the neutral complex is what remains. The two molecular weights differ by about 61.5 g/mol, which is the copper minus those two hydrogens.

That distinction matters when buying. "GHK", "GHK acetate" and "GHK-Cu" are separate catalog items. A colorless solution sold as a copper peptide is either the free tripeptide or a complex that has lost its metal, and work published on the copper complex does not describe it.

How the copper is held

The structural picture comes from coordination chemistry rather than biology. Hureau and colleagues combined X-ray crystallography with EPR, X-ray absorption and NMR spectroscopy and found that, in solution, Cu(II)-GHK is a monomer with three nitrogen atoms around the metal:

• the free amine of glycine, at the peptide's N-terminus;
• the deprotonated backbone nitrogen of the glycine-histidine amide bond;
• a nitrogen of the histidine imidazole ring.

A loosely held oxygen fills the fourth position in the plane. In the solid state that oxygen comes from a carboxylate and the complex crystallizes as a dimer, whereas the dissolved form is a monomer. The lysine side chain sits outside the binding site at neutral pH: Conato and colleagues found its amino group joins the coordination only under alkaline conditions, and is protonated, and free, at physiological pH.

Two further species complicate things. With excess peptide, a second GHK can bind to give Cu(GHK)₂, which Hureau's group linked to the unusually fast exchange of copper between GHK molecules, and Conato's group reported evidence of species carrying two copper ions. Lau and Sarkar's potentiometric work had already shown several copper-GHK species coexisting between pH 3.5 and 10.6. "GHK-Cu" in a vial is therefore better pictured as a pH-dependent population dominated by one form than as a single fixed structure.

How tightly: copper affinity in numbers

Two measurements place GHK's grip on copper.

• Calorimetry. Trapaidze and colleagues measured copper(II) binding by isothermal titration calorimetry, adding glycine as a deliberately weak competitor so that binding this tight could be resolved at all. Binding was mainly 1:1, with a conditional dissociation constant at pH 7.4 of about 7.0 × 10⁻¹⁴ M for GHK, against 2.6 × 10⁻¹⁴ M for DAHK, the copper-binding motif at the N-terminus of human serum albumin.
• Competition with albumin. In Lau and Sarkar's equilibrium-dialysis experiments at pH 7.5 and 6 °C, with GHK and albumin at equal concentrations, about 42% of the copper ended up on the peptide.

Read together, GHK and albumin hold copper with affinities in the same range, and each can take it from the other. For an experiment that is a practical point: serum-containing culture medium is full of albumin that competes for the metal, and the calorimetry paper itself treats the HEPES buffer as a competing chelator that has to be corrected for.

Why GHK-Cu is blue

The color belongs to the copper. A copper(II) ion has a single vacancy among its d electrons, and when it sits in a roughly planar set of nitrogen donors it absorbs light in the orange-to-red part of the visible spectrum; what passes through looks blue. Free GHK, with no metal, is colorless.

That makes color a quick first look at a vial:

• Blue and clear is consistent with copper bound in the complex.
• Colorless means little or no copper: the free peptide, or a complex that has lost its metal.
• Green, cloudy or carrying a deposit usually points to a pH excursion or copper dropping out as an insoluble species.

Color is not an assay. It says copper is present in a bound form; it does not say how much complex the vial holds, or whether the peptide itself is pure.

What pulls the copper off

Since the property everyone is interested in depends on the metal staying put, the useful stability question for GHK-Cu is less "is the peptide intact?" than "is the copper still bound?". The chemistry above predicts the main threats:

• Acid. The binding nitrogens hold copper only while they are deprotonated or neutral. Push the pH low enough and protons win, releasing the metal, which is why copper-GHK speciation is always reported as a function of pH.
• Strong chelators. EDTA and similar ligands outcompete the peptide, so a buffer or medium containing them strips the copper.
• Competing ligands. Amino acids such as histidine and glycine form mixed (ternary) complexes with copper-GHK, and albumin competes outright.
• Alkali. At high pH the lysine amine joins in and hydroxide-bearing species form, shifting the population away from the main complex.
• Strong reduction. Hureau's group found Cu(II)-GHK redox-inert under moderate potentials, but at a strongly negative potential (around -0.62 V against a silver/silver chloride reference) the copper is reduced to Cu(I) and released.
• Warmth and light. As in any solution, heat speeds every change, and the copper complex is the light-sensitive part of the vial.

In practice that means noting the buffer and any chelators in a protocol, keeping serum content in mind whenever copper delivery is the question, and storing the solution cold and dark.

Where GHK came from

GHK was first reported in human serum in 1973 by Pickart and Thaler. By 1980 Pickart's group had found that the peptide co-isolates with roughly equimolar copper, that it readily forms copper(II) complexes, and that adding it increased copper uptake by cultured hepatoma cells; that paper proposed it as a copper transport factor, partly because its histidine-next-to-a-basic-residue pattern resembles the copper sites of albumin. Later reviews from the same group describe GHK in human plasma, saliva and urine. Its origin as a naturally occurring copper-binding peptide, rather than a designed molecule, is why so much of the early literature is about copper transport.

What the published research covers

The biological literature on GHK-Cu is preclinical. Most of it is cultured-cell work, with fibroblast and keratinocyte lines prominent, alongside gene-expression analyses cataloging which genes shift in the presence of GHK. Pickart and Margolina's 2018 review collects that gene-expression data, and a 2015 review from the same group summarizes pathway findings. Three cautions apply when reading it:

1. Both reviews come from the group that first described GHK. They are syntheses, not independent replications, so a claim is worth tracing back to the original experiment, its model and its concentration.
2. Copper controls matter. An effect seen with the complex may come from the peptide, from the copper or from the pair. Studies with copper-salt and copper-free GHK arms can tell those apart; studies without them cannot.
3. Cell findings stay cell findings. A change measured in a culture dish describes that system and nothing beyond it.

GHK-Cu as a cosmetic ingredient

GHK-Cu is used as an ingredient in cosmetic formulations, where it is listed as copper tripeptide-1. A cosmetic containing it is a finished consumer product, made and regulated as a cosmetic. Research-grade GHK-Cu is a characterized reference material supplied with a batch certificate for laboratory work. The two are not interchangeable, we do not supply GHK-Cu for cosmetic or personal use, and nothing on this page is a statement about what it does in a cosmetic product.

Checking identity: color, mass and the certificate

Color is the first look; analysis is the answer. For GHK-Cu a useful certificate covers:

• Purity by HPLC, given as a figure for that lot with the method named, not a bare "99%+".
• Identity by mass spectrometry. Expect the copper complex near 401.9 and the free peptide near 340.4. Copper has two stable isotopes, copper-63 and copper-65, so an ion that carries copper shows a partner peak two mass units heavier at a little under half the height; a peak without that partner is not carrying copper. Acidic LC-MS conditions can strip the metal during analysis, so a spectrum dominated by free GHK is not on its own proof that the vial lacked copper, and it helps when a certificate states how copper content or binding was assessed.
• Appearance: a blue solution, free of particles.
• A batch number and a date that match the vial in hand.

Our GHK-Cu certificates are published by batch in the COA library, and the Certificate of Analysis guide walks through how to read one.

Single vial or blend

GHK-Cu is also a component of two of our blends: the Glow Stack, alongside BPC-157 and TB-500, and the Klow Stack, which adds KPV. None of those partner peptides contains histidine, the residue that anchors copper in GHK, so GHK-Cu is the only component in either vial built around a copper-binding site. A blend is convenient when a study calls for the combination and limiting otherwise, because no component can be varied on its own; when GHK-Cu itself is the subject, the single vial is the cleaner starting point. The Glow Stack guide and the KLOW guide cover the blends.

Format, storage and US supply

Most GHK-Cu offered to US laboratories is lyophilized powder that has to be dissolved before any work begins. Ours ships pre-mixed as a solution, so that step, along with the solvent and pH choices that come with it (the solution stability guide explains why those matter), happens once under controlled conditions instead of at every bench. The trade-off is handling: keep it at 2-8 °C, sealed, away from light, and never frozen. The pre-mixed vs lyophilized guide compares the two formats.

Orders are dispatched cold-chain from the warehouse that serves the United States, with tracked delivery across the country next business day. Prices are in US dollars, and payment is by Visa, Mastercard or Apple Pay. Strengths and batch details are on the GHK-Cu product page.

GHK-Cu and the FDA

GHK-Cu is not an FDA-approved drug and has not been evaluated by the FDA. We supply it for in-vitro laboratory research only; it is not for human or veterinary use.

What this page does not cover

We do not publish dosing or administration information for GHK-Cu. Concentrations in published cell work are specific to each model and endpoint, and the primary literature is the place to find them.

Related reading

• What is the Glow Stack? · What is KLOW peptide? · Bac water and peptide stability · Pre-mixed vs lyophilized peptides · What is a Certificate of Analysis?