What Is GHK-Cu? The Copper Peptide Explained, With Sources

By Sequora Research Team · Updated October 2026

What is GHK-Cu? GHK-Cu is the copper(II) complex of the tripeptide glycyl-L-histidyl-L-lysine (GHK), a peptide first described in human blood in 1973 [R1]. GHK binds a single Cu(II) ion through three nitrogen atoms, forming a tight, blue-coloured complex [R3].

This monograph covers the chemistry, the copper binding, the identifiers and what laboratory studies have measured. Every claim links to its source. It does not cover cosmetic, hair or human use.

GHK-Cu at a glance

Molecular weights above are our own calculations from the PubChem formulas using standard atomic weights. Commercial GHK-Cu can be supplied as a salt with counter-ions, so the formula on a batch certificate of analysis (COA) may differ. Always compare the COA mass against the form it names.

Discovery: a tripeptide in human blood

GHK was first reported in 1973 as a tripeptide in human serum that prolonged survival of normal liver cells and stimulated growth in neoplastic liver tissue in culture [R1]. That paper appeared in Nature New Biology (volume 243, pages 85 to 87) [R1].

Later work linked GHK’s activity to its strong affinity for copper(II). A 2018 review describes GHK-Cu as a naturally occurring human plasma tripeptide that can be released from tissue after injury [R2]. The same review proposes that copper binding plays a role in copper metabolism [R2]. Note that the review’s authors have commercial ties to GHK-based products; weigh its interpretations with that in mind.

GHK-Cu is one member of a wider family. Our overview of what copper peptides are places it among related copper-binding sequences.

Structure and copper binding

How GHK holds copper

GHK binds Cu(II) as a tridentate nitrogen chelate. The three donors are the N-terminal amine of glycine, the deprotonated amide nitrogen between glycine and histidine, and the imidazole nitrogen of histidine [R3]. That leaves a fourth position on the copper open. Water can occupy it, or, when GHK is in excess, the imidazole of a second GHK molecule can bind there to form Cu(GHK)₂ [R3].

How tight the binding is

A 2020 study measured the complex by potentiometry, spectroscopy and calorimetry [R3]. At pH 7.4 and micromolar concentrations, the conditional dissociation constant was about 0.24 picomolar. At pH 6.5 it was about 21 picomolar [R3]. Binding of the second GHK was far weaker, with a conditional constant in the low hundreds per molar [R3].

Two practical points follow for laboratory work:

• The 1:1 complex is very stable at neutral pH, but the affinity drops as pH falls. Buffer choice can change how much copper stays bound.
• Excess free GHK can shift the copper species. A solution’s peptide-to-copper ratio matters as much as its concentration.

Why GHK-Cu is blue

The colour comes from copper. The 1:1 Cu(GHK) complex shows a d-d absorption band near 605 nm [R3]. Forming Cu(GHK)₂ shifts that band about 27 nm toward shorter wavelengths [R3]. The free copper aqua ion absorbs near 816 nm [R3]. These band positions give a quick spectroscopic check on which copper species is present.

What laboratory studies have measured

The published GHK-Cu literature is mostly cell-culture, animal and gene-expression work. The findings below are taken from the 2018 review, which cites the primary papers [R2]. Each is labelled by model. None should be read as evidence of an effect in people.

Gene-expression analysis (computational, cell-line data)

Using the Connectivity Map database of cell-line expression profiles, the review’s authors reported that GHK was associated with a change of 50% or more in 31.2% of human genes, with 59% of those up and 41% down [R2]. This is a computational analysis of cell-line data, not a measurement in tissue.

Cell culture (in vitro)

• In human dermal fibroblast cultures, GHK-Cu at 0.01 to 100 nM was reported to increase collagen and elastin production [R2].
• In one cited study, 1 to 10 nM GHK inhibited growth of SH-SY5Y neuroblastoma and U937 lymphoma cells while stimulating growth of NIH-3T3 fibroblasts [R2].

Animal models

• In rats with ischemic wounds, GHK-Cu was associated with faster wound closure and lower MMP-2, MMP-9 and TNF levels [R2].
• In rats, a GHK-collagen dressing was reported to speed wound closure in both healthy and diabetic animals [R2].
• In a mouse model of acute lung injury, GHK-Cu was reported to reduce inflammatory cytokines and raise superoxide dismutase activity [R2].

These are summaries of what investigators measured in specific models. Effect sizes, methods and reproducibility vary between studies, so go to the primary papers before designing work around any one finding.

Regulatory note

FDA’s page on bulk drug substances that may present significant safety risks in compounding includes GHK-Cu, limited to particular routes of administration [R6]. As of the page’s April 2026 update, it appears in the table of substances whose compounding nominations were withdrawn [R6]. Research-grade GHK-Cu is a laboratory reagent, not a medicine.

Stability and handling of the blue copper complex

Research-grade GHK-Cu is supplied as a lyophilized solid. Standard practice for lyophilized peptides is to keep the vial sealed, dry, cold and out of light until it is needed. Our storage guidance sets out the conditions we recommend.

Points specific to the copper complex:

1. Colour as a first check. GHK-Cu should be blue. A pale or colourless solid suggests the copper complex is not what the label says. Confirm with the COA.
2. pH sensitivity. Copper affinity is lower at pH 6.5 than at 7.4 [R3]. Record buffer pH in your methods.
3. Stoichiometry. Excess free GHK can form Cu(GHK)₂, which shifts the absorption band [R3]. A UV-visible spectrum can confirm which species is present.

Sequora supplies GHK-Cu 50mg and GHK-Cu 100mg as lyophilized powder in sealed, labelled vials with a batch code. Each batch is third-party tested by HPLC for purity and mass spectrometry for identity. The COA for a batch is available by email from research@sequorapeptides.com. Browse the full copper peptides category for related sequences.

GHK-Cu FAQ

What is the GHK-Cu peptide made of?

It is the tripeptide glycine-histidine-lysine bound to one copper(II) ion. Copper is held by the glycine amine, the Gly-His amide nitrogen and the histidine imidazole [R3].

What is the difference between GHK and GHK-Cu?

GHK is the free tripeptide, C₁₄H₂₄N₆O₄ [R4]. GHK-Cu is that peptide with a bound Cu(II) ion, which makes it blue [R3], [R5].

Why is GHK-Cu blue?

Copper(II) in the complex absorbs visible light, with a d-d band near 605 nm [R3]. The free peptide has no copper and is not blue.

Is GHK naturally found in the body?

Yes. GHK was first identified in human serum in 1973 [R1], and it is described as a naturally occurring plasma tripeptide [R2].

What is the difference between GHK-Cu and AHK-Cu?

AHK-Cu replaces the N-terminal glycine with alanine. Our GHK-Cu vs AHK-Cu comparison covers the two side by side.

References

1. Pickart L, Thaler MM. Tripeptide in human serum which prolongs survival of normal liver cells and stimulates growth in neoplastic liver. Nature New Biology. 1973;243(124):85-87. Bibliographic record: wikidp.org/Q34207418; DOI 10.1038/newbio243085a0.
2. Pickart L, Margolina A. Regenerative and protective actions of the GHK-Cu peptide in the light of the new gene data. Int J Mol Sci. 2018;19(7):1987. doi:10.3390/ijms19071987
3. Bossak-Ahmad K, Wiśniewska MD, Bal W, Drew SC, Frączyk T. Ternary Cu(II) complex with GHK peptide and cis-urocanic acid as a potential physiologically functional copper chelate. Int J Mol Sci. 2020;21(17):6190. doi:10.3390/ijms21176190
4. National Center for Biotechnology Information. PubChem Compound Summary for CID 73587, glycyl-L-histidyl-L-lysine. pubchem.ncbi.nlm.nih.gov
5. National Center for Biotechnology Information. PubChem Compound Summary for CID 71587328, prezatide copper. pubchem.ncbi.nlm.nih.gov
6. US Food and Drug Administration. Certain bulk drug substances for use in compounding that may present significant safety risks. Content current as of 04/22/2026. fda.gov

For laboratory research use only. Not for human or veterinary use.