What AHK-Cu is
AHK-Cu is the copper(II) complex of the tripeptide L-alanyl-L-histidyl-L-lysine. It is the closest relative of GHK-Cu, the copper-binding tripeptide isolated from human plasma in 1973, and differs from it by a single methyl group: GHK begins with glycine, AHK with alanine. The complex is a blue lyophilised powder, the colour coming from copper(II) coordinated by the peptide's nitrogen donors.
The identifiers for AHK-Cu are less tidy than for GHK-Cu, and a reader should know that before comparing certificates. The free tripeptide, Ala-His-Lys-OH, is C15H26N6O4 with a formula weight of 354.4 g/mol, one CH2 unit more than GHK [1]. Vendors quote the copper complex in several ways, as the free peptide plus a copper atom (about 417.9 g/mol), as the neutral complex with two protons displaced (about 415.9 g/mol), or as a salt, and CAS registrations for the complex vary between suppliers. A certificate should state which representation it uses, and its mass and copper-content figures should be read against that representation.
| Identifier | Value |
|---|---|
| Sequence | Ala-His-Lys (L-configuration) |
| Molecular formula (free peptide) | C15H26N6O4, 354.4 g/mol |
| Molecular formula (complex, as commonly quoted) | C15H26N6O4Cu, about 417.9 g/mol |
| Copper:peptide stoichiometry | 1:1 |
| Residues | 3 |
| Appearance | Blue lyophilised powder |
| Catalogue sizes | 50 mg |
How the literature describes its mechanism
Copper(II) binding by GHK was characterised in detail by Lau and Sarkar in 1981: the metal is held by the amino-terminal nitrogen, the deprotonated amide nitrogen of the histidine, and the imidazole nitrogen, in a tridentate arrangement with the lysine side chain free [2]. AHK has all three donors in the same positions, and alanine's methyl group on the α-carbon of the first residue does not alter them, so the same binding mode is expected, and the blue colour of the complex is consistent with it. No dedicated coordination study of AHK-Cu equivalent to Lau and Sarkar's work has been located, so the binding constant and geometry are inferred from GHK-Cu rather than measured.
The mechanistic literature on copper tripeptides is almost entirely GHK-Cu literature. GHK-Cu is described as delivering copper into cells, modulating the expression of genes involved in extracellular-matrix synthesis and remodelling, and stimulating collagen synthesis and metalloproteinase expression in fibroblasts [3, 4]. Whether AHK-Cu shares those properties has not been tested directly in a published study. On chemical grounds it is plausible, since the copper-binding chemistry is the same, but plausibility is not evidence, and claims about AHK-Cu and skin or wound healing are extrapolations from a different molecule.
The research record
AHK-Cu's own peer-reviewed record is small and concerns one question. Pyo and colleagues, in 2007, reported that AHK-Cu stimulated the elongation of human hair follicles in organ culture and the proliferation of dermal papilla cells, and reduced apoptosis in those cells, with increased VEGF and decreased TGF-β1 secretion [5]. The complex in that study was L-alanyl-L-histidyl-L-lysine-Cu²⁺, not GHK-Cu. This matters because the paper is the most-cited primary source for the claim that copper peptides promote hair growth, and it is routinely attributed to GHK-Cu by product listings and secondary sources.
Beyond that, a 2021 synthetic-chemistry paper describes dimeric AHK derivatives tested in human follicle dermal papilla cells [1]. We have not found a fibroblast collagen study, an animal wound study, a gene-expression study or a human study for AHK-Cu. A laboratory considering the compound should start from the position that the literature consists of one organ-culture study and its follow-up. Our comparison of GHK-Cu and AHK-Cu sets the two records side by side.
Regulatory status in the United Kingdom
AHK-Cu has no marketing authorisation and is not a medicine. It appears in some hair-care formulations as a cosmetic ingredient, where the regulatory assessment attaches to the finished cosmetic product and the responsible person who places it on the market, not to the raw ingredient. That cosmetic use does not make the research material a cosmetic, and the material supplied here is a chemical for in-vitro laboratory use under the Terms of Sale, not for human or veterinary administration and not for formulation into a product for sale. Purchasers must be 18 or over and are responsible for compliance with the laws and institutional rules that apply to them. Our guide to the UK rules on research compounds sets this out in more detail.
Copper tripeptides are not on the WADA Prohibited List.
Handling, storage and stability
AHK-Cu is supplied as a blue lyophilised powder in a glass vial with a rubber stopper and an aluminium crimp.
Sealed vial. Store at 2–8 °C for routine use and at −20 °C for longer storage. Protect from light and from moisture; the complex is hygroscopic. Allow the vial to reach room temperature before opening.
Reconstitution. The complex dissolves readily in water to a blue solution. Use sterile water or a buffer appropriate to the assay; avoid buffers that chelate copper, since EDTA, citrate and high concentrations of phosphate or Tris can strip the metal from the peptide and change what is being tested. Avoid acidic solvents for the same reason: below about pH 5 the complex dissociates. The reconstitution calculator gives the volume for a target concentration.
Reconstituted solution. Keep at 2–8 °C and use within a few weeks. The blue colour is a useful indicator: a solution that fades towards colourless or turns green-brown has lost or oxidised its copper and should be discarded. Freezing aliquots at −20 °C is acceptable.
Compatibility. Copper(II) is redox-active and will oxidise thiols, ascorbate and some dyes; account for that in cell assays that include reducing agents. The storage and stability guide covers metal–peptide complexes separately.
What a sound certificate for AHK-Cu looks like
Every batch we release carries an independent certificate of analysis, transcribed on the product page and in the certificate register. A certificate for a copper peptide has to answer questions that do not arise for an ordinary peptide.
Peptide purity by RP-HPLC. Reversed-phase HPLC is usually run at low pH with trifluoroacetic acid, which partly dissociates the complex on the column, so the purity figure measures the tripeptide rather than the intact complex. A good batch shows a single dominant peak at 98% or above at 214 or 220 nm. The histidine gives weak absorbance near 210 nm only; 280 nm detection is uninformative.
Identity by LC-MS. Electrospray typically shows the protonated free peptide at about m/z 355.2, and may also show the copper complex at about m/z 416 to 418 with copper's characteristic isotope pattern (63Cu and 65Cu, roughly 69:31). The certificate should say which species it reports. The mass distinguishes AHK from GHK (m/z 341.2) unambiguously, which is worth checking given how often the two are confused.
Copper content. The complex is 1:1, and copper content should be reported by ICP-OES, ICP-MS or atomic absorption, as a weight percentage or a molar ratio. For the complex written as C15H26N6O4Cu the theoretical copper content is about 15.2% by mass; a salt or hydrate will be lower, and the certificate should state the representation it is using.
Colour and appearance. Blue confirms the material is the complex rather than the free peptide. It does not distinguish AHK-Cu from GHK-Cu and says nothing about purity.
Net peptide content and endotoxin. As for other peptides, where reported.
Our guide to reading a certificate of analysis goes through a complete report line by line.
Related compounds
GHK-Cu is the parent compound of the class, with the coordination chemistry and the great majority of the literature; the two are compared in GHK-Cu and AHK-Cu compared. KPV is another short tripeptide in the catalogue, unrelated chemically but often studied in the same skin and inflammation models.
Frequently asked questions
Is AHK-Cu the same as GHK-Cu? No. They differ by one methyl group, and the literature for GHK-Cu is far larger. Findings for one should not be attributed to the other.
Which copper peptide was used in the hair-follicle study? AHK-Cu. Pyo and colleagues' 2007 organ-culture paper tested L-alanyl-L-histidyl-L-lysine-Cu²⁺ [5].
Why do suppliers quote different molecular weights? Because they represent the complex differently: free peptide plus copper, neutral complex, or a salt. Read the certificate's figure against the representation it states.
Why does the solution need to stay blue? The colour comes from copper(II) bound to the peptide. Loss of colour means loss or reduction of the copper, which means the complex is no longer what was tested.
References
- Cayman Chemical. AHK (trifluoroacetate salt), L-alanyl-L-histidyl-L-lysine; item 45938. Product datasheet listing formula C15H26N6O4 and formula weight 354.4, with references to Pyo et al. 2007 and Jeong J, Park K-Y, Kim J. Synthesis and biological evaluation of dimeric peptide derivatives as proliferation-stimulating agents in human follicle dermal papilla cells. Bulletin of the Korean Chemical Society. 2021;42(7):1006–1009.
- Lau SJ, Sarkar B. The interaction of copper(II) and glycyl-L-histidyl-L-lysine, a growth-modulating tripeptide from plasma. Biochemical Journal. 1981;199(3):649–656. doi:10.1042/bj1990649.
- Maquart FX, Pickart L, Laurent M, Gillery P, Monboisse JC, Borel JP. Stimulation of collagen synthesis in fibroblast cultures by the tripeptide-copper complex glycyl-L-histidyl-L-lysine-Cu2+. FEBS Letters. 1988;238(2):343–346. doi:10.1016/0014-5793(88)80509-X.
- Pickart L, Margolina A. Regenerative and protective actions of the GHK-Cu peptide in the light of the new gene data. International Journal of Molecular Sciences. 2018;19(7):1987. doi:10.3390/ijms19071987.
- Pyo HK, Yoo HG, Won CH, et al. The effect of tripeptide-copper complex on human hair growth in vitro. Archives of Pharmacal Research. 2007;30(7):834–839. doi:10.1007/BF02978833.
This monograph summarises the published literature for laboratory researchers. It is not medical advice, and nothing on this site is for human or veterinary use.