GHK-Cu vs AHK-Cu comes down to one amino acid, one methyl group and a very large gap in how much anyone has published.

The two copper peptides look almost identical on paper. Both are tripeptides, both carry histidine in the middle and lysine at the end, and both bind copper. Only the first residue differs.

That small change still matters, both to an analyst checking identity and to a reader weighing the literature. This article compares the two as molecules and as research subjects, and it says plainly where the evidence for one of them runs thin.

Two Sequences, One Letter Apart

GHK is glycyl-L-histidyl-L-lysine. AHK, by contrast, is L-alanyl-L-histidyl-L-lysine. Written in one-letter code, the only difference is the first position: G for glycine, A for alanine.

Chemically, that swap adds a single methyl group. Glycine’s side chain is just a hydrogen atom, whereas alanine’s is CH3. Alanine also has a chiral centre, which glycine lacks, so AHK carries one more stereocentre than GHK.

Identity in Numbers

The methyl group shows up directly in the formula. PubChem gives GHK as C14H24N6O4, which works out to about 340.4 Da. Meanwhile, a supplier datasheet from Cayman Chemical gives AHK as C15H26N6O4 with a formula weight of 354.4. The gap is one carbon and two hydrogens, or roughly 14 Da.

That difference is easy for mass spectrometry to resolve. Consequently, a mass result on a certificate separates the two peptides without ambiguity, provided it reports the observed mass alongside the theoretical one. Note, too, that these figures describe the free peptides; a copper complex or a salt form changes the mass a certificate may quote.

How Each Binds Copper

For GHK, the coordination chemistry is well described. A 2020 study by Bossak-Ahmad and colleagues reports that GHK holds Cu(II) through three nitrogen atoms: the N-terminal amine, the amide nitrogen between the first two residues and the histidine imidazole. It forms a one-to-one complex with a dissociation constant of about 0.24 picomolar at pH 7.4.

AHK shares the same layout, an amino acid followed by histidine. Indeed, the same study compares Cu(GHK) behaviour with that of other peptides carrying histidine in the second position. So the chemistry suggests a similar three-nitrogen grip for AHK. Even so, we found little direct structural or binding data for AHK-Cu itself, and we would not quote a constant for it.

GHK-Cu vs AHK-Cu in the Literature

Here the two diverge sharply. GHK has a research history going back to 1973, when researchers isolated it from human plasma. A 2018 review by Pickart and Margolina surveys decades of work on GHK-Cu across cell culture, animal models of tissue repair and, more recently, gene-expression datasets.

AHK, on the other hand, has a thin record. The Cayman datasheet cites two papers: a 2007 study in cultured human dermal papilla cells and a 2021 paper on dimeric peptide derivatives tested in the same cell type. Beyond that, the published record we could find is sparse. Any honest comparison therefore treats AHK-Cu as a far less characterised compound.

Handling Notes for Both

As materials, the two behave alike. Each carries copper, so a reconstituted solution of either complex will likely show colour, and a sudden change in appearance is worth querying with the supplier. Likewise, both share the general storage rule.

Sealed lyophilised powder is stable at room temperature, kept dry and out of direct light. Cold storage is possible but not required, and repeated cold cycling risks condensation inside the vial. After reconstitution, refrigerate at 2–8°C.

Where SHLabz Fits

SHLabz supplies both as lyophilised research vials: GHK-Cu and AHK-Cu. Sealed lyophilised powder does not require cold chain. SHLabz holds the whole range to it anyway, because it removes a variable and the handling difference is small.

Every batch is tested by an independent laboratory. The GHK-CU certificate is on the lab results page; AHK-Cu does not have a published certificate yet. For more on the better-studied peptide, see our GHK-Cu guide.

The Short Version

In short, GHK-Cu and AHK-Cu differ by one residue: glycine versus alanine. That adds a methyl group and about 14 Da, which mass spectrometry separates easily.

Beyond the chemistry, the literature is lopsided. GHK-Cu has decades of published work, while AHK-Cu rests on a handful of cell-culture papers, and its copper binding is largely inferred from the shared motif.

Frequently Asked Questions

What is the difference between GHK-Cu and AHK-Cu? The first amino acid. GHK starts with glycine and AHK with alanine, so AHK carries one extra methyl group and weighs about 14 Da more.

Do both peptides bind copper the same way? Probably similarly, since both place histidine second. However, GHK’s binding is well measured, while we found little direct binding data for AHK.

Which has more published research? GHK, by a wide margin. Work on it dates back to 1973, whereas AHK appears in only a few cell-culture papers.

How can a lab tell them apart? Mass spectrometry does it simply. The free peptides sit at about 340.4 and 354.4 Da, so a certificate’s observed mass should match the right one.

Do the vials need refrigerating? Not while sealed. Lyophilised powder is stable at room temperature when kept dry and dark, and a reconstituted solution belongs at 2–8°C.

References

• Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data — Pickart and Margolina, International Journal of Molecular Sciences, 2018. GHK history and the scope of its literature.
• Ternary Cu(II) Complex with GHK Peptide and Cis-Urocanic Acid as a Potential Physiologically Functional Copper Chelate — Bossak-Ahmad and colleagues, International Journal of Molecular Sciences, 2020. GHK copper coordination and binding strength.
• AHK (trifluoroacetate salt), Item No. 45938 — Cayman Chemical, supplier datasheet. AHK sequence, formula, formula weight and cited papers.
• Glycyl-L-histidyl-L-lysine (CID 73587) — PubChem, US National Library of Medicine. GHK identity and formula.

Some of these references come from companies working in this field rather than from independent bodies. The underlying chemistry is uncontroversial, though anyone relying on specific figures should confirm them against their own certificates.

Finally, both copper peptides sit side by side in the catalogue.

This article is provided for general research and educational purposes only. All SHLabz products are sold strictly for laboratory research use and are not intended for human or veterinary consumption, diagnosis, treatment, or prevention of any disease. Nothing in this article constitutes medical advice. Always consult a qualified professional and comply with applicable local regulations regarding the handling and use of research compounds.