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GHK-Cu vs GHK: the copper complex and the free peptide compared
Published October 7, 2026 · Facts checked October 9, 2026
Short answer
GHK is the tripeptide Gly-His-Lys (Tripeptide-1, CAS 49557-75-7, 340.38 g/mol). GHK-Cu is the same peptide holding one copper(II) ion (Copper Tripeptide-1, CAS 89030-95-5, 401.91 g/mol for the 1:1 complex). They are different materials: GHK-Cu is blue and contains about 15.8 % copper as a pure complex; GHK is white to off-white and contains none.
Side by side
| GHK-Cu | GHK | |
|---|---|---|
| Also listed as | Copper Tripeptide-1, prezatide copper | Tripeptide-1 |
| CAS | 89030-95-5 | 49557-75-7 |
| Formula | C14H22CuN6O4 (1:1) | C14H24N6O4 |
| Molecular weight | 401.91 g/mol (1:1); 742.3 g/mol (2:1) | 340.38 g/mol |
| Copper | 15.81 % of the pure 1:1 complex; 8.56 % for 2:1 | None |
| Colour | Blue | White to off-white |
| UV-Vis | Cu(II) d–d band at about 606 nm | No band in the visible range |
| HPLC purity | Measures the peptide, not the copper | Measures the peptide |
Sources: PubChem CID 165429100 · PubChem CID 9831891 · PubChem CID 73587 · PubChem CID 71587328 · Bossak-Ahmad et al., Int J Mol Sci 2020
What the copper changes
GHK binds copper(II) very tightly: at pH 7.4 the conditional dissociation constant is 7.0 × 10⁻¹⁴ M, with one copper per peptide. The copper sits between the N-terminal amine, the deprotonated Gly–His backbone nitrogen and the histidine ring, and that square-planar copper site is what absorbs orange-red light and makes the complex blue.
So the two are not two grades of one material. An order for GHK-Cu needs the complex, with its copper content and ratio documented; an order for GHK needs the peptide without copper.
Sources: Trapaidze et al., J Biol Inorg Chem 2012 · Freedman et al., Biochemistry 1982 · Laussac et al., Biochem J 1983 · Schirer et al., J Biol Inorg Chem 2017
Does GHK plus a copper salt give GHK-Cu?
Copper and GHK do complex in water, but which species form depends on pH, the copper-to-peptide ratio and the other ligands present — histidine, for example, joins copper and GHK in ternary complexes. What forms has to be measured. Buying the pre-formed complex with a measured Cu²⁺ : peptide ratio puts that measurement on the COA.
Sources: Lau & Sarkar, Biochem J 1981 · Bossak-Ahmad et al., Int J Mol Sci 2020
How to tell them apart on paper and in the lab
- CAS: 89030-95-5 for the complex, 49557-75-7 for the peptide. A GHK-Cu offer quoting 49557-75-7 names the wrong material.
- Colour: blue means copper is bound; a white powder sold as GHK-Cu has no copper.
- Copper content by ICP or AAS, and the Cu²⁺ : peptide ratio calculated from it.
- UV-Vis: a broad band near 606 nm for GHK-Cu; none for GHK.
Sources: PubChem CID 71587328 · PubChem CID 73587 · Bossak-Ahmad et al., Int J Mol Sci 2020
Where AHK-Cu fits
AHK-Cu swaps the first glycine for alanine (AHK, 354.41 g/mol; 415.94 g/mol as the neutral 1:1 copper complex). It binds copper through the same N-terminal Xxx-His motif.
Sources: PubChem CID 7408502 · Gonzalez et al., Chemistry 2018
Questions
- Is GHK-Cu the same as Copper Tripeptide-1?
- Yes. Copper Tripeptide-1 is another name for GHK-Cu, the copper(II) complex of Gly-His-Lys, CAS 89030-95-5.
- Is Tripeptide-1 the same as GHK-Cu?
- No. Tripeptide-1 is GHK, the peptide without copper (CAS 49557-75-7).
- Why is GHK-Cu blue?
- The copper(II) ion in the peptide's binding site absorbs light in a broad band near 606 nm, in the orange-red part of the spectrum, so the material looks blue.
- What is the molecular weight of GHK-Cu?
- 401.91 g/mol for the neutral 1:1 complex (C14H22CuN6O4). The 2:1 form with two GHK per copper is 742.3 g/mol.
References
- PubChem CID 165429100 — GHK copper complex (C14H22CuN6O4, 401.91) — formula and molecular weight of the neutral 1:1 complex
- PubChem CID 71587328 — prezatide copper (CAS 89030-95-5) — CAS 89030-95-5 belongs to the copper complex; PubChem records it as the singly protonated form, 402.92 g/mol
- PubChem CID 9831891 — bisprezatide copper (C28H46CuN12O8, 742.3) — the 2:1 peptide-to-copper record
- PubChem CID 73587 — glycyl-L-histidyl-L-lysine (C14H24N6O4, 340.38) — GHK identity, formula and molecular weight
- PubChem CID 7408502 — L-alanyl-L-histidyl-L-lysine (C15H26N6O4, 354.41) — AHK formula and molecular weight
- Trapaidze et al., J Biol Inorg Chem 2012 — Cu²⁺ binding to DAHK and GHK by ITC — 1:1 stoichiometry; conditional Kd 7.0 × 10⁻¹⁴ M at pH 7.4
- Freedman et al., Biochemistry 1982 — structure of the GHK–copper(II) complex in solution — mononuclear 1:1 complex at neutral pH; pH transitions at pK 3.6, 9.2 and 11.4
- Laussac et al., Biochem J 1983 — NMR and EPR of copper(II)–GHK — three nitrogens and one oxygen around Cu(II), square-planar, pH 6.0–9.6
- Schirer et al., J Biol Inorg Chem 2017 — copper and zinc binding to GHK and DAHK — Cu(II) bound by the N-terminus, the deprotonated amide and histidine Nπ
- Lau & Sarkar, Biochem J 1981 — interaction of copper(II) and GHK — multiple species across pH 3.5–10.6; ternary complexes with histidine
- Bossak-Ahmad et al., Int J Mol Sci 2020 — ternary Cu(II) complex with GHK — d–d band of Cu(GHK) at 605–606 nm; aqua copper absorbs near 816 nm
- Gonzalez et al., Chemistry 2018 — N-terminal Cu-binding motifs (Xxx-His, Xxx-Zzz-His) — Xxx-His peptides such as GHK form high-affinity Cu(II) complexes
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