Guide
GHK-Cu molecular weight and CAS: which form is 340.4, 401.9, 402.9, 462.0 or 742.3?
Published October 9, 2026 · Facts checked October 9, 2026
Short answer
There is no single molecular weight for 'GHK-Cu': records describe different forms. The neutral 1:1 complex, C14H22CuN6O4, is 401.91 g/mol. CAS 89030-95-5 (prezatide copper) is recorded by PubChem as the singly protonated form, 402.92 g/mol. The 2:1 complex with two GHK per copper is 742.3 g/mol, and GHK without copper is 340.38 g/mol (CAS 49557-75-7). One acetic acid adds 60.05 g/mol, so a 1:1 complex with one acetate works out at about 461.96 g/mol.
The forms side by side
| Form | Formula | Molecular weight | Record |
|---|---|---|---|
| GHK, no copper | C14H24N6O4 | 340.38 g/mol | CAS 49557-75-7 · PubChem CID 73587 |
| GHK-Cu, neutral 1:1 complex | C14H22CuN6O4 | 401.91 g/mol | PubChem CID 165429100 |
| Prezatide copper, singly protonated | C14H23CuN6O4⁺ | 402.92 g/mol | CAS 89030-95-5 · PubChem CID 71587328 |
| 1:1 complex with one acetic acid | C14H22CuN6O4 · C2H4O2 | ≈ 461.96 g/mol (calculated) | 401.91 + 60.05 |
| GHK-Cu 2:1 (bisprezatide copper) | C28H46CuN12O8 | 742.3 g/mol | PubChem CID 9831891 |
Sources: PubChem CID 73587 · PubChem CID 165429100 · PubChem CID 71587328 · PubChem CID 9831891
Why the numbers differ
The records differ in three ways: whether copper is there at all (340.38 against 401.91), how many protons the complex carries (401.91 neutral against 402.92 singly protonated), and how many peptides share one copper (1:1 against 2:1, 742.3). Acetate is a counter-ion from purification; it adds mass to the powder but is not part of the complex.
The neutral complex is GHK plus copper minus two hydrogens: 340.38 + 63.546 − 2 × 1.008 = 401.91 g/mol. The 2:1 form is two GHK plus copper minus two hydrogens: 742.29 g/mol, recorded as 742.3.
Sources: PubChem CID 73587 · PubChem CID 165429100 · PubChem CID 9831891
Which CAS to expect
- 89030-95-5 identifies the copper complex (prezatide copper). It does not fix the charge state, which is why PubChem's record for it is the protonated form.
- 49557-75-7 is GHK without copper. A GHK-Cu document carrying it names the wrong material.
Sources: PubChem CID 71587328 · PubChem CID 73587
Using the right number on a COA
Theoretical copper depends on the form: 15.81 % for the pure 1:1 complex, 8.56 % for the 2:1 form. To calculate the Cu²⁺ : peptide ratio, divide copper by 63.546 and peptide content by 340.38 — the mass of free GHK — whatever form the batch is.
Our catalogue lists GHK-Cu as the neutral 1:1 complex: CAS 89030-95-5, C14H22CuN6O4, 401.91 g/mol.
Sources: PubChem CID 165429100 · PubChem CID 9831891 · PubChem CID 73587
Questions
- What is the molecular weight of GHK-Cu?
- 401.91 g/mol for the neutral 1:1 complex, C14H22CuN6O4 (PubChem CID 165429100). Other records give 402.92 g/mol (singly protonated) and 742.3 g/mol (2:1).
- Why does CAS 89030-95-5 show 402.92 g/mol?
- PubChem records that CAS as prezatide copper in its singly protonated form, one hydrogen heavier than the neutral 1:1 complex at 401.91 g/mol.
- What is the molecular weight of GHK without copper?
- 340.38 g/mol, C14H24N6O4, CAS 49557-75-7.
- Does acetate change the molecular weight?
- It changes the mass of the powder, not of the complex. With one acetic acid (60.05 g/mol) per 1:1 complex the combined figure is about 461.96 g/mol.
References
- PubChem CID 73587 — glycyl-L-histidyl-L-lysine (C14H24N6O4, 340.38) — GHK identity, formula and molecular weight
- 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
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