The short answer
Free GHK is 340.38 Da. The copper complex is 402.92 Da. Figures between 340 and 742 appear in circulation because PubChem indexes several species (different charge states and a 2:1 peptide-to-copper complex), and secondary sources quote whichever they encountered.
Key facts
- Free GHK
- 340.38 Da, C14H24N6O4, CID 73587
- GHK-Cu (1:1 cation)
- 402.92 Da, C14H23CuN6O4+, CID 71587328
- GHK-Cu (anionic form)
- 400.90 Da, C14H21CuN6O4−, CID 139035031
- 2:1 species
- 742.3 Da, C28H46CuN12O8, CID 9831891
- Difference, free to 1:1
- 62.54 Da = Cu (63.55) − H (1.01)
- Most commonly intended
- 402.92 Da
The arithmetic that settles it
Free GHK is C14H24N6O4 at 340.38 Da. The 1:1 copper complex is C14H23CuN6O4+ at 402.92 Da. Count the difference: one copper added, one hydrogen removed. 63.55 minus 1.01 is 62.54, and 340.38 plus 62.54 is 402.92. The numbers reconcile exactly, which confirms the chemistry: copper binds and displaces a proton rather than simply adding to the molecule.
Why more than one figure is in circulation
Copper complexes can be indexed in several ways and PubChem holds several entries. There is the 1:1 cation at 402.92, an anionic form at 400.90 differing by two hydrogens, and a 2:1 peptide-to-copper species at 742.3. All are legitimate database records describing real chemical species. A secondary source quoting one without saying which produces a figure that looks wrong to anyone holding a different one.
Research material referenced
GHK-Cu 100mg, third-party HPLC tested
The error worth knowing about
The most common mistake is not choosing the wrong complex. It is quoting the free peptide's 340 Da while labelling it as GHK-Cu. That was the case in this library's own earlier articles, which stated approximately 340.8 Da as the complex. It is an easy error because both numbers are correct for something; it is a consequential one because it is 15% low, and molarity calculations inherit that directly.
Which figure to use
For material supplied as GHK-Cu, 402.92 Da is the sensible working figure, since the 1:1 complex is what the CAS number 89030-95-5 corresponds to. For anything described as GHK, prezatide or glycyl-histidyl-lysine without copper, use 340.38. If a certificate of analysis does not state which species it describes, that is a question to ask before doing arithmetic with it.
Physical properties
The copper complex is characteristically blue, which is the visible signature of copper(II) coordination and a useful qualitative check: a GHK-Cu preparation that is not blue warrants explanation. Free GHK is not. Both are water-soluble, with the peptide's lysine and histidine contributing basic character.
Quick reference
| Species | Formula | MW | PubChem CID |
|---|---|---|---|
| GHK (free) | C14H24N6O4 | 340.38 | 73587 |
| GHK-Cu, 1:1 cation | C14H23CuN6O4+ | 402.92 | 71587328 |
| GHK-Cu, anionic | C14H21CuN6O4− | 400.90 | 139035031 |
| 2:1 species | C28H46CuN12O8 | 742.3 | 9831891 |
Frequently asked questions
- Is GHK-Cu 340 Da or 402 Da?
- 402.92 Da for the 1:1 copper complex. 340.38 is the free peptide without copper, and quoting it as the complex is a common error.
- Why does PubChem have several entries?
- Copper complexes exist in different charge states and stoichiometries, and each is indexed separately. All are real species; they are not interchangeable.
- How can I tell copper is bound?
- The complex is blue. Copper(II) coordination produces that colour, and its absence in something sold as GHK-Cu warrants an explanation.
Extended research context
The GHK-Cu (Copper Peptide) deep dive
Deep dive: why the copper ion matters
The GHK tripeptide (Gly-His-Lys) coordinates a Cu²⁺ ion through the imidazole nitrogen of histidine, the terminal α-amino group of glycine, and a deprotonated peptide-bond nitrogen. This near-square-planar geometry is what gives the complex its characteristic deep-blue colour and its redox-modulating chemistry. Uncomplexed GHK is a different molecule pharmacologically. Nearly every peer-reviewed study attributes activity to the copper-bound form, which is why suppliers ship the pre-complexed GHK-Cu rather than plain GHK.
GHK-Cu in the transcriptomic literature
The most-cited modern papers on GHK-Cu come from the Pickart & Margolina group and independent transcriptomic re-analyses. GHK-Cu has been reported to modulate expression of >4,000 human genes at nanomolar concentrations in Broad Institute Connectivity Map re-analyses, including genes involved in DNA repair, antioxidant defence, and ECM remodelling. This gene-signature-level activity is the reason GHK-Cu appears in so many research reviews outside of dermatology.
Analytical fingerprinting of GHK-Cu
On reverse-phase HPLC, GHK-Cu elutes as a well-defined peak; free GHK and copper-free peptide impurities are distinguishable. UV-Vis at ~520 nm confirms the copper d-d transition band. Reputable suppliers publish both HPLC (≥98% area) and mass-spec identity (~340 Da complex, 340.4 free peptide) on the batch CoA.
Research applications
- ▸In vitro fibroblast and keratinocyte gene-expression studies
- ▸ECM turnover assays (collagen, elastin, decorin, MMP profiling)
- ▸Wound-healing scratch assays in cell culture models
- ▸Antioxidant-mechanism studies (copper redox modulation)
- ▸Formulation R&D: cosmetic and topical carrier compatibility research
Handling checklist
- ✓Store lyophilised vial at 2–8 °C, protected from light
- ✓Reconstitute with bacteriostatic or sterile water; expect a blue-tinted solution
- ✓Avoid contact with reducing agents (ascorbic acid destabilises Cu²⁺)
- ✓Aliquot reconstituted solution for freeze/thaw minimisation
- ✓Verify blue colour and CoA HPLC ≥98% before use
Common research-handling mistakes
Learnt from thousands of researcher orders across our UK labs.
✗ Buying GHK without copper
Fix: Confirm the CoA reads GHK-Cu (copper-bound); free GHK is a different pharmacology.
✗ Mixing with vitamin C in solution
Fix: Ascorbate reduces Cu²⁺ to Cu⁺ and destabilises the complex, keep them separate.
✗ Exposing to sunlight
Fix: Store in amber vial or foil-wrapped container at 2–8 °C.
Continue researching
Peer-reviewed guides, comparators and matched reference materials.
Related questions researchers ask
- Is GHK-Cu the same as copper peptide?
- What does GHK-Cu do in research studies?
- Is GHK-Cu safe for topical formulation research?
- What concentration of GHK-Cu is used in cell culture?
- How is GHK-Cu different from GHK alone?
Primary sources & clinical trials
Peer-reviewed research and registered trials from PubMed, ClinicalTrials.gov, PubChem, FDA and NIH. All links open in a new tab and point to the primary source, so every claim can be verified at origin.
- PubChemPubChem · Glycyl-L-histidyl-L-lysine (CID 73587)pubchem.ncbi.nlm.nih.gov
- PubChemPubChem · GHK-Cu copper complex (CID 71587328)pubchem.ncbi.nlm.nih.gov
- PubMedPickart L & Margolina A. Biomed Res Int 2015 (PMID 26236730)pubmed.ncbi.nlm.nih.gov
- PubMedPickart L et al., The Effect of the Human Peptide GHK on Gene Expression. Brain Sci 2017 (PMID 28212278)pubmed.ncbi.nlm.nih.gov
- PubMedPickart L, The human tri-peptide GHK and tissue remodeling. J Biomater Sci Polym Ed 2008 (PMID 18644225)pubmed.ncbi.nlm.nih.gov
- PubMedNIH PubMed: GHK-Cu wound healing literaturepubmed.ncbi.nlm.nih.gov
- GuidelineGoogle: Creating helpful, reliable, people-first contentdevelopers.google.com
Written and reviewed by
The UK Peptides Editorial Team · Research library, UK Peptides
The editorial team is responsible for supplier selection, batch release decisions and the content published in this research library. Every article here is sourced to primary literature and every product page to a signed third-party certificate. Corrections are made in place and the review date updated.
More GHK-Cu (Copper Peptide) articles
- GHK vs GHK-Cu: The Free Tripeptide and the Copper ComplexGHK is the free tripeptide at 340.38 Da; GHK-Cu is the copper complex at 402.92 Da. Why the distinction changes what a paper is actually reporting.
- How GHK Binds CopperThe N-terminal amine, backbone nitrogen and histidine imidazole form a copper-binding site. Why this arrangement has high affinity and what it displaces.
- How GHK Was DiscoveredPickart found that plasma from young donors changed protein synthesis in older liver tissue. The active fraction was a tripeptide, isolated in 1973.
- The 4,000 Genes Claim, ExaminedPickart and Margolina reported GHK modulating over 4,000 human genes using the Broad Institute Connectivity Map. What that measures, and what it does not.
- GHK-Cu Mechanism: What Is Actually ProposedThe dominant proposal is copper delivery to enzymes requiring it as a cofactor. What that explains, what it does not, and why no receptor is established.
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