The short answer
GHK is the free tripeptide glycyl-histidyl-lysine. GHK-Cu is the same peptide with a copper(II) ion bound, displacing a proton. They have different masses, different colours and, because much reported activity is attributed to copper delivery, potentially different biology.
Key facts
- GHK
- 340.38 Da, colourless, CAS 49557-75-7
- GHK-Cu
- 402.92 Da, blue, CAS 89030-95-5
- Difference
- One Cu(II) bound, one proton displaced
- Binding site
- Terminal amine, histidine imidazole
- Affinity
- High (GHK binds copper readily)
- Consequence
- Free GHK will acquire copper if available
The chemical difference
GHK carries a copper-binding site formed by the N-terminal amine, the histidine imidazole nitrogen and the intervening backbone nitrogen, a classic arrangement for coordinating a divalent metal. When copper(II) binds, a proton is displaced, which is why the complex is 62.54 Da heavier rather than the full 63.55 of a copper atom.
Why the distinction is not academic
A substantial share of GHK-Cu's reported activity is attributed to copper delivery: to lysyl oxidase, to superoxide dismutase, to enzymes that require copper as a cofactor. If that framing is correct, then the copper is not an accessory to the peptide but a large part of its function. A study using free GHK and a study using GHK-Cu are not necessarily studying the same thing.
Research material referenced
GHK-Cu 100mg, third-party HPLC tested
The complication
GHK binds copper with high affinity, so free GHK introduced into a system containing available copper will not stay free for long. In a biological medium the distinction may partially collapse. That is one reason the literature is not always careful about it, and also why apparently contradictory results between studies can sometimes be reconciled by asking what copper was available.
How to tell them apart
Colour is the simplest indicator. Copper(II) complexes are blue; free GHK is not. Beyond that, the mass difference is unambiguous on a mass spectrometer, and the CAS numbers are distinct: 49557-75-7 for the peptide, 89030-95-5 for the complex.
What suppliers usually mean
Material sold as GHK-Cu is normally the copper complex, and should be blue. Material described only as GHK may be either, and the certificate of analysis is the place to resolve it. Given the mass difference feeds directly into any concentration calculation, this is worth establishing rather than assuming.
Quick reference
| GHK | GHK-Cu | |
|---|---|---|
| Molecular weight | 340.38 Da | 402.92 Da |
| Formula | C14H24N6O4 | C14H23CuN6O4+ |
| CAS | 49557-75-7 | 89030-95-5 |
| Colour | Not blue | Blue |
| Copper | None | One Cu(II) |
Frequently asked questions
- Does free GHK work the same as GHK-Cu?
- Not necessarily. Much reported activity is attributed to copper delivery, so the copper may be central rather than incidental.
- Will free GHK pick up copper on its own?
- In a system with available copper, yes. GHK binds it with high affinity, which partially blurs the distinction in biological media.
- Which one is sold as a research material?
- Normally the copper complex, which should be visibly blue. The certificate of analysis should state which species it describes.
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, The human tri-peptide GHK and tissue remodeling. J Biomater Sci Polym Ed 2008 (PMID 18644225)pubmed.ncbi.nlm.nih.gov
- PubMedPickart L & Margolina A, GHK Peptide as a Natural Modulator of Multiple Cellular Pathways in Skin Regeneration. 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
- 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
- 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.
- GHK-Cu and Collagen Synthesis ResearchLysyl oxidase requires copper to cross-link collagen. That enzyme dependency is the clearest mechanistic route from GHK-Cu to matrix effects in the literature.
Popular across the research hub
One flagship guide from every other research category.
- Retatrutide ResearchRetatrutide vs Mounjaro, Ozempic and Wegovy
- TB-500 (Thymosin β4 fragment)Angiogenesis: What the Literature Reports
- BPC-157 (Pentadecapeptide)BPC-157 CAS Number and Chemical Identity
- CJC-1295 & IpamorelinModified GRF (1-29): What the Name Means
- Peptide ReferenceEndotoxin: The Contaminant That Is Not a Protein
- Bacteriostatic WaterThe Mechanism, Rather Than the Observation
- Research & Regulatory NewsCagriSema After REDEFINE 4
- GLP-1 & Incretin ScienceHy's Law: How Trials Decide a Drug Hurt the Liver
- MOTS-c (Mitochondrial Peptide)What Is MOTS-c? The Mitochondria-Encoded Peptide
- Semax (ACTH Fragment Peptide)What Is Semax? Origin, Sequence and Neurotrophin Mechanism
- Selank (Tuftsin Analogue)What Is Selank? Sequence, Origin and Enkephalin Mechanism
- DSIP (Delta Sleep-Inducing Peptide)What the Antibody Found in Peripheral Tissue
- KLOW (Blend)Half of This Blend Is Small Enough to Share a Route
- GLOW (Blend)Why a Blend Must Be Verified Before It Is Blended
- MT-2 (Melanotan II)The Pharmacology Works. This Compound Was Not Developed.
- IGF-1 LR3A Strong Rationale That Did Not Translate
- GlutathioneA Routine Liver Test That Measures a Glutathione Enzyme
- NAD+Two Products in This Catalogue, One Connected System
- KPVDelete the Transporter and the Effect Disappears