How do GHK and GHK-Cu differ?
GHK is the copper-free tripeptide glycyl-L-histidyl-L-lysine; GHK-Cu is the 1:1 copper(II) coordination complex of the same tripeptide. Both forms appear in published research with overlapping but distinguishable activity profiles. The copper-complexed form is the bioactive species in most published dermal-research contexts.
What the research literature says
The GHK tripeptide naturally occurs in human plasma at concentrations declining with age (~200 ng/mL at age 20, ~80 ng/mL at age 60). In vivo, GHK readily chelates Cu(II) when copper is bioavailable — the chelation is thermodynamically favourable and the resulting complex is the form that engages the copper-dependent signalling pathways characterised across the dermal-research literature.
The Conato coordination-chemistry work characterised the Cu(II) binding site at the histidine imidazole, terminal amine, and adjacent peptide-bond nitrogens (PMID 11325542). The Kang keratinocyte work documented integrin expression and p63 positivity specifically with the copper-complexed form (PMID 19319546). The Pickart synthesis literature consolidates the wider GHK-Cu mechanism map across skin-regeneration pathways (PMID 26236730, PMID 29986520).
Copper-free GHK has overlapping activity but is distinguishable in specific contexts. The Choi work documented stem-cell-recovering effects of copper-free GHK in skin models (PMID 23019153). The Beretta work established GHK as a quencher of the lipid-peroxidation product 4-hydroxy-2-nonenal independent of copper coordination (PMID 17672515). These findings demonstrate that some GHK activity persists in the copper-free form, but the dominant published research framework uses the copper-complexed bioactive species.
Why this matters in research context
Research-supply choice between GHK and GHK-Cu depends on whether the experimental context aligns with the copper-complexed bioactive species (most dermal and skin-regeneration research) or with copper-independent GHK pharmacology (specific stem-cell or anti-oxidative contexts). The Ronin catalog stocks the copper-complexed GHK-Cu form, which covers the great majority of published research applications.
Related compounds
- GHK-Cu 50mg — the copper-complexed form covered by this answer
- GHK-Cu (glossary entry) — coordination chemistry and mechanism summary
Related research questions
References
- Conato C et al. Copper complexes of glycyl-histidyl-lysine and two of its synthetic analogues: chemical behaviour and biological activity. Biochim Biophys Acta 2001;1526(2):199-210. [PMID 11325542]
- Beretta G et al. Glycyl-histidyl-lysine (GHK) is a quencher of alpha,beta-4-hydroxy-trans-2-nonenal: a comparison with carnosine. Chem Res Toxicol 2007;20(9):1309-1314. [PMID 17672515]
- Kang YA et al. Copper-GHK increases integrin expression and p63 positivity by keratinocytes. Arch Dermatol Res 2009;301(4):301-306. [PMID 19319546]
- Choi HR et al. Stem cell recovering effect of copper-free GHK in skin. J Pept Sci 2012;18(11):685-690. [PMID 23019153]
Research-questions pages describe research-context use of peptide-research terminology. They do not constitute medical, veterinary, or clinical advice. Every compound in the Ronin catalog is sold strictly for laboratory and research use only.