GHK-Cu: Why the Copper Complex Is the Point
GHK-Cu is frequently described as a tripeptide, which understates what is actually being studied. The compound of interest is a coordination complex, and the copper ion is not a contaminant or a delivery aid — it is part of the molecule under investigation.
The coordination geometry
GHK is glycyl-L-histidyl-L-lysine. The copper(II) ion is held by the glycine amino nitrogen, the deprotonated amide nitrogen between glycine and histidine, and the histidine imidazole nitrogen, with the lysine side chain remaining free. This arrangement gives a square-planar or distorted square-planar geometry typical of Cu(II) with a nitrogen donor set.
The binding constant is high enough that GHK competes meaningfully for copper with albumin, the main copper carrier in plasma. That competition is the basis for the description of GHK as a copper-exchange ligand rather than simply a copper-containing peptide. Literature: PubMed.
Consequences for laboratory work
Treating GHK-Cu as an ordinary peptide leads to several avoidable errors.
Chelators in buffer
EDTA and other chelating agents present in common buffers will strip copper from the complex. A medium containing EDTA is not a neutral vehicle for this compound.
pH sensitivity
The amide nitrogen involved in coordination must be deprotonated for the complex to form. At acidic pH the complex dissociates. Stock solutions prepared in dilute acid, a routine choice for many peptides, are the wrong approach here.
Colour as a crude indicator
The complex is distinctly blue in solution. Loss of colour indicates dissociation or copper loss, which makes visual inspection a useful first check even though it is not quantitative.
Analysis
Purity determination is more involved than for a free peptide. RP-HPLC conditions using trifluoroacetic acid, standard for peptide analysis, are acidic enough to dissociate the complex, so a certificate may report on the peptide component while the copper stoichiometry is assessed separately. When comparing certificates from different suppliers, check whether the figure quoted describes the peptide or the complex — the two are not equivalent. Our guidance on reading a certificate of analysis covers what to look for.
Products: GHK-Cu 50mg, GHK-Cu 100mg, and the wider copper peptides category.
ExoLabz supplies compounds for laboratory research use only. Nothing on this page is medical advice or a suggestion of human or veterinary use. Certificates of analysis for each compound are published on this site.
