GHK is often written as though the copper were an optional extra. It is not. The copper-bound complex is the studied entity, and separating them changes what you are working with.
The complex is the compound
GHK is a three-residue peptide — glycyl-L-histidyl-L-lysine — originally isolated from human plasma. Its defining property is a very high affinity for copper(II). In physiological conditions it exists overwhelmingly as the copper complex, GHK-Cu, with a combined molecular weight of 404.93 g/mol. Published work on "GHK" almost always means the complex.
This also explains the colour. GHK-Cu solutions are blue; that is the copper coordination, not a dye or an impurity. A colourless GHK-Cu solution is a flag worth investigating.
What the literature measures
- Copper shuttling. The complex acts as a physiological copper carrier, which is the mechanism underlying much of its activity.
- Matrix remodelling. Modulation of matrix metalloproteinases and their TIMP inhibitors — meaning it influences both sides of the remodelling balance, not just synthesis.
- Collagen and glycosaminoglycan synthesis in dermal fibroblast culture.
- Broad transcriptional shifts consistent with tissue-remodelling programmes, reported in gene-expression studies.
Handling notes
Copper complexes are more sensitive to chelators and to pH than the bare peptide. Avoid EDTA-containing buffers unless stripping the copper is the point of the experiment — an EDTA wash will pull the copper and leave you assaying free GHK, which is a different molecule with different activity.
Selected literature
- Pickart L, Margolina A. Regenerative and protective actions of the GHK-Cu peptide. Int J Mol Sci. 2018;19(7):1987.
- Pickart L et al. GHK peptide as a natural modulator of multiple cellular pathways. Biomed Res Int. 2015;2015:648108.
Stocked as a 50 mg HPLC-verified reference standard: GHK-Cu 50 mg · background in the peptide library. For laboratory research use only.