GHK-Cu vs AHK-Cu

Two copper-binding tripeptides differing by a single residue, with research literatures of very different size and focus.

One residue apart

GHK-Cu is glycyl-L-histidyl-L-lysine complexed with copper(II). AHK-Cu is alanyl-L-histidyl-L-lysine complexed the same way. The difference is the first residue: glycine against alanine, a single added methyl group.

That is a small structural change with a disproportionate effect on where each has been studied. GHK is an endogenous plasma peptide with a research history going back to 1973 and a literature spanning dermal matrix biology, gene expression and wound models. AHK is synthetic, its literature is far smaller, and it is concentrated almost entirely on follicular and hair-related endpoints.

Where they differ

Origin. GHK occurs naturally in human plasma, with concentration declining measurably with age. AHK is a synthetic analogue.
Volume of evidence. GHK-Cu has several hundred publications across multiple tissue systems; AHK-Cu has a narrow and much smaller body of work.
Research focus. GHK-Cu spans collagen and glycosaminoglycan synthesis, metalloproteinase balance, transcriptional profiling and wound models. AHK-Cu is studied chiefly for dermal papilla cell proliferation and VEGF expression in follicular models.
Copper coordination. Both bind copper(II) through the histidine imidazole and terminal amine, but affinity and complex geometry are not identical, and the complex rather than the free peptide is the active species in each case.
Interchangeability. None established. Results from one should not be read across to the other.

Which suits which question

For dermal matrix work — collagen, elastin, glycosaminoglycans, fibroblast behaviour, transcriptional response — GHK-Cu is the compound the literature supports and the obvious starting point. For follicular work specifically, AHK-Cu has the more directly relevant, if thinner, evidence base.

A study designing around copper tripeptides generally should be explicit about which it is using, because the two are frequently conflated in secondary sources and in product marketing, and a citation trail that mixes them is not evidence for either.

How both are supplied

GHK-Cu and AHK-Cu are supplied lyophilised in sealed vials, with GHK-Cu also available as a metered intranasal preparation. Each batch is specified at 99% purity or better by HPLC with identity confirmed by mass spectrometry and released against a batch-matched Certificate of Analysis, by the process on the lab testing page.

Both are light and pH sensitive in a way the rest of the catalogue is not, because the coordination complex rather than the peptide is what the research describes. Both sit in the skin and cosmetic group.

Research use only

Both compounds are laboratory reference materials. Neither is a medicine, a cosmetic, a supplement, or for human or veterinary use, and no dosing guidance or administration protocol is provided for either. The full terms are in the research use policy. Every guide is indexed in the research library.