What GHK-Cu is
GHK-Cu is a tripeptide bound to a copper ion. The peptide part is glycyl-L-histidyl-L-lysine — three residues, written GHK — and in the supplied material it is complexed with copper in its +2 oxidation state. That copper is not an impurity or an additive. It is part of what the name describes, and it is the single fact that makes this compound's documentation different from that of an ordinary peptide.
The histidine residue in the middle of the sequence is what does the binding. Histidine's imidazole side chain coordinates transition metals readily, and together with the terminal amine and the backbone it forms a stable square-planar site around the copper. That is also why solutions of the complex carry a blue to blue-violet colour: it is the copper centre absorbing in the visible range, not the peptide.
| Property | Value | Where it is confirmed |
|---|---|---|
| Residue count | 3 (Gly-His-Lys) | Synthesis record |
| Free peptide mass | approximately 340 g/mol | Analytical report |
| Copper complex mass | approximately 404 g/mol | Analytical report |
| CAS, free peptide (GHK) | 49557-75-7 | Certificate of analysis |
| CAS, copper complex | 89030-95-5 | Certificate of analysis |
| Physical form supplied | Lyophilized solid | Label and batch record |
Two CAS numbers exist because two distinct substances exist, and a report should make clear which one it describes. Where this page and a lot's own report disagree, the report governs.
Why colour is a clue and not a result
The blue of a GHK-Cu solution is genuine information — it indicates a copper complex is present — but it establishes almost nothing on its own. Copper salts are blue. A blue solution tells you copper is there; it does not tell you the peptide is the right sequence, that it is pure, or that the copper is bound to it rather than sitting alongside it.
This is the practical reason to read the report rather than the vial. Identity, purity, and metal content are three separate questions, and colour answers none of them.
What the analysis has to cover
- Peptide purity by HPLC. This measures the peptide component: the area of the main peak against everything else the detector integrated. A short sequence like GHK is comparatively easy to synthesise cleanly, so purity figures are typically high and a low one is worth asking about.
- Identity. Either mass agreement or retention-time matching against a reference standard run under the same method. On Arctic Lab Supply reports this appears as HPLC-RTM.
- A heavy-metals panel. For a copper complex this carries more weight than it does elsewhere. The material is supposed to contain one metal; the panel is what demonstrates it does not also contain others. Reports in the batch documentation library run this by ICP-MS across arsenic, cadmium, chromium, mercury and lead.
Reading two lots of the same product
GHK-Cu 50mg is a useful worked example, because two lots are published and they were tested by different laboratories.
| Lot | Reported purity | Report date | Laboratory |
|---|---|---|---|
| GHK-2501-A | 99.285% | Feb 2026 | Janoshik |
| GHK-2501-B | 99.03% | Aug 2026 | ILS Laboratories |
The instinct on seeing 99.285% and 99.03% is to treat the first lot as better. That reading does not survive contact with how the numbers are produced. A purity figure is an area percentage from a single analytical run of one sample, integrated under one laboratory's method, with its own column, gradient and integration thresholds. A quarter of a percentage point between two laboratories running different methods months apart is ordinary method variation, not a quality difference you could act on.
What a cross-laboratory comparison is genuinely good for is different, and more useful:
- Does the identity result agree? Two independent laboratories confirming the same compound is a stronger statement than either report alone. This is the comparison worth making.
- Has a new impurity peak appeared? A peak present in the later lot and absent in the earlier one is informative regardless of what the headline percentage did. See how to read an HPLC chromatogram.
- Do the lot identifiers match the vials? A report for lot A does not describe lot B. See lot traceability.
Reading the decimal places against each other is the least informative thing you can do with two reports. Reading the peak patterns against each other is the most.
Storage of the lyophilized solid
As a freeze-dried solid the complex is comparatively stable, and the same two conditions govern it as govern any lyophilized peptide: temperature and moisture. Cold storage slows every available chemical process, and the solid is hygroscopic, so a vial opened before it has equilibrated to room temperature will draw water out of the air.
The copper adds one consideration. Bound transition metals can catalyse oxidation of nearby residues once water is present, so for this compound moisture control is doing slightly more work than it does for a peptide with no metal centre. Storing lyophilized research materials covers the general case.
What the published literature covers
Research interest in GHK and its copper complex is long-standing, and the published record is largely in vitro and animal-model work, with reported areas of investigation including skin and connective-tissue models, wound-repair models, and gene-expression studies in cell culture. As with any compound in this category, three things should be stated rather than assumed: it has not completed the regulatory process that would establish safety or efficacy for any medical indication; results in cell culture and animal models do not transfer automatically to other species; and a laboratory reading this literature is reading a research record, not a set of instructions.
Arctic Lab Supply does not publish research conclusions, recommend applications, or provide guidance on experimental design.