GHK-Cu research reference: CAS, molecular weight, copper complex, solubility and handling

GHK is a tripeptide, glycyl-L-histidyl-L-lysine, first described by Loren Pickart in human plasma in the 1970s. It binds copper(II) tightly, and the complex is what most researchers mean by GHK-Cu (Pickart and Margolina, 2018). The copper sits in a pocket formed by the N-terminal amine of glycine, a deprotonated backbone amide nitrogen and the imidazole nitrogen of histidine. The lysine side chain stays free.

That chemistry is behind a common mix-up. Search for the GHK-Cu molecular weight and you will see 340, 400, 401, 403 and 404 g/mol, sometimes on the same page. Most of them aren't wrong, they just describe different things. 340.4 is the free peptide. PubChem draws the complex as a cation, C14H23CuN6O4+, at 402.92. Products sold as GHK-Cu are usually a salt such as the acetate or chloride, and the powder also holds water, so a weighed milligram contains less than a milligram of the complex. The Vanguard Laboratory report for our lot GHK42126 states chromatographic purity and quantity only; it does not state a formula or molecular weight. So for arithmetic on this page we use the PubChem value, 402.92 g/mol, and say so.

For lab records, keep it simple. Write down which form a number refers to, and when a lot report gives a measured quantity, use it.

The only identifier printed on that report is the chromatogram peak label, "GHK-Cu CAS 300801-03-0". PubChem lists that CAS number on acetate-salt and bis-complex records (for example GHK-Cu acetate, CID 162343861, C16H26CuN6O6, 461.96 g/mol), not on the 89030-95-5 complex in the table above.

GHK-Cu is small, charged and polar, so water is the natural solvent and it dissolves readily at the concentrations most labs use. The solution should be clear and blue. A preformulation study of the native tripeptide characterized its solubility, partitioning and stability in aqueous systems and is the best single published reference for its physical chemistry (Badenhorst et al., 2016).

What matters more than solubility is keeping the copper on the peptide. The complex is pH dependent: at low pH the binding groups are protonated and copper is released. Strong chelators such as EDTA compete for the copper, and reducing agents can reduce Cu(II) to Cu(I). Albumin also binds copper and can form mixed complexes with GHK, which is relevant for anyone working in serum-containing media (Bossak-Ahmad et al., 2021).

1. Use water or a buffer near neutral pH without EDTA unless stripping the copper is the point of the experiment.
2. Avoid reducing agents such as DTT or ascorbate in stock solutions.
3. A color shift from blue toward green, or loss of color, is worth recording; it suggests the copper environment has changed.
4. Note whether media contain serum albumin, since it competes for copper.

Keep the lyophilized powder sealed, cold (-20 C for long storage), dry and dark. Let the vial warm to room temperature before opening, so atmospheric water does not condense on the powder; GHK-Cu powder is hygroscopic, and absorbed water both changes the effective mass and speeds degradation.

In solution, the free histidine and lysine side chains make GHK a good scavenger of reactive aldehydes (Beretta et al., 2007). It's interesting chemistry, but it also means the peptide reacts with aldehyde contaminants and with some buffer components over time. Make stock solutions fresh or freeze them in single-use aliquots, and keep a record of each thaw.

HPLC of GHK-Cu needs care, because acidic mobile phases can pull the copper off the peptide on the column. Some methods detect the free tripeptide after derivatization; one older HPLC method measured GHK and its breakdown product His-Lys in rat plasma with post-column derivatization (Endo et al., 1997). That breakdown product is also a useful thing to look for on a purity trace.

1. Lot number matching the vial, the lab name, and a way to look the report up.
2. HPLC purity with the method stated, so you know whether the peak is the complex or free GHK.
3. Measured quantity per vial.
4. If identity is claimed, mass data near m/z 402.1 with a smaller 404.1 partner (the copper complex, 63Cu and 65Cu) or 341.2 (free GHK). His-Lys near m/z 284.2 would indicate cleavage.
5. Copper content or a statement of the copper-to-peptide ratio if the experiment depends on it.

GHK-Cu has a long literature, much of it from Pickart's group, covering cell-culture and animal studies on extracellular matrix synthesis, gene-expression profiling and antioxidant chemistry (Pickart and Margolina, 2018). Analytical chemists have studied how GHK quenches reactive aldehydes (Beretta et al., 2007) and how its copper complex behaves alongside albumin (Bossak-Ahmad et al., 2021). These are research findings about a reference compound. We cite them so readers can go to the primary papers, not as claims about any product.

We list GHK-Cu in 50 mg and 100 mg vials for laboratory research. Vanguard Laboratory's report on a sample of lot GHK42126, dated 2026-05-08 (HPLC-UV/VIS), gives purity of >99.80% ± 0.18% and a measured 98.27 mg. That result applies to the tested sample of that lot. The report and the lab's verify link are on the lot page and in the COA dataset.