What Is GHK-Cu? A Copper-Chemistry Sourcing Primer for Buyers

GHK-Cu is the most-sourced copper-bound peptide active in cosmetic and dermatology supply, and also the one most often mis-specified on a purchase order. The reason is a single conceptual point: GHK-Cu is not the GHK peptide with copper added as an afterthought — it is a copper(II) coordination complex in which the metal is part of the active molecule. Sourcing it well means sourcing a defined coordination compound, not a peptide that happens to list copper on the label.

What is GHK-Cu, exactly?

GHK-Cu is the 1:1 complex of the tripeptide glycyl-L-histidyl-L-lysine (Gly-His-Lys, or GHK) with a divalent copper ion, Cu(II). The INCI name is Copper Tripeptide-1; the CAS number for the complex is 89030-95-5. The free peptide has a molecular weight of about 340.4; the copper complex about 401.9. It was first isolated from human plasma in 1973 and is the textbook example of an endogenous copper-peptide complex.

The copper is held in a roughly square-planar coordination sphere — anchored by the imidazole nitrogen of histidine, the N-terminal amino nitrogen, and the deprotonated amide nitrogen of the Gly-His peptide bond. That geometry is what makes the molecule biologically active; it is also what makes the visible blue colour, which is the d-d electronic transition of the bound Cu(II).

Why the copper changes how you source it

Because the active is the complex, sourcing GHK-Cu means verifying two things that an ordinary peptide COA does not capture: how much copper is present, and how much of it is actually bound to the peptide. A lot can carry the right peptide content on HPLC and still be under- or over-loaded with copper — and the bioactivity tracks the bound complex, not the total peptide.

• Peptide content alone (HPLC-UV) does not tell you the copper status.
• Total copper (ICP-MS or atomic absorption) does not tell you whether the copper is bound or free.
• The Cu²⁺ : peptide molar ratio, computed from both, is the number that defines a clean lot — target 1.00, well-coordinated lots between 0.95 and 1.05.
• The visible blue and its UV-Vis d-d band (centred near 620 nm) confirm the copper is in the right coordination environment.

Who buys GHK-Cu, and in what form

GHK-Cu ships as a blue lyophilized powder to cosmetic brands, skincare contract manufacturers, dermatology-adjacent formulators, and scalp/hair product developers. It is a cosmetic-grade active with an established INCI identity, sold for topical finished-product formulation. The copper coordination chemistry — not the peptide synthesis — is the part that separates a characterized supplier from a commodity reseller.

When a buyer orders 'GHK-Cu', they are ordering a copper coordination complex. The peptide is half the specification; the copper status is the other half, and it is the half most commodity COAs leave out.