Why Cu²⁺ : Peptide Ratio Matters — A 90-Second Quality Check for Formulators. Read our briefing →
Why Cu²⁺ Ratio Matters — a field guide. Read →
On the Cu²⁺ ratio. Read →
Tripeptide-1 — the apo-peptide of GHK-Cu
Overview
GHK is the ligand before the copper: the free Gly-His-Lys tripeptide (INCI Tripeptide-1, CAS 72957-37-0, C14H24N6O4, MW 340.4) that Cupratec coordinates into GHK-Cu, supplied here as the metal-free apo-peptide. It is the same sequence Pickart first isolated from human plasma in 1973 — an N-terminal glycine, a central histidine whose imidazole is the primary copper anchor, and a C-terminal lysine — but with the Cu(II) center absent. Where GHK-Cu arrives as a blue lyophilized cake, apo-GHK is a white powder: no d-d band, no 622 nm absorbance, because there is no copper in the coordination pocket to give one. Cupratec characterises the apo-peptide on the same bench as the complex precisely because the two are a matched pair — the peptide is what you load, the complex is what you get when you load it. We ship apo-GHK as a cosmetic-grade Tripeptide-1 active for formulators who want to control the copper-loading step themselves: brands building their own GHK-Cu in-situ from peptide plus a defined copper source, houses that run separate copper budgets across a multi-active base, and chemistry groups studying the apo-versus-complex behaviour side by side. Each lot carries reversed-phase HPLC purity with diode-array detection (≥98.0%), identity by mass, a moisture/peptide-content figure so the loadable amine and carboxylate stoichiometry is known, and a counter-ion/residual note relevant to anyone titrating copper against it. Because there is no coordinated metal, the QC story is a peptide-purity story rather than a Cu²⁺:peptide story — but the documentation is built to hand straight to a copper-loading workflow. The coordination-chemistry rationale for why the apo-peptide and the complex are characterised together lives in our Cu²⁺ : peptide ratio field note.
Who buys this, and why
Cosmetic-peptide buyers fall into two groups: established beauty / med-aesthetic brands extending an existing line, and private-label clients building a catalog from scratch. The first group usually wants lyophilized peptide material plus stability data in their existing carrier matrix; the second usually wants a finished formulation under their label. Both need INCI naming verified, regulator-specific safety files (CPNP for EU, FDA OTC monograph for US where relevant), and packaging-compatibility data.
Primary buyer fit: medical aesthetic clinics and med spas, regional distributors and re-sellers, and academic and contract research laboratories.
Specifications
Documentation available on request
Regulatory note
GHK is supplied as a cosmetic-grade INCI ingredient (Tripeptide-1), the copper-free apo-peptide of Copper Tripeptide-1, not for compounded human-use preparations. Cosmetic-grade material available for beauty private-label brands and finished-product formulators worldwide; INCI name supplied on SDS for cosmetic-notification workflows (CPNP in EU, equivalent registries elsewhere). Finished-product cosmetic claims are the brand's to substantiate under its destination-market rules.
Frequently asked questions
GHK and GHK-Cu are the same Gly-His-Lys sequence; the difference is the copper. GHK-Cu is the 1:1 coordination compound with a Cu(II) center seated in the His/N-terminus pocket — blue powder, with the diagnostic d-d band near 622 nm. Apo-GHK is the bare ligand: white powder, no coordinated metal, no copper colour. A formulator buys the apo-peptide when they want to own the copper-loading step — building GHK-Cu in-situ from peptide plus a defined copper source, running a separate copper budget across a multi-active base, or studying the apo-versus-complex behaviour directly. If you want the finished complex with the Cu²⁺ ratio already certified, that is GHK-Cu; if you want the ligand to load yourself, this is the entry to specify.
Because there is no coordinated metal, the release file is a peptide-identity-and-purity file rather than a Cu²⁺:peptide file. Each lot carries reversed-phase HPLC purity by diode-array detection (≥98.0%), identity confirmed by mass against the C14H24N6O4 / MW 340.4 expected value, a moisture and net-peptide-content figure so the loadable amine/carboxylate stoichiometry is known, and a counter-ion / residual note for anyone titrating copper against the peptide. That last set of figures is the point: the documentation is built to feed straight into a copper-loading workflow, so a customer making GHK-Cu in-situ knows exactly how much peptide they are charging before they add copper.
The same readouts Cupratec uses to release the complex apply to a customer's in-situ loading. The fastest qualitative signal is colour: a correctly loaded GHK-Cu solution develops the characteristic blue and shows the d-d absorbance band near 622 nm by UV-Vis — apo-GHK alone shows neither. For a quantitative check, run the loaded material against a copper-content method (atomic absorption for total copper on the peptide) and reversed-phase HPLC with diode-array detection to confirm a single coordinated peak rather than free peptide plus separate copper salt, targeting the 1:1 Cu²⁺:peptide ratio. Keep the loading water copper-clean, the pH near-neutral, and chelators and reductants out of the system. The coordination-chemistry logic behind these checks is set out in our Cu²⁺ : peptide ratio field note.