DOCUMENTED BY BATCHGHK-Cu is a copper(II) coordination complex of the tripeptide Gly-L-histidyl-L-lysine. It is one of the most extensively catalogued copper-binding peptides in the chemical literature and is used in laboratories as a reference metallopeptide. This profile summarises the verifiable chemistry of GHK-Cu: its amino-acid sequence, molecular formula and weight, copper-coordination geometry, physical appearance, bench solubility and the analytical methods used to confirm identity and purity. It makes no resolving power claims and is intended solely as a reference for research personnel.
Compound identity
The organic ligand is the tripeptide Gly-His-Lys (Gly–L-histidine–L-lysine), assigned CAS 49557-75-7 as the free peptide. When chelated to a copper(II) ion the resulting complex is registered under CAS 89030-95-5 and appears in PubChem as CID 71587328 under the synonyms Copper tripeptide-1 and prezatide copper. The free tripeptide itself is catalogued as PubChem CID 73587. Distinguishing the two registry entries matters at the bench, because the free peptide and its copper complex differ in mass, charge and colour.
Sequence and molecular structure
The peptide is a linear three-residue chain, N-terminus to C-terminus: Gly, then L-histidine, then L-lysine. The imidazole side chain of the central histidine and the free amino terminus of Gly are the two functional groups that give the molecule its metal-binding character. The free tripeptide has the molecular formula C14H24N6O4 and an average molecular weight of 340.38 g/mol, values confirmed against the PubChem record (CID 73587) for Gly-L-histidyl-L-lysine.
GHK-Cu molecular weight and chemistry
On forming the copper complex the peptide coordinates the metal through its amino and amide nitrogens. PubChem catalogues CID 71587328 as the monocationic species C14H23CuN6O4+ with a molecular weight of 402.92 g/mol. Relative to the free peptide this is the addition of one copper atom (atomic mass ≈ 63.5) with the loss of a single coordinating proton, which accounts for the shift from the 340.38 g/mol free peptide. Reference and supplier catalogues frequently quote the neutral 1:1 complex (C14H24CuN6O4) at approximately 403.9 g/mol, because the reported mass depends on which protonation and charge state is being described; laboratories should record which species a given figure refers to.
Copper coordination
Copper(II) is held in a square-planar-to-square-pyramidal arrangement. The primary donor atoms are the imidazole nitrogen of the histidine side chain, the α-amino nitrogen of the N-terminal Gly, and the deprotonated amide nitrogen of the Gly–histidine peptide bond; a carboxylate oxygen (from lysine of a neighbouring complex in the solid state) completes the coordination sphere. The complex has high thermodynamic stability, with a reported copper-binding constant on the order of log β ≈ 16.4, which is why the copper is sequestered rather than free in solution. Understanding this geometry is useful when interpreting spectroscopic and mass-spectrometric data for the compound.
Appearance and bench handling
The free GHK peptide is an off-white to white lyophilised powder. The copper complex is visibly distinct: coordination of Cu(II) produces a characteristic blue to blue-purple solid, and aqueous solutions take on a blue tint. This colour is a simple visual identity cue that separates the complex from the uncomplexed peptide. For bench storage, lyophilised material is typically kept cold and desiccated and protected from light; solution preparation for in-vitro work is generally into water or a compatible aqueous buffer, with the copper complex being water-soluble. These notes describe handling of a laboratory reagent only and are not use instructions.
Identity and purity testing
Two orthogonal techniques are standard for characterising this compound. High-performance liquid chromatography (HPLC) resolves the peptide from process-related impurities and gives a purity percentage from peak-area integration. Liquid chromatography–mass spectrometry (LC-MS), including high-resolution mass spectrometry (HRMS), confirms molecular identity by matching the observed mass to the expected value for either the free peptide (340.38) or the copper complex (402.92), and the isotope pattern of copper provides an additional confirmation that the metal is present. At livvmore, each batch is characterised for identity and purity at the USC Alfred E. Mann Multi-Omics Mass Spectrometry Core by LC-MS/HRMS, and the resulting data is published as a per-batch Certificate of Analysis.
Reading a Certificate of Analysis
A Certificate of Analysis (COA) records the batch or lot number, the analytical method used, the measured purity, and the mass confirming identity. When reviewing a COA for a copper peptide, check that the reported mass corresponds to the intended species (free peptide versus copper complex), that the method line names an identity-confirming technique such as LC-MS or HRMS rather than appearance alone, and that the batch number on the certificate matches the batch in hand. Copper peptides are frequently studied alongside other research tripeptides and pentadecapeptides such as BPC-157; comparing COAs across compounds is good practice for verifying documentation standards.
For broader context on peptide families and their documentation, the GLP research peptide collection follows the same per-batch testing approach described above.
For laboratory research use only. Not for human or veterinary use.
Frequently asked questions
What is the molecular weight of GHK-Cu?
PubChem lists the GHK-Cu copper complex (CID 71587328, CAS 89030-95-5) as the monocation C14H23CuN6O4+ with a molecular weight of 402.92 g/mol; reference and supplier catalogues also commonly cite about 403.9 g/mol for the neutral 1:1 form (C14H24CuN6O4). The free tripeptide Gly-L-histidyl-L-lysine (GHK) without copper is C14H24N6O4 with a molecular weight of 340.38 g/mol (CAS 49557-75-7). The difference reflects the addition of one copper atom with the loss of a coordinating proton.
What is the amino-acid sequence of GHK-Cu?
The peptide portion of GHK-Cu is the tripeptide Gly-His-Lys, read from N-terminus to C-terminus as Gly, L-histidine, then L-lysine. In the complex, a copper(II) ion is coordinated primarily by the histidine imidazole nitrogen, the Gly alpha-amino nitrogen and the deprotonated Gly-histidine amide nitrogen.
What is the CAS number for GHK-Cu?
The GHK-Cu copper complex has CAS number 89030-95-5 and is listed in PubChem as CID 71587328 (also called Copper tripeptide-1 or prezatide copper). The uncomplexed GHK tripeptide has a separate CAS number, 49557-75-7, and PubChem CID 73587.
How is the identity of a GHK-Cu batch confirmed?
Identity is confirmed by liquid chromatography-mass spectrometry (LC-MS) or high-resolution mass spectrometry (HRMS), which matches the observed mass and copper isotope pattern to the expected value, while HPLC quantifies purity. At livvmore, each batch is tested at the USC Alfred E. Mann Multi-Omics Mass Spectrometry Core and the results are published as a per-batch Certificate of Analysis.
How can you tell GHK-Cu apart from the free GHK peptide?
The two differ in mass and colour. Free GHK is an off-white to white powder with a molecular weight of 340.38 g/mol, whereas the copper complex is a blue to blue-purple solid of roughly 403 g/mol whose aqueous solutions appear blue. A mass-spectrometry reading and the CAS number on the Certificate of Analysis (49557-75-7 for the free peptide versus 89030-95-5 for the complex) confirm which species is present.