AHK-Cu

AHK-Cu is the copper(II) complex of the tripeptide L-alanyl-L-histidyl-L-lysine, and it is the closest structural sibling of the copper tripeptide GHK-Cu. PubChem lists the complex as CID 168431292 under CAS 682809-81-0, depicted as the monohydrochloride at C15H24ClCuN6O4 and 451.39 g/mol, while the free tripeptide appears as CID 7408502 under CAS 126828-32-8 at C15H26N6O4 and 354.41 g/mol. The chain is three residues long, with no cysteine and no disulfide bond. Its histidine sits at position 2, and the lysine side-chain amine at position 3 stays free and protonated at neutral pH.

The chemical difference from GHK-Cu is a single methyl group at the N-terminus: alanine in place of glycine. That one CH2 unit separates the free ligands by 14 mass units, 354.41 g/mol against 340.38 g/mol, and introduces an L-stereocentre at residue 1 that glycine does not have. Because the N-terminal residue is part of the copper donor set, the substitution sits inside the coordination sphere rather than at a distance from it. Material is supplied here as a raw cosmetic-ingredient research solid, for research use only and not for human or veterinary use.

The lineage runs through GHK, isolated from human plasma in 1973 and since taken as the reference copper-binding tripeptide. AHK is the analogue made by substituting residue 1.

Three lines of work are relevant. Conato and colleagues measured copper complex formation equilibria for GHK and analogues by potentiometry, calorimetry, UV-visible spectrophotometry, circular dichroism and electron paramagnetic resonance, concluding that complex formation is driven by the first residue while the position-2 histidine plays no specific part (PubMed 11325542). Gonzalez and colleagues reviewed the N-terminal Xaa-His and Xaa-Zzz-His copper motifs these tripeptides belong to (PubMed 29336493). Jung and colleagues examined a vitamin C-conjugated AHK derivative in mouse C2C12 cells (PubMed 29567599).

The evidence base for AHK-Cu specifically is thin. Most coordination data here were measured on GHK, so applying them to AHK is an inference from a shared motif. Every reference was checked against PubMed retraction records; none carries a retraction notice.

The chemistry described in the literature is copper(II) coordination by an N-terminal Xaa-His motif. The terminal amine, the deprotonated backbone amide between residues 1 and 2, and the imidazole nitrogen of histidine-2 supply a three-nitrogen donor set, leaving a fourth equatorial site open to water or an incoming ligand, which is why ternary complexes are reported here (PubMed 29336493). X-ray and solution structures of the copper GHK complex describe the geometry of the glycine parent (PubMed 21780203).

The distinction worth holding onto is against GHK-Cu. The equilibrium work attributes complex formation to the first residue rather than the histidine (PubMed 11325542), so a position-1 change is the substitution expected to move stability constants and speciation. The added methyl also puts steric bulk and a chiral centre next to the amine donor.

A methodology caveat applies. These constants come from measurements in defined buffers, where pH and the ligand-to-metal ratio decide which species dominates, so a figure belongs to its conditions.

Sealed solid AHK-Cu is stored cool and dry, shielded from light, in the unopened container, with -20°C conventional for long-term holding. No duration is asserted here: the stability window is on the batch Certificate of Analysis.

Peptide solids are hygroscopic, meaning they take up atmospheric moisture, so a container reaches ambient temperature before opening. Freeze-thaw cycling is avoided. Copper complexes are redox-active, and reducing agents such as ascorbate change the metal’s oxidation state.

Reconstitution is the term for returning a solid compound to solution; this page defines it and gives no procedure. AHK-Cu sits in the aqueous solubility class, as a short, charged peptide complex.

Two handling points are specific to copper peptides. Speciation is pH-dependent, so one material gives different dominant species across a buffer range. Buffer components such as phosphate, Tris and EDTA compete for copper and can strip or exchange the metal. Preparation parameters belong to the cited methodology and lot COA.

Identity and purity run on two axes: the peptide by reverse-phase high-performance liquid chromatography and mass spectrometry, with a free ligand mass consistent with 354.41 g/mol, and the metal by elemental analysis such as ICP-MS. Verified purity is documented per lot on the COA.

Two checks matter more than usual. The COA states which form is supplied, complex or free tripeptide, since the two are different materials. Copper content and salt form are read alongside the fill weight, because metal and counter-ion sit inside a stated raw material weight.

AHK-Cu is catalogued with tripeptides and cosmetic-ingredient research peptides.

• GHK-Cu.
  The glycine parent of this molecule and its direct comparator.
• Cartalax.
  Another alanine-initiated tripeptide, Ala-Glu-Asp, with no histidine and no metal centre.
• SNAP-8.
  An acetylated octapeptide, also cosmetic-ingredient research material.
• Glutathione.
  A tripeptide whose metal chemistry runs through a thiol rather than an imidazole.

Conato C, Gavioli R, Guerrini R, et al. (2001). Copper complexes of glycyl-histidyl-lysine and two of its synthetic analogues: chemical behaviour and biological activity. Biochim Biophys Acta.
PubMed 11325542

Hureau C, Eury H, Guillot R, et al. (2011). X-ray and solution structures of Cu(II) GHK and Cu(II) DAHK complexes: influence on their redox properties. Chemistry.
PubMed 21780203

Gonzalez P, Bossak K, Stefaniak E, et al. (2018). N-Terminal Cu-Binding Motifs (Xxx-Zzz-His, Xxx-His) and Their Derivatives: Chemistry, Biology and Medicinal Applications. Chemistry.
PubMed 29336493

Jung JI, Park KY, Lee Y, et al. (2018). Vitamin C-linker-conjugated tripeptide AHK stimulates BMP-2-induced osteogenic differentiation of mouse myoblast C2C12 cells. Differentiation.
PubMed 29567599

Peptides.com lists one AHK-Cu research product, a 1g raw material listing from Real Peptides, filed under the Raw Material product type rather than vials, capsules or sprays. The 1g figure is a product specification. AHK-Cu is new to the catalogue with no chemical information page, so identity figures come from PubChem. Each lot ships with a published COA.

• Browse all AHK-Cu research products

• Real Peptides AHK-Cu (Raw Cosmetic), 1g raw material

These products are sold for Research Use Only and are not intended for human consumption.