AHK-Cu (Copper Tripeptide-3)

Structure and copper coordination

AHK is a three-residue peptide whose histidine imidazole and terminal amine provide the nitrogen donors that bind copper(II), with the lysine side chain contributing positive charge that influences solubility and surface interactions. The chemistry is closely analogous to GHK-Cu, and the same caveats apply: the complex is an equilibrium species, so pH, competing chelators and the copper-to-peptide ratio all determine how much of the copper is actually peptide-bound in a given preparation.

What the follicle literature has examined

Published work on AHK-Cu is largely cell-culture based and has looked at dermal papilla cells — the mesenchymal population that governs follicular cycling. Reported endpoints include cell viability and proliferation in culture, expression of vascular endothelial growth factor, and morphological measures in follicle organ culture. These are exploratory findings in model systems; they do not establish an effect in any organism, and results vary with concentration, culture conditions and copper speciation.

Comparison with GHK-Cu

• Both are copper-binding tripeptides with a His-Lys core and comparable coordination chemistry
• GHK-Cu has a far larger literature, weighted toward wound repair, extracellular matrix remodelling and dermal fibroblasts
• AHK-Cu appears more often in follicular and hair-focused investigations
• The two are frequently compared side by side in the same assay to isolate the effect of the N-terminal residue

Formulation and stability considerations

Copper peptides are sensitive to formulation context. Chelating excipients, high ionic strength and acidic pH can strip copper from the peptide, while oxidising conditions can degrade the peptide backbone. Researchers working on topical vehicles commonly verify complex integrity spectrophotometrically, since the visible absorbance band associated with copper coordination provides a convenient readout of whether the complex has survived processing.

Assay design notes

Because free copper ions are themselves biologically active, well-designed studies include a copper-salt control at matched copper concentration alongside the free peptide, so that any observed difference can be attributed to the complex rather than to copper alone.

Store sealed vials at −20 °C, protected from light and moisture, and allow a vial to reach room temperature before opening so condensation does not enter the powder. Reconstitute with bacteriostatic or sterile water directed down the vial wall rather than onto the cake, swirling gently instead of shaking — copper peptides tolerate agitation poorly. Keep reconstituted solution refrigerated at 2–8 °C, protected from light, and record the concentration and date on the vial. Avoid contact with metal chelators and strongly acidic buffers, which dissociate the complex. Handle under your laboratory's chemical hygiene plan; research use only.