AHK-Cu (Copper Tripeptide)

AHK-Cu (Ala-His-Lys copper complex) is a synthetic copper-chelating tripeptide structurally related to GHK-Cu (Gly-His-Lys copper complex), sharing the ATCUN (Amino Terminal Copper and Nickel) binding motif that coordinates Cu(II) in a square planar geometry through the N-terminal amine, deprotonated amide nitrogen, and histidine imidazole nitrogen. AHK-Cu provides a research comparator to GHK-Cu for studying the role of the N-terminal amino acid in copper coordination chemistry and biological activity.

The ATCUN motif requires a free N-terminal amino group, any amino acid at position 2, and histidine at position 3. Both GHK (Gly-His-Lys) and AHK (Ala-His-Lys) satisfy this requirement, with the key structural difference being the N-terminal residue: glycine (no side chain, smallest amino acid) in GHK versus alanine (methyl side chain) in AHK. This single methyl group difference affects: the geometry of the N-terminal amine coordination site, the conformational flexibility of the tripeptide backbone, and potentially the precise copper coordination geometry and redox properties.

Copper coordination chemistry research comparing AHK-Cu with GHK-Cu uses: EPR (electron paramagnetic resonance) spectroscopy to characterise Cu(II) coordination geometry; UV-visible spectroscopy of the d-d transition band (absorption around 600-700 nm) to assess coordination environment differences; cyclic voltammetry to compare Cu(II)/Cu(I) redox potentials; and stability constant determination by competitive chelation assays.

Biological research comparing AHK-Cu and GHK-Cu in parallel fibroblast assays (collagen synthesis, MMP expression, migration) allows attribution of biological effects to the copper coordination chemistry shared between both compounds versus the specific amino acid sequence contributions unique to each peptide.

Like GHK-Cu, AHK-Cu appears blue-green in solution due to Cu(II) d-d electronic transitions. Correctly coordinated AHK-Cu should show characteristic square planar Cu(II) EPR spectrum. Avoid reducing agents throughout all experiments.

MW: approximately 416 Da (copper complex). Reconstitute in bacteriostatic water at 1mg/mL. Avoid DTT, BME, TCEP. Store lyophilised at -20°C. For laboratory and analytical research purposes only.

AHK-Cu copper coordination chemistry research protocols: EPR spectroscopy is the definitive technique for characterising Cu(II) coordination in ATCUN complexes. At X-band (9.5 GHz), square planar Cu(II) in ATCUN coordination shows a characteristic axial spectrum with g∥ > g⊥ > 2.00 and four-line hyperfine splitting in the g∥ region from 63Cu/65Cu nuclear spin (I=3/2). The A∥ hyperfine coupling constant (typically 170-200 × 10-4 cm-1 for ATCUN complexes) reports sensitively on the equatorial donor set. Comparing A∥ values for GHK-Cu versus AHK-Cu quantifies how the N-terminal residue change (Gly→Ala) affects the Cu(II) coordination geometry.

UV-visible spectroscopy comparison: dissolve GHK-Cu and AHK-Cu at equivalent copper concentrations (typically 1-5mM for UV-vis) in 50mM HEPES pH 7.4. Scan from 400-900nm. The d-d transition band position (lambda-max) and extinction coefficient for each compound reflects the Cu(II) coordination environment. A shift in lambda-max between GHK-Cu and AHK-Cu would indicate a difference in ligand field strength attributable to the Gly versus Ala N-terminal residue. For biological comparative research, run GHK-Cu and AHK-Cu at matched copper concentrations in fibroblast collagen synthesis assays, wound healing scratch assays, and MMP expression assays. Any difference in biological activity between GHK-Cu and AHK-Cu at matched copper concentrations is attributable to the N-terminal amino acid identity. Both compounds will appear blue-green in solution — confirm copper coordination by UV-vis before biological experiments. Avoid all reducing agents. MW: approximately 416 Da. Store lyophilised at -20°C. For laboratory and analytical research purposes only.