AHK-Cu

1 Identity

Metal-peptide coordination complex — copper(II) tripeptide. Pal-AHK is a different palmitoylated article and is not a synonym.

Sequence

H-Ala-His-Lys-OH (AHK) as the ligand, coordinated to one copper(II) ion. Three residues, all L-proteinogenic, free-acid C-terminus and free N-terminal amine on the uncomplexed ligand. The article of commerce is the complex and not the free tripeptide, and the two are different substances with different colors, different masses and different specifications. Copper coordination in this ligand class is through the N-terminal alpha-amine, the deprotonated peptide-bond nitrogen and the histidine imidazole; the coordination geometry is a property of the complex and is not established for this specific ligand by any source in the file, so it is described and not asserted. Achiral method not required: all three residues are L and no D-residue is present.

Molecular formula

C15H24CuN6O4 for the 1:1 copper(II) complex of the free-acid tripeptide, with two ligand protons displaced by the metal. C15H26N6O4 for the uncomplexed tripeptide AHK. Salt and hydrate forms are not declared by any seller located and are therefore not stated. The formula and both masses are derived structurally from the declared composition, the Ala-His-Lys copper complex, rather than carried from a primary registry entry, and no CAS number is stated as identity for this article because none has been verified against a primary registry.

Average mass

415.941 Da for the 1:1 complex C15H24CuN6O4. 354.411 Da for the uncomplexed tripeptide C15H26N6O4. The two differ by 61.53 Da, which is copper less two hydrogens; a certificate reporting only 354 has characterized the ligand and not the product. The same coordination arithmetic one methylene down lands on an established number: GHK C14H24N6O4 at 340.384 plus copper less two hydrogens gives C14H22CuN6O4 at 401.914, and 401.9 is the accepted value for GHK-Cu, so the arithmetic that gives 415.941 for this article is the arithmetic that reproduces the known figure for its nearest neighbor.

Monoisotopic mass

415.1155 Da for the 1:1 complex (63Cu). 354.2016 Da for the uncomplexed tripeptide. The isotope envelope is part of the identity and must be reported: copper is 63Cu at 69.15 percent and 65Cu at 30.85 percent, so a genuine copper complex shows an M+2 peak at roughly 45 percent of the monoisotopic peak height. That single-ion-series pattern is what distinguishes a true complex from a physical blend of free tripeptide and a copper salt, which passes ICP-MS for copper content and passes RP-HPLC for peptide purity and fails only on the isotope envelope. For that reason the envelope is a named mandatory release test on this article and not an incidental observation.

Salt / variant note

(1) the uncomplexed ligand, which is the commonest defect in this category: AHK free tripeptide, C15H26N6O4, 354.41 average / 354.2016 monoisotopic. A certificate whose only reported mass is 354 is a certificate for the peptide, not for the product, and the product is the complex. (2) the neighboring copper complex one methylene away: GHK-Cu, C14H22CuN6O4, 401.91 / 401.0999, and its free ligand GHK at C14H24N6O4, 340.38 / 340.1859. The gap from AHK-Cu to GHK-Cu is 14.03 Da, a single methylene, on molecules sold side by side in the same catalog — and GHK-Cu is the one with an FDA Category 1 entry and a real literature, which makes substitution in the wrong direction commercially attractive. The number reads in both directions: a mass reported at 415 to 416 is this article and not GHK-Cu. (3) the physical blend that passes every routine test: free AHK plus a copper salt, weighed to the right copper content. It passes ICP-MS for copper, passes RP-HPLC for peptide purity, and fails only the isotope-envelope test on the intact complex ion. Nothing else on a normal certificate sees it. (4) stoichiometry variants: a 2:1 ligand-to-copper bis-complex is a different article with a different mass and a different color, and exactly this failure is on record for the neighboring GHK-Cu article, where a reported 800.3 corresponds to the 2:1 prezatide bis-complex. The same class of error is available here and no seller located states a ratio. (5) salt and hydrate forms: acetate, chloride and hydrate forms all circulate undeclared in this category, and on that neighboring article a reported 462 without the words "acetate salt" on the same page means the supplier is quoting a salt mass against a free-complex specification. (6) Pal-AHK, the palmitoylated analog, is a separate article in the same catalog and is not a synonym for this one.

2 Class & testing panel

Form

Single article

Testing panel

P5 — panel definition

3 Primary sources & evidence

The index reports the design and provenance of the literature, not a conclusion about effect.

No compound-specific primary literature was located for this molecule under its own name. Cosmeceutical peptide reviews, Cosmetic Ingredient Review safety assessments and INCI-name searches return nothing for it, and the evidence grade for this article is F. No human trial of any member of this cosmetic-peptide group was located and no NCT number is quoted, because none was found; the position is that none has been located, which is not the same as a finding that none exists. No Cosmetic Ingredient Review Expert Panel assessment for this specific ingredient was located, while assessments for other peptide ingredients were, so the absence is specific to this ingredient. What exists in the vicinity belongs to other molecules and does not transfer: the GHK-Cu literature, itself graded D, the systematic review of over-the-counter topical antiaging agents at PMID 32882685, the human-skin penetration study at PMID 24754410 and the palmitoylation delivery work at PMID 25143811. The borrowing of GHK-Cu's literature and regulatory status by AHK-Cu, Pal-GHK and Pal-AHK is a category-wide pattern, and every adjacent citation on this record is labeled as belonging to a different molecule.

4 Storage & specification

Storage

Lyophilized or crystalline solid in a Type I amber glass container with a desiccant sachet and a tamper-evident closure, headspace nitrogen-flushed. Labeled: store at -20 degrees C plus or minus 5 degrees C, protect from light, keep desiccated, close immediately after weighing. The light protection is not boilerplate — copper(II) complexes of this class are photosensitive and the color is part of the specification, so a change in appearance is a stability signal and not a cosmetic observation. The article is incompatible with chelators and with strong reducing agents, which is stated on the label because a buyer who introduces either has destroyed the article rather than diluted it, and pH extremes decompose the complex. Reconstituted aqueous solution is used promptly and is not stored. Ships ambient with a labeled cumulative excursion allowance of 120 hours at or below 30 degrees C on the shipping record.

Shelf life

Provisional 24 months at -20 degrees C plus or minus 5 degrees C from the date of QA release, stated as provisional pending the company's own stability data. Extension only on real-time data at 12, 18, 24 and 36 months, with copper content, the uncomplexed-ligand impurity, appearance and color, the UV-visible d-d absorption maximum and Karl Fischer water as the stability-indicating attributes. Appearance is a real stability-indicating attribute for this article rather than a housekeeping observation, because loss of the complex to free ligand and a copper salt is visible before it is chromatographic. No published compound-specific stability data exist for this molecule, and none exist for any member of its group, so nothing here rests on a supplier assertion. Printed retest date on every unit and first-expiry-first-out enforced against it.