What it is
AOD-9604 is a short peptide corresponding to residues 176 to 191 of growth hormone — a sixteen-residue stretch from the C-terminal region of a much larger protein — with a tyrosine residue added at the N-terminus that is not present in the parent sequence.
The added tyrosine is the distinguishing feature. A preparation of the plain 176-191 fragment is a different material, and the two differ by the mass of one tyrosine, about 163 units.
| Property | Value | Where it is confirmed |
|---|---|---|
| Parent region | Growth hormone residues 176-191 | Published literature |
| Modification | N-terminal tyrosine added | Synthesis record |
| Approximate mass | near 1,817 g/mol | Certificate of analysis |
| Structure | Contains a disulfide bond | Structural characterisation |
| Physical form supplied | Lyophilized solid | Label and batch record |
The disulfide, and why it matters more than the length
This sequence contains two cysteine residues, and in the finished compound they are joined by a disulfide bond, closing part of the chain into a loop. That single bond does more to determine the analytical picture than the chain length does.
- Forming a disulfide removes two hydrogens. The oxidised, bonded form weighs about 2 units less than the reduced, open form. That is a small difference but a resolvable one, and it is the check that the bond actually formed.
- Free cysteines dimerise. Material whose cysteines did not pair internally can pair with another molecule instead, producing a species of roughly double the mass. Dimers are a characteristic impurity for any cysteine-containing peptide and are readily visible on a chromatogram.
- Cysteine is oxidation-prone in other ways too. Beyond the intended bond, further oxidation of sulfur is possible, which is a storage consideration rather than a synthesis one.
Compare this with Melanotan II, where the ring is a lactam and closing it releases water for an 18-unit difference. Same structural idea — a closed loop — two different chemistries and two different numbers to look for.
What a report should establish
Three things, in order: that the added tyrosine is present, which the mass or the named reference standard confirms; that the disulfide is formed rather than the chain left reduced; and that dimeric material is accounted for in the integration rather than excluded silently. See how to read an HPLC chromatogram on why the areas should total 100.
Storage of the lyophilized solid
Supplied as a freeze-dried solid, governed by temperature and moisture. The cysteine content makes an intact seal more important here than for a sequence with no sulfur — atmospheric oxygen plus adsorbed water is the combination that drives both further oxidation and dimer formation.
Stability is a documented property rather than an assumed one: a laboratory establishes it by holding material under defined conditions and re-analysing at intervals. Where a retest date is stated, the question worth asking is what data supports it. See storing lyophilized research materials.
Scope of this documentation
This page concerns material identification and analytical documentation for laboratory research. It does not recommend personal, human, clinical, therapeutic or veterinary applications. Published research findings do not establish the properties of Arctic stock; use the applicable lot record and its stated methods and limitations.
Related documentation
Material on this site
The documentation this article describes is published per lot for the listings below. Match the lot number on a vial label to its record before relying on it.
- Research materials catalog — current listings with batch status
- Batch COA library — every currently published report with its verification link