Description
PrymaLab · Research Use Only
AOD9604 5mg
Not the 176-191 fragment · and the difference is one residue
AOD9604 peptide is sold across this market as hGH fragment 176-191. It is a different molecule. The difference is one residue at the amino terminus, and that residue was added for a reason nobody selling it usually mentions.
Specification Table
| Property | Value |
|---|---|
| Compound | AOD9604 |
| Accurate description | Tyr-hGH(177-191). A tyrosine added ahead of residues 177 to 191 of human growth hormone |
| Common inaccurate description | hGH fragment 176-191, which is a related but different molecule |
| Residue count | 16 |
| Sequence | Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe |
| Molecular weight, calculated | Approximately 1,815.1 g/mol |
| Molecular formula | C78H123N23O23S2 |
| CAS | 221231-10-3 |
| Cysteine residues | Two, at positions 7 and 14 of this construct |
| Disulfide | An intramolecular bridge between those two cysteines, required for the loop geometry |
| Corresponding residues in the parent hormone | Cys182 and Cys189 of human growth hormone |
| Why the tyrosine was added | To provide a handle for radioiodination during early pharmacokinetic work |
| Regulatory status | No approved human or veterinary formulation in any jurisdiction |
| Appearance | White lyophilized powder |
| Storage, lyophilized | 2-8°C short term, -20°C for extended storage, protected from light and moisture |
Why Is AOD9604 Peptide Not hGH Fragment 176-191?
Two names circulate for what buyers assume is one article, and they describe two molecules.
The parent hormone is 191 residues. A region near its carboxy terminus was identified in the early 1990s as carrying lipolytic activity independent of the rest of the protein.
The fragment corresponding to residues 176 to 191 of that hormone is one molecule, 16 residues long, beginning with the leucine at position 176.
AOD9604 peptide is a different construct. It comprises residues 177 to 191, which is 15 residues, with a tyrosine attached ahead of them.
Both total 16 residues. The sequences are not the same.
The first residue of aod9604 peptide is a tyrosine that does not appear at that position in the parent hormone at all. The first residue of the true 176-191 fragment is a leucine that does appear there.
So they differ at position one. Otherwise identical, which makes them close analogues rather than one compound.
The mass difference follows from that substitution and is large enough for any instrument to resolve, which means the conflation survives only where nobody checks.
Verifying it takes one comparison: stated sequence against calculated mass.
What Was the Tyrosine For?
The extra residue on aod9604 peptide was not a pharmacological improvement and was not intended as one, which is worth stating because vendor copy often implies otherwise.
Tyrosine is what radiochemists label. The phenol ring accepts iodination readily under mild conditions, which no other common residue does as cleanly.
A peptide carrying neither tyrosine nor histidine is difficult to label at all, and the true 176-191 fragment carries neither.
Adding a tyrosine at the amino terminus gave the early investigators a labelling handle, which is what pharmacokinetic tracing required at the time.
It was retained afterwards because it turned out to confer a modest stability advantage rather than because it improved activity.
A residue at the amino terminus obstructs aminopeptidase access in the same way any added group does, so the construct survives marginally longer than the unmodified fragment.
That is a small effect and an honest description of it. The tyrosine is a legacy of an analytical technique that became a minor structural feature.
The numbering consequence is the part that causes the confusion. Adding a residue ahead of position 177 makes the construct 16 residues long, the same length as the 176-191 fragment, which invites the assumption that they are the same thing.
Why Does the Disulfide Matter?
The two cysteines in aod9604 peptide form a bridge, and that bridge is the reason the molecule has any defined shape at all.
In the parent hormone the corresponding residues, Cys182 and Cys189, close a small loop near the carboxy terminus.
The fragment reproduces that loop. Without the disulfide it is a linear 16-residue chain with no fixed conformation, and the published activity is attributed to the loop geometry rather than to the sequence alone.
So reduced aod9604 peptide is not a slightly degraded version of the article. It is a structurally different molecule.
The analytical problem is that reduction changes mass by only two daltons on a 1,815 dalton molecule, which is roughly one part in a thousand.
Nominal-resolution mass spectrometry will not see that reliably. High-resolution instruments will, and most certificates do not state which was used.
Chromatography is the more practical check, since the reduced form is measurably less compact and elutes differently on a reverse-phase gradient.
A free thiol assay answers it directly, because intact material has no free thiol and reduced material has two.
Any of those three closes the question and a stated purity percentage on its own does not, which is why the trace matters more than the number here.
Scrambling is a related risk in preparations containing more than one disulfide and does not apply to this one, since two cysteines admit only one pairing.
A short practical note on where reduction actually happens.
It is rarely the vial. Dry lyophilised material with an intact seal is stable, and the risk arrives with the diluent and with whatever the preparation is added to afterwards.
Checking a buffer recipe for reducing species before it meets aod9604 peptide is a thirty-second habit that heads off an unrecoverable problem.
What Should an AOD9604 Certificate Show?
An aod9604 peptide certificate carries seven fields, and the first distinguishes the article from its near neighbour.
The sequence written out in full, since the first residue settles the question: tyrosine identifies aod9604 peptide and leucine identifies the 176-191 fragment.
Observed mass against calculated mass, with the calculated figure stated. Approximately 1,815 is correct for aod9604 peptide.
Confirmation that the disulfide is formed, by whichever of the three methods the laboratory used, stated explicitly rather than implied.
The instrument resolution, since a two dalton difference on 1,815 daltons is not a nominal-resolution measurement.
Purity by reverse-phase HPLC with the chromatogram supplied, since the reduced form and any deletion sequences separate by retention more reliably than by mass.
Counterion identity together with net peptide content. Two arginines in this sequence means multiple counterions, and the resulting correction is not a rounding error.
Lot number and synthesis date.
A certificate that names the construct as Tyr-hGH(177-191) rather than as 176-191 is written by someone who knows which molecule they made, and that is a reasonable proxy for the rest of the document.
What Did the Published Work Measure?
The literature behind this construct is small, specific, and narrower than the way it is usually summarised.
The starting observation, from work in the early 1990s, was that a region near the carboxy terminus of the parent hormone carried lipolytic activity on its own.
That was measured in adipose tissue preparations, with glycerol release into the medium as the readout.
Glycerol release is a direct index of triglyceride hydrolysis and it is an in vitro endpoint. It says nothing by itself about what happens in a whole organism.
Rodent work followed, and later human evaluation was conducted with the construct.
Those studies measured defined metabolic endpoints across defined periods, and the published results are what they are rather than what secondary sources describe.
The useful discipline is to name the endpoint whenever the compound is discussed. An in vitro glycerol release result and a whole-animal metabolic measurement are different claims.
A safety assessment was also published, which is unusual for anything in this catalogue and gives an unusually good toxicological record for a research compound.
What the record does not contain is any approved formulation anywhere, and no regulator has cleared aod9604 peptide for any use in any jurisdiction.
Reading the four primary papers takes an afternoon and it is a better use of time than reading forty vendor summaries of them.
How Should the Vial Be Handled?
Standard peptide handling applies to aod9604 peptide, with one addition that follows from the disulfide.
Sealed dry powder is stable at 2 to 8 degrees Celsius briefly and at minus 20 for longer, with light and moisture both excluded.
Bring the vial to ambient temperature before breaking the seal, since the powder is hygroscopic and condensation on a cold cake adds water to every subsequent calculation.
Reconstitute down the wall with gentle swirling rather than shaking, which is the standard precaution against interface aggregation.
Keep reducing agents away from the preparation. Dithiothreitol, beta-mercaptoethanol and tris(2-carboxyethyl)phosphine all open the bridge. Buffer carried over from another procedure is the realistic route to that happening by accident.
That caution extends to cell culture components and to any preparation containing free thiol at working concentration, which is easy to overlook.
Aliquot on first reconstitution. Freeze-thaw cycling damages the peptide and can promote intermolecular exchange in disulfide-containing material.
Use low-binding consumables at working dilutions, since adsorption removes a measurable fraction of dilute peptide into ordinary plastics.
Record lot, net peptide content, diluent volume, date and whether the diluent contained any reducing species. That last field has no equivalent elsewhere in this range.
A final note on what to write down.
The diluent composition matters more here than for almost anything else in this catalogue, so it belongs in the record in full rather than as a name.
Bacteriostatic water and sterile water are different preparations, and a buffer described only as PBS may or may not carry the additives someone added to it last week.
Writing the actual composition takes one line and it is the line that makes a disulfide-dependent result reproducible.
The same applies to anything the preparation meets downstream, including culture medium and whatever was added to it.
A reducing species three steps away from the vial reaches the molecule just as effectively as one in the diluent.
Published Literature
Selected references on the lipolytic domain of the parent hormone and on this construct.
- Wu Z, Ng FM. Biochemistry and Molecular Biology International. 1993;30(1):187-196. PMID: 8358345
- Ng FM, Sun J, Sharma L, Libinaka R, Jiang WJ, Gianello R. Hormone Research. 2000;53(6):274-278. DOI: 10.1159/000053183
- Heffernan MA, Thorburn AW, Fam B, Summers R, Conway-Campbell B, Waters MJ, et al. International Journal of Obesity. 2001;25(10):1442-1449. DOI: 10.1038/sj.ijo.0801740
- Stier H, Vos E, Kenley D. Regulatory Toxicology and Pharmacology. 2013;66(3):317-324. DOI: 10.1016/j.yrtph.2013.05.008
Frequently Asked Questions
What is AOD9604?
A 16-residue synthetic construct comprising a tyrosine attached ahead of residues 177 to 191 of human growth hormone, calculated at approximately 1,815 daltons and carrying CAS 221231-10-3.
Is it the same as hGH fragment 176-191?
No. That fragment begins with the leucine at position 176 of the parent hormone. AOD9604 begins with an added tyrosine followed by residue 177, so the two differ at position one.
Why do they get confused?
Because both are 16 residues long. Adding one residue ahead of position 177 gives the same total length as the 176-191 fragment, which invites the assumption that they are the same article.
What was the tyrosine added for?
To provide a handle for radioiodination. Tyrosine accepts radioactive iodine readily under mild conditions, and the unmodified fragment carries neither tyrosine nor histidine.
Was it a pharmacological improvement?
Not by design. It was retained because it conferred a modest stability advantage, since a residue at the amino terminus obstructs aminopeptidase access, but that is a small effect.
Why does the disulfide matter?
Because it closes the loop that gives the molecule a defined shape. Without it the construct is a linear chain with no fixed conformation, and the published activity is attributed to the loop geometry.
Can mass spectrometry confirm the disulfide?
Only at high resolution. Reduction changes mass by two daltons on 1,815, roughly one part in a thousand, which a nominal-resolution instrument will not see reliably.
What are the alternatives?
Chromatography, since the reduced form is less compact and elutes differently, or a free thiol assay, since intact material has no free thiol and reduced material has two.
Is disulfide scrambling a risk?
No. Scrambling requires more than one possible pairing and this molecule has two cysteines, which admit only one. Reduction is the risk here rather than rearrangement.
What should be kept away from the preparation?
Reducing agents. Dithiothreitol, beta-mercaptoethanol and tris(2-carboxyethyl)phosphine all open the bridge, and buffer carried over from another procedure is the realistic route to that happening.
How large is the counterion correction?
Not small. The sequence carries two arginines, so it holds multiple counterions, and net peptide content should be read from the certificate rather than assumed from the nominal fill.
What signals a well-written certificate here?
Naming the construct as Tyr-hGH(177-191) rather than as 176-191. A supplier who states it that way knows which molecule they made.
Compliance Statement
AOD9604 is sold exclusively for laboratory research use. It is not a drug, food, or cosmetic product, and it is not a dietary product of any kind. It is not approved by the FDA or any comparable authority for human or veterinary use, it is frequently sold under the name hGH fragment 176-191 which describes a different molecule, published activity is attributed to a disulfide-constrained loop geometry that a reduced preparation does not have, and no compound in this range is offered for any human or veterinary purpose. This product is not intended to diagnose, treat, cure, or prevent any disease. It must not be given to humans or animals. Purchase is restricted to qualified researchers and institutions operating within applicable laws. All handling is the responsibility of the purchasing laboratory.
Other formats of AOD9604
AOD9604 is also stocked as AOD9604 10mg Nasal Spray, AOD-9604 6mg preloaded 3ml pen and HGH Fragment 176-191 10mg preloaded 3ml pen. Each listing states its own quantity and concentration, and the pen and vial comparison explains what changes between formats.
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