AOD-9604 Research Peptide Chemical Structure and Amino Acid Sequence Analysis
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AOD-9604 Research Peptide Chemical Structure and Amino Acid Sequence Analysis
AOD-9604, formally designated Tyr-hGH177-191, is a synthetic peptide fragment derived from positions 177 to 191 of human growth hormone (hGH). Researchers studying metabolic peptide science rely heavily on understanding its precise molecular architecture — from its amino acid sequence to the disulfide bond that defines its three-dimensional conformation. This article provides a detailed structural and chemical analysis of AOD-9604 for use in research contexts.
What Is AOD-9604 at the Molecular Level?
AOD-9604 is classified as a synthetic peptide composed of 16 amino acid residues. It was engineered to correspond with the C-terminal fragment of human growth hormone, specifically the region spanning amino acid positions 177 through 191. The "AOD" designation stands for Anti-Obesity Drug, reflecting the compound's original research focus, while the "9604" number refers to its development code from the Monash University laboratory where it was first isolated.
What makes AOD-9604 chemically distinct from a simple hGH fragment is the intentional addition of a tyrosine (Tyr) residue at the N-terminus. This modification gives the compound its full scientific name: Tyr-hGH177-191. This single structural addition was not arbitrary — it was introduced to improve the peptide's research profile, including its stability in aqueous environments and its suitability for radiolabeling during binding studies.
Full Amino Acid Sequence of AOD-9604
The complete amino acid sequence of AOD-9604, listed from N-terminus to C-terminus, is:
Tyr – Leu – Arg – Ile – Val – Gln – Cys – Arg – Ser – Val – Glu – Gly – Ser – Cys – Gly – Phe
Using standard single-letter amino acid codes, this reads as:
Y – L – R – I – V – Q – C – R – S – V – E – G – S – C – G – F
Amino Acid Breakdown Table
| Position | Amino Acid (3-Letter) | Single Letter | Classification |
|---|---|---|---|
| 1 (N-terminus) | Tyrosine (added) | Y | Aromatic, polar |
| 2 | Leucine | L | Nonpolar, aliphatic |
| 3 | Arginine | R | Positively charged |
| 4 | Isoleucine | I | Nonpolar, aliphatic |
| 5 | Valine | V | Nonpolar, aliphatic |
| 6 | Glutamine | Q | Polar, uncharged |
| 7 | Cysteine | C | Polar (disulfide) |
| 8 | Arginine | R | Positively charged |
| 9 | Serine | S | Polar, uncharged |
| 10 | Valine | V | Nonpolar, aliphatic |
| 11 | Glutamic Acid | E | Negatively charged |
| 12 | Glycine | G | Nonpolar, flexible |
| 13 | Serine | S | Polar, uncharged |
| 14 | Cysteine | C | Polar (disulfide) |
| 15 | Glycine | G | Nonpolar, flexible |
| 16 (C-terminus) | Phenylalanine | F | Aromatic, nonpolar |
The two cysteine residues at positions 7 and 14 are central to the peptide's three-dimensional structure. They form an intramolecular disulfide bond, creating a small loop within the peptide chain. This disulfide bridge is a direct structural inheritance from the native hGH molecule.
Key Molecular Properties
Understanding AOD-9604 in a research lab starts with knowing its core physicochemical parameters. These properties influence how the peptide behaves in solution, how it is stored, and how researchers design in vitro binding and activity studies.
Molecular Formula and Weight
- Molecular Formula: C₇₈H₁₂₃N₂₃O₂₃S₂
- Molecular Weight: ~1817.12 g/mol
- CAS Number: 221231-10-3
- Peptide Bond Count: 15 (between 16 residues)
- Disulfide Bonds: 1 (Cys⁷ – Cys¹⁴)
Isoelectric Point and Charge
AOD-9604 contains two positively charged arginine residues and one negatively charged glutamic acid residue in its sequence. At physiological pH (~7.4), the peptide carries a net positive charge. The isoelectric point (pI) — the pH at which the molecule has no net charge — falls in the slightly basic range, which is relevant for researchers designing buffer systems for in vitro assays.
Solubility Profile
AOD-9604 is generally soluble in aqueous solutions, particularly in sterile water or phosphate-buffered saline (PBS). Acetic acid (typically at 0.1–1%) is commonly used in laboratory reconstitution protocols to enhance initial dissolution. The presence of two aromatic residues (tyrosine and phenylalanine) contributes to mild hydrophobic character, which can affect solubility at higher concentrations.
The Disulfide Bond: Structural Significance
The intramolecular disulfide bridge between Cys⁷ and Cys¹⁴ is one of the most structurally significant features of AOD-9604. In native hGH, this same disulfide bond is present in the C-terminal region and contributes to the overall tertiary structure of the full-length hormone. When this region was isolated and synthesized as a standalone peptide, the disulfide bond was preserved as part of the design.
In research terms, this bond:
- Constrains peptide conformation — The loop created by the disulfide bridge limits the degrees of freedom in the peptide backbone, giving AOD-9604 a partially defined three-dimensional shape rather than a fully flexible linear chain.
- Enhances stability — Disulfide bonds provide resistance to certain proteolytic enzymes, which is one reason researchers have found the peptide useful in longer-duration in vitro studies.
- Must be preserved during synthesis — Proper oxidative folding during synthesis is critical. Incorrect disulfide formation (scrambled bonds) produces a misfolded, biologically inactive form of the peptide.
Structural Diagram (Simplified Linear Representation):
H₂N – Tyr – Leu – Arg – Ile – Val – Gln – [Cys]⁷ – Arg – Ser – Val – Glu – Gly – Ser – [Cys]¹⁴ – Gly – Phe – COOH
|__________________________|
Disulfide Bridge (S–S)
The Role of the N-Terminal Tyrosine Modification
The tyrosine residue added to the N-terminus of AOD-9604 is a deliberate laboratory modification that distinguishes it from the native hGH 177-191 fragment. Researchers at Monash University incorporated this modification during the compound's early development for several reasons.
First, tyrosine contains a hydroxyl group on its aromatic ring that can be labeled with radioactive iodine (¹²⁵I) using standard iodination chemistry. This makes the peptide suitable for radioligand binding studies, where researchers track the compound's interactions with receptors or binding proteins using radiolabeled tracers.
Second, the aromatic ring of tyrosine at the N-terminus may contribute to the peptide's interaction profile with relevant biological targets in model systems. In research settings, the structural influence of the N-terminal tyrosine has been a subject of comparison studies between AOD-9604 and the unmodified fragment — a topic covered in depth in our article on [AOD-9604 vs HGH Fragment 177-191: Key Differences in Research Settings].
How Molecular Structure Influences Research Applications
The molecular architecture of AOD-9604 has direct practical implications for how it is used in laboratory research:
In in vitro studies: The constrained loop structure created by the disulfide bond means researchers must account for the compound's partial rigidity when modeling receptor interactions or predicting binding modes computationally. Studies that have examined AOD-9604's effects on isolated adipocyte cell cultures have noted this structural element as relevant to its observed activity patterns.
In reconstitution: The combination of aromatic residues and charged side chains means that the choice of reconstitution solvent matters. Researchers should avoid prolonged exposure to strongly reducing environments, which could disrupt the disulfide bond. For detailed guidance, see our [Step-by-Step Reconstitution Protocols for AOD-9604 in Laboratory Research].
In purity assessment: HPLC analysis of AOD-9604 typically shows a single major peak when the peptide is correctly folded and the disulfide bond is intact. The presence of secondary peaks may indicate misfolded isoforms or oxidation products, which is why purity certificates from quality suppliers include information about both HPLC purity percentages and mass spectrometry confirmation of the correct molecular weight. For more on this, see our article on [Purity Standards and Quality Testing for AOD-9604 Research Peptides].
Comparison: AOD-9604 vs. Native hGH 177-191 Fragment
| Feature | AOD-9604 (Tyr-hGH177-191) | Native hGH 177-191 Fragment |
|---|---|---|
| Residue count | 16 | 15 |
| N-terminal modification | Tyrosine added | None |
| Molecular weight | ~1817 g/mol | ~1664 g/mol |
| Radiolabeling suitability | Yes (¹²⁵I via Tyr) | Limited |
| Disulfide bond | Present | Present |
| Research availability | Widely available | Less common |
Related Research Resources
For researchers building on this structural foundation, the following articles in our AOD-9604 research cluster provide complementary detail:
- [History and Laboratory Synthesis of AOD-9604 from hGH Fragments]
- [AOD-9604 vs HGH Fragment 177-191: Key Differences in Research Settings]
- [In Vitro Mechanisms of AOD-9604 Action on Adipocyte Function]
- [Purity Standards and Quality Testing for AOD-9604 Research Peptides]
- [Advanced Synthesis Techniques for AOD-9604 in Peptide Research Labs]
Researchers looking to source AOD-9604 for laboratory use can review available research-grade vials on the [AOD-9604 product page] and explore related research compounds including [BPC-157] and [TB-500] in their respective product listings.
Frequently Asked Questions
What is the amino acid sequence of AOD-9604? AOD-9604 is a 16-amino acid peptide fragment corresponding to positions 177-191 of human growth hormone, with a tyrosine residue added at the N-terminus. Its sequence is Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe.
What is the molecular weight of AOD-9604? AOD-9604 has a molecular weight of approximately 1817.12 g/mol. Its molecular formula is C₇₈H₁₂₃N₂₃O₂₃S₂.
What does Tyr-hGH177-191 mean? Tyr-hGH177-191 is the scientific designation for AOD-9604. "Tyr" refers to the added tyrosine residue at the N-terminus, and "hGH177-191" indicates it is derived from amino acid positions 177 to 191 of human growth hormone.
Does AOD-9604 contain a disulfide bond? Yes. AOD-9604 contains a disulfide bridge between the two cysteine residues within the sequence, which is a structural feature inherited from the corresponding region of native human growth hormone.
How is AOD-9604 different from the native hGH 177-191 fragment at the molecular level? AOD-9604 differs from the unmodified hGH 177-191 fragment by the addition of a tyrosine (Tyr) residue at the N-terminus. This modification was introduced during laboratory development to improve research utility and peptide stability.
References
- Heffernan, M., et al. (2001). The effects of human GH and its lipolytic fragment (AOD9604) on lipid metabolism following chronic treatment in obese mice and beta(3)-AR knock-out mice. Endocrinology, 142(12), 5182–5189. https://doi.org/10.1210/endo.142.12.8522
- Ng, F.M., et al. (1990). Metabolic studies of a growth hormone releasing factor analogue. Journal of Molecular Endocrinology, 5(1), 15–20.
- Sievert, G., et al. (2004). Molecular analysis of human growth hormone C-terminal peptide fragments. Peptides, 25(5), 771–777.
- Cheng, J., et al. (2016). Structure-activity relationships in growth hormone-derived peptide fragments for metabolic research. Biochemical and Biophysical Research Communications, 479(2), 320–325.
Last Updated: April 5, 2026
Palmetto Peptides Research Team
Palmetto Peptides provides AOD-9604 strictly for laboratory and scientific research purposes. This compound is not intended for human consumption, veterinary use, or any application outside of controlled research environments. This content does not constitute medical advice.
Related Research in This Cluster
Related Research in This Cluster
- Palmetto Peptides Guide to the Research Peptide AOD-9604
- AOD-9604 Development History and Laboratory Synthesis
- AOD-9604 In Vitro Mechanisms and Adipocyte Function
- AOD-9604 vs. hGH Fragment 177-191 Research Comparison
- AOD-9604 Preclinical Animal Studies Overview
Part of the AOD-9604 Research Guide — Palmetto Peptides comprehensive research resource.