HGH Fragment 176-191
C-terminal fragment of human growth hormone (176–191)
Overview
HGH Fragment 176-191 is the unmodified 16-residue C-terminal segment of human growth hormone, lifted directly from positions 176 through 191 of the 191-residue native HGH protein. The fragment preserves C-terminal-region lipolytic activity while leaving behind the central-region anabolic and IGF-1-stimulating effects that are characteristic of the full-length GH molecule. The critical distinction at the procurement-file level is between this SKU, which is the unmodified native sequence, and AOD9604, which appends an N-terminal tyrosine residue originally introduced to support iodination tracking; the two molecules are chemically distinct and produce different ESI-MS signatures, despite a confusingly similar catalogue naming convention across the broader peptide market. Vialdyne releases HGH Fragment 176-191 against a ≥99.0% main-peak HPLC specification, with the full identity stack documented on every released-batch COA. The relevant values: CAS number 66004-57-7, molecular formula C78H123N23O22S2, average MW 1817.1 g/mol, and primary sequence YLRIVQCRSVEGSCGF. The sequence carries two cysteine residues at internal positions 7 and 13, which under oxidative storage conditions can pair into an intramolecular disulfide bridge. This disulfide-bridging behaviour is the most common identity-confirmation concern at receiving inspection: the reduced and oxidised forms differ by 2 Da in ESI-MS and elute at different RP-HPLC retention times. The released-batch COA documents which form the lot represents. Six nominal strengths from 1 to 15 mg cover bench-scale and dispensing-scale workflows.
Who buys this, and why
GH-axis peptides ship to two main buyer types: compounding pharmacies dispensing under physician supervision, and research labs studying somatotropic-axis pharmacology. Pharmacies typically want sterile-filled vials with the full release packet (sterility, endotoxin, CCI); labs typically want bulk lyophilized powder with sequence verification. Blends (the CJC-1295 / Ipamorelin combination is the canonical example) are usually co-lyophilized rather than solution-mixed for potency stability.
Primary buyer fit: academic and contract research laboratories and 503A / 503B compounding pharmacies.
Specifications
- CAS
- 66004-57-7
- Molecular Formula
- C78H123N23O22S2
- Molecular Weight
- 1817.1 g/mol
- Sequence
- YLRIVQCRSVEGSCGF
- Appearance
- White lyophilized powder
- Purity (HPLC)
- ≥ 99.0%
- Common vial sizes
- 1 mg, 2 mg, 5 mg, 10 mg, 12 mg, 15 mg
- MOQ
- On request
- Lead time
- 10–18 days
- Storage
- -20°C, protect from light
Documentation available on request
- Certificate of Analysis (COA)
- HPLC Chromatogram
- Mass-spec identity (ESI-MS)
- Counter-ion (acetate vs TFA)
- Sterile-fill release pack (sterility, CCI, fill-weight)
- Bacterial endotoxin (LAL, USP <85>)
- Stability data on request
- SDS / MSDS
Regulatory note
Easily confused with AOD9604 (the modified analog with N-terminal tyrosine). Confirm exact fragment identity (unmodified vs. AOD9604-modified) via batch COA before order placement; the two are not chemically equivalent.
Frequently asked questions
How do I distinguish HGH Fragment 176-191 from AOD9604 at the analytical level?▾
Mass spec at receiving inspection is the diagnostic test. The two molecules differ by exactly one residue, AOD9604 carries an additional N-terminal tyrosine, producing a 17-residue molecule with theoretical MW around 1980 Da, while HGH Fragment 176-191 is the unmodified 16-residue sequence at 1817.1 Da theoretical. The +163 Da delta is unambiguous on an ESI-MS scan and is the test we recommend for first-time supplier qualification when sourcing either form. Secondary confirmation comes from RP-HPLC retention time, the additional hydrophobic tyrosine pushes AOD9604 to a slightly later elution under typical gradient conditions. Either way, never rely on label alone; the released-batch mass must match the ordered form.
What does the intramolecular disulfide bond in HGH Fragment 176-191 mean for handling?▾
The fragment sequence YLRIVQCRSVEGSCGF contains two cysteines at internal positions 7 and 13. Under reducing conditions during synthesis the cysteines remain as free thiols; under oxidative conditions during downstream storage and reconstitution they can pair into an intramolecular disulfide bridge. The reduced and oxidised species differ by 2 Da in ESI-MS and elute at distinct RP-HPLC retention times, making the form readily distinguishable at QC. Most published research uses the oxidised (disulfide-bridged) form, which is the more stable solid-state species. The released-batch COA documents which form the lot represents, which matters operationally for any protocol that specifies one form or the other.
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