HGH 191-177

Product Specifications

Research Overview & Mechanism of Action

HGH 191‑177 is a synthetic 15‑amino acid C‑terminal fragment of human somatotropin. The sequence spans residues 177 through 191 — hence the dual naming — and carries an intramolecular disulfide bridge between Cys‑182 and Cys‑189. Its monoisotopic mass weighs 1815.1 Da. The primary structure reads Leu‑Arg‑Ile‑Val‑Gln‑Cys‑Arg‑Ser‑Val‑Glu‑Gly‑Ser‑Cys‑Gly‑Phe.

This fragment has zero growth‑promoting activity. That’s well documented. Instead, it binds the growth hormone receptor through the site‑2 contact surface without triggering the conformational dimerization required for full‑length signalling. In multiple in‑vitro adipocyte models, the peptide shifts the GHR into a partially activated state that uncouples lipolytic readouts from IGF‑1 transcription. Researchers therefore use HGH 191‑177 as a probe to dissect biased signalling downstream of the GHR. Receptor selectivity, molar ratio‑dependent binding curves, and long incubation‑time stability are the aspects that matter most in the lab.

Analytical control is built into every lot. We rely on reverse‑phase HPLC with a C18 column and electrospray ionisation mass spectrometry. The chromatogram routinely lands at >99% area under the curve. The lyophilized cake often looks cracked or slightly displaced. That’s normal. Rapid freeze‑drying and transport vibration cause the dried matrix to fracture without altering peptide integrity.

Handling, Reconstitution & Storage Protocol

Keep the lyophilized vial at –20 °C for long‑term storage. Room‑temperature transit for a few days causes no measurable degradation. Let the sealed vial sit at ambient lab temperature for at least 15 minutes before you crack the cap. Condensation invites moisture‑driven aggregation — skip that step and you risk a cloudy reconstitution.

Reconstitution protocol for analytical concentration:

• Use sterile bacteriostatic water (0.9% benzyl alcohol) or phosphate‑buffered saline, pH 7.4.
• Draw the desired volume into a low‑dead‑volume syringe, then inject gently down the glass wall.
• Target a stock concentration of 1–2 mg/mL. The peptide dissolves readily; gentle swirling is enough. Vortexing or foaming shears the peptide backbone.
  
• For cell‑based assays where plastic‑ware adsorption is a concern, supplement the diluent with 0.1% molecular‑biology‑grade bovine serum albumin as a carrier protein. This step preserves free‑peptide molar ratio at sub‑micromolar working concentrations.

Post‑reconstitution shelf‑life: Store the solution at 2–8 °C and use within 2‑3 weeks for consistent in‑vitro results. Aliquot single‑use volumes and avoid freeze‑thaw cycling. A single freeze‑thaw cycle drops bioactive signal by roughly 15% in our internal stability trials — plan your aliquots accordingly.

Scientific References & External Citations

• PubMed: HGH Fragment 177‑191 Research – Curated studies mapping the lipolytic domain of human growth hormone.
• PubChem Compound: HGH Fragment 177‑191 – Structural identifiers, molecular weight, and chemical classification.
  
  

  Frequently Asked Research Questions

  What is the exact amino acid sequence and molecular weight of HGH 191‑177?
  The peptide corresponds to HGH residues 177‑191 with the sequence H‑Leu‑Arg‑Ile‑Val‑Gln‑Cys‑Arg‑Ser‑Val‑Glu‑Gly‑Ser‑Cys‑Gly‑Phe‑OH. The oxidised form, containing a Cys‑Cys intramolecular disulfide, has a monoisotopic mass of 1815.1 g/mol. Both reduced and oxidised masses are confirmed on every batch CoA via ESI‑MS.

  How should I reconstitute HGH 191‑177 for cell‑culture experiments?
  Aim for a stock analytical concentration of 1‑2 mg/mL in sterile bacteriostatic water or PBS. Add 0.1% BSA to the final diluent if your protocol uses low‑micromolar working solutions on polystyrene plates. Swirl gently; mechanical agitation or prolonged vortexing degrades peptide integrity. Always allow the lyophilized cake to equilibrate to room temperature before adding the diluent.

  Is a batch‑specific Certificate of Analysis provided?
  Absolutely. Each 5 mg research vial leaves our laboratory with a printed and digitally archived CoA containing the HPLC purity reading, retention time, ESI‑MS spectrum, and observed peptide mass. The lot number printed on the vial matches the CoA one‑to‑one.

  Can this peptide be used in human diagnostics or therapeutic research?
  No. HGH 191‑177 is manufactured for in‑vitro analytical research only. It is not intended for human or veterinary administration, clinical diagnostics, or therapeutic use. All purchase orders are screened to ensure compliance with this research‑use‑only restriction.