FRAGMENT 176-191 5mg

Fragment 176-191 is a synthetic 16-amino-acid peptide corresponding to residues 176 through 191 at the C-terminus of human growth hormone (hGH), with a molecular weight of approximately 1799 g/mol.¹

Sequence Relative to Related Analogs

Fragment 176-191 begins with phenylalanine at its N-terminus, matching the native hGH sequence. It is distinct from AOD-9604, a related analog that carries tyrosine in that position, and the two compounds differ in molecular formula and mass.

Peptide Structure and the Cys7–Cys14 Disulfide Bridge

A defining structural feature of Fragment 176-191 is the intramolecular disulfide bond formed between its two cysteine residues, which constrains the peptide into a looped conformation not present in a fully linear hGH-derived fragment.

This structural detail is a frequent point of reference when comparing synthesis routes across suppliers, since correct disulfide formation, rather than a free-thiol reduced state, determines which form of the peptide is present in a given lot.

Analytical Purity and Disulfide Bond Verification

Beyond standard sequence confirmation by mass spectrometry, laboratory-grade Fragment 176-191 requires verification that the Cys7–Cys14 disulfide bond has formed correctly rather than the peptide remaining in its reduced, linear state. Both forms share the same amino acid sequence but differ slightly in mass and in chromatographic behavior.

HPLC combined with mass spectrometry is used to distinguish the oxidized (cyclic) form from residual linear peptide, and researchers designing dose-response experiments are encouraged to review lot-specific analytical data confirming the oxidized state alongside the standard purity percentage.

Storage and Handling in the Laboratory Setting

Peptides containing disulfide bonds are susceptible to reduction under certain storage conditions, particularly in the presence of reducing agents or extended exposure to light and elevated temperature.

Laboratories typically store lyophilized Fragment 176-191 under sub-zero freezer conditions, which helps preserve the oxidized disulfide state.

Comparative Research Context Among hGH-Derived Fragments

Fragment 176-191 is one of several hGH-derived research peptides studied for isolating specific regions of the full-length hormone, distinct from growth hormone secretagogues such as GHRP-class peptides that act upstream at the pituitary.

Researchers comparing these peptide classes often cite Fragment 176-191's restriction to the hormone's C-terminal domain as a way to study this region separately from the IGF-1-associated domains of the full-length hormone.

Product Information

Fragment 176-191 is supplied as a lyophilized white powder at 5 mg per vial.

Important Notice

This product is intended for laboratory research use (in vitro) only. It is not approved for human use under any circumstances, and has not been evaluated for safety or efficacy in humans.

References

1. Harvey S, Martinez-Moreno CG. Growth Hormone: Therapeutic Possibilities—An Overview. Int J Mol Sci. 2018;19(7):2015.