AOD-9604 and the hGH 176-191 Fragment: What a Fragment Keeps

AOD-9604 is a useful illustration of a general principle in peptide research: a fragment of a protein is a different molecule from the protein, with its own pharmacology that has to be established rather than inherited.

Derivation

Human growth hormone is a 191-residue protein. AOD-9604 corresponds to the C-terminal region — residues 176 to 191 — with a tyrosine added at the N-terminus. That single addition is a deliberate stabilisation, not an accident of synthesis.

What the fragment does not carry

The growth hormone receptor binding surface is distributed across the folded protein, not contained in the C-terminal sixteen residues. A short linear fragment cannot reconstruct that surface, so AOD-9604 is not expected to act as a growth hormone receptor agonist, and the literature treats it as mechanistically separate from hGH rather than as a smaller version of it.

This is worth stating plainly because catalogue copy across the industry often implies otherwise. The indexed literature is at PubMed.

Reading the literature

The published work is limited in volume and largely preclinical. As with other compounds in this position, findings reported in one model system and one laboratory should be treated as provisional until independently reproduced. Where a review cites a striking result, it is worth tracing back to the primary paper and checking the model, the concentration and the controls.

Handling

AOD-9604 contains a disulfide bridge derived from the parent sequence, which introduces a consideration most short linear peptides do not have: reducing agents in a buffer will open the bridge and change the molecule. Dithiothreitol and β-mercaptoethanol are not neutral additives here.

Identity confirmation by mass distinguishes the reduced and oxidised forms, since they differ by two mass units — worth checking on a certificate for any disulfide-containing peptide. See HPLC and mass spectrometry verification.

Product: AOD-9604 5mg, listed with other growth hormone pathway peptides.

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