MOTS-C lab tests

Seven checks before you trust a MOTS-C certificate

The same seven questions decide whether a certificate of analysis means anything, whichever compound it describes. Six are about the document; the seventh is about what no document can tell you.

1. An independent, batch-matched COA. The certificate must name the batch or lot in your hands, and must come from a laboratory the vendor neither owns nor pays. A specimen certificate from an earlier lot proves nothing about the vial you were sent.
2. HPLC purity, read against a known band. A purity figure is only informative against the distribution for that compound. "Above 98%" is not a claim — the useful question is whether the result sits inside the range the rest of the market reports. How to read HPLC and mass-spec results.
3. Mass-spectrometry identity. HPLC says how much of the sample is one thing; it does not say which thing. Only a mass-spec result establishes identity, and it is the only check that separates compounds a few daltons apart. Contamination is not hypothetical: research-grade custom peptides from two independent commercial suppliers were found to carry contaminating peptides at roughly 1% by weight, enough to produce false-positive results in immunology assays (Clinical and Vaccine Immunology, 2008 — a study of HIV vaccine peptide libraries rather than of any compound on this site).
4. Net content, measured rather than assumed. Purity and quantity are different questions: a vial can be 99.7% pure and still contain two thirds of the labelled mass. Why 10 mg isn't 10 mg.
5. Endotoxin (LAL) on the batch. An absent endotoxin line means the batch was not tested — not that it passed. Endotoxin testing and LAL interpretation.
6. Who ran the test, and what they left off. A laboratory with a record on this compound, named on the certificate, with a verification route back to it. Testing laboratories we track · Red flags in a certificate of analysis.
7. What no test on the vial can establish. A perfect certificate confirms that a vendor sold the correct molecule at the stated quantity. It says nothing about efficacy, dosing, or long-term safety.

Want a vial tested yourself? How to send a peptide for independent HPLC testing.

What MOTS-c testing has to rule out: salt form, oxidation and truncation

MOTS-c is a 16-residue mitochondrial-derived peptide, Met-Arg-Trp-Gln-Glu-Met-Gly-Tyr-Ile-Phe-Tyr-Pro-Arg-Lys-Leu-Arg (MRWQEMGYIFYPRKLR), CAS 1627580-64-6, encoded inside MT-RNR1 rather than the nuclear genome. Neither of its two characteristic failure modes is a substitution: the right molecule at an unstated mass, or the right molecule with oxygen added to it. Both pass HPLC.

MOTS-c ships at three different molecular weights depending on salt form: 2,174.6 free base, 2,234.64 acetate and 2,288.6 TFA salt. The spread is 114 Da, more than 5% of the mass being weighed, so a vial labelled 10 mg of TFA salt contains roughly 9.5 mg of peptide. That is chemistry rather than a defect; it becomes a defect when the certificate does not say which form was weighed, and the error is silent — a missing salt line does not make a certificate look incomplete or lower its purity figure. Net content stacks with it, because both errors move in the same direction: less peptide than the label implies.

The sequence carries methionine at positions 1 and 6. Methionine oxidises readily, each oxidation event adds 16 Da, and oxidised MOTS-c can still show high HPLC purity while being a different molecule from the one in the mouse studies. A 16-residue peptide also has fifteen places to come up short, and a truncated product still elutes as a clean peak.

• The salt form — free base, acetate or TFA — named on the certificate and consistent with the mass-spectrometry result. It is the check most commonly missing.
• A batch-matched mass spectrum confirming the full 16-mer at 2,174.6 Da free base, read against the declared salt form. A lower mass suggests truncation.
• No peaks heavier than expected by 16 Da per oxidation event (methionine 1, methionine 6, or both), plus an answer on cold-chain handling and shipping conditions: storage matters more for this sequence than for most peptides.
• Endotoxin (LAL) on the batch: FDA's published concern about this substance is specifically immunogenicity risk from aggregates and peptide-related impurities.