MOTS-c: structure, nomenclature and handling

Mitochondria carry their own small genome, separate from the DNA in the cell nucleus, and most of it encodes machinery for the mitochondrion's own use — including two ribosomal RNA genes, which produce structural RNA rather than protein. MOTS-c is encoded by a short open reading frame hidden inside one of them: the 12S ribosomal RNA gene. The name unpacks as mitochondrial open reading frame of the twelve S rRNA, type c.

That placement makes it a member of the mitochondrial-derived peptides, a small class defined by genomic origin rather than by shared sequence or a shared target — humanin, encoded within the 16S ribosomal RNA gene, and the SHLP series are the other named members. The class label says where a peptide comes from, not what it resembles, and the members do not resemble one another.

The peptide itself is a sixteen-residue linear chain: methionine–arginine–tryptophan–glutamine–glutamate–methionine–glycine–tyrosine–isoleucine–phenylalanine–tyrosine–proline–arginine–lysine–leucine–arginine, with a molecular weight of approximately 2,175 daltons. Three arginines and a lysine make it strongly basic, and the composition worth noticing for handling purposes is the pair of methionines and the tryptophan — three residues drawn from the most oxidation- and light-sensitive end of the amino acid set.

The material is catalogued as MOTS-c and MOTSc, and it carries CAS 1627580-64-6. There is no international non-proprietary name and no development code in common circulation — catalogue naming for this compound is unusually uniform, which removes the synonym-matching problem that attends older peptides.

As with most synthetic peptides, the material is typically isolated as an acetate salt, which affects the mass weighed out without altering identity. The synthetic material corresponds to the human sequence; the mitochondrial genome varies between species, and sequences reported for other organisms differ at several positions, so cross-species literature comparisons should be read with the exact sequence in hand.

Mass spectrometry confirms the intact molecular mass near 2,175 daltons. For this sequence the measurement also reports on oxidation state: each oxidized methionine adds a defined sixteen-dalton increment, so a batch carrying sulfoxide forms shows satellite masses above the target at plus sixteen and plus thirty-two. Those are defined deviations, and their absence is part of what a clean identity result asserts.

High-performance liquid chromatography resolves the main peak from related substances and yields the purity figure. A sixteen-residue synthesis produces the familiar deletion sequences, where a residue failed to couple; the compound-specific related substances are the methionine sulfoxide forms, which separate from the unoxidized peptide and typically sit close to the main peak. Tallying what the chromatogram shows near the main peak against the mass data is how the two methods corroborate one another.

HEEZ Research supplies MOTS-c in a single format: a 10 mg lyophilized vial. There is no second strength in the current catalogue, so the format decision that arises with two-size products does not apply here.

The material is supplied as a lyophilized powder. Freeze-drying removes water and leaves the peptide as a solid, markedly more stable than the same peptide in solution, and stable enough at ambient temperature to ship without refrigeration in transit.

Reconstitution converts the dried cake into a working solution, and it is a standard laboratory step rather than a product specification. Which solvent is used, and at what final concentration, is determined by the protocol in force at the receiving facility.

What HEEZ specifies is the contents of the vial: lyophilized MOTS-c in a single 10 mg format, stated on the label and on the batch certificate of analysis. Where a protocol is expressed in molar rather than mass terms, the additional figure it needs is the molecular weight, which the certificate records for the batch supplied.

The strongly basic character of the sequence makes it well behaved in mildly acidic aqueous media, and at sixteen residues it dissolves readily. Vigorous agitation is unnecessary and avoided as a matter of routine.

Sealed lyophilized MOTS-c is ambient-stable for the duration of transit, so no cold chain or insulated packaging is required for shipping. On receipt the vial goes to refrigeration and is kept out of direct light.

Reconstituted material is held refrigerated and used within the window the receiving facility's protocols specify, and repeated freeze-thaw cycling is avoided. Solutions are treated as short-lived relative to the lyophilized form.

This sequence sits at the sensitive end of the storage spectrum. Two methionines give it twice the usual exposure to the most common oxidation route, and the tryptophan is photosensitive — so light protection and limiting the time spent in solution matter more here than for robust sequences. Minimising the number of times a vial is opened, and keeping solutions in amber glass or foil-wrapped during extended handling, is standard practice for a composition like this one.

The certificate records what an independent facility measured for one specific batch. Its value lies in being batch-specific, so the first check is that the lot number on the document matches the vial in hand.

The identity section compares observed molecular mass against the theoretical figure near 2,175 daltons, and the clean result is a single mass without sulfoxide satellites at plus sixteen daltons — a check specific to methionine-containing sequences.

The purity figure is the HPLC main-peak area as a percentage of total peak area, and the attached chromatogram shows how that figure was arrived at. Peaks sitting close to the main peak on this compound are most plausibly oxidized forms, and a batch analysed promptly after synthesis should show little of them.

Peptide content, or net peptide content, is sometimes reported separately. It accounts for counter-ions and residual water, and it is the figure determining how much actual peptide a nominal 10 mg represents.