These two end up in the same conversation because both are discussed in connection with mitochondria. That is where the resemblance stops. One is a coenzyme that every cell already makes; the other is a peptide encoded in mitochondrial DNA. Treating them as two options from one shelf is a category error, and it shows up immediately on their certificates.

Two different kinds of molecule

NAD+ is nicotinamide adenine dinucleotide, a coenzyme built from a nicotinamide, an adenine, two riboses and two phosphates. It is not a peptide and has no sequence. It is central to redox chemistry across metabolism and its turnover is a well-mapped subject. (Reference: Cantó et al., 2015)

MOTS-c is a peptide of sixteen residues, MRWQEMGYIFYPRKLR, and the notable thing about it is where its gene sits: in the mitochondrial genome and not the nuclear one, which was not where short peptides were expected to be found. (Reference: Lee et al., 2015) Our note on MOTS-c covers the discovery.

One is a small-molecule cofactor, the other a short protein fragment. Almost nothing transfers between them analytically.

What that does to the paperwork

A peptide certificate and a small-molecule certificate are different documents that happen to share a name.

For MOTS-c the identity question is whether the chain is the intended chain, answered by comparing a measured mass against a mass calculated from the sequence. Our calculator returns C101H152N28O22S2 for those sixteen letters, which matches its PubChem record, and the purity question is about synthesis by-products such as deletion sequences.

For NAD+ there is no sequence to calculate from and no deletion sequences to look for. Identity rests on the compound matching a known reference, and the impurities of interest are the related species of its own chemistry, chiefly its reduced form and its degradation products. A certificate that applies peptide vocabulary to NAD+ has been produced from the wrong template.

Two methionines, and why only one of them has them

MOTS-c carries two methionine residues, and methionine oxidises. Each oxidation adds sixteen mass units, which is large enough to see on a mass spectrum and small enough to miss if nobody looks for it, so an oxidised fraction is a specific thing to ask about on this compound.

NAD+ has no methionine and no such route. Its stability question is different: it is sensitive to its own chemistry, not to side-chain oxidation. The general principle survives the difference, which is that both are dated on their certificates because a result belongs to a moment, and both degrade by routes that proceed with time and temperature. Our note on storage covers the peptide side.

Public records

Both are well indexed. NAD+ is CAS 53-84-9 with PubChem CID 5892; MOTS-c is CAS 1627580-64-6 with its own record. Either number can be run through the check digit validator and then looked up to read back which substance it returns.

NAD+ is the older and more thoroughly documented of the two by a wide margin, which is what you would expect of a coenzyme described decades ago beside a peptide reported in 2015. Depth of literature is a property of a compound's history, not a measure of how carefully a particular batch was made.

Different mass scales, different expectations

NAD+ is about 663 g/mol; MOTS-c is around 2174. An order of magnitude apart changes what a mass measurement can resolve. On a molecule the size of NAD+, a mass spectrometer can distinguish species differing by a single atom with room to spare. On a peptide of sixteen residues the isotope cluster is wide enough that the distinction between monoisotopic and average mass has to be stated, or two correct figures will look like a disagreement.

This is the practical reason a certificate should name its method and report observed and theoretical values instead of a verdict. Our note on mass spectrometry covers the comparison.

Solubility is a separate conversation for each

A sixteen-residue peptide has a net charge that moves with pH, and solubility is usually at its lowest near the pH where that charge cancels out. Our isoelectric point calculator returns that figure from the sequence, with the caveat that it is theoretical and names the pKa set it used.

NAD+ has ionisable phosphates and behaves quite differently, and none of the peptide reasoning carries across. Mentioning it here only to make the point that two compounds filed under one heading can require entirely separate handling, and that the heading is not what tells you.

What a certificate should show for either

Purity with a named method and its conditions, identity as a measurement and not as a word, a date, a named laboratory, and a batch number that matches the vial. Those are common to both. What differs is the vocabulary: net peptide content and deletion sequences are meaningful on MOTS-c and meaningless on NAD+, while NAD+ needs its own related-substance profile. Our glossary defines the fields.

Why the pairing happens at all

Both are discussed in connection with mitochondrial function, and that single shared word does a lot of work in how catalogues get organised. It is worth separating two senses of it. NAD+ participates directly in the redox chemistry that mitochondria run; its connection is chemical and immediate. MOTS-c is connected by origin, because the sequence is transcribed from mitochondrial DNA.

One molecule is part of the machinery and the other comes out of the blueprint. Neither relationship implies the other, and a shelf label that puts them together is organising by topic, not by mechanism. For reading that is harmless; for deciding what a certificate should contain it is the whole difference.

What this comparison is not

It is not a choice between two things that do the same job, because they are not in the same category. Both are sold here for laboratory research, and the only comparison on offer is of what can be documented about each.

Research use only

All products sold by Codex Research are strictly for laboratory research and development. They are not for human or animal consumption and are not intended to diagnose, treat, cure, or prevent any disease.

These compounds in the catalog

Frequently asked questions

Is NAD+ a peptide?

No. It is a coenzyme built from a nicotinamide, an adenine, two riboses and two phosphates. It has no amino acid sequence, which is why peptide-specific certificate fields do not apply to it.

What makes MOTS-c unusual?

Its gene sits in the mitochondrial genome and not the nuclear one. Short peptides were not expected to be encoded there, which is what made the 2015 report notable.

Why do their certificates look different?

Because the questions differ. A peptide certificate asks whether the chain is the intended one and reports synthesis by-products such as deletion sequences. A small-molecule certificate reports related substances from that compound own chemistry. Peptide vocabulary applied to NAD+ means the wrong template was used.

Why do the two methionines in MOTS-c matter?

Methionine oxidises, and each oxidation adds sixteen mass units. That is large enough to see on a mass spectrum and small enough to miss if nobody looks, so an oxidised fraction is a specific thing to ask about on this compound.

Does NAD+ having more literature mean it is better made?

No. Depth of published work reflects a compound history, not the care taken over a particular batch. Only a batch certificate speaks to the second.

Can I use a sequence calculator for both?

Only for MOTS-c. A sequence calculator works from amino acid letters, and NAD+ has none, so its formula and mass come from its chemical record instead.

References

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