Humanin is listed at 10 mg for $212.80. SS-31 is listed at 10 mg for $95.20, 30 mg for $336.00 and 50 mg for $487.20. They sit in the same catalogue section and are routinely discussed together, and as purchases they have almost nothing in common.
This covers what each molecule is, why one costs more than twice the other at the same strength, what each needs from a certificate, and how the strength ladders compare. Everything about biological activity is reported from published work and named by model. The material is supplied for laboratory research only.
| Compound | Vial strengths | Molecular weight | Amino acids |
|---|---|---|---|
| Humanin | 10 mg | 2687.27 g/mol | 24 |
| SS-31 | 10 mg, 30 mg, 50 mg | 639.80 g/mol | 4 |
From the Restate Health catalog records. Lot-specific values are on each certificate of analysis.
Humanin: a 24-residue peptide with an unusual origin
Humanin is a 24-residue peptide encoded not in nuclear DNA but within the mitochondrial genome, in an open reading frame inside the MT-RNR2 region. That origin is what places it in the class usually called mitochondrial-derived peptides, alongside the MOTS-c sequence that is also encoded in mitochondrial DNA.
Published work describes humanin in cell and animal systems and has produced a number of analogues with substitutions at particular positions. For a buyer the relevant point is that 'humanin' can refer to the natural sequence or to one of those analogues, and the two are different products. The certificate must give the sequence, not just the name.
At 24 residues it is a long peptide by catalogue standards. Solid-phase peptide synthesis explained for buyers covers why cost rises with length — each additional residue is another coupling step, another opportunity for an incomplete reaction, and another contribution to the deletion-sequence burden that purification has to remove.
SS-31: four residues, two of them unusual
SS-31 is a tetrapeptide — four residues — belonging to the Szeto-Schiller series from which it takes its designation. Published work describes it as associating with cardiolipin, a phospholipid of the inner mitochondrial membrane, and it is characterised in that literature as a mitochondria-targeting compound.
Its chemistry is more interesting than its length suggests. The sequence incorporates residues that are not among the twenty standard amino acids, including a D-configured arginine and a dimethylated tyrosine, and the C-terminus is amidated. An alternating pattern of aromatic and basic residues is the structural feature the series was designed around.
For a buyer this means two things. The unnatural residues are the reason a four-residue peptide is not trivially cheap — those building blocks cost more than standard protected amino acids and are not always held in stock. And stereochemistry has to be confirmed, because a D-residue and its L-counterpart have identical masses. Mass spectrometry cannot tell them apart. Mass spectrometry and peptide identity covers that limit directly.
Why the prices sit where they do
| Humanin | SS-31 | |
|---|---|---|
| Length | 24 residues | 4 residues |
| Residues | Standard | Includes D- and modified residues |
| Catalogue strengths | 10 mg | 10 mg, 30 mg, 50 mg |
| Price at 10 mg | $212.80 | $95.20 |
| Per milligram at 10 mg | $21.28 | $9.52 |
| Best per-milligram figure | $21.28 | $9.74 at 50 mg |
| Hardest certificate question | Which sequence or analogue | Stereochemistry of the D-residue |
The two listings compared
Length is most of the price difference. Twenty-four residues against four is roughly six times the chain-building work, with a purification burden that grows faster than linearly because the deletion sequences accumulate. SS-31's unusual building blocks push its price up from where a four-residue peptide would otherwise sit, but not far enough to close the gap.
The strength ladder is worth noting. SS-31's 50 mg listing at $487.20 works out at $9.74 per milligram against $9.52 at 10 mg — so on this listing the largest vial is marginally more expensive per milligram than the smallest, and the 30 mg at $11.20 per milligram is the least efficient of the three. This is exactly the case covered in price per milligram: bigger is not automatically cheaper, and checking takes a minute.
What each certificate needs to say
For humanin, the sequence in full, so that natural humanin is distinguished from any analogue. Purity by a named method with stated conditions, and a related-substances breakdown — on a 24-residue peptide the deletion sequences are the dominant impurity class and a single purity figure hides their distribution. Net peptide content, which at $212.80 a vial is a material fraction of the price.
For SS-31, the sequence with every modification and the stereochemistry explicitly stated. Because mass cannot establish configuration, a certificate that rests identity on mass alone has not confirmed the molecule. Ask what method was used to establish the stereochemistry; chiral chromatography or amino acid analysis after hydrolysis are the usual answers, and a supplier who cannot say is telling you the question was not asked.
Reading a certificate of analysis line by line covers the document, and what a certificate of analysis does not test for covers what remains unknown after a good one.
Buying a long peptide
Humanin at twenty-four residues sits at the length where several things change at once, and a buyer used to short sequences should expect all of them.
The impurity profile broadens. Deletion sequences missing one residue are the dominant class, and on a long chain there are many positions at which a deletion can occur, so the impurity pool is a distribution rather than a handful of identifiable species. A single purity figure summarises that distribution without describing it, which is why a related-substances breakdown matters more here than on a short peptide. Peptide impurities explained covers the categories.
Solubility becomes less predictable. Longer chains have more opportunity for secondary structure and for aggregation, and a sequence that dissolves readily at one concentration may not at another. Why some peptides resist dissolving covers the approaches, and the supplier's compound-specific guidance is worth having before the vial arrives.
And lot-to-lot variation becomes more visible. Two lots of a four-residue peptide are generally interchangeable; two lots of a twenty-four residue peptide can differ enough in impurity distribution to matter in sensitive work. Lot-to-lot consistency covers when to control for it by buying a single lot.
Where they sit in the class
Mitochondrial peptides: MOTS-c, humanin and SS-31 covers the three together as a class and is the place to start if the question is what distinguishes them scientifically rather than commercially. MOTS-c is listed at 10 mg for $81.20 and 40 mg for $240.80, and buying MOTS-c covers that listing.
Of the three, MOTS-c and humanin share the mitochondrial-genome origin; SS-31 is a wholly synthetic design that targets a mitochondrial structure. Grouping them by where they act rather than by what they are is reasonable shorthand and a poor basis for a purchase decision, which is why the certificates differ so much between them.
Choosing between them
They are not substitutes, so the question is rarely which to buy. Where both are on a purchase list, the ordering decision is about strengths and lots rather than about one against the other.
For SS-31, the strength ladder is the live question and the smallest vial is marginally the most efficient. For humanin, there is only one strength, so the decision is how many vials and whether they need to come from one lot. At $212.80 each, a three-vial purchase is $638.40 and worth a conversation about single-lot supply before it is placed rather than after.
Handling
Both dry, cold and dark in the sealed vial. Humanin's length makes aggregation a more realistic concern than for a short peptide, so avoid repeated concentration cycling and aliquot after reconstitution — freeze-thaw cycles and aliquoting covers the practice. Why some peptides resist dissolving is worth reading before reconstituting a 24-residue sequence for the first time.
SS-31's modified residues do not make it fragile, but its small size means a given mass is a larger number of moles than the same mass of a long peptide. Molecular weight for buyers covers why the number on the certificate matters when planning a concentration.