SS-31: four residues, two of them unusual

SS-31, also called elamipretide, is a tetrapeptide built on an unusual principle: charged and aromatic residues alternate. This article collects what can be documented about it.

Charged, aromatic, charged, aromatic

The sequence is D-Arg-Dmt-Lys-Phe-NH₂. Arginine and lysine each carry a positive charge, Dmt and phenylalanine each carry a ring. The four residues alternate, and this pattern is the design principle of this family of molecules.

Dmt stands for dimethyltyrosine, an amino acid that does not occur in proteins. The D in front of arginine denotes the mirror-image form, which also practically never occurs in proteins. The NH₂ at the end is an amide that caps the free acid group and is part of the molecule.

The molecular formula is C₃₂H₄₉N₉O₅, the molar mass 639.79 g/mol and the CAS number 736992-21-5. All of it is on the product page.

Directed there, not encoded there

In laboratory research SS-31 is studied in connection with cardiolipin binding, mitochondrial bioenergetics and oxidative stress. In this it differs from MOTS-c, the other mitochondria-related molecule in this catalogue: MOTS-c is encoded in the mitochondria's DNA, while SS-31 is a synthetic molecule directed to them.

What follows from this in a whole organism is the subject of ongoing research and belongs in the scientific literature. This page sticks to the figures in the specification table.

Three certificates, two from five times the vial size

The certificate library holds three certificates of analysis for this substance. Two come from 50 mg lots, while the vial listed here is 10 mg: the largest size difference in the entire catalogue. The third comes from a 10 mg lot.

The product page states this openly instead of attributing the certificates to a different fill size. A certificate belongs to the lot it comes from; anything else would be a claim about material that was never measured.

All three reports give a measured purity: 99.51% for lot 2024252, above 99.8% for lot 2026305 and 99.650% for lot 231745. This shop does not state a blanket minimum purity; what counts is the measured value in the certificate for each lot. What else to look for in a certificate is covered in How to read a certificate of analysis.

Why mirrored and artificial building blocks

Enzymes that break down chains are tuned to the usual form of the building blocks. A mirrored residue does not fit their binding site, so the chain stays intact for longer. Ipamorelin uses the same principle with two mirrored residues.

Analytically this has one consequence that matters: a mass measurement alone cannot tell the mirrored form from the usual one, because both weigh the same. To check whether the correct variant is present, go by the CAS number and the sequence stated in the certificate, not by the mass.

Before preparing a solution

The product is supplied as a lyophilised powder; what lyophilisation does to the material is explained in Storing lyophilised peptides in the laboratory. It goes into solution with bacteriostatic water, and the glossary entries on reconstitution and concentration explain the terms.

In brief

Four residues alternating between charge and ring, two of them unusual, 639.79 g/mol, CAS 736992-21-5, three certificates of analysis, two from 50 mg lots and one from a 10 mg lot.

Questions

Is SS-31 the same as elamipretide?

Yes, they are two names for the same substance with CAS number 736992-21-5. The product page lists both.

What is Dmt?

Dimethyltyrosine, a building block with two extra methyl groups on the ring. It does not occur in proteins; in the certificate it appears within the stated sequence.

Why do two of the certificates come from 50 mg lots?

Because a certificate belongs to its own lot. Two of the three come from 50 mg lots and one from a 10 mg lot, the size sold here; the product page lists each with its vial size.