What Is SS-31? A Plain-English Look at a Mitochondria-Targeted Research Peptide

SS-31 turns up constantly in mitochondrial research, and almost as constantly under a different name. If you have seen it called elamipretide, MTP-131 or Bendavia and wondered whether those are the same thing, they are. Here is what the compound is, why its structure matters, and what to check before sourcing it.

One compound, five names

SS-31 is the research designation. Elamipretide is the international nonproprietary name. MTP-131, Bendavia and RX-31 appear in older literature and patent filings. All refer to the same tetrapeptide, and they resolve to a single registry entry, CAS 736992-21-5.^[1] This matters practically: a literature search under one name will miss papers filed under the others, and a supplier listing one name is not offering a different product from a supplier listing another.

What “mitochondria-targeted” actually means

Most compounds that accumulate inside mitochondria do so by riding the membrane potential. They carry a positive charge and are pulled across the inner membrane by the voltage gradient that healthy mitochondria maintain. That works until the gradient does not, which is precisely the condition many research models are built to study.

SS-31 is structurally different. Its sequence, D-Arg-Dmt-Lys-Phe-NH2, alternates aromatic and cationic residues. Read that notation carefully, because every part of it is load-bearing: D-Arg is the D-enantiomer rather than the ordinary L form, Dmt is 2,6-dimethyltyrosine rather than plain tyrosine, and the trailing NH2 means the C-terminus is an amide rather than a free acid. A certificate for a material missing any one of those is a certificate for a different molecule.^[2], and that arrangement lets it concentrate in the inner mitochondrial membrane independently of membrane potential. That property is the reason it appears so often in models where mitochondrial function is already compromised.

Cardiolipin, in plain English

Cardiolipin is a phospholipid found almost exclusively in the inner mitochondrial membrane. It helps give that membrane its folded structure, the cristae, and it interacts with several proteins of the electron transport chain. Because cardiolipin is both structurally distinctive and functionally central, an interaction there is what most SS-31 research is actually examining.

What the research looks at

Published work using SS-31 tends to cluster around a few areas: cristae architecture and inner-membrane organization, electron transport chain assembly, mitochondrial respiration and ATP synthesis, and oxidative stress models. These are areas of study, not outcomes. SS-31 is a research compound and nothing here should be read as a claim about effects in any organism.

What to check before you source it

Peptide research is only as good as the material. For SS-31 specifically, four things are worth confirming before you order:

• Identity, not just purity. A purity figure tells you how much of the sample is the main peak. It does not tell you the main peak is the right molecule. Look for mass spectrometry confirming identity alongside the chromatography.
• Purity by UPLC or HPLC, with the actual chromatogram included rather than a number typed onto a page.
• Endotoxin testing, reported as a real result rather than a claim of sterility.
• A COA tied to your specific lot, not a sample certificate from an unrelated batch. If you cannot match the lot number on your vial to a document, the testing is unverifiable.

That last point is worth pressing on. A supplier can show you an impressive certificate for a batch you did not receive. Look up any USA Made Peps lot number and you will get that lot’s purity, test date, testing lab, and the downloadable purity and endotoxin certificates. If you are new to reading one, our guide on how to read a COA walks through it line by line.

Specifications

• Synonyms: elamipretide, MTP-131, Bendavia, RX-31
• Sequence: D-Arg-Dmt-Lys-Phe-NH2
• Molecular formula: C32H49N9O5
• Molecular weight: ~639.8 g/mol
• CAS number: 736992-21-5^[1]
• Form: lyophilized powder
• Storage: -20°C, protected from light and moisture

Ours is made and processed in the USA and independently third-party tested. You can see the current listing on the SS-31 product page.

References

Sources are limited to identity: registry number, molecular formula, mass, synonyms and sequence notation. Nothing here is cited for biological activity. Each was checked on 11 August 2026.

1. CAS Registry Number 736992-21-5, elamipretide: C32H49N9O5, molecular weight 639.8, with MTP-131 and SS-31 listed as synonyms of the same registry entry. Cross-checked 11 August 2026 against a published supplier reference record. No link is given because CAS Common Chemistry carries no free public entry for this substance, which we confirmed rather than assumed, and we do not link catalogue pages as sources.
2. IUPAC and IUBMB Joint Commission on Biochemical Nomenclature, Nomenclature and Symbolism for Amino Acids and Peptides (Recommendations 1983), published 1984, which sets the symbol systems and the conventions for marking modified residues and C-terminal amides. Full recommendations.

Related reading

• What Is MOTS-C? Sequence, CAS and What Its COA Should Say
• MOTS-C Documentation Guide: How to Evaluate the Certificate
• How to Read a COA
• What Is Peptide Purity?
• Endotoxin Testing Explained
• How to Store Research Peptides
• Frequently Asked Questions
• All guides
• BPC-157 and TB-500: What the Blend Actually Contains

For research use only. Not for human or veterinary use, ingestion, injection, or any form of in vivo administration. Not intended to diagnose, treat, cure, or prevent any disease or condition.