Chemical identity, proposed mechanism and published preclinical literature, for laboratory reference.
SS-31 is a mitochondria-targeted tetrapeptide belonging to the Szeto-Schiller class of aromatic-cationic peptides. It concentrates in the inner mitochondrial membrane independently of membrane potential and associates selectively with cardiolipin, the signature phospholipid of that membrane. Published preclinical research has examined this interaction in relation to cristae architecture, cytochrome c binding, electron transport chain coupling and electron leak.
A longer overview of published SS-31 literature on inner-mitochondrial-membrane biology, in our 2026 guide.
WARNING: For research and laboratory use only. Not for human consumption. Not approved by the FDA for human use.
Mechanism of Action — Cited Research
SS-31 concentrates in the inner mitochondrial membrane independently of membrane potential and associates selectively with cardiolipin. SS-31's mechanism has been characterized as membrane-surface electrostatic modulation at the inner mitochondrial membrane, where it binds preferentially to cardiolipin-enriched regions (Mitchell W et al., J Biol Chem 2020; PMID: 32273339). This cardiolipin association is the basis for the cristae-architecture, cytochrome c binding, and electron-leak observations reported across preclinical mitochondrial models.
Chemical Identity
SS-31 is the tetrapeptide D-Arg-Dmt-Lys-Phe-NH₂, in which Dmt is 2′,6′-dimethyltyrosine. Its molecular formula is C₃₂H₄₉N₉O₅ and its molecular weight is about 639.8 g/mol. The alternating aromatic–cationic motif places two aromatic residues (Dmt and Phe) between two basic residues (D-Arg and Lys), giving the peptide a net charge of +3 at physiological pH. The N-terminal D-arginine protects the peptide from aminopeptidase cleavage, and the C-terminal amide removes the terminal carboxylate charge.
Research Context
SS-31 has been examined in published in-vitro and animal research on inner-membrane biology, including cristae organization, cytochrome c binding to cardiolipin and electron leak from the respiratory chain. Typical experimental systems are isolated mitochondria, cardiolipin-containing liposomes and model membranes, and cultured cells, in which membrane potential, oxygen consumption and reactive oxygen species are measured with fluorescent probes and high-resolution respirometry.
Analytical Characterization
Purity is assessed by HPLC and identity by LC-MS against the calculated mass of about 640 Da. Because the peptide is small and strongly basic, ion-pairing reagents in the mobile phase help produce sharp, well-resolved peaks. A Certificate of Analysis is published for this product on our COA page.
Regulatory Status
The SS-31 supplied by Excalibur Peptides is a research chemical sold strictly for in-vitro laboratory research and identification purposes. It is not approved by the FDA for human or veterinary use and is not intended for human consumption.
Frequently asked questions
What is SS-31 examined for in research?
SS-31 is a mitochondria-targeted tetrapeptide examined in published in-vitro and animal research for its selective association with cardiolipin in the inner mitochondrial membrane, and for related effects on cristae structure, electron transport chain coupling and reactive oxygen species generation in isolated mitochondria and cultured cells.
What is the chemical structure of SS-31?
SS-31 is the tetrapeptide D-Arg-Dmt-Lys-Phe-NH2 (Dmt = 2′,6′-dimethyltyrosine), with molecular formula C32H49N9O5 and a molecular weight of about 639.8 g/mol. Its alternating aromatic–cationic sequence gives it a net charge of +3 at physiological pH.
How does SS-31 differ from traditional antioxidants?
General antioxidants scavenge reactive oxygen species stoichiometrically. SS-31 instead associates with a specific structural component of the inner mitochondrial membrane, cardiolipin, so published research has studied it as a membrane-targeted tool compound in mitochondrial models rather than as a free-radical scavenger.
How is SS-31 tested, and where is its COA?
SS-31 is third-party tested by Freedom Diagnostics Testing: purity by HPLC and identity by LC-MS. The Certificate of Analysis is published in our COA database, and the report can be looked up on the lab's own site with search code Exca2608030569.
Is the SS-31 sold here approved by the FDA?
No. The SS-31 sold by Excalibur Peptides is not approved by the FDA for human or veterinary use. It is a research chemical supplied for in-vitro laboratory research and identification purposes only and is not for human consumption.
Where can I buy SS-31 for research?
Excalibur Peptides sells SS-31 on this page as a 10mg vial of lyophilized powder, for in-vitro laboratory research only. Orders ship from Austin, Texas, to addresses within the United States, and the product's third-party Certificate of Analysis is published in our COA database. Buyers must be 21 or older and confirm research-use-only status at checkout.
How should SS-31 be stored in the lab?
Keep lyophilized SS-31 sealed at −20 °C, protected from light and moisture, as listed on this page. Let the vial reach room temperature before opening so moisture does not condense on the powder, and avoid repeated freeze–thaw cycles.
How fast does SS-31 ship?
SS-31 ships from Austin, Texas. Orders placed before 2 PM EST on a business day ship the same day, and delivery within the United States typically takes 2–4 business days. A tracking number is emailed when the order ships.
What payment methods can I use to buy SS-31?
We accept credit and debit cards, Apple Pay, Venmo, Cash App and cryptocurrency. Prices are in U.S. dollars.
