Molecular Structure Explorer
SS-31
Structure of the compound covered in this guide.
Last reviewed: October 2026 · Cleared Peptides research team
Research use only. SS-31 (Elamipretide): Research Guide is supplied for laboratory research. It is not a drug, food, cosmetic, or dietary supplement. It is not FDA-approved. It is not for human or veterinary administration. This page does not give a dose or a method of administration. A study cited on this page describes that study’s own test article. It does not make this lot an approved medicine. To check a fact, open the PubMed or DOI link, confirm the authors and year, and match the paper’s compound name, CAS number, or sequence to the specification table. The full method is on the research desk page. Identity and purity for a lot are only what that lot’s certificate of analysis reports. An HPLC percentage is not a sterility result and not an endotoxin result unless the certificate prints those tests.
SS-31, also known as elamipretide (MTP-131), is a synthetic aromatic-cationic tetrapeptide from the Szeto–Schiller (SS) peptide series. It selectively associates with the inner mitochondrial membrane, where it interacts with the phospholipid cardiolipin, making it a standard tool compound in mitochondrial biochemistry.
In this guide:
- Structure and identifiers
- Design: alternating aromatic and cationic residues
- In-vitro research areas
- Analytical testing
- FAQ
SS-31 Structure and Identifiers
| Name | SS-31 (elamipretide) |
|---|---|
| Synonyms | MTP-131; Bendavia |
| CAS number | 736992-21-5 |
| PubChem CID | 11764719 |
| Molecular formula | C32H49N9O5 |
| Molecular weight | ≈639.8 g/mol |
| Sequence | D-Arg-Dmt-Lys-Phe-NH2 (Dmt = 2′,6′-dimethyltyrosine) |
| Form | Lyophilized powder |
Design: Alternating Aromatic and Cationic Residues
SS peptides alternate aromatic and basic residues, giving a +3 net charge at physiological pH while remaining cell-permeable. The D-arginine at position 1 confers resistance to aminopeptidases, and the dimethyltyrosine residue contributes to its membrane interaction. These features let SS-31 concentrate at the inner mitochondrial membrane independently of membrane potential.
Published In-Vitro Research Areas
- Cardiolipin binding and inner-membrane structure studies
- Electron-transport-chain and cytochrome c peroxidase activity assays
- Reactive-oxygen-species production in isolated mitochondria
- Comparative studies with mitochondrial-derived peptides such as MOTS-c
This summary describes laboratory research only and makes no claim about effects in humans or animals.
Research formats: SS-31 (Elamipretide) and the MOTS-c + SS-31 research set. Lot COAs are on our COA page.
Research materials referenced in this guide
Analytical testing notes for SS-31 (elamipretide)
SS-31 (elamipretide) is identified in this guide as CAS 736992-21-5, formula C32H49N9O5, listed mass ≈639.8 g/mol. The sequence recorded here is D-Arg-Dmt-Lys-Phe-NH2 (Dmt = 2′,6′-dimethyltyrosine). An identity test compares a measurement with those values. A mass spectrum is the usual measurement for a peptide. FTIR, when a certificate uses it, is a supporting infrared fingerprint and is less specific for closely related sequences.
For SS-31 (elamipretide), routine chemical characterization is reversed-phase HPLC for area-percent purity and mass spectrometry for identity against the formula and mass in the table above. Oxidizable residues (cysteine, methionine, tryptophan) and deamidating residues (asparagine, glutamine), when the sequence contains them, are typical related-impurity questions for the chromatogram and the mass spectrum.
HPLC purity for this material is an area-percent result at the wavelength and gradient the laboratory states, commonly ultraviolet detection near 214 nm on a reversed-phase column. The instrument is a gradient pump, injector, column oven, and UV or diode-array detector. That percentage is not the number of milligrams in the vial. Water, acetate, trifluoroacetate, and other UV-silent material can dominate the gross weight while the purity figure stays high. Net peptide content, from an assay or amino-acid analysis, is the separate result to read when the certificate reports it.
A sterility test and an endotoxin test are not included in a chemical purity result. The compendial sterility test is a culture method (USP <71>): membrane filtration or direct inoculation into fluid thioglycollate medium and soybean-casein digest medium, incubated for 14 days. A PCR sterility screen uses a thermal cycler to detect microbial DNA and is a different method. The endotoxin test (USP <85> LAL, or USP <86> recombinant Factor C) reports endotoxin units with an incubating reader or a cartridge reader. Use a result only when that method is printed on the lot certificate. One published example in this catalog states that the report does not cover microbial contamination or endotoxins. The full description of equipment, standards, and how US laboratory accreditation works is in peptide analytical testing. Lot records are on the COA page.
Frequently Asked Questions
Is SS-31 the same as elamipretide?
Yes. SS-31 is the original research code; elamipretide is the nonproprietary name (CAS 736992-21-5).
What does SS-31 bind to?
In laboratory studies SS-31 associates with cardiolipin, a phospholipid of the inner mitochondrial membrane.
Is SS-31 for human use?
No. It is supplied for laboratory research use only.
Written by the Cleared Peptides Research Desk, the editorial desk of Cleared Wellness Group LLC. This is not a personal profile of a physician or a scientist, and it is not a fictional author. The checking method is public on the research desk page. Last reviewed October 2026.
SS-31 research note: a cardiolipin-targeted tetrapeptide
Research use only. This SS-31 material, also called elamipretide or MTP-131, is for laboratory research, CAS 736992-21-5. It is not an approved drug on the strength of this page, and this note does not give a dose.
Class, then the named compound
Zhao, Zhao, Wu, and colleagues (Journal of Biological Chemistry, 2004) described cell-permeable peptide antioxidants aimed at the inner mitochondrial membrane. The motif is alternating aromatic and basic residues, with dimethyltyrosine as the scavenger. They report that the peptides concentrate at that membrane and reduce oxidative injury in the cell and mitochondrial preparations they used. PubMed 15178689, DOI 10.1074/jbc.M402999200. Use that paper for the class. Confirm in the full text which analogue code is which before assigning a sentence to SS-31 specifically.
Birk, Liu, Soong, and colleagues (Journal of the American Society of Nephrology, 2013) name SS-31 and report that it binds cardiolipin, the anionic phospholipid of the inner membrane required for cristae, and that the complex reduces cytochrome c peroxidase activity in their ischemia experiments. PubMed 23813215, DOI 10.1681/ASN.2012121216. That cardiolipin interaction is the mechanism to cite. It is not a tissue-repair slogan, and it is not a result for this lot.
Mitchell, Tamucci, Ng, and colleagues (eLife, 2022) published a structure-activity study of this tetrapeptide series. Use it when the question is which analogue does what in their assays. PubMed 35913044, DOI 10.7554/eLife.75531.
The catalog structure
The specification is D-Arg-Dmt-Lys-Phe-NH2, formula C32H49N9O5, mass about 639.8 g/mol. Dmt is dimethyltyrosine, which is the scavenger residue Zhao’s class depends on. Stereochemistry matters: the arginine is the D isomer in this table. A mass match that ignored stereochemistry would not separate this peptide from a diastereomer. The C-terminal amide is part of the mass. This peptide is not MOTS-c, which is sixteen residues and about 2174.6 g/mol.
How to verify this note
- Open Birk 2013 and confirm the words SS-31 and cardiolipin. Open Zhao 2004 for the dimethyltyrosine class, and check the analogue codes in the full text.
- Match CAS 736992-21-5, D-Arg-Dmt-Lys-Phe-NH2, and mass about 639.8 g/mol on the certificate.
- Do not import a clinical endpoint from an elamipretide drug trial onto this research powder.
Selected References
Peer-reviewed literature on the compounds discussed in this guide, listed as scientific background for laboratory researchers. Citation does not imply endorsement by the authors or any use other than in-vitro research.
- Chavez JD, et al. Mitochondrial protein interaction landscape of SS-31. Proc Natl Acad Sci U S A. 2020;117(26):15363-15373. PubMed 32554501 · DOI
Laboratory note: solubility depends on salt form and solvent. This guide does not state a single solubility figure. Handling of lyophilized material is described in the peptide storage guide.
Research Use Only Notice
This guide is provided for educational and laboratory reference purposes. It summarizes published, primarily in-vitro and structural research literature and does not describe, recommend or imply any use in humans or animals. Products sold by Cleared Peptides are for laboratory research use only; they are not drugs, foods, cosmetics or dietary supplements, are not FDA-approved, and are not intended to diagnose, treat, cure, mitigate or prevent any disease. No dosing, administration or therapeutic information is provided.
