SS-31 (Elamipretide)
A tetrapeptide with a C-terminal amide and an unusual feature that most certificates do not address: the arginine is the D-enantiomer. Identical mass, identical chromatogram, different molecule.
Pricing and pack sizes
| Size | Cat. no. | Pack | Price per kit | Per vial |
|---|---|---|---|---|
| 10 mg | 2S10 | 10 vials | $90.00 | $9.00 |
| 50 mg | 2S50 | 10 vials | $390.00 | $39.00 |
Prices are in USD and are per kit of 10 vials — not per vial. Larger quantities and mixed kits are quoted on request.
Monograph
| Compound | SS-31 (elamipretide), mitochondria-targeting tetrapeptide |
|---|---|
| CAS Registry Number | 736992-21-5 |
| Molecular Formula | C32H49N9O5 |
| Monoisotopic Mass | 639.8 Da |
| Sequence | D-Arg – Dmt – Lys – Phe – NH2 |
| Modifications | D-arginine at position 1; C-terminal amide; Dmt = 2′,6′-dimethyltyrosine |
| Purity | ≥ 99.0% (RP-HPLC, UV 220 nm) |
| Identity Confirmation | ESI-MS mass match; stereochemistry confirmed separately |
| Available pack sizes | 10 mg, 50 mg — supplied as 10 vials per kit |
| Appearance | White to off-white lyophilized cake or powder |
| Solubility | Soluble in water and aqueous buffers |
| Storage | −20 °C, desiccated, protected from light |
| Documentation | Lot-specific COA with HPLC chromatogram and MS spectrum |
What SS-31 is
SS-31 is a synthetic tetrapeptide designed to accumulate in the inner mitochondrial membrane. The design is carried by three features: a cationic D-arginine for membrane partitioning, a dimethyltyrosine (Dmt) that gives the molecule its antioxidant character, and a C-terminal amide that removes the terminal charge and improves stability.
The most commonly reported mechanism is binding to cardiolipin, the phospholipid found almost exclusively in the inner mitochondrial membrane. That interaction is measurable in lipid-binding assays with synthetic vesicles and does not require living cells.
The molecule is unusual in this catalogue because its identity depends on stereochemistry. A peptide built with L-arginine instead of D-arginine has exactly the same mass and nearly the same retention time. Standard RP-HPLC and a mass match will both pass. That is the failure mode to watch for here.
Why a mass match is not enough
D- and L-arginine are enantiomers: same formula, same monoisotopic mass, same behaviour on a standard achiral C18 column. A supplier can ship the all-L diastereomer and the certificate will look perfect — correct mass, 99% purity, clean chromatogram — while the material is not SS-31.
Confirming it requires a chiral method (chiral stationary phase, or derivatisation followed by achiral HPLC) or an orthogonal technique such as specific rotation. When evaluating any SS-31 certificate, ask which method was used to confirm the D-arginine. If the answer is "HPLC and MS", the stereochemistry has not been tested.
The same logic applies to the Dmt residue: 2′,6′-dimethyltyrosine is defined by its substitution pattern, and positional isomers share the mass. Ring substitution is normally confirmed by NMR rather than mass spectrometry.
Research context
Summarises mechanisms reported in preclinical and in-vitro literature, for scientific orientation only. Not a description of any approved or established clinical application.
Cardiolipin binding
The best-characterised property. SS-31 binds cardiolipin with micromolar affinity, and several studies report that this interaction preserves cristae architecture in isolated mitochondria under oxidative stress.
Electron transport and ROS
In vitro work reports reduced reactive oxygen species generation at complex I and improved respiratory efficiency in isolated mitochondrial preparations. These are organelle-level measurements, not organism-level outcomes.
Note on evidence status
SS-31 has been through clinical development as elamipretide and has not obtained regulatory approval in any major market. It is not an approved medicine, and the material here is a research reference standard.
Frequently asked questions
What is the sequence of SS-31?
D-Arg – Dmt – Lys – Phe – NH2, monoisotopic mass 639.8 Da. Dmt is 2′,6′-dimethyltyrosine and the C-terminus is amidated.
Why does the D-arginine matter?
D- and L-arginine have identical mass and near-identical retention on an achiral C18 column. A mass match and a clean chromatogram do not prove the correct stereochemistry. Confirmation needs a chiral method or specific rotation.
What does the C-terminal amide change?
It removes the terminal negative charge and lowers the mass by about 1 Da relative to the free acid. Amidation is part of the specification to SS-31, so the spectrum should show it.
What purity do you guarantee?
≥ 99.0% by RP-HPLC per released lot. The measured value for your lot appears on its certificate of analysis.
What pack sizes are available?
10 mg and 50 mg vials, supplied as 10 vials per kit. Prices per kit are listed on this page; larger or mixed orders are quoted on request.
Is SS-31 approved for human use?
No. It has been investigated clinically as elamipretide but has not obtained regulatory approval in any major market, and is supplied here strictly as a research reference standard.
Research use only
This product is a chemical reference standard intended exclusively for in-vitro laboratory research and analytical method development. It is not a pharmaceutical, drug, food, food additive, cosmetic, or veterinary product. It has not been evaluated or approved by the FDA, EMA, MHRA, TGA, or any other regulatory authority, and it must not be administered to humans or animals.