SS-31 (Elamipretide): Research Compound Profile

This page is a laboratory research reference for the tetrapeptide commonly designated SS-31, also cataloged under the research name Elamipretide. It summarizes the compound’s chemical identity, structural features, and the analytical methods used to confirm identity and estimate purity. Every batch of SS-31 supplied here is characterized at the USC Alfred E. Mann Multi-Omics Mass Spectrometry Core, a university laboratory, with a public Certificate of Analysis available for review.

Chemical identity

SS-31 is a synthetic aromatic-cationic tetrapeptide. Its chemical identifiers, verified against the PubChem record (CID 11764719), are as follows:

• Research name: Elamipretide (SS-31); additional catalog synonyms include MTP-131, RX-31 and Bendavia.
• CAS number: 736992-21-5
• Molecular formula: C₃₂H₄₉N₉O₅ (free base)
• Molecular weight: 639.79 g/mol (average mass, free base)
• Appearance: white to off-white lyophilized powder

Reference material is frequently isolated as an acetate salt, which raises the measured mass above the free-base value; the salt form and counter-ion content are noted on the accompanying documentation where applicable.

Amino-acid sequence and structure

The sequence is D-Arg-Dmt-Lys-Phe-NH₂, read from the N-terminus to a C-terminal primary amide. Two features distinguish it from a conventional peptide. First, the N-terminal arginine is the D-enantiomer rather than the standard L-form, a substitution associated in the literature with resistance to common proteolytic enzymes. Second, position two is Dmt, 2′,6′-dimethyl-L-tyrosine, a non-proteinogenic residue carrying two methyl groups on the aromatic ring. The alternating aromatic and basic residues give the molecule its characteristic net positive charge at physiological pH, a property described in the published research literature indexed on PubChem and PMC.

Identity and purity by HPLC and LC-MS

Two orthogonal methods are used to characterize each lot. Reversed-phase HPLC (typically a C18 column with a water/acetonitrile gradient and 0.1% trifluoroacetic acid, UV detection near 220 nm) separates the target peak from process-related impurities and provides an area-percent purity estimate. Adequate separation performance is important because the Dmt and Phe aromatic residues respond strongly in the UV region.

LC-MS and high-resolution mass spectrometry (HRMS) confirm molecular identity by measuring the accurate mass of the intact peptide and comparing the observed value to the theoretical mass derived from C₃₂H₄₉N₉O₅. Because the molecule is multiply protonatable, singly and doubly charged ions are both commonly observed, and their measured masses must reconcile with the calculated monoisotopic mass within the method’s stated tolerance. Details of the analytical approach used for this catalog are described on the quality and testing page.

How the COA reports SS-31

An SS-31 certificate of analysis typically presents a defined set of fields that a researcher can read directly:

• Identity: a statement that the observed mass matches the theoretical mass for the sequence, usually reported as “identity confirmed” alongside the HRMS or LC-MS value.
• Purity: an area-percent figure from the HPLC chromatogram (for example, a value at or above the stated specification), representing the target peak relative to detected impurities.
• Batch and method: a batch or lot code, the analytical instrument or laboratory, and the technique (LC-MS/HRMS/HPLC).
• Appearance and net content: the physical description and the stated peptide content per vial.

The batch-specific documents for this catalog are collected in the COA library, and each product listing links its own certificate. Because purity is an area-percent estimate from one detection method, it is read together with the identity result rather than in isolation.

Research context

SS-31 has been the subject of published mitochondrial-membrane research, with studies indexed on PubChem and PubMed Central examining its interaction with cardiolipin, an inner-membrane phospholipid. These references are cited here strictly as background describing what the research literature reports, not as any statement about outcomes. For chemistry, the primary reference remains the PubChem record for Elamipretide. Other research peptides in this catalog, such as MOTS-C, are characterized by the same laboratory methods.

Handling and storage (laboratory reference)

As a lyophilized peptide, SS-31 is generally stored sealed and protected from light and moisture; long-term storage is typically at freezer temperature, with repeated freezing and thawing minimized to preserve peak integrity. For solution preparation in a research setting, sterile water is the common solvent, and prepared solutions are kept cold and used within the working window indicated by the receiving laboratory’s own procedures. These handling notes describe standard reference-material practice only.

For laboratory research use only. Not for human or veterinary use.

Frequently asked questions

What is the CAS number and molecular formula of SS-31 (Elamipretide)?

SS-31, research name Elamipretide, carries CAS number 736992-21-5. Its molecular formula is C32H49N9O5 with an average molecular weight of 639.79 g/mol for the free base, as recorded on PubChem (CID 11764719). Reference material supplied as an acetate salt will show a higher measured mass reflecting the counter-ion.

What is the amino-acid sequence of SS-31?

The sequence is D-Arg-Dmt-Lys-Phe-NH2, a tetrapeptide with a C-terminal primary amide. It includes two non-standard features: a D-configured N-terminal arginine and Dmt (2',6'-dimethyl-L-tyrosine) at position two, a non-proteinogenic residue with two aromatic methyl groups.

How is SS-31 identity and purity reported on a certificate of analysis?

An SS-31 certificate of analysis reports identity by LC-MS or HRMS, confirming the observed accurate mass matches the theoretical mass for the sequence, and reports purity as an area-percent figure from reversed-phase HPLC. It also lists the batch code, appearance, peptide content, and the testing laboratory or method.

What analytical methods characterize SS-31?

Two orthogonal methods are standard: reversed-phase HPLC (usually a C18 column with a water/acetonitrile gradient and UV detection near 220 nm) for the purity estimate, and LC-MS/HRMS for molecular identity by accurate-mass comparison. For this catalog, batches are characterized at the USC Alfred E. Mann Multi-Omics Mass Spectrometry Core.

What synonyms refer to SS-31?

SS-31 is also cataloged as Elamipretide and appears under the research designations MTP-131, RX-31 and Bendavia. All refer to the same tetrapeptide, CAS 736992-21-5, formula C32H49N9O5.