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Modified tetrapeptide dossier

Which stereochemistry and salt-form fields matter for an SS-31 record?

A research dossier for the elamipretide/SS-31 free molecular entity, D-arginine, dimethyltyrosine, C-terminal amide, and counter-ion separation.

Reviewed by Peptide Harbor editorial reviewUpdated 2026-08-03Educational research-data guidance

Answer first

SS-31 should be recorded as the modified tetrapeptide elamipretide, not as an ordinary four-letter natural sequence. The defined entity includes D-arginine, 2,6-dimethyltyrosine, lysine, phenylalaninamide, and a specific stereochemical record; TFA and other salts require separate formula and mass accounting.

Reviewed Chemical LedgerSS-31 / Elamipretide
Molecular form representedFree elamipretide molecular entity represented by PubChem CID 11764719
CAS number
736992-21-5
Molecular formula
C32H49N9O5
Average molecular weight
639.8 g/mol average molecular weight
Exact mass
639.38566570 Da
Reviewed peptide designationH-D-Arg-2,6-dimethyl-Tyr-Lys-Phe-NH2
Sequence representationIncludes stated terminal and modification notation
D-Arg-Dmt-Lys-Phe-NH2
Structural notes
  • D-arginine
  • 2,6-dimethyltyrosine
  • C-terminal phenylalaninamide
Salt or counter-ion scopeFree molecular entity; TFA and other salt records must be handled separately
Known Aliases / Code Names:SS-31ElamipretideMTP-131Bendavia

Field-level sources

PubChem CID 11764719: Elamipretide

National Library of Medicine / PubChem · accessed 2026-08-03

Supports: name, molecularForm, cas, formula, weight, exactMass, sequence, peptideDesignation, modifications, saltForm, aliases

Where this framework helps

  • Defining a modified tetrapeptide identity record
  • Separating free entity and TFA or other salt forms
  • Planning evidence for stereochemistry, terminal amide, and intact mass

Limits to keep visible

  • The one-letter shorthand RXKF does not encode every non-standard structural feature.
  • The free-entity formula must not be applied to a salt without composition review.
  • This dossier excludes medical, administration, dosing, and outcome guidance.
01

Expand the shorthand before analysis

The public record identifies elamipretide as H-D-Arg-Dmt-Lys-Phe-NH2. Dmt represents a dimethylated tyrosine residue, and the terminal amide contributes to the defined formula and mass.

02

Record the salt independently

PubChem provides separate free-entity and TFA-related records. The packet should identify which form is present and request counter-ion or composition evidence when the weighed-material basis matters.

03

Do not collapse stereochemistry into a sequence code

An expected intact mass may agree while a stereochemical question remains unanswered. The required identity depth should therefore be defined before selecting the evidence workflow.

Primary and official sources

References used for this page

Visible FAQ

Questions research teams ask

Is RXKF a complete SS-31 identity description?

No. It is a compact sequence representation that does not fully state D-arginine, dimethyltyrosine, stereochemistry, or the C-terminal amide.

Which mass does this page report?

It reports the free elamipretide entity from PubChem CID 11764719: 639.8 g/mol average molecular weight and 639.38566570 Da exact mass.

Can a TFA salt use the same formula?

No. A TFA-associated material has additional composition. Use a separately defined salt record and state the counter-ion basis.