SS-31 + TB-500 + MOTS-c - Mitochondrial+

1 Identity

Fixed-ratio three-component article: two all-L peptide free acids co-lyophilized with one C-terminally amidated tetrapeptide containing a D-amino acid and a non-proteinogenic aromatic residue. No metal center, no disulfide, no acyl chain. Each component's full identity lives on its own record and is cross-referenced from here rather than restated. Two of the three names fix no molecule: 'TB-500' is sold as the 43-residue chain at 4,963.506 Da and as the Ac-LKKTETQ heptapeptide at 889.018 Da, and 'MOTS-c' covers five articles including the K14Q polymorph peptide, the rat and mouse sequences and two truncations. 'SS-31' is the research designation for elamipretide, which now has an approved United States product and a proprietary name attached to it.

Contains SS-31 + TB-500 + MOTS-c

Sequence

Per component, cross-referenced. SS-31: H-D-Arg-Dmt-Lys-Phe-NH2, four residues, position 1 D-arginine and position 2 2',6'-dimethyl-L-tyrosine, C-terminal amide. Thymosin beta-4: Ac-SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES-OH, 43 residues. MOTS-c: H-MRWQEMGYIFYPRKLR-OH, 16 residues, free acid. One amide and two free acids share the vial; one N-terminus is acetylated and two are free.

Molecular formula

Per component; a mixture has no combined formula and none is written. SS-31 C32H49N9O5 free base - research material is normally the acetate or trifluoroacetate while the clinical substance is the hydrochloride. Thymosin beta-4 C212H350N56O78S. MOTS-c C101H152N28O22S2 (mono-sulfoxide C101H152N28O23S2). Three sulfur atoms sit across two components and none in the third, so an elemental sulfur figure cannot separate thymosin beta-4 from MOTS-c and is not accepted as a ratio method.

Average mass

Per component, IUPAC 2021 abridged conventional atomic weights: SS-31 639.802; thymosin beta-4 4,963.506; MOTS-c 2,174.621. Worked example at a stated nominal 10 + 10 + 10 mg fill, 30 mg total: 15.630, 2.015 and 4.599 micromol - a 7.76 : 1.00 : 2.28 molar ratio out of a 1 : 1 : 1 mass ratio. That fill is a stated nominal for arithmetic, not a market standard. No single blend molecular weight is printed; a mixture does not have one.

Monoisotopic mass

Per component, neutral: SS-31 639.3857; thymosin beta-4 4,960.4863; MOTS-c 2,173.1077. SS-31 is observed singly and doubly protonated and is lost below the low-mass cut-off of a method tuned for a 4,963 Da chain, so a single acquisition across the 640 to 4,964 Da span is demonstrated on the actual blend or it is not accepted. The two larger chains require deconvoluted spectra alongside the raw charge envelopes.

Salt / variant note

(1) ratio: none standard. (2) 'TB-500' identity: 4,963.506 against 889.018, a 5.58-to-1 mass ratio under one name. (3) 'MOTS-c' identity: five articles, the K14Q polymorph sitting 0.036 Da from the parent and unresolved by intact mass at any practical resolution. (4) SS-31 salt: acetate and trifluoroacetate in the research channel against the hydrochloride as the clinical substance; the counterion is declared per component and the clinical form is not a research-channel default. (5) MOTS-c mono-sulfoxide at +15.9949. The marker set for this article carries three unique residues and needs no subtraction, and the procurement condition that makes it real is an authentic 2',6'-dimethyl-L-tyrosine standard bought before method validation rather than after. Arginine is a chirality-separated marker rather than a compositional one, which is a distinction a laboratory running achiral analysis alone would miss.

2 Class & testing panel

Form

Fixed-ratio blend

Testing panel

P3 — panel definitionfor SS-31 and P1 for thymosin beta-4 and MOTS-c, run per component and never once for the vial. The P3 element belongs to one component: chiral amino acid analysis for D-Arg1 and an authentic standard for 2',6'-dimethyl-L-tyrosine are SS-31 determinations, and a chirality figure reported once for the vial is diluted by two components that contain no D-residue

3 Primary sources & evidence

The index reports the design and provenance of the literature, not a conclusion about effect.

Published literature exists for each component, is graded on that component's record and is cross-referenced rather than restated. None of it is literature about this three-component mixture. No published study of this fixed combination, and no consensus specification for it, was located.

4 Storage & specification

Storage

Taken as the most restrictive of the three components: co-lyophilized solid, minus 20 degrees C plus or minus 5 degrees C, desiccated, protected from light, nitrogen headspace re-blanketed after subdivision. The inert headspace is set by MOTS-c, whose two methionines, one tryptophan and two tyrosines make it the most oxidation-labile article in the vial, with thymosin beta-4's single methionine adding to the same load.

Shelf life

The blend runs its own stability protocol and inherits no component study, so it is dated on that protocol rather than on any component interval. The question that protocol answers rather than assumes is whether the phenolic Dmt residue of SS-31 participates in the oxidation chemistry of a cake already carrying three oxidizable methionines and a tryptophan. The stability-indicating attributes that limit the interval are per-component content, the three-way ratio, methionine sulfoxide, tryptophan oxidation, SS-31 free-acid content, water and counterion.