What is SS-31?
Our records give SS-31 as CAS 736992-21-5, formula C32H49N9O5, average molecular weight 639.79, sequence H-D-Arg-Dmt-Lys-Phe-NH2, with the synonyms elamipretide and MTP-131. Two of those building blocks are unusual: the amino-terminal arginine is the D enantiomer, and Dmt is 2,6-dimethyltyrosine rather than plain tyrosine.
The alternating pattern of basic and aromatic groups is the functional core of the design. It pairs a net positive charge with aromatic surface, the combination the literature associates with partitioning into the inner mitochondrial membrane and binding cardiolipin, in a manner described as independent of membrane potential. The D-arginine and C-terminal amide remove the two easiest points of proteolytic attack, which is why so short a sequence survives in biological media.
Published work uses the peptide as a cardiolipin-targeting tool. Cell studies report better-preserved cristae architecture, tighter electron transport chain coupling and lower reactive oxygen species output in models of mitochondrial stress, and rodent work has used it in ischaemia-reperfusion and mitochondrial myopathy models. Whether the primary action is stabilisation of cardiolipin and cytochrome c interactions, redox chemistry from the dimethyltyrosine, or both, is still argued.
Reconstitution & handling
Sterile or bacteriostatic water dissolves this peptide readily; the two basic groups make it strongly water soluble. Add diluent down the vial wall and swirl to clear. Small, highly charged peptides adsorb at low concentration, so prepare stocks at a workable concentration and dilute from those. Concentration is labelled mass over volume, corrected by net peptide content.
Storage & stability
Store the sealed dry vial at -20 °C, desiccated and protected from light, since the dimethyltyrosine chromophore is photolabile. Reconstituted solution holds at 2 to 8 °C in single-use aliquots and should not be frozen repeatedly. The D-arginine and terminal amide make the peptide robust to enzymatic attack but do nothing about oxidation of the phenolic side chain, so amber containers and short hold times remain right.
How it's tested
Reversed-phase HPLC at 214 and 220 nm carries the purity determination, and the aromatic groups give a usable signal near 275 nm for a secondary check. Identity is confirmed by mass spectrometry against the theoretical average mass of 639.79. Because the D-arginine configuration is essential, chiral integrity is a specification point alongside chemical purity. Net peptide content and water are reported, and a lot-matched certificate of analysis is available on request.