SS-31 FAQ: Storage, Mixing and Stability

The questions below are the ones researchers ask most about storing, mixing and handling SS-31. Each answer reflects the peptide’s sequence, D-Arg-Dmt-Lys-Phe-NH2, where Dmt is 2′,6′-dimethyltyrosine, and links to the fuller page where there is one.

How long does SS-31 last in the fridge after mixing?

Mixed with bacteriostatic water and kept at 2 to 8 °C in the dark, SS-31 lasts 8 to 12 weeks under Vistara Labs’ handling guidance, with quality slowly fading from around week 6 to 8. Its developer describes it as very stable in solution, but no published study gives a figure in weeks, so the window is general guidance that its chemistry supports. The full table is on how long SS-31 lasts.

How long does unmixed SS-31 powder last?

A sealed lyophilised vial keeps for the weeks it is in use at 2 to 8 °C and for long periods at minus 20 °C, where a supplier rates the powder in years. The dry cake has almost no water or oxygen, so the oxidation that slowly affects SS-31 in solution has little to work with. Days at room temperature in transit do not harm it, so it ships without an ice pack.

Is SS-31 the same as elamipretide?

Yes. Elamipretide is the name the same molecule carries in clinical research, and PubChem lists SS-31, elamipretide and MTP-131 as synonyms of one compound (CID 11764719). Our research vial is the four-residue peptide D-Arg-Dmt-Lys-Phe-NH2, supplied for laboratory work. More in what is SS-31.

Why is SS-31 so resistant to enzymes?

Its first residue is D-arginine, the mirror-image form, and its end is capped as an amide. Its developer credits those two changes with greatly enhanced stability against peptidase degradation (Szeto, British Journal of Pharmacology, 2014). In a sterile vial there are no enzymes anyway, so for storage the more important point is what it lacks: no methionine, cysteine, asparagine, glutamine or aspartic acid.

What is the weak point of SS-31 in solution?

The dimethyltyrosine ring. Its phenol is what lets SS-31 scavenge oxidants (Zhao et al., Journal of Biological Chemistry, 2004), and a residue that reacts with oxidants can slowly oxidise in the vial. Light, trace metals and warmth speed that reaction, so a mixed vial is kept cold, dark and sealed. The details are on the SS-31 stability page.

What do you mix SS-31 with?

Bacteriostatic water, which is sterile water with 0.9% benzyl alcohol so a refrigerated vial can be accessed more than once. SS-31 carries three positive charges at that pH and is very water-soluble, so it dissolves fully without acid or other solvents. The reasons are on the SS-31 solubility guide.

How much bacteriostatic water goes in a 10 mg SS-31 vial?

There is no single correct volume. With 2 mL a 10 mg vial gives 5 mg/mL; with 1 mL it gives 10 mg/mL. More water spreads the same amount of peptide through a larger volume, so write the chosen concentration on the vial. The tables and calculator are on the SS-31 reconstitution page.

Why is my SS-31 cloudy or tinted after mixing?

Brief cloudiness that clears within 10 to 15 minutes is usually trapped air from adding water too fast or shaking. Haze that persists, particles, or a yellow tint that appears later point to warm storage, light, freezing or contamination, and the solution is discarded. More in why peptides gel or go cloudy.

Can you freeze mixed SS-31?

Not a vial that will be opened again, because repeated freezing and thawing promotes aggregation in peptide solutions. Laboratories that need frozen solution divide it into single-use aliquots and thaw each one once. Sealed powder can be frozen at minus 20 °C without concern.

Does SS-31 need to be kept out of the light?

Yes, more than most peptides in this series. It has two aromatic rings, the Dmt phenol and phenylalanine, and aromatic residues absorb ultraviolet light, which can start oxidation of tyrosine-type residues. Keep the vial boxed in the main body of the fridge and return it after each access.