SS-31 is the compound we get asked about more than everything else in our catalogue put together. Some of the people asking have read every paper going. Others saw the name once in a forum thread and want to know what it actually is before they spend money. This article is for the second group, though the first might still find a thing or two worth checking.
We sell SS-31, so we are not neutral. What we can do is tell you what we know from handling it, shipping it and answering the same questions week after week. Nine facts, in the order people usually need them.
Table of Contents
Table of Contents
1. SS-31 is a four amino acid peptide, and that is unusually small
Most peptides people order for research run from ten to forty amino acids. SS-31 has four. Its sequence is D-Arg-Dmt-Lys-Phe-NH2, which gives it a molecular weight of about 639.8 g/mol. You could draw the whole thing on a napkin.
Two of those four residues are not standard. The first is D-arginine, the mirror image of the arginine your cells normally use. The second is Dmt, short for 2,6-dimethyl-L-tyrosine, which is tyrosine with two extra methyl groups bolted on. Neither was chosen by accident. D-amino acids are hard for enzymes to chew through, so the peptide survives longer. The dimethyltyrosine is what gives the molecule its ability to mop up reactive oxygen species.
Small size matters for practical reasons too. A short peptide is easier to make cleanly, easier to purify and easier to verify. When a supplier says their SS-31 is 99 percent pure, that claim is far more believable for a tetrapeptide than for a 40 residue chain with a fatty acid hanging off it.
2. The name comes from the two people who made it
The SS stands for Szeto and Schiller. Hazel Szeto was a pharmacologist at Weill Cornell in New York. Peter Schiller ran a peptide chemistry lab in Montreal. In the late 1990s and early 2000s they were working on opioid peptides, trying to build better painkillers, and they noticed that some of their compounds were ending up inside mitochondria. That was not supposed to happen. Charged peptides are not meant to walk through cell membranes.
They followed the odd result instead of ignoring it. What came out was a small family of numbered compounds. The number 31 is simply where this one sat in the series. There is no deeper meaning to it. We wrote more about the rest of the family in our piece on the Szeto-Schiller peptide group if you want the longer story.
You will see SS-31 under other names. Elamipretide is the official generic name. MTP-131 was a company code. Bendavia was an early brand name that was later dropped. They all refer to the same molecule. If you are searching the literature, you need all of them, because papers from different years use different labels and the search engines do not always connect them.
3. It goes to the mitochondria without needing a push
This is the property that made people sit up. Most compounds designed to reach mitochondria, such as MitoQ, hitch a ride on the electrical charge across the inner mitochondrial membrane. That works well in healthy cells. It works badly in damaged ones, because damaged mitochondria lose that charge, and those are exactly the mitochondria researchers tend to care about.
SS-31 does not rely on membrane potential in the same way. Its alternating pattern of aromatic and positively charged residues lets it slip across the cell membrane and settle on the inner mitochondrial membrane. Early studies reported it concentrating there a thousand fold or more compared with the surrounding fluid. It gets in fast as well, within minutes in cell culture.
For anyone designing an experiment, the upshot is simple. You do not need a delivery vehicle, a transfection reagent or a carrier. You add it to the medium.
4. What SS-31 actually does once it gets there
For years the short answer was that it is an antioxidant. That turned out to be only part of the picture, and probably not the most important part.
The current view is that SS-31 binds to cardiolipin, a phospholipid found almost only in the inner mitochondrial membrane. Cardiolipin is not a passive bit of fat. It holds the folds of the membrane in shape and helps the protein complexes of the electron transport chain sit together properly. When cardiolipin is damaged or oxidised, those complexes drift, electrons leak and energy production drops.
By sitting on cardiolipin, SS-31 seems to protect it and to keep the membrane organised. A 2013 paper from the Szeto lab showed the interaction directly and linked it to better energy output in stressed mitochondria. Later work using cross-linking found the peptide near a number of the proteins involved in making ATP.
We would be careful with any stronger claim than that. The mechanism is still being argued over. What is not in dispute is that the cardiolipin interaction is real and that it is the starting point for nearly every current study.
5. There is a large body of published research on SS-31
If you search PubMed for the peptide, you will get hundreds of results. Not many compounds sold as research peptides can say that. The work falls into a few broad groups.
- Heart and kidney models, especially injury caused by cutting off and then restoring blood flow.
- Skeletal muscle in ageing animals, where a well known 2013 study in mice reported improved mitochondrial energetics after a single treatment.
- Eye models, including work on retinal cells.
- Inherited mitochondrial conditions, most notably Barth syndrome, which is caused by a fault in cardiolipin processing.
- Neurological models, a smaller and more recent area.
Most of this is preclinical, meaning cells and animals. Some of it went on to human trials run by the company that licensed the molecule. We covered that history, including the trials that failed, in our article on elamipretide. It is worth reading if you want a sober view, because the story is not one long success.
6. The material sold for research is not a medicine
This needs saying plainly. In September 2025 the US Food and Drug Administration granted accelerated approval to a pharmaceutical form of elamipretide for Barth syndrome. You can read the FDA trial snapshot for the details. That product is made under pharmaceutical manufacturing rules, prescribed by doctors and supplied through pharmacies.
The SS-31 we sell is a research chemical. Same molecule, different purpose and different regulatory status. It is sold for laboratory and in-vitro work only. It is not for human or animal consumption, and we do not answer questions about dosing or personal use. If that is what you are after, we are the wrong shop, and so is every other research supplier.
We say this early because it saves everyone time.
7. Purity grades exist for a reason
We stock SS-31 in four grades. People sometimes assume that is marketing. It is not. Different experiments need different things, and paying for purity you will not use is a waste of a grant.
- Standard Grade is 98 percent or better. Fine for method development, practice runs and work where you are checking that an assay behaves at all.
- High Purity Grade is the one most labs settle on for routine cell work.
- Ultra-Pure Research Grade is 99.5 percent or better, verified by both HPLC and mass spectrometry. This is for studies where a reviewer will ask what was in the vial.
- Bulk Research Grade comes in 100 mg, 250 mg and 500 mg vials for groups that go through a lot.
If you are unsure, start one grade lower than you think you need and run a pilot. You can always step up. We have a longer guide to choosing between them in the SS31 buying guide.
8. How SS-31 is tested, and what to ask any supplier
Every lot of SS-31 we ship is checked two ways. HPLC tells you how much of the sample is the main compound and how much is something else. Mass spectrometry tells you whether the main compound has the right molecular weight. You need both. A sample can be 99 percent pure and still be 99 percent of the wrong thing.
The results go on a Certificate of Analysis, which ships with the order. A proper COA has a lot number, a date, the method used and the actual chromatogram or at least the numbers from it. A COA with no lot number is a brochure.
Questions worth asking any supplier, us included:
- Is the COA for the lot I am receiving, or a generic one?
- Was identity confirmed by mass spec, or only purity by HPLC?
- What is the counter-ion, and is the stated weight the peptide content or the gross weight?
- Can I see the COA before I pay?
We answer yes to the last one. Ask through the contact page and name the grade you are interested in. For more on reading the document itself, see our piece on SS31 peptide purity testing.
9. Storage is simple, but people still get it wrong
SS-31 ships as a freeze-dried powder in a sealed vial. In that form it is stable. Keep it at minus 20 degrees Celsius, in the dark, and it will sit happily for a long time. Short trips at room temperature during shipping do not hurt it.
The trouble starts once you add liquid. A peptide in solution is on a clock. Keep it in the fridge at 2 to 8 degrees, use it within the window on your COA and do not freeze and thaw the same tube again and again. If you need to use it over weeks, split it into small portions on day one and freeze those, so each portion is only thawed once.
The other common mistake is opening a cold vial straight from the freezer. Water from the air condenses on the powder. Let the vial come up to room temperature first, then open it. It takes twenty minutes and saves a lot of grief. The full routine is in our SS-31 peptide storage guide.
How ordering SS-31 from us works
We are a wholesale supplier. The minimum order is 50 units, and there is no upper limit. That suits labs with ongoing projects, institutions buying for several groups and resellers.
The process is short.
- Go to the main SS-31 peptide page and look at the sizes and prices.
- Press Order next to the one you want. The enquiry form opens with that item filled in.
- Add the number of units and your delivery address, and pick how you would like to pay.
- We reply by email with the total and payment details.
We accept Apple Pay, Zelle, Chime, Cash App, USDT and Bitcoin. Once payment clears, the order goes out with its COA. Most enquiries get a reply the same day, and we try hard to keep it that way, because we know a stalled order can stall a whole project.
If you need something we do not list, such as a different vial size or a mixed order across grades, just say so in the message. We would rather have that conversation than have you guess.
A few things SS-31 is often confused with
Because it gets discussed alongside other popular research compounds, SS-31 is sometimes lumped in with peptides that work in completely different ways. A quick sort-out.
BPC-157 is a 15 amino acid peptide studied mostly in tissue repair models. It has nothing to do with mitochondria. TB-500 is synthetic thymosin beta-4, an actin-binding peptide studied in cell migration. GHK-Cu is a copper-binding tripeptide from the skin and matrix biology world. Retatrutide is a much larger metabolic peptide that acts on three hormone receptors.
None of those is a substitute for SS-31, and it is not a substitute for any of them. If a study design calls for a mitochondria-targeted compound, this is the one in our catalogue that fits. We stock the other four because labs that order one often need another, not because they are interchangeable.
What we would tell a colleague
If a friend running a lab asked us whether SS-31 was worth looking at, we would say this. It is one of the better characterised research peptides you can buy. The mechanism is interesting and still open enough to be worth studying. The molecule is small and stable, which makes it forgiving to work with. And the literature is deep enough that you will not be working blind.
We would also say: read the negative trials as well as the positive papers, buy from someone who will show you a lot-specific COA, and do not pay for ultra-pure material to run a pilot.
What SS-31 costs, and what you are paying for
People are often surprised that SS-31 is cheaper per milligram than many longer peptides. It should be. There are only three coupling steps in the synthesis, and the purification is quick because there are few by-products to separate.
The one costly ingredient is the dimethyltyrosine. It is a specialty amino acid, made in small volumes, and it accounts for a good part of the raw material bill. The rest of the price is labour, analysis, freeze-drying, vials and shipping.
Our own prices run from $39 for a 5 mg Standard Grade vial to $1,599 for a 500 mg Bulk Research Grade vial. Per milligram, that is under eight dollars at the small end and a little over three at the large end. The step up from Standard to Ultra-Pure adds roughly half again to the price of a given size. Whether that is worth it depends entirely on what the material is for, which is why we keep saying to decide that first.
A quick way to sanity-check any quote for SS-31: divide the price by the milligrams, then ask whether the weight is net peptide or gross powder. Two offers that look thirty percent apart can turn out to be the same once you correct for that.
Who actually orders it
It may help to know who else is buying. Our orders come from four kinds of customer.
University labs working on mitochondrial biology, ageing, kidney or heart models. They tend to order High Purity or Ultra-Pure in 10 mg and 25 mg vials, a box at a time, on a steady rhythm through the academic year.
Contract research organisations running studies for someone else. They want Ultra-Pure, full paperwork, one lot for the whole study and a quote on letterhead. They ask the most questions before ordering and the fewest afterwards.
Analytical labs that use SS-31 as a reference material for method development. They buy small quantities of the highest grade and care more about the certificate than the price.
Resellers and distributors who supply labs in their own country. They buy Bulk grade or large mixed orders and usually want a standing arrangement.
If you are in one of those groups, tell us which when you write. It lets us skip the generic reply and go straight to what you are likely to need.
A short glossary
A few terms come up in every conversation about this compound. If you are new to peptides, these are the ones worth knowing.
- Lyophilized. Freeze-dried. The form in which the powder ships.
- Reconstitute. To dissolve the powder in a liquid before use.
- COA. Certificate of Analysis, the document reporting test results for a specific lot.
- Lot or batch. One production run. Everything from the same lot was made and tested together.
- HPLC purity. The share of the peptide material that is the intended compound, as measured by liquid chromatography.
- Net peptide content. The share of the powder weight that is actually peptide, once salts and water are subtracted.
- Counter-ion. The negative ion paired with the positively charged peptide. Usually acetate or trifluoroacetate.
- Cardiolipin. The mitochondrial membrane lipid that SS-31 binds.
- In vitro. In glassware or culture, as opposed to in a living animal.
None of these is complicated once you have seen it used a couple of times. If a supplier uses a term you do not recognise and will not explain it, that is useful information about the supplier.
When SS-31 is the wrong choice
It is only fair to say when not to buy it. If your question is about general oxidative stress in the cell body and not about mitochondria, a cheaper untargeted antioxidant will tell you more. If your cells are healthy and you are hoping for a boost, SS-31 is unlikely to give you one. And if what you need is a medicine for a person, a research vial is not that. We would rather lose a sale than have someone order the wrong thing and feel misled afterwards.
Common questions about SS-31
Is SS-31 the same as elamipretide?
Yes. Elamipretide is the international non-proprietary name for the same molecule. MTP-131 and Bendavia are older labels for it. The Wikipedia entry for elamipretide lists them all.
What does SS-31 look like when it arrives?
A small amount of white to off-white powder or a thin cake at the bottom of a sealed glass vial. Five milligrams is not much to look at. That is normal. Do not judge the fill by eye.
Can I order fewer than 50 units?
Our standard terms are wholesale. If you need a smaller quantity to evaluate before committing, write to us and explain. We deal with that case by case.
How fast do you ship?
We confirm by email first, then ship once payment is received. Tell us in your enquiry if you are working to a deadline and we will tell you honestly whether we can meet it.
Do you provide a COA with SS-31?
Every order ships with the Certificate of Analysis for its lot. You can also ask to see it before you order.
That is the short version of what we know about SS-31. When you are ready, the sizes and current prices are on the SS-31 peptide page, and the contact form is the quickest way to reach us.