Szeto Schiller 31 is the long-hand name for SS-31, and it is how a surprising number of people first type it into a search box. They have heard Szeto Schiller 31 mentioned in a talk or seen it in a slide, caught the two surnames and the number, and gone looking. If that is how you got here, welcome. You are in the right place.
This article is about how Szeto Schiller 31 has actually been studied. Not the mechanism, which we cover elsewhere, and not the clinical trials. The models. Which cells, which tissues, which kinds of stress, and what was measured. If you are planning your own work with Szeto Schiller 31, seeing what others did, and what they wished they had done differently, is the fastest way to a sound design.
We supply Szeto Schiller 31 for research and have talked through a great many study plans with customers. What follows draws on the published literature and on those conversations.
Table of Contents
Table of Contents
A quick word on what Szeto Schiller 31 is
Szeto Schiller 31 is a synthetic peptide of four amino acids, D-Arg-Dmt-Lys-Phe-NH2, made by Hazel Szeto and Peter Schiller in the early 2000s. It enters cells without help, concentrates at the inner mitochondrial membrane and binds a lipid called cardiolipin. It is also known as elamipretide and MTP-131.
If any of that is new, three of our other articles fill in the background: the Szeto-Schiller peptide family, MTP131 and cardiolipin, and the essential facts about SS-31.
One principle runs through every model below and is worth stating now. Szeto Schiller 31 does very little to healthy mitochondria. Its effects show up when mitochondria are stressed, damaged or old. A study in unstressed cells is likely to find nothing, and that null result will not mean much.
Model 1: Isolated mitochondria
The simplest system. Mitochondria are purified from tissue, usually liver, heart or kidney, and studied in a buffer.
This is where the earliest work was done. Researchers showed that Szeto Schiller 31 was taken up by isolated mitochondria, that it reduced the production of hydrogen peroxide, and that it prevented the swelling and membrane rupture that calcium overload causes.
Typical measurements:
- Oxygen consumption, with different fuels to isolate each respiratory complex.
- ATP production rate.
- Hydrogen peroxide release.
- Swelling, followed by light scattering.
- Cytochrome c release.
What this model is good for: clean mechanistic questions with no interference from the rest of the cell. What it is bad for: anything that takes longer than an hour or two, because isolated mitochondria do not last.
A practical note. The isolation procedure itself damages mitochondria to some degree, and how much depends on the hands doing it. That damage is, in a sense, the stress Szeto Schiller 31 acts on. Results can vary between labs for this reason. Keep your preparation consistent and report its quality.
Model 2: Cultured cells under oxidative stress
One step up. Cells grown in a dish are exposed to something that generates reactive oxygen species, and Szeto Schiller 31 is added before, during or after.
Common stressors include hydrogen peroxide, tert-butyl hydroperoxide, high glucose, and inhibitors of the electron transport chain such as antimycin. Cell types have ranged from kidney tubule cells and heart muscle cells to neurons, retinal cells and endothelial cells.
Typical measurements:
- Cell survival.
- Mitochondrial membrane potential, using fluorescent dyes.
- Reactive oxygen species, with probes such as MitoSOX.
- Markers of apoptosis.
- Oxygen consumption on a plate-based analyser.
This is the most accessible model and the one most new users of Szeto Schiller 31 start with. A few things we have seen go wrong.
Too much stress. If the insult kills ninety percent of cells in an hour, nothing will rescue them. Titrate the stressor so that you get partial damage with room to improve.
Too little stress. The opposite problem. Healthy cells, no effect.
Glucose-fed cells. Many cell lines in standard high-glucose medium barely use their mitochondria. They make their ATP by glycolysis. Switching to galactose medium forces them to rely on oxidative phosphorylation, and mitochondrial effects become far easier to see.
Dye artefacts. Some membrane potential dyes are themselves positively charged and compete for the same space. Confirm with a second method.
Model 3: Ischaemia and reperfusion
This is the classic. Blood supply to an organ is interrupted for a set time and then restored. The return of oxygen causes a burst of reactive species and a wave of mitochondrial damage that kills more tissue than the oxygen shortage alone.
Szeto Schiller 31 has been tested in ischaemia-reperfusion models of the heart, kidney, brain, liver and skeletal muscle. The kidney work is especially thorough. In rats, treatment preserved the internal structure of mitochondria in tubule cells, sped up the recovery of ATP, and reduced cell death and later scarring.
Typical measurements:
- Infarct size or area of tissue death.
- Organ function, such as serum creatinine for kidney or ejection fraction for heart.
- Mitochondrial structure by electron microscopy.
- Tissue ATP content.
- Markers of inflammation and fibrosis at later time points.
The lesson from this model is about timing. In animals, Szeto Schiller 31 is usually given shortly before blood flow is restored, under tightly controlled conditions. When the same idea was tried in heart attack patients, where timing cannot be controlled so precisely, the main endpoint was missed. Our article on elamipretide covers that trial. If you work in this model, think carefully about when Szeto Schiller 31 is present relative to reperfusion, and say so clearly in your methods.
A cell culture version exists too: deprive cells of oxygen and glucose for a period, then restore both. It is a reasonable first step before animal work.
Model 4: Ageing
Mitochondrial function declines with age in most tissues. Old mitochondria make less ATP and leak more.
The best-known study of Szeto Schiller 31 in this setting was published in 2013. Old mice were given a single treatment, and mitochondrial energetics in leg muscle were measured in the living animal using magnetic resonance and optical spectroscopy. Within an hour, ATP production and the efficiency of oxygen use had moved back toward the values seen in young mice. Young mice given the same treatment did not change. After a week of daily treatment, the old mice had better resistance to fatigue and ran for longer.
Later work extended this to the ageing heart, where eight weeks of treatment improved the relaxation phase of the heartbeat in old mice, and to ageing kidney and brain.
Typical measurements:
- In vivo ATP production.
- Exercise capacity and fatigue resistance.
- Heart function by ultrasound.
- Protein oxidation and redox state in tissue.
What makes ageing an attractive model is that the stress is natural and no injury has to be inflicted. What makes it hard is cost and time. Old mice are expensive and scarce. If you plan such a study, order animals well ahead and make sure you have enough compound from a single lot to cover the whole thing. Our SS31 buying guide has a section on sizing an order.
Model 5: Heart failure
Failing hearts have abnormal mitochondria, reduced cardiolipin and poor energy reserves.
Szeto Schiller 31 has been tested in mice with heart failure caused by pressure overload or by angiotensin, in rats after heart attack, and in dogs with failure induced by repeated tiny blockages of the coronary arteries. In the dog study, three months of daily treatment improved the heart's pumping function and normalised several measures of mitochondrial respiration in heart tissue.
There is also work on human tissue. Heart muscle taken from failing hearts at the time of transplant was treated in the lab, and mitochondrial oxygen use improved within hours.
Typical measurements:
- Ejection fraction and chamber volumes.
- Blood markers of cardiac stress.
- Mitochondrial respiration in tissue samples.
- Cardiolipin content and composition.
- Assembly of respiratory supercomplexes.
Human trials in heart failure did not reproduce the animal benefit over four weeks. Whether that is a question of duration, dose, patient selection or biology is not settled. For bench researchers it argues for longer treatment periods and for measuring tissue-level changes, not only organ function.
Model 6: Genetic mitochondrial disease
Some of the most informative work has been done in models of inherited disease, because the defect is defined.
Barth syndrome is the clearest example. It is caused by loss of tafazzin, the enzyme that matures cardiolipin. Researchers have used cells from patients, including stem-cell derived heart muscle cells, and mice with reduced tafazzin. In these systems Szeto Schiller 31 improved mitochondrial structure and function despite the underlying lipid defect remaining.
Other models include cells from patients with Friedreich ataxia and with defects in mitochondrial DNA maintenance.
Typical measurements:
- Cristae structure by electron microscopy.
- The ratio of immature to mature cardiolipin.
- Respiration and ATP output.
- Contractile function in heart cells.
If you have access to patient-derived cells, this is where Szeto Schiller 31 can be tested most directly against its proposed target. It is also the area where a pharmaceutical form of Szeto Schiller 31 eventually won approval, in 2025, for Barth syndrome.
Model 7: The eye
The retina uses a great deal of energy, and its cells are packed with mitochondria. Mitochondrial decline is thought to contribute to several eye diseases.
In the lab, Szeto Schiller 31 has been tested on retinal pigment epithelial cells and other retinal cell types under oxidative stress, and in animal models of diabetic eye disease, glaucoma and retinal degeneration. Reported effects include better cell survival, preserved mitochondrial membrane potential and less cell death.
Typical measurements:
- Cell viability.
- Mitochondrial morphology by imaging.
- Visual function tests in animals.
- Retinal thickness and layer structure.
This model is worth knowing about because it is technically approachable. Retinal pigment epithelial cell lines are widely available and easy to grow, and they respond well to mitochondrial stressors.
Controls that make a study convincing
Whichever model you choose, the controls matter more than anything else. A list we would hand to anyone starting out.
- Vehicle. The same solvent with no peptide, handled identically.
- Unstressed plus peptide. To show that Szeto Schiller 31 alone does nothing to healthy cells. This is a feature, not a failure.
- A general antioxidant, such as N-acetylcysteine. If it does not reproduce the effect, simple scavenging is unlikely to be the explanation.
- A different mitochondria-targeted antioxidant, such as MitoQ, where relevant.
- SS-20, if you can obtain it. It reaches mitochondria but cannot scavenge radicals, so it separates location from chemistry.
- More than one concentration. Published cell studies have used a wide range, from nanomolar to micromolar. Run a series and find where your system responds.
- More than one time point.
And one that is easy to forget: confirm Szeto Schiller 31. Keep the Certificate of Analysis, note the lot number in your records, and if you can, run your own HPLC on arrival. Our piece on SS31 peptide purity testing explains how.
Practical points on preparing Szeto Schiller 31
Szeto Schiller 31 dissolves readily in water. Make a concentrated stock in sterile water or buffer, split it into single-use portions, and freeze them. Dilute into medium on the day. Avoid repeated freezing and thawing.
When calculating concentrations, remember that the powder is a salt. Szeto Schiller 31 itself may be 65 to 85 percent of the weight depending on the counter-ion. Ask your supplier which convention their label uses. The arithmetic is worked through in our article on elamipretide peptide chemistry, and the storage routine is in the SS-31 peptide storage guide.
Choosing a grade for your model
Different models make different demands on the material.
- Screening stressors and concentrations in cells: Standard Grade is enough.
- Routine cell culture experiments: High Purity Grade.
- Isolated mitochondria, mechanistic or analytical work that will be published: Ultra-Pure Research Grade or the 50 mg vial.
- Animal studies and anything needing large amounts from one lot: Bulk Research Grade, up to 500 mg per vial.
How to order Szeto Schiller 31 from us
We list it as SS-31. Our minimum order is 50 units with no upper limit, and you can mix grades and sizes or add other compounds such as BPC-157, TB-500, GHK-Cu and Retatrutide.
Open the SS-31 peptide page, press Order beside the size you want, and enter the quantity and your delivery address. Tell us in the message if you need the whole order from a single lot, which we recommend for any study. We reply by email with the total, normally the same day. We accept Apple Pay, Zelle, Chime, Cash App, USDT and Bitcoin. The Certificate of Analysis ships with the order, or ahead of it if you ask through the contact page.
All material is sold for laboratory and in-vitro research only. It is not for human or animal consumption.
A four-week pilot plan
If you are starting from nothing, here is a pilot we have seen work in several labs. It uses cultured cells and needs no special equipment beyond a plate reader. Adjust it to your own system.
Week one. Get your cells growing well in galactose medium. This alone can take a few passages, and some lines do not tolerate it, which is worth knowing early. Reconstitute one vial of Szeto Schiller 31, make single-use aliquots, and freeze them.
Week two. Find your stressor dose. Treat cells with a range of concentrations of your chosen stressor and measure survival a day later. You are looking for the dose that leaves about half to two-thirds of cells alive. Too gentle or too harsh and there is nothing to rescue.
Week three. Run Szeto Schiller 31. Using the stressor dose from week two, add Szeto Schiller 31 across a wide range, say six concentrations spanning three orders of magnitude, with a short pre-treatment. Include vehicle, peptide-only and stressor-only wells. Measure survival and one mitochondrial readout, such as membrane potential.
Week four. Repeat week three exactly, with fresh aliquots, on a different day. If the result holds, you have a working model. If it does not, you have learned that cheaply.
The whole pilot uses a few milligrams of compound. Standard Grade is fine for it. Only once the model is behaving do you need to think about higher grades and larger quantities.
What to report when you write it up
A lot of published work on Szeto Schiller 31 is hard to compare because key details are missing. If you want your study to be useful to others, include these.
- The supplier, grade and lot number of Szeto Schiller 31.
- Its purity and how that was determined.
- Whether stated concentrations refer to the salt or the free peptide.
- The solvent and stock concentration.
- How long before, during or after the stress Szeto Schiller 31 was present.
- The medium, including glucose or galactose and serum content.
- Passage number and source of cells, or age, sex and strain of animals.
- Every control you ran, including the ones that showed nothing.
- How many independent repeats, and what counts as one.
The ones that showed nothing matter. A clear statement that Szeto Schiller 31 had no effect on unstressed cells is a result, and it supports the specificity of whatever effect you did see.
Budgeting compound for each model
How much you need varies enormously between models, and running out mid-study is a common and avoidable problem.
Cell culture uses very little. At micromolar concentrations in a few millilitres of medium, a single 5 mg vial covers dozens of plates.
Isolated mitochondria use more, because concentrations are often higher and preparations are repeated many times. Plan on tens of milligrams for a full study.
Animal work is where the quantity jumps. Daily treatment of a cohort of mice for several weeks can run to hundreds of milligrams. Larger animals need more again. This is where Bulk Research Grade makes sense, and where it is most important to get the whole amount from a single lot of Szeto Schiller 31.
Whatever the model, work out the total before you order, add a third for losses and repeats, and round up. Then tell your supplier you want it from one lot. A study that changes lot halfway is a study with an extra variable, and reviewers will ask about it.
One more thing on negative results
Not every experiment with this compound works, and not every model responds. The clinical record makes that plain. If you run a careful study with proper controls and see no effect, that is worth knowing and worth publishing. The field has more than enough positive reports from small studies. What it lacks is a clear map of where Szeto Schiller 31 does not help, and that map can only be drawn from honest negative results.
Questions about working with Szeto Schiller 31
Which model should a new lab start with?
Cultured cells under a titrated oxidative stress, ideally in galactose medium. It is cheap, quick and tells you whether your system responds.
Why did I see no effect?
The most common reasons are unstressed cells, cells running on glycolysis, too severe an insult, or too short an exposure.
What concentration should I use?
There is no single answer. Published work spans a wide range. Run a concentration series in your own system.
Is Szeto Schiller 31 toxic to cells?
At the concentrations used in the published literature it has generally been well tolerated. Always include a peptide-only control.
Where can I find the published studies?
Search PubMed for SS-31 or elamipretide and filter by the tissue or model you are interested in.
Final thoughts
Seven models, one recurring theme. Szeto Schiller 31 acts on mitochondria that are in trouble and leaves healthy ones alone. Build your study around a real, measurable mitochondrial stress, treat for long enough, measure structure as well as function, and include the controls that let you say why something happened and not merely that it did.
If you would like to talk through a design before ordering, write to us. We cannot run your experiment, but we have seen enough of them to help you avoid the usual mistakes.