· For research use only. Not for human consumption.
For research use only. Not for human consumption.
Mitochondria research is having a moment. And SS-31 — a small four-amino-acid peptide — has become one of the most studied compounds in this space. Scientists have been investigating it across a wide range of animal models since the early 2000s, and the volume of published preclinical work has grown steadily each year. If you’ve come across the name and wondered what it actually is, this guide is for you.
We’ll cover what SS-31 is, why researchers care so much about mitochondria in the first place, what animal studies have found so far, and how it differs from other mitochondria-focused compounds under investigation. No jargon, no medical advice — just a plain-English look at a genuinely interesting area of research.
TL;DR: SS-31 is a synthetic tetrapeptide designed to target the inner mitochondrial membrane. Preclinical studies published in journals including the Journal of the American Society of Nephrology have documented its effects across multiple animal model types. It is sold for research use only, not for human consumption, and all findings to date come from animal studies.
What Is SS-31?
SS-31 is a synthetic tetrapeptide — meaning it’s made of just four amino acids. It was developed by Dr. Hazel Szeto and Peter Schiller, which is how it got its name: Szeto-Schiller 31. A 2011 paper by Szeto in the Biochimica et Biophysica Acta described SS-31 as a cell-permeable peptide that selectively targets cardiolipin, a lipid found almost exclusively in the inner mitochondrial membrane. ([Szeto HH, Biochim Biophys Acta](https://pubmed.ncbi.nlm.nih.gov/21884755/), 2011)
That targeting mechanism is what sets SS-31 apart. Most compounds studied in mitochondria research have difficulty crossing into the mitochondria itself. SS-31’s structure allows it to accumulate specifically at the inner membrane — the site where the cell’s most critical energy processes take place. That specificity is a big part of why it attracted early research attention.
The four amino acids in SS-31 are arranged in an alternating pattern of aromatic and basic residues. That structure isn’t accidental — it was deliberately designed by Szeto and Schiller to allow the peptide to interact with cardiolipin on the inner membrane. It’s a rare case of a compound engineered from the ground up with a specific cellular address in mind.
SS-31 (Szeto-Schiller 31) is a synthetic four-amino-acid peptide designed to selectively target cardiolipin on the inner mitochondrial membrane. In a 2011 review in Biochimica et Biophysica Acta, Dr. Hazel Szeto documented its cell-permeable properties and selective mitochondrial accumulation in preclinical models, establishing the mechanistic basis for subsequent animal research into its effects. (PMID: 21884755)
Why Are Researchers So Interested in Mitochondria?
Mitochondria are the structures inside cells responsible for producing energy. You’ve probably heard them called “the cell’s power plant” — that’s accurate. A 2017 review in Cell Metabolism by Lopez-Otin and colleagues noted that mitochondrial dysfunction appears across a remarkably wide range of disease models studied in animals, making it one of the most active research targets in modern biology. ([Lopez-Otin C et al., Cell Metabolism](https://pubmed.ncbi.nlm.nih.gov/28380383/), 2017)
Here’s why that matters to researchers. Mitochondria don’t just make energy — they also regulate processes like cell death, calcium signaling, and the production of reactive oxygen species (a type of cellular byproduct). When mitochondria don’t function properly in animal models, researchers observe changes across multiple biological systems simultaneously. That makes mitochondrial dysfunction a compelling focal point for preclinical science.
What makes this especially interesting is the inner membrane specifically. It’s where the energy-production machinery lives. Cardiolipin — the lipid that SS-31 targets — plays a structural role in keeping that machinery organized and functional. Disruptions to cardiolipin have been observed in a range of animal disease models. That’s the research context that makes SS-31’s targeting mechanism so relevant to scientists.
What Has Research Found About SS-31?
Preclinical investigations into SS-31 have spanned multiple animal model types over roughly two decades. A 2015 study by Birk and colleagues in the Journal of the American Society of Nephrology examined SS-31 in rodent models of ischemia-reperfusion injury — a condition where blood flow is cut off and then restored — and documented measurable changes in mitochondrial structure and function. ([Birk AV et al., J Am Soc Nephrol](https://pubmed.ncbi.nlm.nih.gov/25326583/), 2015)
That’s a representative example of the research approach. Scientists create a controlled injury or stress condition in an animal model, administer SS-31, and then examine mitochondrial behavior. It’s not a simple picture, and the results vary by model type and context. But the consistency of interest across research groups is notable.
Here’s a plain-English look at the major areas preclinical scientists have explored:
Cardiac and Muscle Tissue Models
A significant portion of SS-31 research has been conducted in rodent cardiac models. The heart relies heavily on mitochondria — cardiac cells contain more mitochondria per cell than almost any other cell type in the body. Several studies have examined SS-31 in models of cardiac stress, observing changes in mitochondrial membrane integrity and energy output markers in treated animals.
Kidney and Organ Stress Models
The Birk 2015 study mentioned above is part of a broader body of work examining SS-31 in kidney models. Researchers have investigated how the compound interacts with mitochondria in renal tissue under various stress conditions in rats and mice. This is one of the more developed branches of SS-31 preclinical research in terms of published volume.
Neurological Animal Models
A smaller but growing body of preclinical literature examines SS-31 in nervous system models. Neurons are highly energy-dependent, making mitochondrial function especially critical in neural tissue. Researchers have begun investigating SS-31’s behavior in animal models involving neurological stress, though this branch of the research is less mature than the cardiac and renal work.
Aging-Related Research in Animals
Some investigators have placed SS-31 in the context of mitochondrial aging research. A 2020 paper by Chiao and colleagues in Aging Cell administered SS-31 to aged mouse models and examined mitochondrial function alongside physical performance markers in the animals. ([Chiao YA et al., Aging Cell](https://pubmed.ncbi.nlm.nih.gov/32677032/), 2020) This is preclinical work only — no conclusions about human aging can be drawn from animal studies.
A 2020 preclinical study by Chiao and colleagues published in Aging Cell examined SS-31 administration in aged mouse models, measuring mitochondrial function markers and physical performance indicators in the animals. All findings are from rodent models and do not constitute evidence of therapeutic benefit in humans. (PMID: 32677032)
SS-31’s research trajectory is unusual because it has attracted rigorous attention from academic medical centers — including Cornell and the University of Washington — rather than primarily from commercial research groups. That pattern suggests the compound’s mechanistic basis (targeting cardiolipin at the inner membrane) is taken seriously by scientists with no commercial stake in the outcome.
How Does SS-31 Compare to MOTS-c in Research?
SS-31 and MOTS-c are both studied in the context of mitochondria, but they’re very different compounds with different research questions behind them. MOTS-c is a naturally occurring mitochondria-derived peptide — it’s encoded in the mitochondrial genome itself. A 2015 study by Lee and colleagues in Cell Metabolism first described MOTS-c as a regulator of metabolic processes in mouse models. ([Lee C et al., Cell Metabolism](https://pubmed.ncbi.nlm.nih.gov/25738459/), 2015)
SS-31, by contrast, is entirely synthetic. It wasn’t discovered — it was designed. That’s a fundamental distinction in the research context. MOTS-c research tends to focus on how the body’s own mitochondrial signaling works. SS-31 research focuses on what happens when a purpose-built compound specifically targets the inner membrane from outside.
Think of it this way: MOTS-c research asks “what is the body already doing with mitochondria?” SS-31 research asks “what happens when we intervene at the inner membrane directly?” They’re complementary questions, not competing ones. Researchers studying one are often interested in the other, but the mechanistic frameworks are distinct.
For a deeper look at MOTS-c, see our overview of MOTS-c research.
MOTS-c, first described in a 2015 Cell Metabolism study by Lee and colleagues, is a naturally occurring peptide encoded in the mitochondrial genome. Unlike SS-31, which is a synthetic compound designed to target the inner mitochondrial membrane, MOTS-c originates from within the mitochondria itself — making the two compounds mechanistically distinct subjects of preclinical research. (PMID: 25738459)
In conversations with researchers sourcing mitochondria-focused peptides, SS-31 and MOTS-c are consistently requested together — not as alternatives, but as complementary tools for studying different aspects of mitochondrial biology from different angles.
What Researchers Need for Quality SS-31
For any preclinical study, compound purity is a non-negotiable starting point. A 2011 review by Szeto in Biochimica et Biophysica Acta emphasized that SS-31’s effects in animal models are attributed to the specific four-amino-acid sequence — meaning contamination or degradation in a sample can fundamentally alter what a study is actually measuring. ([Szeto HH, Biochim Biophys Acta](https://pubmed.ncbi.nlm.nih.gov/21884755/), 2011) The certificate of analysis (COA) is where all of that gets verified.
Here’s what to look for when sourcing SS-31 for research:
HPLC Purity Above 98%
High-performance liquid chromatography (HPLC) separates the target compound from everything else in the sample and measures the ratio. For research-grade peptides, 98% or higher is the standard threshold. Anything below that introduces uncertainty about what’s actually driving the results in your study.
Mass Spectrometry Confirmation
Mass spectrometry confirms the molecular weight of the compound matches SS-31’s expected value. HPLC tells you how pure the sample is. Mass spec tells you it’s actually SS-31 and not something else at a high purity. Both data points should appear on a reliable COA.
Third-Party Laboratory Verification
The most credible COAs come from independent labs — not the supplier’s own in-house testing. Third-party verification removes any conflict of interest. If a supplier can’t provide a third-party COA, that’s a significant red flag for any serious research application.
You can view the COAs for Alpha Peptides’ SS-31 on our Certificates of Analysis page. Full purity specifications and available sizes for research use are listed on the SS-31 product page.
Alpha Peptides provides third-party HPLC and mass spectrometry COAs for SS-31, with purity verified at above 98% — consistent with the purity threshold referenced in preclinical SS-31 literature for research-reliable compound samples.
Frequently Asked Questions About SS-31
Is SS-31 a natural compound?
No. SS-31 is entirely synthetic. Unlike MOTS-c, which is encoded in the mitochondrial genome and occurs naturally in the body, SS-31 was designed from scratch by researchers Hazel Szeto and Peter Schiller. Its four-amino-acid sequence was deliberately engineered to interact with cardiolipin on the inner mitochondrial membrane. It does not occur in nature. ([Szeto HH, Biochim Biophys Acta](https://pubmed.ncbi.nlm.nih.gov/21884755/), 2011)
What does SS-31 stand for?
SS-31 stands for Szeto-Schiller 31. The “SS” refers to its two developers — Dr. Hazel Szeto of Cornell University and Dr. Peter Schiller of the Clinical Research Institute of Montreal. The “31” is the compound’s designation within their research series of mitochondria-targeted peptides. It is also sometimes called elamipretide in the clinical research literature, though SS-31 remains the most common name in preclinical research contexts.
Is SS-31 related to aging research?
It has appeared in aging-related preclinical studies, yes. The 2020 Aging Cell study by Chiao and colleagues (PMID: 32677032) is among the most cited examples — it examined SS-31 in aged mouse models and measured mitochondrial function markers alongside physical performance indicators in the animals. All findings are from animal studies. No conclusions about SS-31 and human aging can be drawn from this research. ([Chiao YA et al., Aging Cell](https://pubmed.ncbi.nlm.nih.gov/32677032/), 2020)
Where can researchers source SS-31?
Research-grade SS-31 should only be sourced from suppliers who provide full third-party COAs with HPLC purity data and mass spectrometry confirmation. Alpha Peptides carries research-grade SS-31, independently tested and verified above 98% purity. Review all COA documentation at alpha-peptides.com/coas/ before using any peptide in a research context.
Where Does SS-31 Research Go From Here?
SS-31 has an unusual profile for a research peptide. It was designed with a specific biological target in mind, it has accumulated a substantial body of animal model data across multiple tissue types, and it has attracted attention from academic research institutions with no commercial stake in the outcome. That combination doesn’t happen often in this space.
The research is still preclinical. That’s worth repeating clearly. Animal model results — even compelling ones — don’t translate automatically to human biology. The scientific community is careful about this distinction, and so should anyone reading the literature be. What preclinical research does is build a mechanistic foundation that can inform whether and how human studies might eventually be designed.
For researchers working in mitochondrial biology, SS-31 remains one of the most mechanistically specific tools available for studying the inner membrane. That specificity, combined with its established research track record, is likely why it keeps showing up in new studies.
Explore related mitochondria peptide research: What Is MOTS-c? A Beginner’s Guide to the Mitochondria-Derived Peptide
For research use only. Not for human consumption. SS-31 is an experimental synthetic peptide with no FDA-approved therapeutic applications. All information on this page is provided for educational purposes relating to laboratory and preclinical research. It does not constitute medical advice, and it should not be interpreted as a recommendation for any personal use.
