What Is SS-31 Peptide? Elamipretide Research Guide (2026)
What Is SS-31 Peptide?
SS-31 is a synthetic aromatic-cationic tetrapeptide developed by Drs. Hazel Szeto and Peter Schiller at Weill Cornell Medical College. The name Szeto-Schiller peptide 31 reflects its inventors and its position in a series of related mitochondria-targeting compounds. Its International Nonproprietary Name is Elamipretide. Its amino acid sequence is D-Arg-Dmt-Lys-Phe-NH2 — four amino acids engineered specifically so that alternating cationic and aromatic residues produce selective affinity for cardiolipin on the inner mitochondrial membrane.
What separates SS-31 from virtually every other research peptide is where it works. Most peptides bind cell-surface receptors and trigger downstream signaling cascades. SS-31 crosses both the outer mitochondrial membrane and the inner mitochondrial membrane and physically associates with cardiolipin — the signature phospholipid of the inner membrane. It does not work through receptor-mediated signaling. It works through direct membrane chemistry at the most fundamental level of cellular energy production.
What Is Cardiolipin and Why Does It Matter?
Cardiolipin is a phospholipid found almost exclusively in the inner mitochondrial membrane, where it serves three critical functions. It is required for the structural assembly and activity of the electron transport chain complexes — particularly Complex I and Complex III — that produce ATP through oxidative phosphorylation. It maintains the architecture of the cristae, the folded inner membrane structures that provide the surface area for ATP synthase. And it regulates the mitochondrial permeability transition pore (mPTP), whose opening under oxidative stress initiates the intrinsic apoptotic cascade through cytochrome c release.
Under oxidative stress, cardiolipin is highly vulnerable to peroxidation by reactive oxygen species generated within the electron transport chain itself. When cardiolipin is peroxidized, electron transport chain complex activity drops, ATP production falls, and cytochrome c detaches from the inner membrane — triggering cell death signaling. SS-31 concentrates at the inner membrane, binds cardiolipin, and stabilizes its structure against peroxidation before this cascade can begin.
How Does SS-31 Work?
SS-31 reaches the inner mitochondrial membrane through a combination of its positive charge (which attracts it toward the negatively charged mitochondrial membrane potential) and its aromatic residues (which allow it to partition into the lipid bilayer). Once at the inner membrane, it binds cardiolipin through the same alternating cationic-aromatic interaction pattern that drove its original molecular design.
The downstream effects of cardiolipin stabilization are interconnected. Electron transport chain Complex I and Complex III activity is preserved, reducing electron leak that generates superoxide radicals at the source rather than scavenging radicals after they form. Cytochrome c remains anchored to the inner membrane rather than releasing into the cytosol. Mitochondrial membrane potential is maintained. ATP production is sustained. And mPTP opening under oxidative stress conditions is limited, protecting against the apoptotic cascade that follows.
This mechanism is qualitatively different from general mitochondrial antioxidants. SS-31 concentrates specifically at the inner membrane at reported levels hundreds of times higher than in the surrounding cytosol — a targeted intervention at the site of ROS generation rather than systemic free radical scavenging.
SS-31, MOTS-C, and Humanin — Three Levels of Mitochondrial Research
SS-31, MOTS-C, and Humanin are frequently studied together in mitochondrial biology research, and understanding how they differ clarifies when each is the appropriate research tool.
SS-31 operates at the inner mitochondrial membrane chemistry level — direct cardiolipin interaction, no receptor involved. MOTS-C is encoded in mitochondrial DNA and operates at the metabolic signaling level — AMPK activation through the folate-purine pathway, systemic glucose metabolism. Humanin is encoded in mitochondrial DNA and operates at the cytoprotective receptor signaling level — STAT3, AKT, and Bax inhibition through FPRL1 and gp130 receptors.
They address three different dimensions of mitochondrial biology without mechanistic overlap, which is why comparative and combined MDP research uses all three. For more on MOTS-C see our What Is MOTS-C research guide and for Humanin see our What Is Humanin Peptide guide.
SS-31 Research Applications
Cardiac mitochondrial research uses SS-31 in ischemia-reperfusion injury and heart failure models, where the published preclinical literature documents cardiolipin stabilization preserving cytochrome c anchor, reducing infarct area, and maintaining mitochondrial membrane potential under ischemic conditions. Electron transport chain research examines how cardiolipin stabilization affects Complex I and Complex III activity and superoxide generation at their active sites.
Aging and sarcopenia research uses SS-31 in aged skeletal muscle models, drawing on published data showing improvements in mitochondrial membrane potential and ATP production. Neurodegenerative disease research examines how inner membrane protection affects neuronal mitochondrial function in models relevant to Parkinson’s and Alzheimer’s disease research. Kidney injury research uses SS-31 in models of acute kidney injury where mitochondrial dysfunction is a primary driver of tubular cell death. Barth syndrome research draws on the FDA approval of Elamipretide for this cardiolipin deficiency disorder as the validated clinical reference for the mechanism.
FDA Approval and Regulatory Status
SS-31 was FDA-approved as Elamipretide for Barth syndrome — a rare X-linked genetic disorder caused by mutations in the tafazzin gene that impair cardiolipin remodeling. This approval is the most direct clinical validation that the cardiolipin-targeting mechanism is biologically meaningful in a human disease context where cardiolipin abnormality is the primary pathology.
Stealth BioTherapeutics also advanced Elamipretide into Phase 3 trials for primary mitochondrial myopathy and heart failure before the pharmaceutical program was interrupted by financial challenges. The clinical safety and pharmacokinetic data from those trials are part of the published record.
For laboratory research, SS-31 is available under the research use only framework. It is not available through US compounding pharmacies as a prescription compound.
Storage and Handling
SS-31 (5mg) is supplied as lyophilized powder in a sterile glass vial. Store at -20°C, protected from light and moisture, for up to 24 months. Allow the vial to reach room temperature before opening. Reconstitute with bacteriostatic water by running solvent slowly down the inside vial wall — 5 to 10 minutes passive dissolution, no shaking. Store reconstituted solution at 2 to 8°C and use within 28 days. For full guidance see our How to Store Lyophilized Peptides guide.
Frequently Asked Questions
What is SS-31 peptide?
SS-31 (Elamipretide) is a synthetic tetrapeptide with the sequence D-Arg-Dmt-Lys-Phe-NH2, developed by Drs. Hazel Szeto and Peter Schiller at Cornell University. It selectively concentrates in the inner mitochondrial membrane and binds cardiolipin, stabilizing membrane structure, reducing electron transport chain electron leak, and protecting against oxidative stress-induced apoptosis. FDA-approved as Elamipretide for Barth syndrome. For laboratory research use only.
What does SS-31 peptide do?
SS-31 binds cardiolipin on the inner mitochondrial membrane, protecting it from peroxidation under oxidative stress. This preserves electron transport chain Complex I and Complex III activity, maintains cytochrome c anchor to the inner membrane, sustains mitochondrial membrane potential, limits mPTP opening, and protects against the apoptotic cascade that follows cardiolipin peroxidation. It reduces superoxide generation at the source rather than scavenging radicals after they form.
What is the difference between SS-31 and MOTS-C?
SS-31 works through direct cardiolipin binding at the inner mitochondrial membrane — a membrane chemistry intervention without receptor involvement. MOTS-C is encoded in mitochondrial DNA and works through AMPK pathway activation as a systemic metabolic signal. They address mitochondrial biology at different levels and are used in combination research for that reason.
Is SS-31 the same as Elamipretide?
Yes. SS-31 is the original research designation. Elamipretide is the International Nonproprietary Name assigned during pharmaceutical development. The compound sequence is identical.
Is SS-31 peptide FDA approved?
Elamipretide (SS-31) is FDA-approved for Barth syndrome. Research-grade SS-31 is available for laboratory research use only and is not intended for clinical application.
Where can I buy SS-31 peptide?
Patriot Peptides SS-31 (5mg) is manufactured in a cGMP-certified US facility and independently third-party tested for HPLC purity, mass spectrometry identity, endotoxin, and sterility. Batch-specific Certificates of Analysis available. For laboratory research use only.
All content is for informational and educational purposes only. All Patriot Peptides products are strictly for laboratory research use only. Not for human consumption, veterinary use, or clinical application.
Related reading: What Is MOTS-C? | What Is Humanin Peptide? | Are Research Peptides Legal in the USA? | How to Store Lyophilized Peptides