Quick answer
SS-31 is a synthetic, cell-permeable tetrapeptide (D-Arg-2',6'-Dmt-Lys-Phe-NH2) from the Szeto-Schiller family of aromatic-cationic peptides. Published studies report that it concentrates at the inner mitochondrial membrane and binds cardiolipin, a phospholipid linked to electron transport chain assembly — studied in cell and animal models, not claims about human use. Pepspan will supply a 10 mg vial at €64.90, shipped from Spain, with every lot independently tested; coming soon — join the waitlist with Notify me. Updated 30 September 2026.
What SS-31 Is
SS-31 is a synthetic tetrapeptide with the sequence D-Arg-2',6'-dimethyl-Tyr-Lys-Phe-NH2. The name SS stands for Szeto-Schiller, after Hazel Szeto and Peter Schiller, whose laboratories developed this family of small, cell-permeable, aromatic-cationic peptides.
SS-31 alternates basic and aromatic residues and carries a net positive charge of +3 at neutral pH. Its molecular formula is C32H49N9O5, with a molecular weight of approximately 639.8 g/mol. It is supplied as a white lyophilized powder — a reference material for laboratory research, not a drug, food, cosmetic or dietary supplement.
| Property | SS-31 |
|---|---|
| Sequence | D-Arg-2',6'-Dmt-Lys-Phe-NH2 |
| Length | 4 amino acids (tetrapeptide), C-terminal amidation |
| Molecular formula | C32H49N9O5 |
| Molecular weight | ≈639.8 g/mol |
| Net charge (neutral pH) | +3 |
| Primary research target | Cardiolipin, inner mitochondrial membrane |
What Research Looks At
According to published studies, SS-31 accumulates at the inner mitochondrial membrane independently of membrane potential and binds cardiolipin, an anionic phospholipid concentrated in that membrane and closely tied to the assembly and stability of the electron transport chain complexes. This cardiolipin interaction is the main reason SS-31 is described as a mitochondria-targeted research peptide.
In cell and animal models, SS-31 has been studied for its relationship to mitochondrial membrane organization, electron transport chain function, and markers of oxidative stress. Published research spans models of ischemia-reperfusion, age-related mitochondrial decline, and cellular bioenergetics. These findings describe research settings in cell and animal models; they are not claims about human use or about any specific product.
SS-31 and Mitochondrial Research at Pepspan
SS-31's cardiolipin-binding mechanism places it alongside other compounds studied in mitochondrial and cellular energy metabolism research. Pepspan's catalogue includes MOTS-c, a mitochondrial-derived peptide studied in metabolic research, and NAD+, the coenzyme central to cellular energy metabolism — see the MOTS-c research guide for that separate compound.
These are separate compounds with distinct mechanisms — SS-31 is a cardiolipin-binding tetrapeptide, MOTS-c is a mitochondrial-derived peptide, and NAD+ is a coenzyme — grouped here only because published research on each relates to mitochondrial or cellular energy function in laboratory models. Researchers comparing the three should note that each has its own published mechanism and its own literature; none is a substitute for another in an experimental design.
What to Check When Sourcing SS-31 in the EU
Before ordering an SS-31 vial from an EU shop, a few things are worth checking on the product page itself:
- A per-lot report from an independent laboratory. A report tied to the specific production lot on the vial, issued by an independent laboratory, with a way to verify it.
- A working verification link. Ideally a link that opens the result directly on the laboratory's own site, not only a PDF or image hosted by the seller.
- Content per vial against the label claim. A purity percentage and a measured content in milligrams per vial are two different figures; check which one, or both, the report gives.
- Shipping inside the EU and the seller's returns policy. An EU-based shipping point usually avoids customs processing; check the return window for unopened products.
At Pepspan, the first lot of SS-31 will be analysed on arrival by an independent laboratory, with the report and a verification link published on its public lot page; every later lot is analysed and published the same way. Orders ship tracked from Spain: after dispatch, delivery typically takes 1-3 business days within Spain, 1-2 to Portugal, 3-5 to Germany and Italy, up to 5 to the Netherlands, and usually 2-5 business days across the rest of the EU. EU shipping is free on orders from €50 (otherwise €6), and unopened products can be returned within 14 days — see the shipping policy and refund policy.
Availability at Pepspan
SS-31 is not in stock yet at Pepspan. The product page lists a 10 mg lyophilized vial at €64.90, with a purity specification of ≥98% by HPLC; leave your email with the Notify me button to be told as soon as the first lot is in stock. Its independent report will be published on the lot page.
Once available, the lot report will also appear on the purity reports page alongside Pepspan's other published results, and it can be checked as described in the COA verification guide.
Frequently asked questions
What is SS-31?
SS-31 is a synthetic tetrapeptide, D-Arg-2',6'-dimethyl-Tyr-Lys-Phe-NH2, developed by the Szeto-Schiller laboratories. It is a small, aromatic-cationic peptide studied for its ability to concentrate in the inner mitochondrial membrane and bind cardiolipin.
What does SS-31 stand for?
SS stands for Szeto-Schiller, after Hazel Szeto and Peter Schiller, whose laboratories developed this family of small aromatic-cationic peptides, several of which, including SS-31, were later found to concentrate in mitochondria.
How does SS-31 interact with mitochondria?
Published studies report that SS-31 accumulates at the inner mitochondrial membrane independently of membrane potential and binds cardiolipin, a phospholipid linked to the organization of the electron transport chain, through electrostatic and hydrophobic interactions.
What research areas study SS-31?
Published research on SS-31 covers mitochondrial membrane organization, electron transport chain function, and oxidative-stress markers, in models of ischemia-reperfusion, age-related mitochondrial decline, and cellular bioenergetics.
Is SS-31 related to MOTS-c or NAD+?
They are separate compounds with different mechanisms. SS-31 is a cardiolipin-binding tetrapeptide, MOTS-c is a mitochondrial-derived peptide, and NAD+ is a coenzyme central to cellular energy metabolism. Each is studied independently, though all three appear in mitochondrial and metabolic research literature.
When will SS-31 be available at Pepspan?
SS-31 is coming soon. Use the Notify me button on the product page to receive an email as soon as the first lot is in stock; its independent lab report will be published on the lot page.
Where can I buy SS-31 in Europe?
Pepspan will supply SS-31 as a 10 mg lyophilized vial at €64.90, shipped tracked from Spain; EU shipping is free on orders from €50 (otherwise €6). It is not in stock yet: join the waitlist with the Notify me button. Rules on buying and handling research peptides differ by country; check your local regulations. Research use only.
Research Use Only: all products mentioned are intended exclusively for laboratory research and are not for human or veterinary use. Information about other suppliers reflects their public websites as checked on the date stated and may change.