SS-31 5mg

A synthetic tetrapeptide alternating aromatic and basic residues. It contains a non-proteinogenic amino acid, 2′,6′-dimethyltyrosine (Dmt), and a D-arginine at the N-terminus. It is used in in-vitro work on cationic short peptides, cellular mitochondrial models and analytical characterisation. 5 mg vial, lyophilized powder, ≥99% HPLC purity verified by third-party analysis. For laboratory research use only.

Research areas

• Synthetic cationic short peptides
• In-vitro mitochondrial models
• Analytical characterisation (HPLC, mass spectrometry)

Technical data

Reading a tetrapeptide COA: three checkpoints

• The measured mass. Four residues and an amidated end: the expected mass is about 639.8 Da for the free base. A clearly different mass points to another compound.
• The salt form. A cationic peptide like this one is isolated as a salt (acetate or hydrochloride, for example). The counter-ion adds weight to the lyophilisate without being peptide, so HPLC purity, which measures the share of peptide among the detected compounds, and net peptide content are not the same measurement.
• The non-natural residues. Dmt and the N-terminal D-arginine make the sequence resistant to common aminopeptidases. Keep this in mind when comparing its stability in biological media with that of a fully natural tetrapeptide.

Worked example: reconstituting a 5 mg vial

With 2 ml of bacteriostatic water added to the 5 mg vial:

• resulting concentration: 5 mg ÷ 2 ml = 2.5 mg/ml, i.e. 2,500 µg/ml;
• as a molar concentration: 2.5 g/l ÷ 639.8 g/mol ≈ 3.9 mmol/l;
• with 1 ml instead of 2 ml, the concentration doubles (5 mg/ml, i.e. 7.8 mmol/l) for the same total mass.

The trap most people fall into: the solvent volume never changes the mass of peptide in the vial. Only the dilution changes. Our reconstitution calculator runs this calculation for any volume.

Why choose this NEXUS product

• Third-party verified purity: every batch is HPLC-tested by an independent laboratory, and the certificate of analysis (COA) can be consulted before ordering.
• Shipped from France: parcels prepared within 24 business hours, delivered in 2 to 5 business days in France and 8 European countries. Free shipping from €120.
• Consistent quality: same supplier, same controls, same packaging from one batch to the next.
• Verified reviews: our customers leave their feedback on Trustpilot; we do not edit it.

Reconstitution and handling

The lyophilisate is reconstituted with bacteriostatic water, which preserves the solution once the vial has been opened. Add the solvent slowly down the vial wall, let it run, then swirl gently: no vigorous shaking and no vortexing, as shear denatures peptides.

Storage

The lyophilized powder keeps at -20 °C or below, protected from light and moisture; unopened and stored this way, the lyophilisate is stable for several years. After reconstitution, store at 2–8 °C, protected from light, with a reference shelf life of 28 days. For longer storage, freezing aliquots is preferable to repeated freeze–thaw cycles.

Common laboratory mistakes

• Confusing HPLC purity with net peptide content. 99% purity does not mean that 99% of the lyophilisate mass is peptide: the counter-ion and residual water count too.
• Using plain sterile water for a vial that will be opened several times. Without a preservative the solution is unprotected once the stopper has been pierced several times.
• Vortexing the vial. Gentle swirling is enough, even if dissolution takes a minute.
• Repeatedly refreezing the reconstituted solution. Each cycle degrades a fraction of the peptide. Aliquot right after reconstitution.