1. Solvent selection
The default solvent for lyophilised research peptides is bacteriostatic water — sterile water preserved with 0.9% benzyl alcohol. The preservative suppresses microbial growth once the vial is pierced, allowing a reconstituted peptide to remain usable for multiple weeks under refrigeration. Sterile water (unpreserved) and 0.9% sodium chloride are appropriate only when the reconstituted vial will be consumed within 24 hours.
A small number of hydrophobic sequences require a co-solvent — typically 1–2% acetic acid or a trace of DMSO — to fully dissolve before dilution into bacteriostatic water. Always consult the peptide-specific data sheet before deviating from BAC water.
2. Reconstitution technique
- Allow both the lyophilised vial and the bacteriostatic water to reach room temperature.
- Swab both rubber stoppers with 70% isopropyl alcohol and let dry.
- Draw the calculated volume of BAC water into a sterile syringe and inject it slowly against the side wall of the peptide vial — never directly onto the powder.
- Do not shake. Gently swirl or invert the vial until the powder is fully dissolved. Agitation shears peptide bonds and accelerates degradation.
- Label the vial with date of reconstitution, concentration, and batch number.
3. Calculating volume & concentration
Concentration is a function of peptide mass ÷ solvent volume. A 10 mg vial reconstituted with 2 mL of BAC water yields 5 mg / mL, i.e. 5000 µg per mL. Choose the reconstitution volume that lets the target aliquot fall between the 10–50 unit range of a standard U-100 insulin syringe for measurement precision.
| Vial mass | BAC water | Concentration | Per U-100 unit |
|---|---|---|---|
| 5 mg | 1 mL | 5 mg/mL | 50 µg |
| 10 mg | 2 mL | 5 mg/mL | 50 µg |
| 30 mg | 3 mL | 10 mg/mL | 100 µg |
4. Storage temperatures
- Lyophilised (unopened): stable at −20 °C for 24+ months; 2–8 °C for short-term holding; room temperature is acceptable during transit up to two weeks.
- Reconstituted: 2–8 °C (standard laboratory refrigerator) for typically 28 days when BAC water is used.
- Long-term aliquots: −20 °C or −80 °C in single-use fractions. Avoid repeated freeze/thaw — each cycle measurably degrades peptide integrity.
- Protect from light: amber vials or opaque secondary containers reduce photodegradation of aromatic residues.
5. Stability factors
Peptide half-life in solution is governed by four variables: temperature, pH, agitation, and sequence composition. Sequences containing Met, Cys, Trp,or N-terminal Gln are particularly oxidation- and cyclisation-prone. Maintain a cold chain, avoid vigorous mixing, and never store reconstituted peptide near a freezer defrost cycle where temperature drift is common. Purity is validated at manufacture by RP-HPLC and mass spectrometry; downstream handling determines how much of that purity survives to the workbench.
6. FAQ
- Can I use tap or bottled water?
- No. Only sterile bacteriostatic or sterile water intended for injection is suitable — any other water source introduces contaminants and endotoxins that invalidate the sample.
- What if the powder does not dissolve fully?
- Warm the vial gently in the hand and swirl. If a residue remains after 10 minutes, the sequence may require a mild acidic co-solvent — check the peptide's technical sheet.
- How do I know my peptide is still active?
- Cold storage from day one, minimal freeze/thaw cycles, and use within the validated window are the strongest indicators. For definitive confirmation, submit an aliquot for third-party HPLC analysis.
Compliance
All materials supplied by Pro-Peptides Supply are for laboratory in-vitro research use only, by qualified professionals, in jurisdictions where such use is lawful. Not for human or veterinary consumption. See our Research & Legal Policy for full compliance information.