Laboratory guide
Solvents, aseptic technique, concentration math and storage for lyophilized research peptides.
Quick answer: to reconstitute a lyophilized peptide, bring the vial to room temperature, disinfect both stoppers, slowly add bacteriostatic water down the inside wall of the vial, then swirl gently — never shake — until the solution is clear. Concentration equals peptide mass divided by solvent volume. Store the reconstituted vial at 2–8 °C, away from light.
Remove the lyophilized vial from cold storage and let it reach room temperature (about 15–20 minutes) before opening. This prevents condensation from forming on the powder.
Work on a clean, disinfected surface with gloves. Swab the rubber stoppers of both the peptide vial and the solvent vial with a 70% isopropyl alcohol pad and let them air-dry.
Using a sterile syringe, draw the planned volume of solvent — usually bacteriostatic water (sterile water with 0.9% benzyl alcohol). Decide the volume first using the concentration formula below.
Insert the needle at an angle and let the solvent run gently down the inside wall of the vial. Never spray it directly onto the powder cake, which can damage fragile peptide chains.
Swirl or roll the vial slowly until the solution is clear. Do not shake. Most peptides dissolve within a few minutes; let a stubborn vial rest a few minutes, then swirl again.
The solution should be clear and free of particles. Label the vial with compound, concentration and date, then store it refrigerated at 2–8 °C, protected from light.
Concentration (mg/mL) = peptide mass (mg) ÷ solvent volume (mL). Adding less solvent gives a stronger solution; adding more gives a weaker one.
| Peptide in vial | Solvent added | Concentration | Per 0.1 mL (10 units, U-100) |
|---|---|---|---|
| 5 mg | 1 mL | 5.00 mg/mL (5000 mcg/mL) | 500 mcg |
| 5 mg | 2 mL | 2.50 mg/mL (2500 mcg/mL) | 250 mcg |
| 10 mg | 2 mL | 5.00 mg/mL (5000 mcg/mL) | 500 mcg |
| 10 mg | 3 mL | 3.33 mg/mL (3333 mcg/mL) | 333 mcg |
FAQ
Bacteriostatic water is the standard laboratory solvent for most research peptides because its 0.9% benzyl alcohol inhibits bacterial growth, allowing a vial to be sampled multiple times. Sterile water is used for single-use preparations. Peptides that resist dissolving in water are often prepared with a dilute acetic acid solution, such as 0.6%.
Divide the peptide mass by the solvent volume. For example, 5 mg of peptide in 2 mL of bacteriostatic water gives 2.5 mg/mL, which equals 2,500 mcg/mL. With a U-100 insulin-style syringe (100 units = 1 mL), each unit then contains 25 mcg.
No. Shaking creates foam and mechanical stress that can denature or aggregate peptides. Swirl or roll the vial gently until the solution turns clear.
Store reconstituted peptides refrigerated at 2–8 °C, away from light. Lyophilized (unmixed) peptides are most stable frozen at −20 °C for long-term storage. Avoid repeated freeze–thaw cycles of reconstituted solutions.
Stability depends on the specific compound. As a general laboratory guideline, many peptides prepared with bacteriostatic water remain usable for several weeks when refrigerated. Always follow the batch Certificate of Analysis and your laboratory's own protocols.
Cloudiness or visible particles can indicate incomplete dissolution, contamination or degradation. Let the vial rest and swirl again; if it remains cloudy, it should not be used for research.
New to peptides? Start with What are peptides, check batch results in the COA library, or browse reconstitution supplies.
For in-vitro and pre-clinical research purposes only. Not for human or animal consumption. Not intended for use as a drug, food additive, cosmetic, or household chemical.