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How to Reconstitute Peptides: A Step-by-Step Method

Reconstitution means dissolving a freeze-dried peptide into liquid so it can be measured and studied. Done cleanly it's simple — here's the method, plus the maths.

What you'll need

• The lyophilised peptide vial
• A solvent — bacteriostatic water for multi-use, or sterile/distilled water for single-session use
• A clean syringe and alcohol swabs
• Labels for the reconstituted vial

The step-by-step method

1. Let the vial reach room temperature if it was refrigerated, so condensation doesn't form inside.
2. Sanitise the peptide and solvent vial stoppers with an alcohol swab; let them dry.
3. Draw your solvent — the volume you've calculated for your target concentration (see below).
4. Add it slowly — insert the needle and let the solvent run down the inside wall of the vial. Never squirt it directly onto the powder.
5. Dissolve gently — swirl or roll the vial, or leave it to stand. Do not shake — shaking froths and can damage the peptide.
6. Label and refrigerate — mark compound, concentration and date; store at 2-8°C.

The concentration maths

Concentration is set by how much solvent you add to a known amount of powder. For example, a 5 mg vial reconstituted with 2 mL of solvent gives 2.5 mg/mL. Add more solvent and the concentration drops; add less and it rises. The amount of peptide in the vial never changes — only how much liquid it's dissolved in.

Common mistakes to avoid

• Shaking the vial instead of swirling
• Squirting solvent straight onto the powder
• Leaving the reconstituted solution at room temperature
• Forgetting to label concentration and date