How to Reconstitute Lyophilized Peptides with Bacteriostatic Water

Most research peptides ship lyophilized — freeze-dried into a powder or "puck" — because peptides are far more stable dry than in solution. Before use in the lab, they are reconstituted with a sterile diluent. Here is a clean, repeatable process.

Choose the right diluent

Bacteriostatic water is sterile water containing 0.9% benzyl alcohol, a preservative that inhibits bacterial growth. That makes it the common choice when a vial will be accessed more than once. Plain sterile water has no preservative and is generally intended for single use.

You can find Bacteriostatic Water 10 mL in our supplies collection.

What you need

• The peptide vial and bacteriostatic water, both at room temperature
• Alcohol prep pads
• A sterile syringe sized for your planned volume
• A clean, uncluttered work surface

Step by step

• Wipe the rubber stopper of both vials with an alcohol pad and let it air dry.
• Draw the planned volume of bacteriostatic water into the syringe.
• Insert the needle into the peptide vial and let the water run slowly down the inside wall — do not spray it directly onto the powder.
• Gently swirl or roll the vial until the solution is clear. Do not shake; vigorous agitation can damage fragile peptide chains.
• Label the vial with the compound, concentration and date.

Calculating concentration

Concentration is simply the peptide amount divided by the diluent volume. For example, a 10 mg vial reconstituted with 2 mL of bacteriostatic water gives 5 mg/mL (5,000 mcg/mL). Adding more water lowers the concentration; it does not change the total amount in the vial.

After reconstitution

Store reconstituted vials refrigerated at 2–8 °C, protected from light, and avoid repeated warming and cooling. See our peptide storage guide for details.