How to Reconstitute Peptides

Reconstitution is the process of dissolving a lyophilised (freeze-dried) peptide powder into a liquid solvent to create a solution suitable for laboratory use. Research peptides are supplied in lyophilised form because this maximises stability and shelf life during storage and transport. Before use in any laboratory application, the powder must be reconstituted correctly to preserve the peptide's integrity and ensure accurate concentration calculations.

The most important decision in reconstitution is solvent selection. Bacteriostatic water (BAC water) is the recommended solvent for most research peptides and is the standard across the industry. It contains 0.9% benzyl alcohol as a preservative, which prevents bacterial growth and allows the reconstituted solution to be stored at +4°C for up to 4 weeks without contamination risk. Sterile water contains no preservative and should only be used when the reconstituted solution will be used immediately. For any laboratory situation where the vial will be accessed multiple times over days or weeks, bacteriostatic water is the correct choice. Acetic acid solution (0.1-1%) is occasionally used for peptides that are poorly soluble in water, such as some growth hormone releasing peptides. Always consult the specific peptide's handling documentation before selecting a solvent.

• Lyophilised peptide vial • Bacteriostatic water (BAC water), available from UK Peptide Lab • Sterile insulin syringe (1ml) • Alcohol swabs • Clean, dust-free work surface Bacteriostatic water contains 0.9% benzyl alcohol as a preservative and is the recommended solvent for most research peptides. It prevents bacterial growth and allows the reconstituted solution to be stored at +4°C for up to 4 weeks.

1. Allow both the peptide vial and the bacteriostatic water to reach room temperature. 2. Wipe the rubber stopper of both vials thoroughly with an alcohol swab and allow to air dry for 30 seconds. 3. Draw the required volume of bacteriostatic water into a sterile syringe. For a standard 5mg vial, 2ml is a common starting point (giving 2.5mg/ml). 4. Insert the needle into the peptide vial at an angle and slowly inject the bacteriostatic water down the inner side of the glass vial wall. Do not inject directly onto the powder. Inject slowly over 10-15 seconds. 5. Gently swirl the vial in a slow circular motion. Never shake, shaking introduces air bubbles and can break peptide bonds. Allow 1-2 minutes for full dissolution. 6. Once reconstituted, store the vial at +4°C (standard refrigerator temperature). Label the vial with the reconstitution date. Use within 4 weeks. Use the UK Peptide Lab reconstitution calculator for instant concentration calculations.

Concentration (mg/ml) = total peptide mg ÷ volume of BAC water added in ml Example: 5mg peptide + 2ml BAC water = 2.5mg/ml concentration To calculate the volume to draw for a specific quantity: volume (ml) = required mass (mg) ÷ concentration (mg/ml) The reconstitution calculator linked below works this arithmetic for any combination of vial size and water volume, including the conversion to insulin syringe units.

• Shaking instead of swirling, always swirl gently • Using tap water or non-sterile water, always use bacteriostatic water • Injecting directly onto the powder, always inject down the glass wall • Not labelling the vial with the reconstitution date • Repeatedly freezing and thawing a reconstituted vial, aliquot first if long-term storage is needed

Reconstituted peptides remain stable at +4°C for up to 4 weeks. For longer term storage, draw the solution into multiple small syringes or vials (aliquots) and store at -20°C. This prevents repeated freeze-thaw cycles which degrade peptide quality over time. Never refreeze a vial that has already been thawed and partially used.