What is Reconstitution?
Reconstitution is the process of dissolving a freeze-dried (lyophilized) peptide powder back into a liquid solution. When you receive peptides from a supplier, they typically arrive as a dry, fluffy "cake" or powder at the bottom of a vial. This lyophilized form is very stable for shipping and storage, but peptides must be dissolved in liquid before they can be used in research.
Think of it like powdered drink mix: the powder is concentrated and shelf-stable, but you need to add water before you can use it. The key difference is that peptide reconstitution requires more precision and sterile technique.
What You'll Need
- Lyophilized peptide vial — should have been stored at -20°C or colder
- Bacteriostatic water (BAC water) — sterile water containing 0.9% benzyl alcohol as a preservative
- Alcohol swabs — 70% isopropyl alcohol wipes
- Insulin syringe — typically 1mL with a 29-31 gauge needle
Why Bacteriostatic Water?
The benzyl alcohol in BAC water prevents bacterial growth, allowing the reconstituted solution to remain stable for weeks when refrigerated. If you use plain sterile water, you must use the entire vial within 24-48 hours or divide it into single-use aliquots immediately.
Step-by-Step Reconstitution Process
Step 1: Let the Vial Warm Up
Remove the peptide vial from the freezer and let it sit at room temperature for 20-30 minutes before opening. This is critical — if you open a cold vial, moisture from the air will condense onto the cold peptide powder, causing it to clump and potentially degrade.
Step 2: Prepare Your Workspace
Work on a clean, flat surface. Have all your supplies within reach. Use an alcohol swab to clean the rubber stopper on both the peptide vial and the BAC water vial.
Step 3: Calculate Your Volume
Decide how much BAC water to add based on your desired concentration. A common approach:
- 5mg peptide + 2mL BAC water = 2.5mg/mL (or 250mcg per 0.1mL)
- 5mg peptide + 1mL BAC water = 5mg/mL (or 500mcg per 0.1mL)
- 10mg peptide + 2mL BAC water = 5mg/mL
Higher concentrations use less water but may approach solubility limits for some peptides. When in doubt, use more water — you can always adjust your dosing volume.
Step 4: Draw the BAC Water
Insert your syringe needle through the rubber stopper of the BAC water vial. Turn the vial upside down and slowly draw your calculated amount of water into the syringe.
Step 5: Add Water to the Peptide Vial
Insert the needle through the rubber stopper of the peptide vial at an angle.Slowly release the water so it runs down the inside wall of the vial — do not squirt it directly onto the peptide cake. This gentle approach prevents foaming and protein denaturation.
Step 6: Let it Dissolve
Allow the vial to sit for 2-3 minutes. The peptide should dissolve on its own without agitation. If needed, you can gently roll the vial between your palms — never shake vigorously, as this can damage the peptide structure.
Step 7: Inspect the Solution
The final solution should be clear and colorless. If you see cloudiness, particles, or gel-like material, there may be a solubility problem (see our Troubleshooting guide).
Storage After Reconstitution
After reconstitution, store the vial in the refrigerator (2-8°C / 36-46°F). When reconstituted with bacteriostatic water, most peptides remain stable for 3-4 weeks. With sterile water, use within 24-48 hours or freeze aliquots immediately.
Never freeze a reconstituted peptide solution unless you're creating single-use aliquots. Repeated freeze-thaw cycles damage peptides significantly.
Common Mistakes to Avoid
- Opening a cold vial — always let it warm to room temperature first
- Squirting water directly onto the powder — run it down the vial wall instead
- Shaking vigorously — this damages peptide structure; gentle swirling only
- Using too little water — some peptides have solubility limits
- Reusing needles — always use a fresh, sterile needle for each vial