Peptide Reconstitution: A Technical Reference
What reconstitution means
Reconstitution just means mixing a dry powder back into a liquid. With peptides, you take a lyophilised (freeze-dried) peptide powder and dissolve it in a liquid — usually bacteriostatic water — to make a solution where you know exactly how strong it is, ready for lab use. (A peptide is a short chain of amino acids, the building blocks that make up proteins.) Research peptides are shipped freeze-dried so they last longer, so doing this step right — using the correct liquid, the correct amount, and careful handling — matters both for getting the strength right and for keeping the peptide in good shape.
Use the reconstitution calculator to work out the exact amounts for the strength you want.
Choosing a solvent: bacteriostatic water
The liquid most people use to reconstitute research peptides is bacteriostatic water — clean (sterile) water that has 0.9% benzyl alcohol in it. That small amount of benzyl alcohol stops bacteria from growing, so a mixed vial keeps for longer than it would with plain sterile water. A few peptides do not dissolve well in water (low "solubility" means they do not mix easily). Those may need a tiny bit of a second liquid first, which depends on the exact compound.
Always add the liquid slowly. Aim it at the inside wall of the vial instead of squirting it straight onto the powder, and let the peptide dissolve gently — do not shake it hard.
Concentration calculations
Concentration (how strong the solution is) is just the amount of peptide divided by the amount of liquid you add. For example, mixing a 10 mg vial with 2 mL of bacteriostatic water gives 5 mg/mL. So the amount of liquid you choose sets the strength — less liquid makes a stronger solution.
The reconstitution calculator works both ways: type in your vial size and the strength you want to get the amount of liquid, or type in the amount of liquid to get the strength it gives.
Sterile handling and storage
Keep everything clean while you work: wipe the rubber top of the vial with an alcohol swab before you put a needle through it, use a fresh sterile syringe, and do not touch the needle or the rubber top. Once mixed, peptides are usually kept in a fridge at 2–8°C and out of the light. Un-mixed freeze-dried vials last longer and are usually kept cold and dry (desiccated means kept dry) for long-term storage.
How long a mixed solution stays good depends on the compound. Bacteriostatic water makes it last longer than plain water would, but a mixed solution should still be used within the time that suits that peptide. Try not to freeze and thaw it over and over.
