How to reconstitute a lyophilised peptide
Lyophilised (freeze-dried) peptides ship as a fine white solid at the bottom of the vial. Before a lot can be used in any in-vitro assay it has to be reconstituted — dissolved back into a liquid. Done carefully, reconstitution is routine; done roughly, it can shear sensitive sequences or introduce contamination that ruins downstream results.
This is a general laboratory handling overview for research use only. It is not medical, clinical or dosing guidance.
What you need at the bench
- The sealed peptide vial, equilibrated to room temperature.
- An appropriate solvent — most commonly bacteriostatic or sterile water; some hydrophobic sequences need a small amount of dilute acetic acid first.
- A clean syringe and needle, or a calibrated pipette.
- An alcohol swab for the stopper, and a clean, draught-free surface.
The procedure
- Let the vial reach room temperature before opening. Adding cold solvent to a cold vial encourages condensation and uneven dissolution.
- Swab the rubber stopper and let it dry. Never pop the stopper off — inject through it.
- Draw your chosen volume of solvent. Decide the volume in advance so your final concentration is known and reproducible.
- Aim the stream against the glass wall, not directly onto the powder. Let the solvent run down slowly so it dissolves the cake gently.
- Do not shake. Swirl gently, or let the vial stand for a few minutes, until the solution is completely clear.
- Inspect against the light. A properly reconstituted lot is clear and particle-free.
Mechanical agitation introduces air, foams the solution and can fragment longer peptide chains. Patience beats force every time.
Working out your concentration
Concentration is simply the mass of peptide in the vial divided by the volume of solvent you add. Adding 2 mL of solvent to a 10 mg vial gives 5 mg/mL. Choosing a round solvent volume in advance keeps later calculations clean and your records reproducible.
Always cross-check the stated mass against the lot-specific Certificate of Analysis that ships with every Pepteed vial.
After reconstitution
- Reconstituted peptides are far less stable than the dry solid — refrigerate and use within the window appropriate to the sequence.
- Label the vial with the concentration and the date you reconstituted it.
- Avoid repeated warming and cooling; aliquot if you need many small uses over time.