Storing, handling and reconstituting lyophilised peptides

Lyophilised peptides are stable for a long time when stored correctly, and easy to ruin when they are not. The failure modes are moisture, heat, light and repeated freezing. This is how to avoid them.

Storage before opening

Keep the lyophilised powder at −20 °C, desiccated and protected from light. Sealed vials stored this way remain stable for extended periods. Short excursions to room temperature during shipping are normal and not harmful for most sequences; prolonged warmth, humidity and light exposure are what cause degradation.

Bringing a vial to room temperature

Before opening, let the sealed vial warm to room temperature. Opening a cold vial draws condensation onto the powder, and lyophilised peptides are hygroscopic — once they take on water they degrade faster and weigh inaccurately. Allow twenty to thirty minutes on the bench, then open and work in dry conditions where possible.

Reconstitution

Add the solvent slowly down the inside wall of the vial rather than squirting it directly onto the powder, then swirl gently until dissolved. Do not shake vigorously; foaming and shear can damage some peptides. Sterile water and bacteriostatic water suit most sequences. Very hydrophobic or highly charged peptides may need a small proportion of an organic co-solvent or a pH adjustment to dissolve — the specification sheet for the compound will say so. If a protocol requires it, filter-sterilise through a 0.22 µm filter immediately before use.

Aliquoting and freeze–thaw

Once in solution the peptide is far less stable than as a powder. Divide the reconstituted solution into single-use aliquots and freeze them at −20 °C or below. Every freeze–thaw cycle degrades the sample, so thaw one aliquot at a time and discard what is not used. For short-term use, reconstituted peptide can be held at 2–8 °C, but working days rather than weeks is the sensible assumption.

Signs of a problem

Powder that has clumped or discoloured, a solution that will not clear with gentle swirling, or precipitation on freezing all suggest the compound has been compromised. Check the batch number against its Certificate of Analysis and contact the supplier rather than proceeding with an experiment on doubtful material.

For laboratory research use only — not for human or veterinary use. This article is general laboratory reference information and is not advice on the use of any product.