How to reconstitute a lyophilised research peptide

Research peptides are supplied lyophilised — freeze-dried to a stable powder — because that's how they keep longest. Before they can be used in laboratory work, they're reconstituted: dissolved back into liquid. This is a standard bench procedure, and getting it right is mostly about cleanliness, the right solvent, and knowing your final concentration. The notes below are general laboratory-handling information for qualified researchers; they are not guidance for human or veterinary use.

Choosing a solvent

The usual choice for reconstitution is bacteriostatic water (water with a small amount of benzyl alcohol, which inhibits microbial growth) or sterile water, depending on the protocol. Bacteriostatic water is common because the prepared solution keeps longer under refrigeration. Some peptides with poor water solubility may call for a different solvent — always follow the requirements of your own protocol. DNR stocks bacteriostatic water as an add-on alongside the peptides.

The method, in outline

1. Let the sealed vial reach room temperature to reduce condensation.
2. Wipe the stopper with alcohol.
3. Draw up your chosen volume of solvent and add it slowly down the inside wall of the vial — not directly onto the powder — to avoid frothing.
4. Don't shake. Let it dissolve gently, swirling if needed. Vigorous agitation can degrade a peptide.

Working out concentration

The concentration of your prepared solution depends on two numbers: the mass of peptide in the vial and the volume of solvent you add. For example, 10 mg of peptide reconstituted in 2 mL of solvent gives 5 mg/mL. For in-vitro assay work you'll often want the result expressed as a molar concentration, which also needs the peptide's molecular weight.

Rather than do the arithmetic by hand, you can use our reconstitution & molarity calculator — enter the vial mass, solvent volume and molecular weight and it returns concentration in mg/mL, µg/mL and molarity. Understanding those units is covered here.

Storing the prepared solution

Once reconstituted, a peptide is less stable than in its lyophilised form. Prepared solutions are generally kept refrigerated and used within the working window your protocol specifies; for longer storage, aliquoting and freezing avoids repeated freeze-thaw cycles. The lyophilised vial itself keeps best at -20°C, desiccated and out of the light — more on storage here.

The takeaway

Reconstitution is straightforward: a suitable solvent, gentle handling, and a clear idea of your final concentration. Do the concentration maths up front with the calculator, keep everything clean, and store the prepared solution cold. Every DNR lot is supplied lyophilised with a batch-specific Certificate of Analysis you can verify before you order.