How long do lyophilised peptides last at -20°C?

Held at -20°C, dry, dark and desiccated, with the seal intact, lyophilised peptides are stable over long periods, commonly cited in years rather than months. Stability is sequence-dependent, so the storage line on the batch certificate is the figure to work to.

How long does reconstituted peptide last?

Typically two to four weeks refrigerated at 2°C to 8°C. Reconstituted with bacteriostatic water, which contains 0.9% benzyl alcohol as a preservative, around 28 days refrigerated is the common working figure.

Can peptides be stored in a domestic freezer?

A domestic freezer runs at roughly -18°C, close to the -20°C target, but frost-free models cycle their temperature deliberately in order to defrost. That cycling is exactly the freeze-thaw stress you are trying to avoid. A laboratory freezer holds a stable temperature and is the correct equipment.

Does light really degrade peptides?

For several sequences, yes. Tryptophan-containing peptides are notably light-sensitive. Amber vials, foil, or simply a closed box solve it. It costs nothing to store material dark, so store it dark.

5 min read · 4 July 2026

How to store research peptides

The short answer

Store lyophilised peptides at -20°C or colder in a dry, dark, desiccated environment, and always let a vial reach room temperature before opening it. Repeated freeze-thaw cycles are the single biggest cause of activity loss in stored material.

Lyophilised material

Lyophilised peptide is freeze-dried solid, and in that state it is comparatively stable. Held at -20°C, dry and dark, it is stable over long periods. At -80°C it is stable longer still.

The enemies are moisture, heat, light and oxygen. The vial is sealed against most of them, which is why the seal should stay intact until the material is actually needed.

Always equilibrate before opening

Take a vial from a freezer and open it immediately, and the cold glass and cold solid will pull moisture straight out of the room air and condense it inside the vial. You have just introduced water into material whose stability depends on being dry.

Let the sealed vial reach room temperature first. It costs twenty minutes and it prevents the most common avoidable degradation in a laboratory.

Freeze-thaw cycles are the real problem

Every freeze-thaw cycle costs some activity. The mechanical stress of ice crystal formation, and the concentration changes at the freezing front, break the material down. It is cumulative, and it is irreversible.

The fix is aliquoting. At the point of first reconstitution, split the solution into single-use aliquots, five to ten of them, and freeze those at -20°C. Each one is thawed once and used. The stock is never repeatedly cycled.

This one habit does more for the integrity of stored material than any other single practice.

Reconstituted material

Once in solution, the clock speeds up considerably. Refrigerated at 2°C to 8°C, reconstituted peptide is typically usable for two to four weeks.

Bacteriostatic water, which is sterile water with 0.9% benzyl alcohol as a preservative, extends usable refrigerated life to around 28 days. Sterile water without a preservative does not.

Keep solutions dark. Wrap the vial or store it in a closed box. Several peptide sequences are light-sensitive, and tryptophan-containing sequences particularly so.

Why a cloudy solution is usually a temperature problem

Cloudiness on reconstitution is most often caused by mixing a cold solid with a cold solvent, or by adding solvent too fast and too directly.

Bring both the vial and the solvent to room temperature. Run the solvent slowly down the inside wall of the vial rather than firing it into the solid. Then leave it to dissolve rather than shaking it, because shaking denatures peptides through the air-liquid interface. Roll it gently instead.

Common questions

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