Storing Research Peptides: Temperature, Freeze-Thaw and Shelf Life

How well a peptide was stored decides how good it still is. Degraded material looks exactly like intact material in the vial, but it adds noise to every experiment it goes into. Fortunately, storage isn't complicated once you know the three factors that count: temperature, how long it has been in solution, and freeze-thaw.

Note: the one-line version is powder in the freezer, solution in the fridge, and no repeated freezing and thawing.

Before you add any liquid

Dry, lyophilized peptide is sturdy. Kept cold and dry, most compounds last a long time, often years at -20 °C depending on the compound. Moisture is the main threat at this stage, so leave the vial sealed until you actually need it.

General guidance for lyophilized (dry) material, with the compound's COA taking priority where it says otherwise:

• -20 °C (freezer) — months to years depending on the compound; the normal home for lab inventory
• 2–8 °C (fridge) — shorter term; fine for material you'll get to soon
• Room temperature — avoid, apart from brief periods while handling

After reconstitution the clock is running

As soon as the powder is in solution it becomes more fragile. Keep the solution at 2–8 °C and use it within the stability window for that particular compound. Don't keep it in the fridge door, where the temperature jumps every time the door opens.

Freeze-thaw does quiet damage

This is the factor people most often underestimate. Each time a solution freezes and thaws, ice crystals form again and a bit more peptide is damaged. If reconstituted material has to be kept for a long time, split it into single-use aliquots first so each portion is thawed only once.

Light, heat and air

• Keep vials out of light; amber glass or a closed box works.
• Spend as little time at room temperature as you can while handling.
• Don't leave vials open to air; reseal them straight away.
• Put the reconstitution date on every vial so you can see how old it is.

Note: look up the batch's certificate of analysis by lot number and follow any storage information that comes with the compound.

FAQ

How long does a reconstituted peptide keep?

That depends on the compound. As a rule, reconstituted peptides are kept at 2–8 °C and used inside their validated stability window. For longer storage, aliquot and freeze.

Does repeated freezing and thawing harm a peptide?

Yes. Every cycle damages a little more of the material. Divide solutions into single-use aliquots so each one only thaws once.

Should peptides be kept out of light?

In general, yes. Light and heat both speed up degradation, so keep vials somewhere dark and limit their time at room temperature.

Related guides

• Reconstituting a lyophilized peptide