Research use only. Not for human or veterinary consumption. 18+.

Storage and stability

What is known about keeping lyophilised peptides, what is not, and why we give ranges rather than dates.

Why there are no dates on this page

A shelf life is a property of a specific material in a specific container, established by testing it. We commission no batch testing, so any date we printed would be a number we made up. What follows is the general behaviour described in the peptide stability literature, which is genuinely useful and is not a statement about the vial you receive.

Sealed and lyophilised

• AmbientDays to weeks
• Refrigerated, 2 to 8°CMonths
• Frozen, −20°C or belowLongest

A lyophilised peptide under vacuum or inert gas is far more stable than the same peptide in solution, which is the entire reason it is sold that way. The limiting factor is usually moisture rather than temperature: a vial that has been opened, or whose stopper has been compromised, will take up water from the air and that is what starts the degradation.

In solution

Refrigerate and use over a short period. Solutions degrade by routes that the dry powder is protected from: hydrolysis of the backbone, oxidation of methionine and cysteine residues, and deamidation of asparagine and glutamine. A sequence containing those residues is more vulnerable than one that does not, which is why two peptides stored identically can behave differently.

What to avoid

• Repeated freeze-thaw. Each cycle concentrates solutes at the ice boundary and exposes the peptide to an interface. Aliquot before freezing rather than thawing one vial repeatedly.
• Light, particularly for anything containing tryptophan or a cobalamin.
• Mechanical stress. Peptides denature at the air-liquid interface, which is why the guidance everywhere is to swirl rather than shake.
• Plastic, for some sequences. Highly cationic peptides adsorb to polypropylene. Glass is the safer default when the amount matters.

Write down what you did

Date of reconstitution, volume of solvent, which solvent, and storage temperature. A solution whose history is not recorded is a solution you cannot use quantitatively later, and this is the single most common gap we are asked about.

Reconstitution arithmetic · How to read a certificate of analysis