Lyophilised (freeze-dried) peptides are among the most stable forms a research peptide can take — but "stable" is relative. Moisture, heat, light and repeated temperature cycling all degrade peptides over time, and most of that damage is avoidable with simple handling discipline.
This guide covers how to store lyophilised material long term, how to receive and log incoming stock, and why reconstituted solutions need far more care than the dry powder.
Why peptides are supplied lyophilised
Freeze-drying removes water from a frozen peptide solution under vacuum, leaving a dry powder or "cake". Because most degradation pathways — hydrolysis, deamidation, microbial growth — need water, removing it dramatically slows them down. That is why research peptides are almost always shipped as lyophilised powder rather than as solutions.
The trade-off is that the powder is hygroscopic: it readily absorbs moisture from the air once a vial is opened, and absorbed moisture undoes much of the benefit of lyophilisation.
Long-term storage of the dry powder
For long-term storage, the general laboratory guidance for lyophilised peptides is:
- Temperature: −20 °C is the standard long-term condition; some laboratories use −80 °C for very long holding periods. Always follow the storage condition stated on the batch label and Certificate of Analysis.
- Sealed: keep vials closed and stoppered. Store vials in a sealed secondary container with desiccant.
- Dark: protect from light, particularly for peptides containing light- or oxidation-sensitive residues such as tryptophan, methionine or cysteine.
- Stable temperature: avoid frost-free freezers that cycle temperature, and minimise how often stock is taken in and out.
Short periods at ambient temperature — such as during transit — are generally tolerated by lyophilised peptides, but they should be moved to their stated storage condition on arrival.
Receiving and logging incoming stock
A simple goods-in routine prevents most handling problems:
- Inspect packaging for damage and confirm any cold-chain packs are intact.
- Match batch numbers on the vial labels to the Certificate of Analysis.
- Record compound, batch number, quantity, date received and storage location.
- Transfer promptly to the storage condition stated on the label.
- File the CoA where it can be found by batch number. Our CoA guide explains what to check on it.
Opening a vial: avoid condensation
The single most common handling mistake is opening a cold vial straight from the freezer. Warm room air meets a cold surface, moisture condenses on the powder, and the peptide begins absorbing water immediately.
Let the sealed vial reach room temperature before opening it — typically 20–30 minutes, longer for larger containers — and keep it in a desiccator while it warms if possible. Work quickly, reseal promptly and return unused stock to storage.
After reconstitution: a different stability picture
Once a peptide is dissolved, it is far less stable than the dry powder. Hydrolysis, oxidation, deamidation, aggregation and adsorption to container surfaces all proceed faster in solution. Good practice for reconstituted material:
- Reconstitute only what you need, using the diluent specified on the product documentation. Our reconstitution guide and calculator help you plan volumes.
- Aliquot the solution into single-use portions rather than repeatedly drawing from one container.
- Avoid repeated freeze–thaw cycles, which can damage peptide structure; thaw each aliquot once.
- Refrigerate short-term working solutions at 2–8 °C and freeze aliquots for longer holding, unless the product documentation says otherwise.
- Use aseptic technique and sterile containers to prevent microbial contamination.
- Label every aliquot with compound, batch, concentration and preparation date.
Stability in solution varies widely between peptides, pH values and diluents, so treat any general guidance as a starting point and validate it for your own work where it matters.
Peptides that need extra care
Some structural features make a peptide more sensitive:
- Methionine, cysteine and tryptophan residues are prone to oxidation — minimise air exposure and light.
- Asparagine and glutamine residues, especially next to glycine, are prone to deamidation in solution.
- Lipidated peptides such as semaglutide carry fatty-acid chains that change solubility behaviour.
- Coenzymes and small biomolecules such as NAD+ and glutathione are also sensitive to moisture and oxidation and benefit from the same dry, cold, dark storage.
How Peptide Direct packs and ships
Every compound we supply is shipped as lyophilised powder, packed with desiccant, labelled with batch-specific storage conditions and dispatched with cold-chain protection where required. Recommended storage conditions are stated on both the label and the Certificate of Analysis. See our quality assurance page for the full standard.