How to Store Lyophilized Research Peptides in the Lab

Lyophilization (freeze-drying) removes water from a peptide so it can be stored and shipped as a dry solid, usually a white "cake" or powder in a sealed vial. Dry peptides are far more stable than peptides in solution. But they don't last forever, and how a lab stores them decides how long the material stays true to its original specification.

Scope: this post covers dry, sealed, lyophilized material in laboratory storage only. It doesn't cover preparing solutions.

Why dry peptides still degrade

A lyophilized peptide is mostly protected from the reactions that need water. It's still exposed to four things:

• Heat, which speeds up every chemical reaction
• Moisture from the air. Peptides are hygroscopic, and absorbed water both lowers the effective peptide content and reduces stability (Bachem).
• Oxygen and light, which drive oxidation, especially of methionine, cysteine and tryptophan residues (Hoofnagle et al., Clin Chem 2016)
• Sequence-specific reactions, such as deamidation at Asn/Gln (particularly next to Gly), and cleavage at Asp-Pro bonds (Hoofnagle et al.)

Bachem notes that peptides containing Asn, Gln, Met, Cys and/or Trp have limited shelf lives. Before you plan storage, look at the sequence. MOTS-c, for example, contains two methionines and one tryptophan.

Temperature

Long-term storage: frozen. Manufacturer guidance is consistent here:

• Bachem recommends keeping lyophilized peptides in a tightly closed container below −15 °C, with lower temperatures preferred (e.g., −50 °C or lower for long-term storage).
• A consensus paper on peptide handling for mass-spec assays lists −20 to −80 °C for storage of lyophilized peptides beyond a year (Hoofnagle et al.).

Short-term: refrigerated is acceptable. Bachem notes that peptides may be kept at about 4 °C for short periods.

Keep the temperature steady. Repeated warming and re-freezing brings moisture in each time a cold vial is exposed to room air. Practical steps:

• Store vials at the back of a dedicated lab freezer, not in the door.
• Log freezer temperature if you can.
• Frost-free freezers deliberately warm up to defrost. If a manual-defrost or ultra-low unit is available, it's the steadier choice for long-term stock.

Light

Keep vials in their outer packaging or an opaque box. Amber vials help, but a closed box in a dark freezer is simpler and just as effective. Light protection matters most for sequences with tryptophan, tyrosine or other residues that absorb UV.

Moisture: the step people skip

The most common storage mistake has nothing to do with temperature. It happens when a cold vial is opened in warm room air: water condenses straight onto the powder.

Standard lab practice:

1. Take the vial out of the freezer and let it reach room temperature before opening it, ideally inside a desiccator. Bachem and Hoofnagle et al. both recommend this.
2. Work quickly. Weigh out what you need and reseal promptly (Bachem).
3. Store opened dry material under dry conditions, in a desiccator or with desiccant packs in a sealed secondary container. For sensitive sequences, add an inert-gas blanket (argon or nitrogen).
4. Consider dry aliquots. If a vial will be opened many times, dividing the dry powder into smaller portions under low humidity means each portion is exposed only once. Hoofnagle et al. describe storing dry aliquots under argon or nitrogen, or in a desiccator, at −20 °C or lower.

A dry peptide should look like a uniform cake or loose powder. Shrinkage, a glassy or sticky appearance, clumping or discoloration can mean moisture got in. Note it in your records.

Shipping and cold chain

What the guidance says. Bachem states that lyophilized peptides may be shipped at room temperature, because a few days in transit is short compared with their dry-state stability. Many research suppliers still ship with cold packs or insulated mailers as a margin against extreme heat.

What "cold-chain" means. Strictly, cold-chain means a documented, temperature-controlled path from sender to receiver, often with data loggers. Most research-peptide parcels are temperature-buffered (insulation plus cold packs) rather than monitored cold-chain. If a supplier says "cold chain", it's fair to ask whether there's a temperature record or just an ice pack.

On arrival:

1. Check that the vial seals and caps are intact.
2. Check the cake or powder looks normal and hasn't collapsed or melted.
3. Record the lot or batch number and the date received.
4. Move the vials to frozen storage promptly. There's no need to open them.

A warm parcel isn't automatically a problem for dry material. A melted, discolored or damaged vial is, so photograph it and contact the supplier.

Record keeping

For each vial, log:

• compound, label amount, and any batch or reference number on the label or paperwork
• date received and condition on arrival
• storage location and temperature
• every date it was opened

Good records are what let you tie a result back to a specific vial later.

Quick reference

Our product listings give the storage condition for each compound. See the Quality page for how we document material, or browse the shop.

Research Use Only. Sold for in vitro laboratory research. Not for human or veterinary use. Not a drug, food, cosmetic, or medical device. These materials have not been evaluated by the FDA. 21+.