Peptides are more sensitive to heat, light, and repeated freeze-thaw cycles than most reagents on a bench. Cold-chain handling doesn't stop at the courier's door — how a compound is stored after it arrives matters just as much as how it was shipped.
On arrival
Check the packaging for any sign the cold-chain material has fully melted or the container has been compromised in transit, and move the contents to appropriate storage as soon as possible rather than leaving them at room temperature while you attend to other things.
The storage condition printed on the product label — frozen or refrigerated — reflects how that specific compound was validated for stability, and it's worth following exactly rather than assuming a nearby product's storage instructions apply equally.
Before reconstitution
Lyophilized (freeze-dried) peptides are generally far more stable in powder form than once reconstituted into solution, which is why most are supplied as lyophilized vials rather than pre-mixed liquid wherever possible.
Keep vials away from direct light where practical — some peptide sequences are photosensitive and can degrade under prolonged exposure, particularly once in solution.
After reconstitution
Once a peptide is reconstituted, it typically has a much shorter usable window than its lyophilized form, and generally needs to be kept refrigerated rather than left at room temperature between uses.
Repeated freeze-thaw cycles are one of the more common, avoidable causes of degradation in a research setting. Where a protocol allows it, aliquoting a reconstituted solution into smaller single-use portions before freezing avoids subjecting the whole stock to repeated temperature swings.
- Avoid leaving vials at room temperature longer than necessary.
- Minimise freeze-thaw cycles — aliquot where practical.
- Keep solutions away from direct light.
- Follow the specific storage condition on the label over general assumptions.