Cold chain

The cold chain is the unbroken sequence of refrigerated storage and transport that keeps a temperature-sensitive product stable from the factory to the point of use. For research peptides the target is 2 to 8 °C, the ordinary refrigerator range, with protection from light. Long-term storage of lyophilised peptide is often at −20 °C, which extends shelf life further.

The chain is more forgiving before reconstitution than after. Lyophilised peptide tolerates days at room temperature in transit with little measurable loss, because the reactions that degrade peptides need water. A reconstituted vial is a solution, and its stability is measured in weeks refrigerated and hours at room temperature; freezing it is worse still, because ice crystals and freeze-concentration damage the peptide. The practical rule is to refrigerate the sealed vial on arrival, reconstitute only what will be used within the solution's shelf life, and never freeze a reconstituted vial.

Different peptides degrade at different rates, and a few, such as GHK-Cu with its bound copper, have their own quirks. The cold-chain guide covers storage in general and the article on storing peptides goes into the chemistry.