Most research peptides ship as a lyophilized (freeze-dried) powder. Removing water makes peptides far more stable than they are in solution, so the powder holds up well during shipping and storage. Good storage habits help keep samples consistent for laboratory work.
What can degrade a peptide
The main enemies of peptide stability are heat, moisture, light and oxygen. Some amino acids, such as cysteine, methionine and tryptophan, are especially sensitive to oxidation. Repeated temperature changes can also speed up breakdown.
Temperature
Unopened lyophilized vials are commonly kept cold. Refrigeration (about 2–8 °C) is often used for short periods, and freezing (−20 °C or colder) for long-term storage. Brief time at room temperature during shipping is generally fine for freeze-dried powder.
Avoid repeated warming and cooling. If you store vials frozen, keep them in a part of the freezer that does not go through defrost cycles.
Light and moisture
Keep vials sealed, dry and away from direct light. Let a cold vial reach room temperature before opening it, so moisture from the air does not condense on the powder inside. Some labs store vials in a sealed container with a desiccant pack.
Reconstituted samples
Once a peptide is dissolved for an experiment, it is much less stable than the powder. Labs commonly keep solutions refrigerated, use them within a set time, and split them into small portions (aliquots) so the main supply is not repeatedly warmed and cooled. Bacteriostatic water is a common laboratory solvent for this purpose.
Record keeping
Label every vial with the compound, lot number, date received and storage conditions. Note the date of reconstitution if applicable. Good records make it easy to match material back to its COA and explain any unexpected results.