Most research peptides arrive as a small amount of white powder, or sometimes a barely visible film, at the bottom of a sealed vial. That is lyophilised, or freeze-dried, material. Understanding what freeze-drying does helps explain how to store a peptide, what to expect when you open the vial, and why the material changes once it is back in solution.
What lyophilisation is
Lyophilisation removes water from a frozen solution without melting it. The peptide solution is frozen, the pressure is lowered so the ice turns straight into vapour, and a second drying stage removes most of the remaining bound water. What is left is a dry, porous solid with very little residual moisture, sealed into the vial.
Why peptides are supplied this way
Water is the main driver of peptide degradation. In solution, peptides can hydrolyse, deamidate (at asparagine and glutamine residues), oxidise (at methionine, cysteine and tryptophan) and aggregate. Taking the water out slows all of these down, which gives lyophilised material a far longer shelf life than the same peptide in solution, and makes it much more tolerant of shipping.
What you'll see in the vial
The dried material can look like a neat disc, a loose powder, or a thin film on the glass, and it may have shrunk or cracked. At low milligram amounts there can be very little to see at all. None of this means the vial is short-filled: the amount is set by weight before drying, and the appearance of the cake varies with the fill volume and drying cycle. Some vials also contain excipients that bulk out or stabilise the cake.
Storing lyophilised material
General good practice, always secondary to the storage guidance on the batch label:
- Keep the vial sealed until you are ready to use it.
- Store it cool, dry and away from light; freezer storage is common for longer periods, refrigeration for shorter ones.
- Let a cold vial reach room temperature before opening it, so moisture doesn't condense on the powder.
- Avoid repeated freeze–thaw cycles.
After reconstitution
Once the peptide is back in solution, the clock speeds up again. Reconstituted material is usually kept refrigerated and used within the period set by your protocol, and splitting it into single-use aliquots avoids repeated warming and cooling. Record the date, the diluent and the volume used, so the concentration of every aliquot is traceable.