Peptide storage basics: lyophilized vs. reconstituted

Starter thread for storage questions. Below are general principles from peptide-handling literature and manufacturer guidance. Always check the specific compound’s documentation, because stability varies a lot by sequence.

Lyophilized (powder)

• Lyophilized peptides are much more stable than solutions. For long-term storage, −20 °C is the common standard, and −80 °C is better for very long horizons.
• Moisture is the main enemy. Let a cold vial come to room temperature before opening it, or condensation will form on the powder.
• Protect vials from light, especially for sequences containing Trp, Tyr, Cys, or Met, which are prone to oxidation.

Reconstituted (solution)

• Solutions degrade much faster. Refrigeration at 2–8 °C is typical for short-term use.
• Avoid repeated freeze–thaw cycles. If something has to be frozen in solution, aliquot it first so each portion is thawed only once.
• Sequences with Asn-Gly, Asp-Pro, Met, or Cys are more susceptible to deamidation, cleavage, or oxidation in solution.

Signs something has gone wrong

Cloudiness, visible particles, color change, or a powder that has collapsed into a sticky film all suggest degradation or moisture exposure. Appearance alone can’t confirm integrity, though. Only analytical testing (HPLC/MS) can.

Questions about specific compounds or storage setups are welcome below.