How should lyophilized peptides be stored, and for how long?

Lyophilized (freeze-dried) peptide powder is the most stable form. Manufacturer handling guidance converges on storing it desiccated at −20°C or colder, protected from light, air, and moisture, where many peptides stay stable for years; −80°C is preferred for long-term storage. Because peptides are hygroscopic, let a cold, sealed vial warm to room temperature in a desiccator before opening, to avoid condensation. Sequences containing Met, Cys, Trp, Asn, or Gln are more prone to oxidation or degradation and have shorter shelf lives. Brief room-temperature shipping is generally tolerated for the dry powder, but long warehouse storage at room temperature is not ideal.