Two different substances, two different rules
A lyophilized peptide and a reconstituted one behave like different materials. The freeze-dried cake is remarkably stable: moisture removed, degradation pathways mostly frozen out. The moment water enters the vial, hydrolysis and oxidation begin, and the clock starts.
Lyophilized (unopened)
- Short term (weeks): a cool, dark cabinet at or below room temperature is generally adequate. Avoid light and temperature swings.
- Medium term (months): refrigeration at 2–8 °C.
- Long term: −20 °C or colder. At freezer temperatures, well-sealed lyophilized peptides commonly retain integrity for a year or more; consult the COA date and re-test when in doubt.
- Condensation is the silent killer. Let a cold vial reach room temperature before opening it, or ambient moisture will condense directly onto the cake.
Reconstituted
- Store at 2–8 °C, protected from light. With bacteriostatic water as the diluent, working solutions are typically used within a few weeks; degradation varies by sequence, so shorter is safer for sensitive compounds.
- Do not freeze-thaw repeatedly. Each cycle stresses the peptide. If a protocol spans months, aliquot once after reconstitution and freeze aliquots individually.
- Discard any solution that turns cloudy, discolors, or shows particulates: visual change means chemical change.
Handling notes
- Swab septa before every draw; the preservative in BAC water suppresses growth but does not sterilize a contaminated vial.
- Use fresh, sterile draws each time. Never return solution to a vial.
- Keep a log: compound, lot, reconstitution date, diluent, concentration. Six months later, the label and the log are the only memory that survives.
Transit and receiving
Brief room-temperature transit does not meaningfully degrade lyophilized peptides. The cold-chain anxiety that surrounds shipping mostly concerns reconstituted or inherently unstable material. On receipt, move vials to appropriate storage promptly and check each against its certificate of analysis.