Why Storage Matters
Peptides are inherently less stable than small-molecule chemicals. They are susceptible to degradation by oxidation, hydrolysis, microbial contamination, and UV light. Proper storage can extend usable shelf life from weeks to multiple years — improper storage can render a vial unreliable in days.
Lyophilized Form: -20 °C
Lyophilization (freeze-drying) removes water from the peptide, producing a dry powder that is dramatically more stable than aqueous solutions. Sealed lyophilized peptides stored at -20 °C in a standard laboratory freezer typically remain stable for 24+ months. Some peptides remain stable for longer; some sensitive sequences (those with methionine or cysteine residues vulnerable to oxidation) benefit from -80 °C storage.
Protect From Light and Moisture
Even in lyophilized form, peptides are hygroscopic — they absorb moisture from the air. Always store vials sealed. If a vial is opened, it should be resealed immediately and returned to the freezer. UV light degrades peptide bonds; amber vials or opaque containers minimize photodegradation.
Reconstituted Form: +2 to +8 °C
Once reconstituted with bacteriostatic water, peptides become significantly less stable. The standard guideline is 14–28 days at +2 to +8 °C (refrigerator temperature), with the exact stability window depending on the peptide. Sequences with aspartate, glutamate, or methionine residues tend toward the shorter end; cyclic or capped peptides tolerate the longer end.
Freezing Reconstituted Solutions
For research extending beyond the 28-day window, aliquot the reconstituted solution into single-use volumes before freezing at -20 °C. Avoid repeated freeze-thaw cycles — each cycle damages peptide integrity. Frozen aliquots typically remain stable for 3–6 months.
Concentration Calculations
For research protocols requiring precise dosing, see our guide on calculating reconstitution concentrations — covers volume-to-concentration math, IU conversion, and blend-vial calculations.
The Bacteriostatic Water Choice
Bacteriostatic water contains 0.9% benzyl alcohol as a preservative. This enables 14–28 day refrigerated storage without microbial contamination. Sterile water (without preservative) requires single-use protocols — once the vial is pierced, the solution must be used within 24 hours.
See the full Storage & Reconstitution Protocol for step-by-step reconstitution instructions. Browse research peptide catalog or check the FAQ for storage-related questions.