How should peptides be stored?

Storage practice differs based on whether the vial is lyophilized or reconstituted. Lyophilized (dry) peptide vials tolerate room temperature for short periods (days to weeks depending on the compound) but achieve longest shelf life at refrigerator temperature (2–8 °C) or freezer temperature (−20 °C or lower). For research-supply lyophilized peptides intended for use within months of receipt, refrigeration is generally adequate; for long-term reserve storage, freezing is preferred.

Reconstituted (aqueous) peptide solutions should be refrigerated. The chemistry that degrades peptides in solution — hydrolysis, oxidation, aggregation — accelerates roughly exponentially with temperature. A peptide stable for months at refrigerator temperature might be stable for only days at room temperature.

Practical refrigerator placement matters. Storage on the door produces temperature cycling every time the door opens — the peptide vial may repeatedly cycle above 8 °C. The back of the middle shelf is usually the most temperature-stable location. Storage near the freezer compartment (some refrigerators have it at the top) can inadvertently freeze reconstituted vials, causing freeze-thaw stress that reduces potency. Verify actual temperature at the storage location with a thermometer; do not assume.

For freezer storage, minimise freeze-thaw cycles. Repeated freezing and thawing stresses peptides through concentration effects at the ice interface and drives aggregation. If long-term storage of reconstituted material is required, aliquot into single-use portions before freezing so each portion is thawed only once.