A correctly synthesised, ≥99% pure peptide can lose 10–30% of its activity to bad storage in a single quarter. This guide describes the storage and handling decisions that preserve a research peptide from the moment it leaves cold storage at our facility to the day it is consumed at the bench.
Lyophilised storage
Lyophilised (freeze-dried) peptide is the most stable form. Stored properly, most sequences are stable for 24 months from the date of manufacture.
Recommended conditions:
- −20 °C in a frost-free freezer, double-bagged with desiccant.
- −80 °C for sequences with known oxidation liabilities (Met, Cys, Trp, free N-terminal Gln) or for archival lots.
- Desiccated. Lyophilisation removes water; reintroducing it is the fastest path to hydrolysis and degradation.
- Dark. UV light catalyses oxidation and disulfide rearrangement.
Avoid frequent door-opening freezers and shared −20 °C units that cycle through frequent thaws.
Receiving a shipment
Vials shipped on dry ice or with cold packs should be inspected on arrival:
- Confirm the vial is intact and the seal is undamaged.
- Check the lot number against the COA in the shipment.
- Place the vial directly in
−20 °Cstorage; do not open until you are ready to reconstitute. - Equilibrate to room temperature (20–30 min, sealed) before each opening to prevent moisture condensation.
Reconstituted storage
Once dissolved, the same peptide is dramatically less stable.
| Solvent | Storage | Typical shelf life |
|---|---|---|
| Bacteriostatic water | 2–8 °C | 2–4 weeks |
| Sterile water for injection | 2–8 °C | 5–7 days |
| 0.1% acetic acid | 2–8 °C | 1–2 weeks |
| 1× PBS | 2–8 °C | 24–72 hours (most sequences) |
| DMSO | −20 °C, sealed | 6–12 months |
| Aqueous, frozen as aliquots | −80 °C | 6–12 months |
Single-use aliquots in low-binding tubes at −80 °C are the gold standard. Each freeze–thaw cycle costs roughly 5–15% of effective concentration for sensitive peptides; the second and third cycles cost more.
Sequence-specific liabilities
| Residue / motif | Failure mode | Mitigation |
|---|---|---|
| Met | Oxidation to Met sulfoxide (+16 Da) | Avoid air, store dark, add 1 mM TCEP if appropriate |
| Cys (free) | Disulfide scrambling, Cys oxidation | N₂ overlay, low-O₂ storage, single freeze–thaw |
| Trp | Oxidation to N-formylkynurenine (+32 Da) | Dark amber tubes, no UV |
| N-terminal Gln | Pyroglutamate formation | Acetylate or pyroglutamate the N-terminus during synthesis |
| Asp-Pro | Acid-catalysed cleavage | Avoid low pH for prolonged periods |
| Asn-Gly | Deamidation, isoaspartate | Neutral pH, low temperature |
If your peptide contains any of these, request the sequence-specific stability note from technical support.
Plasticware and adsorption
Short, hydrophobic, or highly cationic peptides adsorb to standard polypropylene within minutes. Use:
- Protein LoBind (Eppendorf) or equivalent low-binding tubes for stocks.
- Glass HPLC vials for analytical work.
- 0.1% BSA pre-coat of plasticware where the assay tolerates BSA.
- Polypropylene pipette tips rather than glass for small aqueous volumes; rinse three times before final transfer to saturate non-specific binding sites.
Shelf-life monitoring
For long-running studies, re-verify a stock that has been stored more than 6 weeks at 2–8 °C or 6 months at −80 °C:
- Visual: clear solution, no precipitate.
- A280 (Trp/Tyr peptides): concentration within 10% of fresh.
- Activity in a known-good assay: within 20% of historical performance.
If any of these drifts, retire the stock and reconstitute from a fresh vial.
Cross-references
- Peptide reconstitution & dilution guide — for the upstream step.
- Lyophilised vs liquid peptides — why the lyophilised form is the stable starting point.
- How to read a peptide COA — for the net peptide content used to recalculate concentrations after long storage.