Why handling matters
A peptide that left the manufacturer at ≥99% purity can degrade meaningfully before it ever reaches an experiment if stored or reconstituted poorly. Peptide bonds are robust, but oxidation, deamidation, aggregation and simple microbial contamination all degrade real-world samples. This guide summarises accepted laboratory practice.
Storing lyophilised (powder) peptides
- Short term (weeks): a cool, dark, dry environment — refrigeration at 2-8°C is sufficient for most sequences.
- Long term (months to years): -20°C or colder, ideally with desiccant. Lyophilised peptides stored frozen and dry routinely remain stable for years.
- Avoid freeze-thaw of the powder's environment: repeated condensation cycles introduce moisture — the main enemy of a lyophilised cake. Allow vials to reach room temperature before opening so moisture doesn't condense onto the powder.
- Light: sequences containing tryptophan, tyrosine or methionine are photo-sensitive; store dark.
Reconstitution technique
- Solvent choice: bacteriostatic water (0.9% benzyl alcohol) is the standard for research stock solutions because it suppresses microbial growth over multi-week storage — see bacteriostatic water. Sterile water is acceptable for solutions used immediately. Poorly soluble sequences may first require a small volume of dilute acetic acid (for basic peptides) or ammonium bicarbonate (for acidic peptides).
- Add solvent gently: run it down the vial wall rather than jetting it into the powder, then swirl — do not shake. Foaming denatures and aggregates peptides.
- Give it time: some sequences take several minutes to dissolve fully. Cloudiness that does not clear signals aggregation or an unsuitable solvent.
Storing reconstituted solutions
- Refrigerate at 2-8°C and treat the solution as far more fragile than the powder.
- Most research solutions in bacteriostatic water are used within 3-4 weeks.
- For longer storage, aliquot and freeze at -20°C — and never refreeze a thawed aliquot. Each freeze-thaw cycle measurably degrades peptide integrity.
Verifying what you actually have
Storage discipline only preserves the purity you started with — which is why batch verification matters. Every peptide BioSupply UK ships includes an HPLC + mass-spectrometry Certificate of Analysis; our guide to reading a CoA explains what those chromatograms mean.
All products mentioned are supplied strictly for laboratory research purposes only and are not intended for human consumption, diagnosis, or treatment. Nothing in this article constitutes medical advice.