On arrival
- Check the lot number. The number on the vial must match the record published in our COA library. If they disagree, stop and contact us.
- Inspect the cake. A properly lyophilised peptide is a white or off-white solid cake or fine powder. It may have shifted in transit — that is cosmetic and harmless. A cake that has melted into a film, gone sticky, or discoloured indicates a temperature excursion.
- Do not open it yet. Transfer directly to storage. Every opening admits humidity, and lyophilised peptides are hygroscopic.
- Log it. Record compound, lot, quantity and arrival date. When a result looks strange months later, this record is what lets you rule the material in or out.
Vials arriving warm are usually fine. Lyophilised peptides tolerate short ambient excursions well — this is precisely why they are shipped dry rather than in solution. The certificate's stability data applies to the powder, not to a solution you make from it.
Storage temperatures
| Lyophilised, −20 °C | The default. Desiccated and light-protected, most sequences are stable for 24 months or more. Suitable for anything you will use within two years. |
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| Lyophilised, −80 °C | For long-term archival or unusually labile sequences. Worthwhile beyond two years; unnecessary below that for most compounds. |
| Lyophilised, 2–8 °C | Acceptable for weeks, not months. Use when freezer space is unavailable and the material is in active use. |
| Reconstituted, 2–8 °C | Days to weeks depending on sequence and diluent. Never store reconstituted peptide at room temperature. |
| Reconstituted, −20 °C | Extends solution life, but only if aliquoted first. Repeated freeze-thaw is more damaging than short refrigerated storage. |
Three environmental factors do the damage: moisture drives hydrolysis of the peptide bond, oxygen oxidises methionine, cysteine and tryptophan residues, and light accelerates both. Keep vials desiccated, sealed and dark. A silica desiccant pack in the storage box is cheap insurance.
Choosing a solvent
- Bacteriostatic water (0.9% benzyl alcohol) — the default for multi-withdrawal stock solutions. The preservative permits repeated vial entry over roughly 28 days. Note that benzyl alcohol has its own biological activity, so include it in your vehicle control.
- Sterile water — preservative-free, single use. Use when benzyl alcohol would interfere with your assay.
- Sterile saline or PBS — where physiological ionic strength matters.
- Dilute acetic acid (0.1%) — for basic peptides that resist dissolution in neutral water.
- DMSO — where a compound is not water-soluble. Keep final DMSO below 0.1% in cell culture and always run a vehicle control.
Check the diluent listed under Specifications on the product page before you open anything. Adding the wrong solvent to a vial is not reversible.
Reconstitution technique
- Let the vial reach room temperature before breaking the seal. Opening a cold vial condenses atmospheric moisture directly onto the powder.
- Wipe the septum with a 70% isopropyl prep pad and let it dry.
- Draw the calculated diluent volume.
- Angle the needle against the inner glass wall and let the diluent run down slowly. Never inject a jet directly onto the cake — the shear force denatures peptide at the impact point.
- Do not shake. Swirl gently, or leave the vial to stand for a few minutes. Most peptides dissolve without agitation. Shaking causes foaming, and the air-liquid interface denatures peptide.
- Inspect against a dark background. The solution should be clear and free of particulates.
- Label immediately with compound, concentration, diluent and date.
Concentration: divide the vial's net peptide mass by the diluent volume. Using the label weight rather than net peptide content from the COA introduces a systematic error — typically 10–20% — into every downstream calculation.
Aliquot immediately
This is the highest-value habit in peptide handling and the most frequently skipped. Immediately after reconstitution, split the solution into single-use volumes in low-binding tubes.
The reason is arithmetic. A stock solution thawed twenty times has been through twenty freeze-thaw cycles; twenty aliquots have each been through one. Freeze-thaw drives aggregation and precipitation, and the peptide lost is not evenly distributed — it concentrates on tube walls and at the surface, so your effective concentration drifts downward in a way that is invisible.
Use low-protein-binding tubes for dilute solutions. At low micromolar concentrations, adsorption to standard polypropylene can remove a meaningful fraction of your peptide before it ever reaches the assay.
Stability windows after reconstitution
| Bacteriostatic water, 2–8 °C | Typically 21–30 days. Prepare fresh if in any doubt. |
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| Sterile water, 2–8 °C | Days only — no preservative. Prepare fresh. |
| Aliquoted, −20 °C | Several months for most sequences, single thaw only. |
| Any solvent, room temperature | Hours. Return to refrigeration immediately after use. |
Some materials are shorter-lived than these general figures because they oxidise on air exposure. The storage line on each product page is the figure that applies to that item.
Recognising degradation
- Cloudiness or precipitate in a previously clear solution — aggregation. Do not use; centrifuging the particulate away does not restore concentration.
- Discolouration — yellowing typically indicates oxidation.
- A cake that will not dissolve when it previously did — a strong indicator of moisture ingress and hydrolysis.
- Declining potency across a study with everything else constant — usually freeze-thaw or adsorptive loss rather than biology.
If material fails within its stated stability window under correct storage, contact us with the lot number. We re-test the retention sample and replace the order if the lot is at fault.