Storage & handling – stability starts at goods receipt
A certificate of analysis describes a batch on the day it was tested. Whether the material stays in that state in your lab depends on storage and handling. Peptides are sensitive to heat, moisture, light and oxygen. Controlling these factors gives reproducible results and lets you attribute deviations to the experiment rather than the material.
This page summarises the ground rules and links to in-depth articles in the magazine. Everything here refers to in-vitro research. It is not guidance for use in humans or animals.
Lyophilisate: the most stable form
Peptides are supplied as freeze-dried powder (lyophilisate). Freeze-drying leaves very little water, so most degradation reactions proceed only slowly.
| Situation | Recommendation |
|---|---|
| Short term (days to a few weeks) | 2–8 °C, sealed, protected from light |
| Longer term | −20 °C or colder, in the original vial with desiccant in a secondary container |
| Transport | A few days at room temperature is not critical for most lyophilisates |
| After opening | Reseal promptly, keep exposure to room air short |
The product data sheet takes precedence. Some sequences are more sensitive than others — for example those containing cysteine, methionine or tryptophan, which oxidise easily, or asparagine and glutamine, which tend to deamidate.
Avoid condensation
The most common handling error is opening a cold vial. Moisture condenses on the cold surface and the hygroscopic powder takes up water. Let closed vials reach room temperature first, typically 15 to 30 minutes.
Reconstitution in vitro
For experiments the lyophilisate is dissolved in a suitable solvent. The right choice depends on the sequence: charge, hydrophobicity and assay design decide. Common options are sterile water, buffer solutions or — for poorly soluble peptides — small fractions of organic solvent. Bacteriostatic water contains benzyl alcohol and is not suitable for every cell assay.
Ground rules:
- Add solvent slowly down the vial wall, not directly onto the cake.
- Swirl, don't shake; vigorous shaking promotes foaming and aggregation.
- Check visually for complete dissolution; turbidity can indicate aggregation or an unsuitable solvent.
- Record concentration, solvent, date and batch number straight away.
Calculate the concentration
The target concentration follows from peptide amount and solvent volume. The calculator helps with stock and working solutions. Note that the net peptide content can be lower than the gross amount, because lyophilisates contain counter-ions and residual water — see Endotoxin and water content.
Concentration calculator (in vitro)
Stock solution: 5 mg/ml = 5 µg/µl = 5,000 µg/ml
Dilution (C₁·V₁ = C₂·V₂)
Required volume of stock solution: 200 µl (0.2 ml)
Calculation aid for laboratory solutions. No dosing information.
Storing and aliquoting solutions
Peptides are far less stable in solution than as lyophilisate. Hydrolysis, oxidation and microbial growth become more likely. Good practice:
- Only dissolve what you will need soon.
- Split the stock solution into single-day aliquots immediately.
- Freeze aliquots at −20 °C or −80 °C; avoid repeated freeze–thaw cycles.
- Use low-protein-binding tubes, especially at low concentrations.
- Define a short, internally agreed use-by period for solutions kept at 2–8 °C.
Light, oxygen and pH
Light-sensitive residues such as tryptophan and tyrosine benefit from amber glass or foil. Small headspaces and prompt resealing limit oxygen; for very oxidation-prone sequences an inert-gas overlay can help. A pH near neutral suits many peptides; extreme pH accelerates hydrolysis and deamidation.
Documentation and traceability
Every Peptidkauf batch has a batch number and a certificate of analysis. Copy both into your lab notebook together with receipt date, storage location and every reconstitution, so results can later be linked to a specific batch. See Batches & traceability; all certificates are in the lab report archive.