Best Practices for Peptide Storage and Handling

Peptide stability is one of the most critical factors in ensuring reproducible research results. Improper storage or handling can lead to degradation, aggregation, or loss of biological activity, potentially invalidating experimental findings. This guide covers essential best practices for peptide storage and handling in research settings.

Storage of Lyophilized Peptides

Lyophilized (freeze-dried) peptides are the most stable form for long-term storage. In their dry state, peptides are protected from hydrolysis and many other degradation pathways. However, proper storage conditions are still essential:

• Store at -20°C or lower for long-term storage (months to years)
• Keep at 2-8°C for short-term storage (up to a few weeks)
• Protect from light using amber vials or foil wrapping
• Keep containers tightly sealed to prevent moisture absorption
• Use desiccants when possible to maintain low humidity

Reconstitution Guidelines

Proper reconstitution is crucial for peptide stability and activity. The choice of solvent depends on the peptide's chemical properties:

For Most Peptides

Sterile water or bacteriostatic water (containing 0.9% benzyl alcohol) is suitable for most research peptides. Bacteriostatic water is preferred when multiple aliquots will be drawn from the same vial, as it inhibits bacterial growth.

For Hydrophobic Peptides

Peptides with high hydrophobic amino acid content may require initial dissolution in a small amount of DMSO, acetic acid, or acetonitrile, followed by dilution with aqueous buffer.

Storage of Reconstituted Peptides

Once reconstituted, peptides are more susceptible to degradation. Follow these guidelines:

• Store reconstituted peptides at 2-8°C for short-term use (up to 2-4 weeks)
• For longer storage, aliquot into single-use portions and freeze at -20°C
• Avoid repeated freeze-thaw cycles (maximum 2-3 cycles)
• Use sterile technique to prevent microbial contamination
• Note the reconstitution date and concentration on the vial

Common Degradation Pathways

Understanding how peptides degrade helps researchers take appropriate precautions:

• Oxidation: Methionine, cysteine, and tryptophan residues are susceptible to oxidation. Store under inert gas (nitrogen or argon) when possible.
• Deamidation: Asparagine and glutamine can undergo deamidation, especially at elevated pH. Use buffers at pH 4-6 for sensitive peptides.
• Hydrolysis: Peptide bonds can be cleaved in aqueous solution, particularly at elevated temperatures or extreme pH values.
• Aggregation: Some peptides tend to form aggregates over time. Fresh reconstitution and appropriate buffer conditions can minimize this.