Peptide stability is a critical yet often overlooked aspect of research quality. Even the highest-purity peptides can degrade rapidly if stored or reconstituted improperly. This guide covers the essential principles and practical techniques for maintaining peptide integrity from delivery to experiment.
Lyophilized (Freeze-Dried) Peptide Storage
Why Peptides Are Lyophilized
Most research peptides are supplied as lyophilized powders. Lyophilization removes water while the peptide is frozen, producing a dry, stable cake or powder. In this form, peptides are significantly more stable than in solution because the absence of water slows hydrolysis, deamidation, and other degradation reactions.
Storage Conditions for Lyophilized Peptides
Short-term (up to 30 days): Room temperature (20-25 degrees C) is acceptable for most peptides if kept dry and away from light.Medium-term (1-6 months): Refrigeration at 2-8 degrees C (standard refrigerator) is recommended.Long-term (6+ months): Freezer storage at -20 degrees C or below is ideal. For archival storage, -80 degrees C provides maximum stability.Key Storage Principles
**Keep it dry**: Moisture is the primary enemy of lyophilized peptides. Use desiccant in storage containers and minimize exposure to humid air.**Protect from light**: UV light can cause oxidation and degradation. Store in amber vials or wrap containers in foil.**Minimize freeze-thaw cycles**: Each thaw exposes the peptide to moisture. Aliquot the peptide before freezing if you'll need portions at different times.Reconstitution Procedures
Choosing a Solvent
The choice of reconstitution solvent depends on the peptide's properties:
Bacteriostatic water: The most common choice for general reconstitution. The 0.9% benzyl alcohol preservative inhibits microbial growth, extending the usable life of reconstituted peptides.Sterile water: Used when bacteriostatic water is not available or when the preservative might interfere with research assays.Dilute acetic acid (0.1%): Helps solubilize basic peptides that are poorly soluble in water alone.DMSO: A last-resort solvent for very hydrophobic peptides. Use the minimum concentration necessary and note that DMSO may affect some biological assays.Reconstitution Technique
Allow the lyophilized vial to reach room temperature before opening to prevent condensation.Using a sterile syringe, add the solvent slowly down the inside wall of the vial. Do not inject directly onto the peptide cake.Gently swirl the vial to dissolve. Do not vortex or shake vigorously, as this can cause foaming, denaturation, and peptide loss to the air-liquid interface.If the peptide does not dissolve completely, allow it to sit at room temperature for 10-15 minutes, gently swirling periodically.Once fully dissolved, the solution should be clear. Cloudiness or persistent particles may indicate degradation or solubility issues.Post-Reconstitution Storage
Bacteriostatic water reconstitutions: Stable for up to 30 days at 2-8 degrees C.Sterile water reconstitutions: Use within 48-72 hours if stored at 2-8 degrees C; freeze aliquots for longer storage.All reconstituted peptides: Protect from light and avoid repeated freeze-thaw cycles.Aliquoting Strategy
For peptides that will be used across multiple experiments:
Reconstitute the entire vial.Immediately divide into single-use aliquots using sterile microcentrifuge tubes.Flash-freeze in liquid nitrogen or place directly in -20 degrees C freezer.Thaw only the aliquot needed for each experiment.Never refreeze a thawed aliquot.This approach minimizes the degradation caused by repeated freeze-thaw cycles and ensures each experiment uses peptide of consistent quality.
Signs of Peptide Degradation
Change in appearance (discoloration, precipitate formation)Reduced or absent biological activity in established assaysUnexpected HPLC peaks if you perform re-analysisGel formation in solutionUnusual odorConclusion
Proper storage and reconstitution are not optional steps in peptide research; they are fundamental to experimental reproducibility and data quality. By following the guidelines above, researchers can maximize the usable life of their peptides and maintain confidence in their research outcomes. Premium vendors like MedgePeptides include reconstitution guides with their products and use appropriate packaging to protect peptide integrity during shipping.