Every Peptide Has an Expiry Clock
From the moment a peptide is synthesized, degradation pathways are at work. The rate depends on storage conditions, amino acid composition, and formulation — but understanding these pathways lets you slow the clock dramatically. Researchers who understand degradation chemistry design better experiments and get more reproducible results.
Chemical Degradation
Oxidation
The most common chemical degradation pathway. Methionine (Met) and tryptophan (Trp) residues are particularly susceptible. Exposure to air, light, and trace metals accelerates oxidation. Oxidized peptides often show new peaks on HPLC (shifted retention times) and altered biological activity.
Prevention: Purge vial headspace with nitrogen or argon before sealing. Store in amber vials. Avoid contact with metal spatulas.
Deamidation
Asparagine (Asn) and glutamine (Gln) residues undergo deamidation — converting to aspartate/glutamate via a succinimide intermediate. This occurs faster at neutral to basic pH and elevated temperatures. Deamidation introduces a charge change that can alter peptide folding and function.
Prevention: Store at acidic pH (4-5) when possible. Maintain cold chain (-20°C lyophilized).
Hydrolysis
Peptide bonds can cleave in aqueous solution, particularly Asp-Pro bonds and near N-terminal residues. Elevated temperature and extreme pH accelerate hydrolysis. The result is truncated peptide fragments with altered or absent biological activity.
Physical Degradation
Aggregation
Peptides can form soluble or insoluble aggregates through hydrophobic interactions, disulfide bonding, or van der Waals forces. Freeze-thaw cycles, mechanical agitation, and high concentrations promote aggregation. Aggregated peptides may show turbidity, precipitation, or anomalous HPLC profiles.
Prevention: Aliquot reconstituted peptides into single-use portions. Avoid vigorous shaking — gentle swirl only. Maintain concentration below aggregation threshold.
Adsorption
Peptides adsorb to container surfaces (glass, polypropylene, polystyrene), reducing effective concentration. This is particularly problematic at low concentrations where a significant fraction may bind to the container wall.
Prevention: Use low-binding tubes (siliconized glass or specially treated polypropylene). Avoid unnecessary transfers between containers.
Stability by Form
Lyophilized peptides are dramatically more stable than solutions:
- -20°C lyophilized: Years of stability for most peptides
- 2-8°C lyophilized: 1-6 months depending on peptide
- 2-8°C reconstituted: ~4 weeks in bacteriostatic water
- Room temperature: Days to weeks — avoid extended exposure
Monitoring Integrity
For critical research, verify peptide integrity over time using HPLC. Compare peak profiles at day 0 vs. later timepoints. A decrease in main peak area or appearance of new peaks indicates degradation. Document these stability checks in your lab notebook.
See our comprehensive storage guide for per-peptide temperature recommendations.
For research purposes only.