Peptide Storage Science

Peptide stability depends on storage conditions. Understanding the degradation pathways helps researchers maintain sample integrity from receipt to use. This page covers the chemistry of peptide degradation and QSC's recommended storage conditions for lyophilised and reconstituted peptides.

Degradation Mechanisms

Peptide degradation in storage occurs through several distinct chemical pathways. Understanding which pathway is most relevant for a given peptide informs appropriate storage strategy:

Hydrolysis

Water cleaves peptide bonds, particularly at Asp-Pro and Asp-Gly sequences. Hydrolysis is minimised by lyophilisation (removal of water) and by maintaining lyophilised peptides at low temperature and low humidity. This is why QSC ships peptides as lyophilised powder rather than in solution.

Oxidation

Methionine, cysteine, tryptophan, and histidine residues are susceptible to oxidation by atmospheric oxygen or hydrogen peroxide. Oxidation converts Met→Met(O), reduces disulfide bonds in Cys-containing peptides, and can alter bioactivity. Storage in sealed, argon-blanketed vials minimises oxidation. Avoid repeatedly opening vials unnecessarily.

Aggregation

Hydrophobic peptides (particularly growth hormone-releasing sequences) can aggregate in solution, forming oligomers that are functionally inert. Aggregation is accelerated by elevated temperature, high concentration, and freeze-thaw cycling. Keeping solutions dilute and minimising freeze-thaw cycles reduces aggregation risk.

Racemisation

Some amino acid residues (particularly aspartate) can undergo base-catalysed racemisation at elevated pH. Maintaining acidic pH (where relevant) and low temperature reduces this risk. Most stored peptide solutions acidified with 0.1% acetic acid are stable against racemisation.

QSC Storage Recommendations

Key Principles

• Keep lyophilised peptides cold and dry. Even –20°C cannot prevent degradation if moisture enters the vial. Store sealed until use.
• Protect from light. UV exposure degrades tryptophan, tyrosine, and phenylalanine residues. Store in opaque containers or wrap vials in foil.
• Do not freeze reconstituted peptide solutions. Freeze-thaw cycling causes aggregation and mechanical stress to the peptide structure. Use BAC water and keep reconstituted solutions refrigerated throughout their use period.
• Allow to warm before opening. Opening a cold vial creates condensation. Allow vials to reach room temperature before piercing the septum to prevent moisture ingress.
• Aliquot if needed for long-term use. For peptides used over extended periods, consider reconstituting smaller volumes to avoid repeated freeze-thaw cycles on the main stock.