Peptide Shelf Life and Stability

There is no universal expiry for research peptides. A lyophilised vial kept cold, sealed and dark is remarkably durable; the same sequence in solution on a bench at room temperature can lose measurable content in days.

The main degradation pathways

• Hydrolysis — the backbone splits, accelerated by water, heat and extremes of pH.
• Oxidation — methionine, cysteine and tryptophan residues react with dissolved oxygen and light.
• Deamidation — asparagine and glutamine convert, shifting mass and charge.
• Aggregation — chains associate and drop out of solution, often visible as haze.
• Adsorption — peptide sticks to glass or plastic surfaces, quietly reducing concentration.

Realistic expectations

Treat manufacturer statements as conditional: they assume the storage condition on the label was maintained continuously. A vial that spent a week in a warm room is not covered by the number on the datasheet, whatever the date says.

Signs a vial should be discarded

1. 1Discolouration of the cake or the solution.
2. 2Persistent particulates or haze after gentle mixing.
3. 3A compromised stopper, loose crimp or damaged seal.
4. 4Any vial you cannot tie to a batch number and a storage history.

Confirming stability

If a batch matters to a long study, retest rather than assume. A repeat HPLC run against the original chromatogram shows directly whether the impurity profile has grown.