Foundations · 3 min read
Lyophilized (freeze-dried) peptides are chemically stable in powder form, but that stability depends heavily on how the material is stored and handled before and after reconstitution. Most of the degradation researchers encounter in practice traces back to storage conditions rather than the synthesis itself.
Before reconstitution, lyophilized peptide powder should be kept in a sealed, dry container at -20 degrees C for long-term storage, and protected from light. Peptides are generally more stable in this state than once dissolved, since moisture and light both accelerate degradation pathways such as oxidation and hydrolysis. Repeated freeze-thaw cycles of the sealed vial should be avoided where possible, as condensation introduced each time the vial warms up can introduce moisture into the powder.
Reconstitution, the process of dissolving the lyophilized powder in a diluent such as bacteriostatic water, should be done slowly, directing the liquid down the side of the vial rather than directly onto the powder, to avoid denaturing the peptide through excess agitation. Gentle swirling rather than shaking is generally recommended once the diluent has been added.
Once reconstituted, a peptide solution is considerably less stable than the lyophilized form and should typically be stored refrigerated at 2-8 degrees C, used within the timeframe indicated for that specific compound, and protected from light and repeated temperature fluctuation. Reconstituted solutions are also more susceptible to microbial contamination over time, which is part of why bacteriostatic water (containing a preservative) is commonly used as the diluent rather than plain sterile water.
Shipping introduces its own handling considerations. Peptides are typically shipped with cold packs or dry ice to maintain a low temperature in transit, and it's good practice to transfer received material to proper freezer storage promptly on arrival rather than leaving it at ambient temperature.
RESEARCH NOTES
Lyophilized (freeze-dried) peptides are generally stable at room temperature for shorter periods but are recommended to be stored frozen (-20°C or lower) for longer-term stability, since the freeze-drying process removes water but does not eliminate the underlying degradation reactions that heat and moisture can accelerate. Once reconstituted in bacteriostatic water, most peptides are substantially less stable and are typically kept refrigerated, with researchers tracking beyond-use timeframes since reconstitution restarts the clock on degradation.