Lyophilized peptide powders are chemically stable at −20°C for extended periods. Reconstitution, however, is where most stability losses occur — and where most methodological errors enter. This note walks through the general considerations a researcher should weigh when returning a lyophilized research peptide to solution. It is not a human-use protocol.
Match the solvent to the sequence
Peptides vary widely in solubility. Hydrophobic sequences, or those with aromatic-rich regions, may require a small fraction of organic cosolvent before dilution into aqueous buffer. Highly basic peptides dissolve readily in slightly acidic media. Consult the primary literature for the sequence under study before reaching for a solvent.
Add slowly, swirl gently
The lyophilized cake should be reconstituted by adding solvent to the side of the vial rather than directly onto the powder, and by swirling rather than vortexing. Foaming is a common cause of peptide loss to denaturation at the air-liquid interface.
Aliquot after reconstitution
Repeated freeze-thaw cycles are one of the leading causes of potency loss in reconstituted peptide stocks. Aliquot into single-use tubes at the time of reconstitution, flash freeze, and store at −80°C if possible.