Peptides are shipped at room temperature, and are highly stable in lyophilized form in sealed bags (Why in sealed bags?). Peptides should not be kept in solution for long periods.
Peptide storage guidelines: For long-term storage, peptides should be stored in lyophilized form at -20°C, or preferably at -80°C with desiccant in sealed containers to minimize peptide degradation. Under these conditions, peptides can be stored for up to several years. This type of storage prevents bacterial degradation, oxidation, and the formation of secondary structures.
Opening the package: It is better to equilibrate the peptides to room temperature in a desiccator before opening and weighing. Failure to warm the peptides beforehand can cause condensation to form (peptides tend to be hygroscopic) on the product when the bottle is opened. This will reduce the stability of the peptides.
Before reconstitution, centrifuge the vial of the lyophilized peptide at 12,000 x g for 20 seconds. This will help pellet the entire peptide sample for reconstitution.
Weighing peptides: Weigh out your required quantity of peptides rapidly and store all unused peptides at -20°C or below. Sequences that contain cysteine, methionine, tryptophan, asparagine, glutamine, and N-terminal glutamic acid will have a shorter shelf life than other peptides.