Peptide Storage & Handling
Storage Sonication can be helpful as it improves the rate of dissolution.
The lyophilized peptides should be stored in a cool, dark and dry place. For best preservation, store the peptides at -20°C or colder and away from bright light. Most peptides stored at this temperature will remain stable for several years.
Absorption of moisture will greatly decrease stability of the peptide and may reduce overall peptide content. A vial containing a peptide should be allowed to warm to room temperature prior to being opened. This will reduce the uptake of moisture from the air onto the cold surface of the solid peptide or the inside of the container. The vial should be re-sealed as soon as possible after removing the desired quantity, preferably under an atmosphere of dry nitrogen, and then return it to cold storage.
The shelf life of peptides containing Met, Cys or Trp residues in solution is limited due to oxidation. To avoid repeated freeze-thaw cycles it is recommended to divide the stock solution into aliquots. If storage of peptides in solution is absolutely unavoidable, use sterile buffers at pH 5-6 and store aliquots at -20°C to prolong the storage life of peptides in solution.
The solubility of peptides depends on the sequence. Solubilizing peptides can be difficult, particularly if the peptides are very hydrophobic. In general, try to dissolve peptides in sterile distilled water. If the peptide remains insoluble, try the following steps:
Addition of 10% acetic acid or 0.1% TFA for basic peptides; 1% ammonium hydroxide or 10% ammonium bicarbonate for acidic peptides with further sonication should improve solubility.
For peptides that remained insoluble add organic solvents such as acetonitrile, DMSO or DMF up to a concentration of 20% (v/v). Please note that these solvents may interfere with some biological assays. For peptides with secondary structures, it may be necessary to add chaotropic agents such as urea or guanidium-HCl.