Our peptides are delivered lyophilized in a sealed glass vial, and for better stability they should be stored at -20°C. Peptides without cysteine residues and stored lyophilized at -20°C are stable for years. Peptides containing sensitive amino acids like cysteine (C), methionine (M), and tryptophane (W) should be stored lyophilized at -20°C in an inert gas environment to avoid oxidation. Peptides in solution are stable for 1-2- weeks at +4°C, for 3-4 months at -20°C, and for 1 year at -80°C. Repeated freeze and thaw cycles should be avoided. If you have to weigh the peptides, do it quickly and in a glass vial, because they are often very hygroscopic and absorb water rapidly. Make sure that the peptide is at room temperature before weighing. It is a good idea to test the solubility of your peptide on a small sample and then try to re-suspend the peptide in de-ionized water. If it is insoluble, add 0,1% NH4OH for peptides with a negative charge and 0,1% TFA for peptides with a positive charge. If the peptide is very hydrophobic, start to dissolve the peptide with small quantities of DMSO and then add the buffer you will subsequently use in order to reach the desired concentration. For difficult cases, repeated sonication (30- 60 seconds) may help with solubilization.
