F.A.Q.
How to keep your peptide safety
Peptides are more stable as a lyophilized powder rather than in solution in water or in a buffer. Keep your peptide at -20°C for a better stability. To prevent oxidation and moisture, aliquots of peptides are preferred.
Solubility and Handling
Some peptides may be difficult to solubilize in pure water. If you are facing this problem, some additives may be used to promote solubilization:
- Peptides with a positive net charge, add acetic acid (1 – 10%), 0.1% TFA for example;
- Acid peptides, add 0.1% ammonia;
- Hydrophobic peptides, acetonitrile at 10% may be an alternative as well as isopropanol, DMSO or DMF.
In all cases, sonication may facilitate the solubilization of aggregate removal. Following sonication add your buffer solution to reach your peptide stock solution. It is always better to keep in the freezer a stock solution rather than the final working peptide solution. The final concentration of these additives may be compatible with the biological tests that you will conduct.
Some specific recommendations
Peptides containing free cysteine (Cys, C), methionine (Met, M) or tryptophane (Trp, W) residues:
The peptides containing free cysteine residues are highly susceptible to spontaneous polymerization. For this reason it is better to keep such peptides in the presence of a reducing agent. For peptides containing Met or /and Trp, use filtered water or buffer in order to remove entrapped air, then fill the tube with argon. In any case banish highly basic buffers and DMSO.
Glutamine (Q) :
N-terminal glutamine (Gln, Q) may be cyclisized in acidic conditions in a pyroglutamic acid (pGlu) preventing the sequencing of the peptide by Edman chemistry.
