The peptide is very stable at -20 ° C, especially freeze-dried and stored in a desiccator. Freeze-dried peptides can be placed at room temperature before they are exposed to air, which will reduce the effects of humidity. When it is not possible to freeze dry, the best method is to store it in a small working sample.
For peptides containing cys, met or trp, deoxygenation buffers are essential for their dissolution. Because this polypeptide can be easily oxidized by air. Before sealing, Nitrogen or argon flowing slowly through the peptide also reduces oxidation. Peptides containing Gln or Asn are also susceptible to degradation. All of these peptides have a limited lifetime compared to polypeptides that do not contain these problematic cleavage. Residues Ala, Cys, Ile, Leu, Met, Phe and Val will increase the solubility of the peptide. The lyophilized peptide should be stored in the refrigerator, preferably -20 ° C. Most peptides can be stored in this way for several years.
Preservation of solution peptide
The solution peptide is much more unstable than the lyophilized form, and the solution should be neutral PH (pH 5-7), -20 ° C preserved. In order to avoid repeated freezing and thawing of the sample, it is best to store it in small samples. A sample that has not been used up after freezing should be discarded. Bacterial degradation can sometimes become a problem with solution peptides. To overcome this problem, the peptide should be dissolved in sterile water or the peptide solution filtered through a 0.2μM membrane. Most peptides are soluble in sterile distilled water. When dissolving for the first time, care should be taken to make the initial concentration larger than the required concentration. This allows the addition of other solubilizing or buffering salts if the peptide has only limited solubility.
Application and preservation of peptides
Peptides have a wide range of solubility. The main problem with the insolubilization of the peptide is the formation of secondary structures. This happens except for the most peptides. More pronounced in polypeptides with multiple hydrophobic residues. Salt promotes the formation of secondary structures. It is generally recommended to dissolve the peptide in sterile distilled water or deionized water. If you need to increase the dissolution rate, you can use sonication. There is still a problem with the dissolution. Adding a small amount of dilute acetic acid (10%) or ammonia will facilitate dissolution.
To preserve the polypeptide for a long time, it is best to freeze it. The lyophilized powder can be stored for several years at -20 ° C or lower with little or no degradation. The peptide in solution is far unstable. The peptide is susceptible to bacterial degradation and is dissolved using sterile purified water. Peptide solutions containing Met, Cgs or Try residues should be soluble in an anaerobic solvent due to oxidation and limited lifetime. To prevent repeated freezing and thawing damage, it is recommended to dissolve excess peptide to facilitate the experiment. The remaining peptides are stored in solid form.