Q: How to save synthetic polypeptide?
A: Generally, polypeptide is stable at -20℃, especially stored in a freeze-dried desiccator. Before it’s exposed to air, freeze-drying polypeptide can be placed at normal temperature. This can help reduce the humidity. When it can’t be freeze-dried, the best method is to store the samples at a small amount. In addition, as for polypeptide containing Cys, Met or TrP, deoxygenated buffer is essential for its dissolution because such polypeptide can be oxidized easily. Polypeptide comprising Gln or Asn is also susceptible to degradation. Compared with those who have glycosides, these peptides have a limited lifetime.

Q: How about the solubility of polypeptide? What kind of solvent is applicable for polypeptide?
A: Most peptides prefer to choose ultrapure extraction water. Dilute acetic acid or ammonia are very important for the dissolution of the alkaline or acidic polypeptide. While as for those which cannot dissolve through these methods, DMF, urea, guanidinium, chloride or acetonitrile might be helpful. Whereas, these solvents may have side effects in some experiments. Therefore, we recommend to increase attention while designing polypeptides. Residues such as Ala, Cys, Ile, Leu, Met, Phe and Val will increase difficulty for the dissolving process, as well as other substances like oxytocin.

Q: How to operate the preservation of polypeptide?
A: Polypeptide less than 1mg should choose net packaging, and declared vials are free of water and relevant anti-heavy ions. For example, the decided peptide content through amino acid analysis is 80%, so bottle’s gross weight should be 1.25mg in 1mg samples. Do not confuse peptide content and purity.

The purity of peptide might be 100%, while the content of peptide is decided by the amount of ions in related charged groups (such as Arg, Lys) and peptide’s hydrophilic feature (Pramlintide). This is the characteristics of synthetic peptide. All the peptide products should be stored in the refrigerator, preferably -20℃. Most peptides can be stored in this way to remain unchanged for a few years.

Q: What is HPLC analysis? How to use HPLC to purify polypeptide?
A: HPLC analysis uses the column and pump systems that can withstand high pressures to complete more accurate result analysis. In addition, it can use extremely fine particles (3-10μ m) to act as the filler. Whereby the polypeptide could be analyzed within minutes. This analysis method has been used widely in practical trails.

But, one more point is noted by most researchers, that is, HPLC could be divided into two types: ion exchange and reverse phase, which means experimental experience is required during the process of HPLC analysis. Typically, the first step starts with a solution of low ionic strength, gradually strengthening or reinforcing until peptides get eluted from the fire pillar. Exchange column of strong cation is needed in the next step. Finally, it can be separated successfully.

Put it simply, a large variety of buffers could contain many different agents, such as heptafluorobutyric acid, sodium acetate/ammonia, TFA/TEA, sodium phosphate or potassium, and amyl phenol. Given the fact, many different combinations can form a buffer, but be sure to note that: column material of silicon reversed phase cannot be exposed to substances with high pH for a prolonged time, even micro-alkaline pH, because it would undermine the pillars.