Dissolution and preservation of polypeptides

It is suggested that a small amount of peptide should be used to test the optimum dissolution method. Only when the peptide is completely dissolved, the solution can be added and diluted to the final concentration. Dissolve first, then add buffer. Note: always add the peptide to the appropriate solvent and not otherwise.

Dissolution of lyophilized polypeptides

1 the main problem in the dissolution of peptides is the formation of the two - level structure.

Although the formation of hydrophobic peptide chain structure is more obvious, but in addition to the shortest peptide chain, the phenomenon occurs in almost all peptide chain, and has nothing to do with the polarity of the two. Therefore, the first principle of dissolving the peptide is to use sterile distilled water or deionized water (if conditions permit).

Peptide solutions may encounter bacterial degradation. In order to avoid the occurrence of the phenomenon, the polypeptide should be dissolved in the sterile distilled water, or with 0.45 or 0.2 M pore size membrane filtration sterilization.

Peptides containing Cys, Met, and Trp are particularly susceptible to oxidation and therefore should be soluble in oxygen free water. Oxygen free water can be removed by injecting inert gas (nitrogen, helium, argon).

2 if the polypeptide is insoluble in pure water, ultrasonic treatment can help to break the particles and increase the solubility. Note: ultrasonic treatment can cause solution heating and peptide degradation.

3 if the polypeptide contains a number of basic amino acids, the use of (1-10%) acetic acid aqueous solution; for very hydrophobic polypeptide, the use of 50% acetic acid.

4 if the polypeptide contains a large number of acidic amino acids, can be dissolved in ammonia solution (1-10%) or ethyl acetate or bicarbonate and other volatile alkaline buffer solution. PH value must be adjusted before chromatography.

5 isopropyl alcohol and acetonitrile dissolve medium sized peptides. If the peptide to the column, the amount of organic solvent must be little, otherwise it will seriously affect the residence time.

6 if the polypeptide contains Val, Leu, Met, Phe, Tyr, DMSO, Ala and other aromatic side chain and highly hydrophobic, or neutral peptide, the use of DMF or other membrane denaturant, help dissolve the polypeptide.

The A. high concentration membrane denaturant can dissolve the two grade structure of the polypeptide.

B. membrane denaturant is suitable for the preparation of peptide analytical solution, but it may interfere with its biological activity.

C. DMF is the best denaturing agent (up to 30%) and drops to the peptide.

D. reversed phase chromatography, DMF will be out of the peak with the elution fluid, according to the amount of injection, the peak may be high. Most peptides can flow in a few minutes after a large amount of DMF is released. If the peptide is small, elution is too early, and the amount of peptide will be reduced.