How to purify protein

How to purify protein, protein is a macromolecule, and albumin with various molecular sizes, there are some simpler methods to separate the protein and small molecule materials, and also separate the protein mixture. Separation of proteins of different molecular sizes is mainly done by dialysis, ultrafiltration, gel filtration, centrifugation, etc. Dialysis and ultrafiltration are commonly used in protein separation methods. The dialysis mixture to be separated is placed in a dialysis bag consisting of a semipermeable membrane and then immersed in the dialysis solution for separation. Ultrafiltration is the process of passing water and other small molecules and proteins through a semipermeable membrane using centrifugal force or pressure. Both methods can separate small molecules from protein-based macromolecules and inorganic salts. They are often salted out, used in conjunction with the salt dissolution method, or can be introduced to take out after salting out using an inorganic salt solution for both methods.

1. How to purify protein by salting out method: the basis of salting out method is that the solubility of protein in dilute salt solution will increase with the increase of salt concentration, but when the salt concentration increases to a certain value, the water activity will be reduced. In turn, some proteins can be gradually neutralized through the charge generated on the surface of the molecular structure, and the hydration film is gradually destroyed, which can eventually cause related proteins and molecules to develop and coagulate with each other and precipitate from different solutions.

2. Organic solvent precipitation method: There are two reasons to reduce the solubility of protein in organic solvents: how to purify protein, as a salt solution with dehydration; secondly, the dielectric constant of organic solvents is lower than that of water, so that it can be reduced in polar solvents

3. Protein precipitant: As a precipitant, protein only acts on one type or one through protein precipitation, and the common ones are alkalinity, protein, lectin and heavy metal.

4. Polyethylene glycol precipitation: How to purify water-soluble non-ionic polymers, such as polyethylene glycol and dextran sodium sulfate, to precipitate proteins.