. A well-known property is the salinization effect, in which the solubility of a non-electrolyte in water is reduced by the addition of electrolyte. For example, the solubility of ethyl ether in water at 25 ° C is 0.91% mol, but in an aqueous solution containing 15% by weight of sodium chloride it is. The solubility of proteins is influenced by ions. At low ionic concentrations (<0.5 M), protein solubility increases with ionic strength. The ions in the solution protect the protein molecules from the charge of other protein molecules, which is called "salting". At very high ionic strength, protein solubility decreases as ionic strength increases in the process called salting. Thus, salting can be used to separate proteins according to their solubility in the presence of a high salt concentration. In this protocol, ammonium sulfate is gradually added to an E. coli cell lysate to isolate a recombinant protein overexpressed by 20 kDa that does not contain cysteine residues or labels. Our editors will review what you have submitted and decide if the article needs to be revised. A disadvantage of salting in protein purification is that in addition to the precipitation of a certain protein of interest, impurities are also precipitated.

Therefore, in order to obtain a protein of purer interest, additional purification methods such as ion exchange chromatography may be required. [7] Saline compounds dissociate into aqueous solutions. This property is exploited during salting. When the salt concentration is increased, certain water molecules are attracted to the salt ions, which reduces the number of water molecules that can interact with the charged part of the protein. [3] Because different proteins have different amino acid compositions, different protein molecules precipitate at different concentrations of saline. [ref. needed] Salting (also known as salt-induced precipitation, salt fractionation, anti-solvent crystallization, precipitation crystallization or drowning)[1] is a purification technique that takes advantage of the reduced solubility of certain molecules in a solution with very high ionic strength. Salting is usually used to precipitate large biomolecules such as proteins or DNA. [2] Since the concentration of salt required for a particular protein to precipitate from solution varies from protein to protein, a certain concentration of salt can be used to precipitate a target protein. This method is also used to concentrate dilute protein solutions. Dialysis can be used to remove salt if necessary.

There are hydrophobic amino acids and hydrophilic amino acids in protein molecules. After protein folding in an aqueous solution, hydrophobic amino acids normally form protected hydrophobic zones, while hydrophilic amino acids interact with solvation molecules, allowing proteins to form hydrogen bonds with surrounding water molecules. If a sufficient part of the surface of the protein is hydrophilic, the protein can be dissolved in water. [4] Soaps are easily precipitated by concentrated saline, the metal ion in the salt reacts with the fatty acids that form soap and glycerin. To separate glycerin from soap, the pasty boiling mass is treated with brine (NaCl solution). The contents of kettle salt (separated) into an upper layer, which is a curved mass of impure soap, and a lower layer, which consists of an aqueous saline solution with dissolved glycerin. The slightly alkaline saline solution, called spent lye, is extracted from the bottom of the pan or boiler and can then be treated for glycerin recovery. [ref.

needed]. Undesirable proteins can be removed from a protein solution mixture by salting, provided that the solubility of the protein at different saline concentrations is known. After removal of the precipitate by filtration or centrifugation, the desired protein can be precipitated by changing the salt concentration to the level at which the desired protein becomes insoluble. [6] Keywords: ammonium sulphate; cell lysate; Dialysis; Hofmeister series; protein solubility; Salting. When salt is added to the solution, interactions between solvent molecules and salt ions occur more frequently. As a result, protein and salt ions compete for interaction with solvent molecules, so fewer solvent molecules are available for interaction with protein molecules than before. Protein-protein interactions thus become stronger than solvent-dissolved interactions and protein molecules associate by entering into hydrophobic interactions with each other. [5] After dissociation in a given solvent, the negatively charged atoms of a selected salt begin to compete for interactions with positively charged molecules in the solution. Similarly, positively charged cations compete for interactions with the solvent`s negatively charged molecules. This process is called salting. [ref.

needed].