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Salting out (also known as salt-induced precipitation, salt fractionation, anti-solvent crystallization, precipitation crystallization, or drowning out) [1] is a purification technique that utilizes the reduced solubility of certain molecules in a solution of very high ionic strength.
At high salt concentrations, the solubility is given by the following empirical expression. [citation needed] log S = B − KI. where S is the solubility of the protein, B is a constant (function of protein, pH and temperature), K is the salting out constant (function of pH, mixing and salt), and I is the ionic strength of the salt.
z i is the ion charge of the salt and c i is the salt concentration. The ideal salt for protein precipitation is most effective for a particular amino acid composition, inexpensive, non-buffering, and non-polluting. The most commonly used salt is ammonium sulfate. There is a low variation in salting out over temperatures 0 °C to 30 °C.
Ammonium sulfate is an inorganic salt with a high solubility that disassociates into ammonium (NH + 4) and sulfate (SO 2− 4) in aqueous solutions. [1] Ammonium sulfate is especially useful as a precipitant because it is highly soluble, stabilizes protein structure, has a relatively low density, is readily available, and is relatively inexpensive.
The "salting out" effect is commonly exploited in protein purification through the use of ammonium sulfate precipitation. [16] However, these salts also interact directly with proteins (which are charged and have strong dipole moments) and may even bind specifically (e.g., phosphate and sulfate binding to ribonuclease A ).
Salting roads, the application of salt to roads in winter to act as a de-icing agent; Salting a bird's tail, a superstition; Salting out, a method of separating proteins using salt; Figuratively, adding ("sprinkling") a small quantity of something to something else for various reasons Salt (cryptography), a method to secure passwords
The salting-out process used in the manufacture of soaps benefits from the common-ion effect. Soaps are sodium salts of fatty acids. Addition of sodium chloride reduces the solubility of the soap salts. The soaps precipitate due to a combination of common-ion effect and increased ionic strength.
Sea salt being added to raw ham to make prosciutto. Salting is the preservation of food with dry edible salt. [1] It is related to pickling in general and more specifically to brining also known as fermenting (preparing food with brine, that is, salty water) and is one form of curing.