Protein Solubility

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innate protein particles or aggregates.However, there is a mechanistic difference between the two aspects. In the case of a pure solubility issue, i.e. a protein becomes insoluble in a certain solution (no changes in protein structure and integrity) and a solid phase is formed, a strong dilution of the system may lead to the dissolution of the protein. In such a circumstance, the term “protein associates” may more appropriately describe the formed protein solid .In this instance, protein particles are formed, especially protein aggregates and often such aggregates cannot be dissolved by a dilution step. The reason for the formed aggregates is typically related to a unsettlement of the protein structure, protein integrity, orchemical changes. …show more content…
This effect is generally observed at low ionic interactions. The solubility of a protein is a complexed function of the physiochemical nature of the protein, pH, temperature, and the concentration of the salt used. It is also dependent on whether the salt is kosmotropic (stabilizes water) the proteins usually increases slightly (salting in). But at high concentrations of salt, the solubility of the proteins drop sharply .
PRINCIPLE : Proteins are surrounded by the salt counterians (ions of opposite net charge) and this screening results in decreasing electrostatic free energy of the protein and increasing the activity of the solvent, which in turn, leads to increasing solubility. This theory predicts in the logarithm of solubility to be proportional to the square root of the ionic strength. The abundance of the salt ions decreases the solvating power of the salt ions, the solubility of the proteins decreases and precipitation results.
At high salt concentrations, the solubility is given by the following empirical
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Salting out

Salting out is used for the purification process which is apply on the basis of protein solubility. It actually relies on the principle that much of the protein have low solubility in higher salt concentration solutions. The reason is that the more addition of ions of salt protect proteins with multi ion charges.
There are two method of salting out.
Salting out which is known as anti-solvent crystallization, precipitation, or crystallization drowning out is an effect based on the electrolyte and non electrolyte interaction where the less soluble at high salt concentrations will be non electrolyte. It is used as a process for the purification for proteins, as well as preventing the protein from denaturation.The salt concentration required for the proteins to precipitate out of the solution vary from protein to protein.

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