| Salting-out (ammonium sulfate fractionation)
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| The solubility of a protein is dependent on the concentration of dissolved salts, and the solubility may be increased by the addition of salt at a low concentration (salting-in) or decreased by high salt concentration (salting-out). When ammonium sulfate, one of the most soluble salts, is added to a solution of a protein, some proteins precipitate at a given salt concentration while others do not. Human serum immunoglobulins are precipitable by 33-40% saturated (NH4)2SO4, while albumin remains soluble. Saturated ammonium sulfate is about 4.1 mol/L. Most proteins will precipitate from an 80% saturated (NH4)2SO4 solution.
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