Ammonium Sulfate Precipitation
A method of protein purification is precipitation an anti-chaotropic salt. Ammonium sulfate can be used to precipitate out certain proteins of interest, such as LDH in protein mixtures. Ammonium sulfate should be added slowly when precipitating a protein because proteins precipitate out at different concentrations of ammonium sulfate. Ammonium sulfate decreases the amount of water available to the protein, causing proteins to precipitate out of solution. Ammonium sulfate is used instead of sodium chloride because it is an anti-chaotropic salt, meaning that it favors protein folding rather than protein denaturation. Sodium chloride is moderately chaotropic and denatures proteins.
