Ammonium sulfate is a widely used reagent in molecular biology and chromatography. It is useful in the isolation and purification of enzymes and proteins. It is used for the precipitation or fractionation of proteins or for purification of antibodies.It is also useful for crystallographic analysis of nucleic acids and proteins. Ammonium sulfate is also widely used in HPLC of proteins, such as in hydrophobic interaction chromatography.