title: Salting out of proteins using ammonium sulfate precipitation.
abstract: Protein solubility is affected by ions. At low ion concentrations (<0.5 M), protein solubility increases along with ionic strength. Ions in the solution shield protein molecules from the charge of other protein molecules in what is known as 'salting-in'. At a very high ionic strength, protein solubility decreases as ionic strength increases in the process known as 'salting-out'. Thus, salting out can be used to separate proteins based on their solubility in the presence of a high concentration of salt. In this protocol, ammonium sulfate will be added incrementally to an E. coli cell lysate to isolate a recombinantly over-expressed protein of 20 kDa containing no cysteine residues or tags.
authors.affiliation: Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors.forename: Krisna C
authors.initials: KC
authors.lastname: Duong-Ly
authors.affiliation: Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA. Electronic address: gabelli@jhmi.edu.
authors.forename: Sandra B
authors.initials: SB
authors.lastname: Gabelli
mesh_terms: D000645:Ammonium Sulfate / Q000737:chemistry*; D011232:Chemical Precipitation; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000302:isolation & purification; D009994:Osmolar Concentration; D011506:Proteins / Q000737:chemistry* / Q000302:isolation & purification*; D012995:Solubility
chemical_list: D029968:Escherichia coli Proteins; D011506:Proteins; D000645:Ammonium Sulfate
keywords: Ammonium sulfate; Cell lysate; Dialysis; Hofmeister series; Protein solubility; Salting-out