Salting out of proteins using ammonium sulfate precipitation

Krisna C. Duong-Ly, Sandra B. Gabelli

Research output: Chapter in Book/Report/Conference proceedingChapter


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' (Fig. 7.1). 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.

Original languageEnglish (US)
Title of host publicationLaboratory Methods in Enzymology
Subtitle of host publicationProtein Part C
PublisherAcademic Press Inc.
Number of pages10
ISBN (Print)9780124201194
StatePublished - 2014

Publication series

NameMethods in Enzymology
ISSN (Print)0076-6879
ISSN (Electronic)1557-7988


  • Ammonium sulfate
  • Cell lysate
  • Dialysis
  • Hofmeister series
  • Protein solubility
  • Salting-out

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology


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