Protein solubility after amm.sulphate precipitation

Daniel Gonzalez meton at
Thu Apr 24 12:24:16 EST 1997

I would suggest that you use another method to concentrate your protein, and see what happens.  It may be that your protein is insoluble when concentrated or you may be separating out a componenent that stabilises the protein.  Another problem is pH, you should try to maintain the same pH your protein is in when you concentrate it with Ammonium sulphate--check your pH, you may need to add concentrated buffer solution to the precipitation to keep the pH at 7.5, I have experienced the problem of pH induced denaturation when I do ammonium sulphate ppts and have been forced to use PEG.  Also, if you avoid dialysing your protein against 500mM NaCl you might be able to concentrate it on an ion exchange column.  If you can provide more details about your protein, then I may be able to suggest a more detailed solution to your problem.

Daniel Gonzalez

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