To remove ammonium sulfate from the protein, pellet the protein in a centrifuge. Dissolve the pellet in a suitable buffer. Remove residual ammonium sulfate either by dialysis or by gel filtration chromatography. Measure the final protein concentration.

Hi Vinyas, just to add to Adam's answer, if you are going to do toxicity studies in animals, then you should do endotoxin testing on the proteins after removing the ammonium sulfate.

Is the same OECD guide lines 425 must be followed for the above purified protein

Hi Vinyas, the OECD guidelines are very specific.

OECD GUIDELINE FOR TESTING OF CHEMICALS..... 425

Adopted: 17th December 2001

http://www.oecd.org/chemicalsafety/risk-assessment/1948378.pdf

But this protocol does not mention proteins. Do you have a newer version of this guideline that mentions proteins? 

No, Sir I don`t . Is there is any specific guidelines for testing the toxicity of proteins in rats?

I can only give you a ppt that I found.

http://www.oecd.org/chemicalsafety/testing/40575405.pdf