[YULivin4]

I am working on a lab for the purification of HMG-CoA reductase...One of the purification procedures we used was a 40% ammonium sulfate precipitation...When deciding what % AS has something to do with the pI of the solution...I also know that if you have too low of a concentration the solubility is not high enough to precipitate the proteins because all the water can do this and if it is too high this can destroy the protein.  I also know that this is related to the pI and the pH of the buffered protein solution(or is it the pI of AS)...Can someone better explain the relation to pI and/or point me to an article that I can use as a source in my paper...Thanks so much....Finishing all the loose ends of my paper and this was just not sounding right, especially with no source (the concentration relation was related by a peer)...Thanks again

DSO

[Arkcon]

As I understood it, although pI and pH are important concepts in other protein purification methods, and important in general for maintaining stability, when you do an ammonium sulfate precipitation, you're just doing a "salting out."  You can check the Wikipedia link here, but you should go for a textbook reference for your paper.  And don't forget to check the see also: links on the Wikipedia page, they will help you understand the idea better.

http://en.wikipedia.org/wiki/Salting_out