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pH and precipitation - (Sep/18/2005 )

Hey every one
i'm new here ...i wish i can find answers for my qs here...

we have an enzyme z(buffered at 7) and we need to purify it so we decide to lower the pH in order to precipitate what cause the protein to precipitate at lower ph is it because at low pH the protein start to aggregate and this cause the precipitation.
what if we increase the ph by using equivalent amount of base instead of acid are we gonna get same result and why?
also why increasing the temp cause it to precipitate cause as i know that heat denature the enzyme and in some cases they precipitate?
i'm looking for ur help



the short answer to your question: yes, at lower or higher pH the protein will become unstable, unfold, and possibly precipitate. a protein is usually only stable about two or three pH units away from its pI.

long answer can be found here:

what methods are you using to purify your protein? why do you want to unfold it?


Just do remember that once denatured by chaning temp the protein will usually not revert back to its active state, so if u need it in an active state, then u might want to use some other method of precipitation