Tell me more ×
Biology Stack Exchange is a question and answer site for biology researchers, academics, and students. It's 100% free, no registration required.
up vote 3 down vote favorite

In general does the pH effect the precipitation, e.g. would a pH of 6 cause less precipitation than pH 7.5. Or are they unrelated?

share|improve this question

1 Answer

up vote 3 down vote accepted

I think it would affect some proteins, but ammonium sulfate precipitation usually requires such large amounts of salt, that you would have to add a lot of base to adjust the pH.

When I have done ammonium sulfate precipitation, its to take a rough cut of proteins out of a whole cell/whole organ lysate - its more like a hammer than a pair of tweezers as far as protein purification is concerned. I would rather use a charged plastic resin or a sizing column if I were to care about the isoelectric purification.

share|improve this answer
Thanks. I'm actually trying to stop precipitation when incubating a protein in ammonium acetate, and I wondered if an acidic pH would reduce this. Do you have any suggestions – Anake Oct 9 '12 at 12:30
1  
Do you know the pI of your protein? Proteins are least soluble at pH=pI. – Alan Boyd Oct 9 '12 at 13:10
also consider detergent - might the protein be a bit hydrophilic? – shigeta Oct 9 '12 at 13:51
@Anake, I would look up en.wikipedia.org/wiki/Hofmeister_series – bobthejoe Oct 10 '12 at 8:45
the protein isn't hydrophobic, it is the ammonium's precipitating tendency as in the Hoffmeister series. I HAVE to use an ammonium salt, so the hoffmeister series cannot help me in that respect – Anake Oct 10 '12 at 13:48
show 1 more comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.