Protein Precipitation

[Doug Portman]

In article <johnmcd-180494124838 at john-mcd.nfh.uit.no> John McDougall,
johnmcd at fagmed.uit.no writes:
> In article <2oejvv$scv at fermat.mayo.edu>, volcs at fermat.mayo.edu (Sam
> Volchenboum) wrote:
> 
> > I need to precipitate a protein sample coming off a FPLC column for
> > subsequent SDS-PAGE.  I was going to precipitate with 10% TCA and
then wash
> > with 10% TCA, but I read that the TCA can change the pH so as to
affect the
> > PAGE.  Then someone told me to wash with acetone.  Fine, but can't I
just
> > precipitate with one volume of acetone from the start?  Anyways, do
any of
> > you have ideas/protocols/refs which will precipitate small amounts of
> > protein and not affect the PAGE? (Or should I just use TCA and be
done with
> > it...)
> > 
> > Thanks,
> > Sam

I routinely wash the (often invisible) TCA pellets with ice-cold 70%
ethanol and spin down again (15 min) before adding sample buffer.  This
seems to get rid of most of the TCA -- no problems with gel mobility.

Good luck--
Doug Portman

doug at genetics.upenn.edu