Basic question about PMSF

[Dennis]

On 2006-12-13 12:03:47 -0500, "Breslauer" <breslauer1981 At gmail.com> said:

> Listen,
> is it normal that when adding PMSF (250mM solution in MeOH) to cell
> free extract from E.coli (broked by sonication and spinned 12000g for
> 30min) to the final concentration of 0,5mM buffer becomes cloudly and
> st become to precipitate (probably protein?).
> 
> Thans for any clue
> 
> Julio

You are alkylating at least some protein and increasing its 
hydrophobicity, so a precipitate is not surprising.

Why on earth are you adding PMSF to a protein extract?  The common use 
of PMSF is to add it to a water solution to alkylate and inactivate 
RNAses.

Dennis (I was listening)