Basic question about PMSF

[Dr Engelbert Buxbaum]

Breslauer wrote:

> 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?).

No. At this concentration PMSF should not precipitate proteins, nor
should it precipitate itself (provided that excessively high local
concentrations are avoided during mixing).