Basic question about PMSF

Dennis via (by Dennis)
Thu Dec 14 17:47:46 EST 2006

On 2006-12-14 17:42:43 -0500, Dennis said:

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

OOps, I was thinking of TPCK.  Yes, PMSF would be useful to inhibit 
proteases, but it is a rather nondiscriminate alkylator and could cause 

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