Sonication with PMSF/EGTA produces a precipitate.....why?

[Rebecca Mills]

>In article <01bce8a7$e01cfd70$373412ac at dough>, "Doug Hubatsch"
><Doug.Hubatsch at arcm.ca.astra.com> wrote:
>
>> Anybody else come across this?  When I sonicate bacteria in .1 mM PMSF/10
>> mM EDTA, add 1% SDS and incubate for 30 min. at RT I get a DNA-like
>> precipitate.  I don't think its because of the SDS, boiling the mixture
>> doesn't put the precipitate back into solution.  The concentrations for
>> PMSF and EDTA are well below other reported concentrations so I don't
>> really have any idea what could be causing it.
>> 
>> Any ideas?
>
>Is there any reason to think that this precipitate is something
>other than DNA?  It's been a while since I lysed bacteria, but
>I remember the early steps of the process being quite gelatinous
>in consistancy, not clearing up until after DNase treatment.
>
PMSF precipitates in aqueous solutions. 
-- 
Rebecca Mills