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

Rebecca Mills rebecca at
Wed Nov 5 13:43:46 EST 1997

>In article <01bce8a7$e01cfd70$373412ac at dough>, "Doug Hubatsch"
><Doug.Hubatsch at> 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

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