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Floating white pellet in miniprep - (Jan/30/2010 )

Hi all,
Everytime I do the miniprep (Qiagen), after adding buffer N3 and centrifuge at max. speed for 10 minutes, there are always some small white pellets floating around in the supernatant. I have tried to spin it at 15,000 rpm for 20 miniutes or ttransferred the supernatant to a new tube and spin it again, but the result is still the same. What is the reason for that? Is it because I am adding too much culture medium (3ml LB)?
Thank you.


i used to use this kit, but to be honest i forgot this buffer's role ...
but u can refer to the kit insert it is an excellent source of info. ... specially from Qiagen :P
read the troubleshooting section ...

some points from my memory... :
either u need to put ur sample on ice for 10 min and recentrifuge back or
these are lipid contaminants that u should avoid taking in the next step

to give you an answer,
kindly specify the next step and this N3 buffer's role ...

to have the right answer go and read the troubleshooting section,
as i stated before u'll be amazed how useful it is :)

good luck..


I see that stuff occasionally (I agree that it's a lipid or polysaccharide), but it usually doesn't interfere with anything -- if it's bothering you, you can twirl a pipette tip or a toothpick in your cleared lysate to remove it, or use a Qiafilter or whatman paper to remove it.