plasmid DNA purification - which kit should I buy? (Aug/10/2007 )

Hi!
I'd like to ask you which kit you used for midiprep protocols?
...I' ve been using one from Qiagen, but lately I been having problems with the yield of purification.

any ideas....

biotech!

while not really on topic, how about trying simple alkaline lysis. No kits involved. The yields are better.

i use the one of qiagen. I think also the recovery rate is quite poor, but these are the only one that works in in vitro transcription...

i've noticed that doubling the amount of culture they propose is better and don't saturate the column
and you may perfomr greater cultures. Do alkaline lysis step till precipitation of DNA. then resuspend DNA in buffer P1 of quiagen and wait at this time (because there is the RNAse in this buffer. then add P2 wait only 2' and P3. then procceding of the column. This wway gave me also nice results (doubling the amount recovered) active in transcription too.

Check buffers again, unless omeone mixed things up. Happens many times with students around. Is this a new plasmid which you are growing? Different plasmids give differing yields. How long are you growing these plasmids.

We use Qiagen for miniprep cultures and Invitrogen's for maxi preps. We donot do midi preps. I actually tried out a midi prep from Macherey-Nagel and it was good too.

You can also try using the Qiagen kits , but using fresh lysis buffer. This increased the yeild of some of my plasmid preps.
Lysis Buffer:
.2 N NaOH
1% SDS

we routinely use Qiagen midiprep kits, yield is 150-200 ug/60 ml culture for puc18 or pGEM based vectors. Works well for tranfection or in vitro transcription. You can speed things up by missing out the post P3 centrifgue step and simply filter through a folded tissue instead, squeeze gently to get as much liquid out as possible.

I use QIAGEN kits too. I have the yield the manual says or more, but most of the time I use 50 % more wet biomass that the manual says, and I’ve notice that if I warm elution buffer at 50°C, I have a considerable better yield.