Desalting of Plasmid DNA after Cesium Preps

Bernard Murray bpmurray*STUFFER* at
Tue Jul 14 20:37:43 EST 1998

In article <35AC094E.DB706FB5 at>, "J.C. Rodriguez"
<bc2roagj at> wrote:

> Try Qiagen Kit Qiaex II, Cat # 20021. Don´t loose time, it works
> excellent. 
> J.C.

But isn't this kit for extraction of DNA from gels rather than
plasmid purification?

Because of this I will take the lenient view that this is not
a Qiagen rep in disguise...

Anyway, you will note that even in Qiagen's adverts they use
CsCl banding as the "gold standard" by which to judge their
products (as do other manufacturers of plasmid purification
kits).  Yes, because of ridicule by fellow lab members I did
do a side-by-side (split culture) of Qiagen, Wizard and double
banded CsCl DNA for mammalian cell transfection.  The db CsCl
won hands down as far as the percentage of transfected cells
is concerned (and the yield of DNA).  However, the two kits
were perfectly adequate.  A co-worker also uses much cruder
DNA (boiling maxiprep then PEG precipitation) and still gets
very good transfection efficiency for his purposes.
If I need lots of plasmid then CsCl is "more scalable" than
the Qiagen etc. columns (with their rather optimistic binding
capacities) but yes the kits (or crude methods) are quicker
and you can more easily do lots of samples at once.

     Bottom line: You pays your money...

Bernard Murray, PhD
Dept. Cell. Mol. Pharmacol., UCSF, San Francisco, USA

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