Cesium Chloride precipitation

rafamaldo at my-deja.com rafamaldo at my-deja.com
Sun Sep 19 19:29:01 EST 1999


In article <37D96E54.940D6506 at ufl.edu>,
  edmason at UFL.EDU (Edward Mason) wrote:
> Got problem! We use cesium chloride for continues gradient in
> purification of plasmid DNA. Recently we had cesium chloride
> precipitated after ultracentrifugation. Solution we make: dissolve
> propanol precipitate in 59.2 mL of TE, add 60.0 g of CsCL plus 3.43 mL
> of EtBr (this is for two 1 by 3 1/2 in. tubes) We spin in the
> ultracentrafuge using 70Ti rotor 65K overnight. And here you are!
We've
> got a pellet of CsCl at the bottom of the tube.
> We've tried to change the temperature from 15 to 18 C, change rotors
> 60Ti or 80Ti and speed accordingly.
> Can anyone help? Any suggestions would be appreciated!!

Spining temperature must be 20 degrees, not 15 nor 18. Make sure that
the cooling system of the centrifuge really is setting that temperature.
Also, 55 K for 14 hours or 45 K for 20 hours could fix the problem.

-Rafa


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