Zonal gradients

Dr E. Buxbaum EB15 at le.ac.uk
Thu Mar 14 09:43:24 EST 1996

First of all: Never ever use the pump which Beckman supplies for its 
zonal rotors, as they are very difficult to maintain (and very expensive 
too). We have good results with a peristaltic pump and a homemade 
gradient former of the conventional 2 chamber design. Another option is 
to fill in a step gradient with 5% steps. Diffusion will level these 
steps out.

With the large zonal rotor you may encounter problems with condensation, 
if you load cold gradients into a cooled centrifuge. Simple solution: 
fill the maschine at room temperature the evening before you want to use 
it. Allow to cool down over night (while running, of course) and load 
your sample the next morning. Vacuum will be a lot better this way.

I always wonder why so few people use zonal rotors. If they are properly 
maintained, they run very reliable and reproducible. Good luck with your 

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