Concentrating proteins already in SDS sample buffer?

Dr E. Buxbaum EB15 at
Mon Sep 2 07:59:58 EST 1996

You may try ultrafiltration. Small volumes are handled in centrifugation 
devices (Millipore, Centricon, Whatman too, I think), but larger volumes 
(several ml) are better handled in stirred cells (Amicon). I would not 
use any precipitation techniques, because it is usually difficult to get 
proteins into solution again afterwards. I had this problem with both TCA 
precipitation and Chloroform/Methanol, even Phenol/Ether resulted in most 
of the protein staying in the wells during electrophoresis (but then I am 
handling a 160 kDa membrane protein, yours may be less fastidious). 

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