On Thu, 2010-08-26 at 11:35 -0400, Roger Rowlett wrote:
> We routinely polish protein preps on Q-sepharose (Mono-Q should be
> even better) with at least 10 CV gradients over a narrower range of
> NaCl concentrations, maybe 0-0.5 M or even smaller.
Just wanted to add that in my experience the resolution of ion exchange
columns depends hugely on flow rate (in addition to the steepness of the
gradient). Some columns (e.g. BioRad's UnoQ/UnoS) can be run at really
high flow rate (up to 4 ml/min) which is tempting given the small size
of these columns (with 6ml UnoQ you can be done with 10CV gradient in 15
minutes). It's more common to use 0.5-1 ml/min, but I've seen some
unbelievable resolution when slowing down about an order of magnitude.
You'd have to run overnight, but it's worth it.
Cheers,
Ed.
--
"I'd jump in myself, if I weren't so good at whistling."
Julian, King of Lemurs
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