Anion Exchange Question

Michael Witty mw132 at
Wed May 9 05:20:35 EST 2001

Dear Patrick,
            it depends on how strongly your protein binds.  In fact for a
protein I used to work with I would purposefully load a sample in
phosphate (I forget how much, maybe 100mM) so that the binding in my
desired protein was improved.  This was after a lot of preliminary work
of course.  What is the pI of your protein?  Have you tried small
scale experiments?  Mike.

On 9 May 2001, Patrick Lynch wrote:

> Hi all,
> I'm going to carry out anion exchange chromatography on eluted fractions
> from a Histidine binding column.  Normally, I just dilute with Tris buffer
> (to reduce the 0.5M NaCl from the His binding column) and apply to the
> Mono-Q column.  Question!  There's 20 mM phosphate in the eluted fraction as
> well - how much should this be diluted for application to the Mono-Q as you
> are not supposed to use negatively charged buffer ions with anion exchange?
> Thanks,
> Patrick
> PS  I've tried using a buffer exchange column but the protein of interest
> didn't like it and anyway, it's another step!
> ---

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