Ab purification problem

D.K. dk at no.email.thankstospam.net
Fri Oct 18 07:21:06 EST 2002

Dr Engelbert Buxbaum <engelbert_buxbaum at web.de> wrote:
>"D.K." wrote:
>> - Purify IgG on Protein A, elute with 100 mM Glycin, pH 2.5,
>> immediately neutralize to pH 8.0 with 2 M Tris, pH 9.0,
>> add NaCl to 0.35 M final.
>> - Run over an antigen column, load 2 times to ensure saturation
>> of binding sites, with 3.6 M MgCl2, pH 6.5. Dialyse extensively,
>> make sure to leave room for water in dialysis bag. MgCl2
>> elution is a lot milder on most native proteins than standard
>> acid elution.
>Elution with caotropes from an affinity column selects for mediocre
>antibodies, as the realy high affrinity ones stick or elute at
>concentrations of denaturants, which are destructive.

Not in my experience. Various polyclonals that I purified 
using the above method were extremely inhibitory in functional
assays (yes, controls with IgG from depleted serum were always
done). I routinely analyse what elutes from the column(s)
during regeneration pH 1.8 and there was never any more than 
5% of what I eluted (I do let the column sit for 15 min in MgCl2
between elutions with 1 column volumes). 


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