pI=9.5 protein will not bind to cation exchanger at pH 6.5

Joe Mack mack at ncifcrf.gov
Wed May 4 08:21:11 EST 1994

In article <2q6job$21t at news.iastate.edu> bipin at iastate.edu (Bipin K Dalmia) writes:
>i'm trying to purify a protein expressed in e. coli. there is tons of it
>in the soluble extract. the pI is about 9.5. so naturally i tried using
>a cation exchanger at pH 6.5 but my protein flows right thru it. i've
>checked the ionic strengths etc. and they look good. the resin was
>properly equilibrated too. i'm using bio-rad's biorex-70 resin in the
>sodium form and eluting with a gradient of NaCl. 

I wouldn't worry about it just yet, proteins don't have to bind just because
they have the opposite charge to the column, the charged might be in a hollow
or spread evenly over the surface. Go finf something that it will bind to.
Joe Mack
mack at ncifcrf.gov
>any clues?
>bipin k. dalmia               the other night i was lying on my bed, looking
>bipin at iastate.edu             up at the beautiful stars, and i said to myself, 
>n2.bkd at isumvs.iastate.edu     'where the F*CK is my ROOF !!'

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