Best way to adjust pH of a protein?

Andrew, Tel. +39-6-91093434 WALLACE at IRBM.IT
Tue Jul 19 04:12:11 EST 1994


Jim Owens <jow at helix.nih.gov> wrote:

>I found this posted on bionet.molbio.methds-reagnts and thought it more
>properly belongs on bionet.molbio.proteins:

>In article <305vv0$754 at news.iastate.edu> Bipin K Dalmia,
>bipin at iastate.edu writes:
>>what is the best way (quickest) to adjust the pH of a protein solution?
>>dialysis takes too long and desalting/buffer exchange columns are out
>>'cause i have 100 mL of solution and it would take a 10-story high
>>column. directly adding acid/base would cause extreme local pH values
>>and denature the protein. 
>>
>>i have to do this prior to running an ion-exchange column so i can't
>>increase the ionic-strength too much either.

>I wonder about the answer I posted:

[good ideas deleted]

I agree with Jim's suggestions and would add the following possibility:
If Bipin K Dalmia has access to a hollow-fibre concentrator this might be
a gentler way of concentrating the sample prior to diluting with the ion-
exchange loading buffer. Such devices can easily handle 100 ml of sample.
Only thing is that the original poster didn't say what the concentration
of the protein in the 100 ml of solution was, so any treatment to concentrate
the sample may cause precipitation of the protein if you already start from
a high value. This may or may not be a problem, no way to tell without more
information.

Andrew <wallace at irbm.it>



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