[Protein-analysis] Re: Recombinant Protein precipitate out under 20 mM KPB/100 mM NaCl ???

incrediblyhigh from hotmail.com via proteins%40net.bio.net (by incrediblyhigh from hotmail.com)
Wed Feb 20 09:14:55 EST 2008

On Feb 18, 9:37 pm, "Dr Engelbert Buxbaum"
<engelbert_buxb... from hotmail.com> wrote:
> Am 14.02.2008, 20:21 Uhr, schrieb Nico <brighttomor... from gmail.com>:
> > Under 20mM KPB/500mM NaCl, it was good. But when change to 20 mM KPB/100  
> > mM NaCl,
> > the protein precipitate out. What should I do? Change to Tris-HCl Buffer  
> > or.....
> Looks like your protein is an albumin, with elongated shape and asymetric  
> charge distribution. At low ionic strength they form head-to-tail  
> aggregates, which precipitate. You can either keep the ionic strength high  
> or change the pH and hence the charges on the protein.

I agree with Dr Buxbaum. Try increasing the NaCl concentration (you
could try between 200-500mM if you really need to drop the
concentration), clearly the main reason for the precipitation.
Changing the buffer/pH will probably not help much...

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