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

[Dr Engelbert Buxbaum]

Am 14.02.2008, 20:21 Uhr, schrieb Nico <brighttomorrow 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.