Dear Theresa, You could try to add 50 mM of L-Arg and 50mM L-Glu to your buffers during purification. These amino acids are effective in preventing protein aggregation and precipitation and protect samples from proteolytic degradation.
Cheers, Arnaud On Aug 21, 2012, at 10:15 PM, Theresa Hsu wrote: > Dear all > > I made deletion mutation of a stretch of 20 amino acids on my protein. I can > purify and crystallize wild type protein but not the mutated. Mass spec on > gel separated protein shows degradation of mutant losing about another 150 > amino acids. Is there any way of purifying this non-stable protein? I know > nature has designed proteins to be stable. > > All steps are done at 4 C and protease inhibitor added during cell lysis for > both proteins. > > Thank you.
