Does anyone know what could be causing the SDS to precipitate out of my
SDS-PAGE sample buffer when I mix it with my sample?
I have a Triton x-114 membrane prep and i've used Amberlite
XAD-1180/Biorad Biobeads to remove most, but not all, of the detergent.
The solution I have left over is concentrated about 10 fold in a
centrifugal filter device. The sample is prepared in PBS+5mM MgCl2 at
pH 7.2, but after the prep the pH is about pH 10 (as is shown by
indicator strips). The solution is clear, with no precipitated
material. As soon as i put this in my 2xSDS-PAGE sample buffer
(standard stuff, 2% SDS, B-ME, bromo blue) it causes the SDS to come
out of solution. I tested that it was the SDS by adding some of my
sample directly to a 2% SDS solution and the same thing happens.
There's no guanidine, and no K+ salts in my sample, by the way!