my IB solubilizing buffer is 2M Urea, 10mM Tris, 1mM DTT and 1mM EDTA @pH 12.5 .
If i check the conductivity of that buffer that is 10mS/cm. After diluting the protein present in solubilization buffer with refolding buffer 5% sucrose, 5% glycerol, 10mM Tris, 1mM DTT, & 1mM EDTA @ pH 9.0 then conductivity is 1.4 mS/cm.
so is there any possibility of disturbance in protein binding to capto-q resin @ pH 9.0 at that 1.4 mS/cm conductivity?
Urea has a weak conductivity, which probably accounts, at least in part, for the higher conductivity of the solubilizing buffer. There can also be some contaminants in the urea solution.
A conductivity of 1.4 mS/cm is quite low and should not interfere with protein binding to an anion-exchange resin, as long as the protein has a net negative charge at that pH.
Normally, urea is not ionized and should contribute very little, if at all, to conductivity. However, it will isomerize to cyanate, which will contribute to conductivity, if heated. Since cyanate will modify proteins by creating adducts, stock solutions of urea (e.g. 8 M) should not be prepared by heating above 30-40 °C, and only for a short time. Removal of resudual cyanate can be achieved by storing urea stock solutions with ion exchage resin like Bio-Rad AG501-X8.
Thanq @Pierre Beguin & Adam B Shapiro. Yes i have heated the 2M Urea solution @ 100 °C.
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