Western Blotting of Nuclear Extracts - Does high salt inhibit western blotting? (Jul/13/2010 )

Hi everyone,

I am having a problem with my nuclear extraction. I am looking for phosphorylated proteins in nuclear extracts from T84 cells. I use a high salt extraction procedure. Do I need to precipitate my proteins before running a western because of the high salt concentration? I tried TCA precipitation, but I did not get a good yield. Does anyone have a good recommendation? I resuspend my nuclear pellet in buffer B and then add an equal amount of buffer C.

Buffer B:
20 mM Hepes
1.5 mM MgCl2
420 mM NaCl
.2 mM EDTA
25% glycerol
.5 mM DTT
and protease and phosphatase inhibitors.

Buffer C:
20 mM Hepes
50 mM KCl
.2 mM EDTA
.5 mM DTT
and protease and phosphatase inhibitors.

Thanks for any help!

You will probably get in trouble if using the non-desalted extract directly to a gel; a very good alternative to TCA is the precipitation method by of Wessel & Flügge (Anal Biochem, vol 138:141-143 (1984))

add to 100 µl aqueous extract

+400 µl methanol
+100 µl chloroform
+300 µl water

overhead shaking for 10 s

centrifuge 14,0000 g , 2 min

aspire the overlay aqueous phase, be careful, the precipitated proteins are the interphase

add 300 µl methanol

overhead shaking for 10 s

14,0000 g , 2 min

proteins are precipitaed

aspire the aqueous/methanol phase

dry to light humidity but not to fully dryness

hjc05 on Jul 13 2010, 06:49 PM said:

I had not tried loading my samples directly because they were too dilute. Now that I know what yield I'm getting, I'll use a smaller volume and try loading directly. Thanks for the help.