precipitating proteins w/ ethanol

Ishwar S. Singh isingh at umaryland.edu
Fri Mar 5 10:33:10 EST 1999

If running a SDS page is the only motive you can try ppting using TCA.
Bring the final volume of sample to 5% TCA (10% if very dilute-- use 10% to
be on the safe side).  Keep on ice for 5-10 min and spin in
cold--microfuge, table top, anything depending upon your volume).
Wash ppt with ethanol (1/4 to 1/2 your total volume of sample)--this
removes any residual TCA
Dissolve ppt in loading buffer.
Sometimes you still have some TCA left which decolorises the bromophenol
Just add a microliter of .01N NaOH or 100mM Tris.... anything to raise the
It worked for me........You may give it a shot too
It also helped me to desalt samples before running.

Katherine Walstrom wrote:

> I have some dilute protein samples that I need to concentrate and run on
> an SDS-PAGE gel.  I can't find a detailed protocol for precipitating
> proteins, although what I've read suggests that ethanol works well.  I
> want to precipitate all the proteins, not just selectively precipitate
> some of them.  Does anyone have a general protocol for this?
> Thanks much.
> Katherine M. Walstrom, PhD
> Division of Natural Sciences
> New College of USF
> 5700 N. Tamiami Trail
> Sarasota, FL  34243
> kwalstro at sar.usf.edu

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