Even though the protein should be denatured by all that urea, we find such gels sometimes look nicer if stop the reaction with SDS and protease K, and/or phenol extract the remains of the protein before loading the high-urea gel.

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Phoebe A. Rice
Dept. of Biochemistry & Molecular Biology
The University of Chicago
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________________________________________
From: CCP4 bulletin board [[log in to unmask]] on behalf of Opher Gileadi [[log in to unmask]]
Sent: Saturday, September 30, 2017 3:44 PM
To: [log in to unmask]
Subject: Re: [ccp4bb] Off topic: denaturing urea gels

In addition to the previous suggestions:

With very small gels, the sample composition and depth (in the well) have a strong effect on the resolution.
Rinse the wells with TBE buffer just before loading, as urea from the gel diffuses into the well and may prevent the sample from settling at the bottom. Minimize the amount of salt in the samples; try to load very small volumes (1-3 ul), even if this means longer exposures later.