E. coli and SDS-PAGE

Michael Kertesz mkertesz at micro.biol.ethz.ch
Fri May 20 04:07:38 EST 1994

In article <bushnt.1119742558A at usenet.rpi.edu>, bushnt at rpi.edu (Timothy Bushnell) says:
>    In an undergraduate lab, we are having the students prepare protein
>profiles of a stationary phase E. coli culture using SDS-PAGE. 
>    The problem is that the sample is very viscous and near impossible to>successfully load on a gel.  Typically, after the sample is loaded into the
>wells, and the pipet tip removed, the sample sticks to the tip and is
>removed as a gob into the upper tank buffer.. 

If you sonicate the extracts briefly, it should be possible to break the DNA
 in the extract into small enough bits that the viscosity problem is 
overcome. A few seconds with a standard sonication tip should do the
trick. Foaming shouldn't be too much of a problem with this volume. Addition of DNase
 is also a good (and quick) method, but has the drawback, in principle, that you
are adding an additional protein to a mixture where you wish to analyse the
protein composition, and thereby introducing an unnecessary artefact. In practice. however, the amount 
of DNase added can be so small that you can't see it, especially if you are using
 Coomassie Blue staining to visualize the proteins.

Michael Kertesz

ETH Microbiology
Zürich, Switzerland

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