another GST story #2

Stephen R. Lasky Stephen_Lasky at brown.edu
Fri Jul 15 10:13:24 EST 1994


In article <303hue$g7s at mserv1.dl.ac.uk>, "Matthias Zeiner"
<mzei at sun0.urz.uni-heidelberg.de> wrote:

> 
> It's not that easy. The charge of a protein is not necessarily proportional 
> to it's molecular weight on a SDS gel. Modifications like phosphorylations 
> or carboxy-methylations in fact do influence the run on a SDS gel. Also the 
> gel system you use may play a role. I made the observation that the 
> relative positions of the same two proteins to each other are different on 
> 30:1 and 60:1 PAA gels. Why? No idea!
> 
> Matthias Zeiner
> Inst. Biol. Chem.
> Heidelberg

I aggree about the charge changes due to phosphorylation and some other
post-translational modifications: you will note that the point that I was
responding to was that proteins should not be folded on an SDS gel . 
(Emma stated:

 >The problem could be due to the
> protein not folding properly I suppose and consequently not running as a
> nice globular protein should on SDS-PAGE. )

In general though,  we use denaturation in the presence of SDS so that a
protein will migrate at a rate relative to its mass and not be effected by
amino acid composition.

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Stephen R. Lasky, Ph.D.       Brown University/Roger Williams Medical Center
e-mail: Stephen_Lasky at brown.edu         LandLine: 401-456-6572
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America may be unique in being a country which has leapt from barbarism to decadence without touching civilization:  John O'Hara
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