Michael Witty mw132 at
Tue Nov 28 08:25:01 EST 2000

> Since PEG is not charged and would not co-polymerize with AA, 
> I can't see how trace amounts of PEG (the only kind possible as 
> far as water supply contamination is concerned) can 
> affect PAGE behavior appreciably. 
> I think you need to look elsewhere. What does "gels go bad"
> mean exactly? What do you observe?
>         - Dima

Dear Dima, the gels have protein bands which are really smeary upon
staining.  Having read the article recommended by Harold (thanks again
Harold), there are some clues that might interest you:

An effect of polyethylene glycol 8000 on protein mobility in sodium
dodecyl sulfate polyacrylamide gel electrophoresis and a method for
eliminating this effect.  Odom,O.W., Kudlicki,W., Kramer,G., Hardesty,B.
Analytical Biochemistry 245:249-252

p249 "The mobilities of the three largest proteins (in the standard
proteins used) increase with PEG, while those of the two smallest proteins
p249 "It is seen that those proteins behind the PEG move front move
faster than normal, while those ahead of the PEG move more slowly".

Which is similar to what I see, but I get much more smearing.

p250 "Kurfurst reported that the PEG migrates during PAGE only in the
presense of SDS this is undoubtedly due to the fact that PEG binds to
the SDS micelle".


(though PEG can also cause anomolies in DNA gels which contain no SDS!)

p250 the authors reduced the formation of PEG/SDS micelles and
the bad PEG effect by reducing the concentration of SDS from 0.1 to 0.05%
and tris from 125 t 93.8mM.

p250.-1.4 "It is still unclear exactly how the PEG-micelle complex affects
protein mobility...".

Any ideas out there?  Mike.

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