Seq Gel Spots"

DAVID MITCHELL mitcheld at
Wed Sep 7 09:33:19 EST 1994

        Robert Minto writes

>I am in need of some help removing interfering black dots from my 
>polyacrylamide sequencing gels.  The gels are prepared by the U.S. 
>Biochemical Sequencing support guide protocol which contains 8M urea (and 
>appears to be identical to Maniatis, 6% acrylamide, 19:1 
>acrylamide:bisacrylamide).  The gels contain black dots which are 
>concentrated at the top of the sequencing gel and are ONLY in the lanes.  
>They actually interupt the lanes, suggesting particles in  the gel. (Stuff

Saw exactly the same problem a couple of years ago.  Turns out is was a problem
with the stop buffer from the sequencing kit I was using.  When I threw that
particular tube away and used one from a different kit the problem disappeared.  
This explained why it only appeared in the wells and why (as a later poster
points out) they are only in the top third of the gel.  

Cheers David

David Mitchell
Mitcheld at

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