DNA "refusing" to be run in agarose gel

Anyname r.lombardi at utoronto.ca
Fri Aug 25 10:23:33 EST 1995

> I have a peculiar problem with persuading some of my DNA samples 
to run in 
> agarose gels.
> When loading DNA samples on agarose gels I have on several 
occasions observed 
> a strange (to me) phenomenon: after application of a sample into 
a well a 
> streak of the sample may follow the pipette tip upon withdrawal. 
When the 
> sample in this way comes in contact with the buffer surface, the 
sample very 
> rapidly spreads out to cover the entire surface. During this 
process most of 
> the sample in the well is "sucked" out.
> There is no recognizable pattern as to what sample this may 
happen with. It 
> is, however, frustrating when precious samples are lost (the 
last one was a 
> 1.9 kb DNA probe)  :í-(
> Could anyone enlighten me as to what I am observing, and how to 
> this from happening again?
> Thank you very much,
> Ketil Thorstensen, Ph.D.
> Dept. Clinical Chemistry
> University Hospital
> Trondheim, Norway
This, or something like this, sometimes happens if the sample 
being loaded has just been ethanol precipitated and the ethanol 
was not completely evaporated.  That little bit of ethanol is 
enough to make your resuspended DNA sample float.

Rocco Lombardi
Dept. of Microbiology
U. of Toronto
r.lombardi at utoronto.ca 

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