DNA "refusing" to be run in agarose gel

[RPA Groot]

In article <ECS9508251125D at utoronto.ca>, r.lombardi at utoronto.ca (Anyname) says:
>
>
>
>> 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 
>prevent 
>> 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 
>
>
>

It also happens with, mineral oil overlayed, PCR products.


Richard Groot