DNA "refusing" to be run in agarose gel

Dan Deaguiar ddeaguia at oeb.harvard.edu
Fri Aug 25 07:49:19 EST 1995

Ketil Thorstensen (ketilt at dmf.unit.no) wrote:
: Honored contributors to the molbio.methds-reagnts!

: 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 may happen when loading PCR samples if some oil is carried over 
during the loading of the gel. The oil will float up and push the sample 
out. This doesn't seem to be your problem, though. The only thing I can 
suggest is to load as quickly as possible and immediately run the ge1. 

Dan D. 

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