In article <4ao1da$f9d at aggedor.rmit.EDU.AU>, Dr Patrick HJ Falckh <p.falckh at rmit.edu.au> says:
>>>In article <4ad9fc$km2 at dub-news-svc-2.compuserve.com>,
>100414.220 at compuserve.com (Stefan Kley) says:
>>>>I have a problem with ethidium bromide. I ran a PAGE today to check
>>the integrity of a few cDNA probes that I'm about to use in Northern
>>Hybridisations. In order to visualize the DNA with UV light, I put the
>>gel into an ethidium bromide bath for 45 minutes after the run.
>>However, under UV light, the gel appeared empty, lacking a signal even
>>from the slot where I loaded the DNA standard.
>I stain my DNA PAGE gels 15-30 min with enough EtBr to make the pink in
the staining solution barely noticible. No destaining is necessary. If grossly
overstained, the EtBr can quench the signal from bands, making modest
bands disappear; at least this is also a problem with agarose gels. Destaining
solves this problem. Usually, however, one can at least see the biggest
bands from the standard. Did you see your dye bands on the gel? Otherwise,
you may have reversed polarity (i.e. put the red electrode in the black
hole, etc), in which case, your valuable samples were electrophoresed
out of your wells into the running buffer. The archives of this
discussion group (and I think a TIBS article as well) discuss how old
running buffer can also disappear bands.