agarose gel electrophoresis

[David Winterbourne]

In article <333208DD.517B at agrar.uni-giessen.de>, Rod Snowdon says...
>
>> I have observed the following phenomenon several times: when I cut
>> out a piece of agarose gel containing a single DNA band and place this
>> piece of gel on it's side, then I see two bands.
>
>Normal.  Assuming you've stained by immersing the gel in EtBr after
>electrophoresis, it's probably just that the staining solution hasn't
>diffused completely into the gel.

Yes. To overcome this problem you need to stain longer to allow saturation of 
ethidium bromide binding to the DNA. If insufficient time is given, you may 
expect to have a non-linear relation between fluorescence and DNA 
concentration.

-- 
Dr. David Winterbourne
Department of Surgery
St George's Hospital Medical School, London SW17 0RE, England
Tel: 0181-725-5581   Fax: 0181-725-3594