EtBr/CsCl:strange color change - help???

Michael blaesse at biochem.mpg.de
Mon Oct 5 11:59:44 EST 1998


On Wed, 30 Sep 1998, Patrick wrote:

> Hi all.
> 
> A request from first-time user of CsCl/EtBr for plant DNA purification:
> Upon addition of ethidium bromide to my phenol/chloroform purified
> Plant-DNA solution in CsCl, I observe a change of color from normal
> orange-red to light cherry red.

If I remember correctly this was also the case, when I have purified DNA 
with CsCl density gradient centrifugation.

> Check http://www.biologie.uni-ulm.de/bio2/knoop/images/ethidium.jpg
> for visual impression...

Unfortunatly my display doesn't show the correct colours.

> After centrifugation color accumulated COMPLETELY with a sluggish
> material on top of the gradient. Considering the possibility that some
> remaining protein/polysaccharides may be responsible for this, I have
> taken the remainder of clear solution and repeated the EtBr addition. No
> improvement - same color change (even after repeating this for the 4th
> time!)
> 
> Anybody ideas what is going on?
> 

I don't know, what is going on, but I have done a centrifugation step at 
about 10.000 rpm in a Beckman JA20-rotor bevore the gradient 
centrifugation and got a pellet like you describe it. 

Hope this helps
Michael 

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Michael Blaesse
Forstenrieder Allee 6a
81476 Muenchen
Tel.: 089/75079206
E-Mail: blaesse at biochem.mpg.de

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