Est DNA conc from phenolicky tissue?

Florence CABON cabon at infobiogen.fr
Mon Oct 14 05:18:40 EST 1996


Mike wrote:
> 
> Does anyone know whether traces of phenolics in DNA can lead to an
> overestimate of DNA conc. using absorbance at 260nm?  Most of my
> extractions have a 260/280 of 1.8-2.0, but occasionally a 3-3.6 appears
> that leads me to suspect phenolics bound to the DNA may be producing
> screwy results.  I would expect my DNA to be too fragmented to allow for
> easy determination of concentration on an EtBr gel (the extent of
> shearing isn't really important for what I want the DNA for).
> Any advice or ideas would be greatly appreciated.

If you perform phenol chloroform extractions, traces of phenol increase
the 260 nm OD. If you want to measure that, measure your OD at 260nm
(nucleic acid), 270nm (pic of phenol) and 280nm (proteins).
You can get rid of phenol with a simple chloroform extraction.
-- 
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Florence Cabon. CNRS Villejuif, France. cabon at infobiogen.fr
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