260/280 OD

Barry Moore barrym at stella.med.utah.edu
Thu May 18 18:05:36 EST 1995

I have been using a Beckman DU-64 spectrophotometer to quantify
concentrations of DNA suspended in H2O or TE.  I expect and sometimes
get a 260/280 ratio of 1.8 for pure DNA, and when the ration is 
around 2.0 I suspect the presence of RNA.  However, I have not been
able to find an explination for the occasional 260/280 readings of
2.5-3.0.  What type of contamination or situation would elevate the
260/280 ratio above 2.0?

Thanks for any comments that you might have.

Barry Moore

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