Is 260:280 ratio good for oligos?

Michael T. MacDonell sendero at
Mon Sep 14 17:42:59 EST 1998

Dear Richard:

The oligo may be defective, but 280/260 will not indicate whether it
is or not.  That ratio derived from an attempt to determine whether
the protein was sufficiently removed from a DNA prep.  It isn't
actually very good for that either, but has no relevance at all to
oligos.  Just contact the supplier and tell them you want them remade.
If they hesitate, get a new supplier.

Best Regards,

On Mon, 14 Sep 1998 10:48:01 -0400, Rich Dudley <rdudley+ at>

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>I purchased some oligos, and haven't had any success at PCR.  Controls
>pointed to the oligos as the problem.  I extracted the oligos twice with
>n-butanol, and EtOH precipitated, and resuspended.  I quantitated at
>260, but out of habit, I also took the 260:280 ratio.  Were these
>midipreps, I would throw out the DNA and start over--ratios ranged from
>1.1 to 1.4.  Does the 260:280 definition of "clean" hold for oligos, or
>are these oligos probably ok to use?
>--- --- --- -- -- -- --- --- ---
>Richard J. Dudley (rdudley+ at
>Research Specialist V
>Dept. of Cell Biology and Physiology
>University of Pittsburgh
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