Discrepancy between OD-value on spec and DNA on agarose gel
bbbbd at sprynet.com
Tue Aug 20 00:47:39 EST 1996
I have found the same problem. The spec sometimes overestimates the
DNA concentration; the agarose gel says it is lower.
Routinely, after I run the Qiagen maxi prep, I let the sample stand for 2-3
days in a microfuge tube at -20 C, then take the A260:A280 readings to
calculate the plasmid DNA conc.
I then run the sample on a gel and compare it with known concentrations
of some other DNA sample (like lambda cut with HindIII).
As far as the spec reading, we never measure a absorbance greater than 0.2.
Hope this helps,
Graduate Student - Cell & Molecular Biology
CSU Long Beach
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