I have prepared some bacteriophage DNA but I'm suspicious of my
quantitation of it. When run on agarose and compared to a dilution of
lambda commercial DNA standard I estimate the concentration to be much
lower (by at least an order of magnitidue) than when I take OD260
readings. The OD260/280 ratio is fine (1.966), and particularly strikingly
when I take OD260/280 readings of a dilution of the lambda standards the
spec readings correleate extremely well with the known concentration of
the lambda DNA.
I'm wondering whether there's any possibility that modifications of the
phage DNA may result in the EtBr not intercalating properly, or
fluorescing differently to 'standard' DNA.