I have performed many chromatin extractions, but at the end of every experiment I have a large peak at 220-240nm when measuring DNA concentration with a nanodrop. I have had some very limited success by including diethyldithiocarbamic acid (DIECA) and pvp-40 in all of my solutions, but the peak remains. I assume that it is DNA oxidation and not polysacharides because multiple ethanol washes through a cellulose column does not eliminate this peak from the spectra. Anyone have any suggestions