DNA Responds to Ionizing Radiation as an Insulator, Not as a “Molecular Wire”

The yields of radicals trapped on DNA, measured by EPR spectroscopy of oligodeoxyribonucleotide crystals (the EPR spectrum of a single crystal of d(CCCTAGGG) is shown), are found to be very high (0.7 µmol J(-1)) and insensitive to long-range (>10(6) base pairs) versus short-range stacking (8 base pairs) of the bases. These observations are evidence that DNA at 4 K has the properties of an insulator and argue against DNA acting as a "molecular wire".