Local conformational changes in DNA induced by UV and ionizing radiation

Changes in the DNA conformation after UV and gamma irradiation were studied by means of pulse polarography and circular dichroism (CD). It was found that moderate doses of radiation (of the order of 104 erg mm-2, 104 rad) do not lead to DNA denaturation, but to local conformational changes in the double helix. The latter are manifested by a rise of the pulse-polarographic peak II characteristic of the double-helical DNA, and by a rise of the positive CD band around 275 nm. Only high radiation doses (> 105 erg mm-2, > 105 rad) result in a drop of the positive CD band and in a shift of the pulse-polarographic peak toward the more negative potential values (close to potential of peak III of denatured DNA). (author)