title: Changes in DNA secondary structure after gamma-irradiation.
abstract: Native calf thymus DNA was gamma-irradiated at 500 mug/ml in 0.01 M NaCl in the presence or absence of oxygen. By irradiation, an increasing amount of DNA becomes reactive with a water-soluble carbodiimide-derivative (CMEC). In the DNA sections reactive with CMEC the nucleotide strands are separated, a phenomenon previously described as radiation-induced denaturation. The dose-effect curve for the formation of denatured DNA shows an upward-bent form; a distinct oxygen effect of about 2 is observed. By a comparative study with DNA samples, degraded partially with DNAse I, it was shown that a minor part of the radiation-induced denaturation results from the formation of the radiation-induced single strand breaks, whereas the major part is a local denaturation independent of the strand breaks. In these locally denatured regions 20 to 50 nucleotide pairs are separated.
mesh_terms: D000818:Animals; D003028:CME-Carbodiimide; D002417:Cattle; D004247:DNA / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D008970:Molecular Weight; D009691:Nucleic Acid Denaturation / Q000528:radiation effects; D011830:Radiation Effects; D013950:Thymus Gland
chemical_list: D003028:CME-Carbodiimide; D004247:DNA