COMPUTER-SIMULATION OF DNA-INCORPORATED I-125 AUGER CASCADES AND OF THE ASSOCIATED RADIATION-CHEMISTRY IN AQUEOUS-SOLUTION

Using a set of Monte Carlo simulation models, track structures of I-12 5 Auger electrons generated in liquid water are superimposed on a stra ight DNA plasmid model able to localise precisely energy deposition ev ents on submolecular units of DNA strands. After scoring direct hits t aking place during the physical phase (at about 10(-15) s) the radiati on chemistry of the whole system is simulated between 10(-12) and 10(- 8) s, taking into account all known reactions between water radio-chem ical species, radicals, submolecular units of DNA (ribose, adenine, th ymine, guanine and cytosine), and scavengers like Tris or formate ions . The model's ability to distinguish between direct and indirect hits has been used to introduce different assumptions for strand break indu ction by both hit modes. The influences of different scavenger concent rations on the ssb and dsb yields per decay are presented as well as t he distributions of breaks on both DNA strands as a function of time. The results are compared with experimental and theoretical data from t he literature.