Comments on the Estimated Distance over Which Electrons Can Migrate in Solid DNA before Being Trapped by Misonidazole

During the preparation of our recent paper (1) there was a question as to whether it is possible to fit the experimental data to a model or models where the migration distance of radiation-induced electrons in DNA molecules incorporated with misonidazole could be estimated. In this letter we describe five different models (Table I) which yield the electron migration distance in solid DNA. These models are based upon the experimentally obtained luminescence quenching curve by the trap misonidazole where the observed migration distance for 50% quenching has been estimated to be about 25 base pairs (1). In these models we have assumed that misonidazole, as an electron-affinic agent, is acting as an electron "trap." It is assumed that the misonidazole molecules are distributed randomly within the DNA. Electrons emitted from a site of ionization may travel along the DNA molecule, in either direction, for a distance a which varies in a stochastic fashion between electrons. If an electron encounters a misonidazole molecule within a distance a, it will be irreversibly trapped, irrespective of the depth of that trap. Simple probabilistic arguments show, using this model, that the proportion of elect ons which are not trapped and therefore can result in light emission is P, where