| Popis: |
Energy transport by secondary electrons is a well known example of energy transfer on the naonometer scale, but intramolecular energy and charge transfer after collisional excitation and ionization of molecules have received much less attention. Recent findings have raised questions about the common assumption that radiation-induced DNA damage remains fixed on the nanometer scale during formation of biologically significant lesions. We have investigated mechanisms for the observation that DNA base radicals induced by neutrons are dependent on the orientation of DNA fibers relative to the neutron flux. We show radicals produced by direct irradiation of DNA with protons do not show dependence on DNA orientation. This may have been due to the high doses and dose rates of our experiments. Experiments with larger samples, higher proton energies, and improved detection sensitivity might reveal orientation effects not seen in our samples. 17 refs., 4 figs., 1 tab. |
