Hyperihernial (1-100 eV) nitrogen ion scattering damage to D-ribose and 2-deoxy-D-rsbose films

摘要

Highly charged heavy ion traversal of a biological medium can produce energetic secondary fragment ions. These fragment ions can in turn cause collisional and reactive scattering damage to DNA. Here we report hyperthermal (1-100 eV) scattering of one such fragment ion (N~+) from biologically relevant sugar molecules D-ribose and 2-deoxy-D-ribose condensed on polycrystalline Pt substrate. The results indicate that N~+ ion scattering at kinetic energies down to 10 eV induces effective decomposition of both sugar molecules and leads to the desorption of abundant cation and anion fragments. Use of isotope-labeled molecules (5-~(13)C D-ribose and 1-D D-ribose) partly reveals some site specificity of the fragment origin. Several scattering reactions are also observed. Both ionic and neutral nitrogen atoms abstract carbon from the molecules to form CN~- anion at energies down to ~5 eV. N~+ ions also abstract hydrogen from hydroxyl groups of the molecules to form NH~- and NH_2~+ anions. A fraction of O/O~- fragments abstract hydrogen to form OH~-. The formation of H3O~+ ions also involves hydrogen abstraction as well as intramolecular proton transfer. These findings suggest a variety of severe damaging pathways to DNA molecules which occur on the picosecond time scale following heavy ion irradiation of a cell, and prior to the late diffusion-limited homogeneous chemical processes.