DNA Damage

Dissociative Electron Attachment of water co-adsorbed with simple bio-molecules

There is strong interest in understanding the elastic and inelastic scattering of low-energy electrons with complex targets such as phosphate-linked sugars, nucleotides, nucleosides, DNA, RNA, and small proteins. Excitations in the inner and outer valence levels of atoms and molecules can decay via electron emission, and this process is very sensitive to the molecular environment.

We will directly examine the roles of dissociative electron attachment (DEA) and co-adsorbed water on the low-energy-electron-induced dissociation of condensed sodium phosphate, phosphoric acid, a series of simple phosphate-linked sugars, and small oligonucleotide sequences such as GCAT. We are interested in understanding solvation and local potential effects on electron scattering and will focus on examining the neutral desorption products as well as the state of the remaining molecular collision partners. Thus, we plan to examine the:

  • -- identities and energy distributions of the primary neutral desorption products
  • -- threshold energy necessary for formation and desorption of the primary products
  • -- kinetic energy distributions of each fragment
  • -- yield dependence on water coverage
  • -- importance of any isotope effect by comparing D2O and H2O
  • -- identity of the remaining adsorbed products

For example, we intend to examine the neutral atomic oxygen yield from phosphate-linked sugars and small oligomers containing phosphate groups as a function of incident electron energy using resonance-enhanced multiphoton ionization (REMPI). The general stability of the phosphate group will be moderated by the presence of counter-ions and the degree of hydration. This moderation will be examined by controlling the amount of co-adsorbed water and by carrying out experiments about 130 K, the temperature regime that allows free radical diffusion in ice.