Dissociative electron attachment to hydrated single DNA strands.

Area of Science:

• Physical Chemistry
• Biophysics
• Materials Science

Background:

• Understanding electron interactions with biological molecules like DNA is crucial for radiation biology and astrobiology.
• The role of water, a ubiquitous solvent, in modifying electron-induced processes in DNA is not fully understood.
• Previous studies have focused on condensed phases or isolated DNA, leaving gaps in knowledge regarding thin films with controlled hydration.

Purpose of the Study:

• To investigate the desorption of negative ions (H-, O-, OH-) from short single DNA strands hydrated with water upon electron impact.
• To identify the mechanisms responsible for anion formation and desorption.
• To quantify the effect of water on the overall anion yield from DNA.

Main Methods:

• Experiments involving electron interactions with a DNA film covered by 3 monolayers of water (5.25 water molecules per nucleotide).
• Electron beam energy varied from 3-20 eV to induce desorption of H-, O-, and OH- anions.
• Analysis of anion yields and their dependence on electron energy and the presence of water.

Main Results:

• Desorption of H-, O-, and OH- anions was observed from the hydrated DNA film.
• Below 15 eV, anions primarily originated from dissociative core-excited transient anions formed by electron capture in a DNA-H2O complex.
• A minor contribution to H- desorption came from weakly bonded water molecules.
• The presence of water increased the overall anion yield from DNA by a factor of 1.6.

Conclusions:

• Water significantly influences electron-induced anion desorption from DNA.
• A novel mechanism involving DNA-water complex transient anions contributes to anion formation.
• Hydration enhances the susceptibility of DNA to electron-induced dissociation, with implications for understanding radiation damage and extraterrestrial organic chemistry.