Damage to Model DNA Fragments by 0.25−1.0 eV Electrons Attached to a Thymine π* Orbital

Abstract

In earlier studies on damage to model DNA systems caused by low-energy electrons, we considered electrons that attach either to cytosine's lowest π*-orbital or to a P=O π*-orbital of a phosphate unit. We examined a range of electron kinetic energies (E) (e.g., representative of the Heisenberg width of the lowest π*-resonance state of cytosine), and we determined how the rates of cleavage of the sugar-phosphate C-O σ-bond depend on E and on the solvation environment. In the P=O attachment study, we showed that electrons of ca. 1.0 eV could attach to form a π*-anion, which then could break either a 3' or 5'O-C σ-bond connecting the phosphate to either of two attached sugar groups. In the present study, we extend the base-attachment aspect of our work and consider electrons having kinetic energies below 1 eV attaching to thymine's lowest π*-orbital, again examining the energy and solvation dependence of the resulting rates of C-O σ-bond cleavage.