Interactions of Slow Electrons with Biomolecules

We report on results of computational studies of the interaction of slow electrons with the purine and pyrimidine bases of DNA, as well as with their associated nucleosides and nucleotides. The calculations focus on characterisation of the π∗ resonances associated with the bases and also provide general information on the scattering of slow electrons by these targets. High-level studies of the π∗ resonances in pyrazine, a close analogue of the pyrimidine bases, indicate that the higher-energy π∗ resonances in these bases may in fact contain large admixtures of core-excited character built on low-lying triplet states. Decay into such triplet states may provide a mechanism for damage to DNA.