Damage to amino acid-nucleotide pairs induced by 1 eV electrons.

We have investigated the role of two selected amino acids, glycine and arginine, on damage induced to a short chain of single stranded DNA, the tetramer GCAT, during 1 eV electron exposure. At this energy, DNA has a high cross section for DNA damage via exclusively dissociative electron attachment. Surprisingly, at low ratios of glycine:GCAT, an increase in the total fragmentation yield is observed, whilst at higher ratios, glycine and arginine appear to protect DNA from the direct action of electrons. In addition, binding energies were calculated by molecular modelling of the interactions between these amino acids and either nucleobases or nucleotides. These binding energies appear to be related to the ability of amino acids to protect DNA against low energy electron damage.