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

Abstract

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.

Fig. 1

Total fragmentation yields induced by 1 eV electrons as a function of amino acid : GCAT ratios for arginine (■) and glycine (○). The data points represent the average of at least 10 independent experiments. The error bars represent the standard derivation of 1 eV electron exposures for a given molar ratio.

Fig. 2

Total fragmentation yields induced by 1 eV electrons as a function of film thickness for arginine–GCAT (■) and glycine–GCAT (○) films. The data points represent the average of at least 10 independent experiments. The error bars represent the standard derivation of 1 eV electron exposures for a given molar ratio.

Fig. 3

The lowest energy configurations for all nucleotides and glycine (Gly) pairs obtained by using Dreiding forcefield.

Fig. 4

The lowest energy configurations for all nucleotides and arginine (Arg) pairs obtained by using Dreiding.