Abdoul-Carime, H., Cecchini, S. and Sanche, L. Alteration of Protein Structure Induced by Low-Energy (<18 eV) Electrons. I. The Peptide and Disulfide Bridges. Radiat. Res. 158, 23–31 (2002).
We present measurements of low-energy (<18 eV) electron-stimulated desorption of anions from acetamide (CH3CONH2) and dimethyl disulfide [DMDS: (CH3S)2] films. Electron irradiation of physisorbed CH3CONH2 produces H−, CH3− and O− anions, whereas the H−, CH2−, CH3−, S−, SH− and SCH3− anions are observed to desorb from the DMDS film. Below 12 eV, the dependence of the anion yields on the incident electron energy exhibits structures that indicate that a resonant process (i.e. dissociative electron attachment) is responsible for molecular fragmentation. Within the range of 1–18 eV, it is found that (1.7 and 1.4) × 107 H− ions/incident electron and (7.8 × 10−11 and 4.3 × 10−8) of the other ions/incident electron are desorbed from acetamide and DMDS films, respectively. These results suggest that, within proteins, the disulfide bond is more sensitive to low-energy electron attack than the peptide bond. In biological cells, some proteins interact closely with nucleic acid. Therefore, the observed fragments, when produced from secondary low-energy electrons generated by high-energy radiation, not only may denature proteins, but may also induce reactions with the nearby nucleic acid and damage DNA.
