Abstract
Secondary electrons with kinetic energies below 20 eV are abundant species generated in living cells by the irradiation with ionizing radiations. It is unclear whether such low-energy electrons are able to induce damage on DNA. In this study, we have directly observed the structural changes of DNA molecules under the irradiation with 4-40 eV electrons which are field-emitted from the tip of a scanning tunneling microscope. Single- and double-strand breaks of linear DNA molecules (λDNA and ΦX DNA) are induced by the electron irradiations. By the electron irradiations of circular DNA molecules (pUC18 DNA) in an entanglement, some parts of the DNA were lost or spread by the dissociation of the molecules. These electron-induced reactions are strongly dependent on the electron energies.
