title: Absolute measurements of radiation damage in nanometer-thick films.
abstract: The problem of absolute measurements of radiation damage in films of nanometer thicknesses is addressed. Thin films of DNA (∼2-160 nm) are deposited onto glass substrates and irradiated with varying doses of 1.5-keV X-rays under dry N(2) at atmospheric pressure and room temperature. For each different thickness, the damage is assessed by measuring the loss of the supercoiled configuration as a function of incident photon fluence. From the exposure curves, the G-values are deduced, assuming that X-ray photons interacting with DNA deposit all of their energy in the film. The results show that the G-value (i.e. damage per unit of deposited energy) increases with film thickness and reaches a plateau at 30±5 nm. This thickness dependence provides a correction factor to estimate the actual G-value for films with thicknesses <30 nm thickness. Thus, the absolute values of the damage can be compared with that of films of any thickness under different experimental conditions.
authors.affiliation: Groupe en Science des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et des Sciences de la santé, Université de Sherbrooke, Sherbrooke, Canada J1H 5N4. elahe.alizadeh@usherbrooke.ca
authors.forename: Elahe
authors.initials: E
authors.lastname: Alizadeh
authors.forename: Léon
authors.initials: L
authors.lastname: Sanche
mesh_terms: D004247:DNA / Q000032:analysis / Q000528:radiation effects*; D004249:DNA Damage / Q000528:radiation effects*; D004583:Electrons; D036103:Nanotechnology; D017785:Photons / Q000009:adverse effects*; D014965:X-Rays
chemical_list: D004247:DNA