title: Lethal effect of carbon K-shell photoionizations in Chinese hamster V79 cell nuclei: experimental method and theoretical analysis.
abstract: To test a possible specific effect of carbon K-shell ionizations in DNA, survival curves for Chinese hamster V79 cells were measured for X irradiations at energies below and above the carbon K-shell ionization threshold. Specific values of the X-ray energies (250 and 340 eV) were chosen to ensure isoattenuation of the two kinds of radiation within the cell. An enhancement of lethality by a factor of about 2 was found for X rays at 340 eV compared to below the threshold at 250 eV. This may be attributed to the production of highly efficient carbon K-shell ionizations located on DNA. A model of X-ray lethality (Goodhead et al., Radiat. Prot. Dosim. 52, 217-223, 1994) was extended to allow for a possible lethal effect from clusters of reactive species induced by K-shell photoionizations (K-shell clusters). Within this model, the increase in lethality above the carbon K-shell threshold may be explained by a value of 2% for the lethal efficiency of K-shell clusters overlapping the DNA. An extrapolation to the lethal effect of more complex ion-induced K-shell ionizations indicates that K-shell ionization may be a major process in the biological effectiveness of heavy ions.
authors.affiliation: Groupe de Physique des Solides, Universités Paris 7 et Paris 6 (CNRS UMR 75-88, CEA LRC No.6), France.
authors.forename: M A
authors.initials: MA
authors.lastname: Herve du Penhoat
authors.forename: B
authors.initials: B
authors.lastname: Fayard
authors.forename: F
authors.initials: F
authors.lastname: Abel
authors.forename: A
authors.initials: A
authors.lastname: Touati
authors.forename: F
authors.initials: F
authors.lastname: Gobert
authors.forename: I
authors.initials: I
authors.lastname: Despiney-Bailly
authors.forename: M
authors.initials: M
authors.lastname: Ricoul
authors.forename: L
authors.initials: L
authors.lastname: Sabatier
authors.forename: D L
authors.initials: DL
authors.lastname: Stevens
authors.forename: M A
authors.initials: MA
authors.lastname: Hill
authors.forename: D T
authors.initials: DT
authors.lastname: Goodhead
authors.forename: A
authors.initials: A
authors.lastname: Chetioui
mesh_terms: D000818:Animals; D002244:Carbon; D002460:Cell Line; D002467:Cell Nucleus / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000528:radiation effects*; D020450:Heavy Ions; D012062:Relative Biological Effectiveness; D014965:X-Rays
chemical_list: D002244:Carbon; D004247:DNA