Herve du Penhoat M A, Fayard B, Abel F, Touati A, Gobert F, Despiney-Bailly I, Ricoul M, Sabatier L, Stevens D L, Hill M A, Goodhead D T, Chetioui A
Groupe de Physique des Solides, Universités Paris 7 et Paris 6 (CNRS UMR 75-88, CEA LRC No.6), France.
Radiat Res. 1999 Jun;151(6):649-58.
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.
为了测试碳 K 壳层电离对 DNA 可能产生的特定效应，对中国仓鼠 V79 细胞在低于和高于碳 K 壳层电离阈值的能量下进行 X 射线照射，测量其存活曲线。选择特定的 X 射线能量值（250 和 340 eV）以确保两种辐射在细胞内的等衰减。结果发现，与 250 eV 的阈值以下相比，340 eV 的 X 射线导致的致死率提高了约 2 倍。这可能归因于 DNA 上产生的高效碳 K 壳层电离。扩展了一个 X 射线致死模型（古德黑德等人，《辐射防护剂量学》52，217 - 223，1994），以考虑 K 壳层光电离诱导的反应物种簇（K 壳层簇）可能产生的致死效应。在该模型中，碳 K 壳层阈值以上致死率的增加可以用与 DNA 重叠的 K 壳层簇的致死效率为 2%来解释。对更复杂的离子诱导 K 壳层电离的致死效应进行外推表明，K 壳层电离可能是重离子生物效应中的一个主要过程。
