Scholz V, Weidner J, Köhnlein W, Frekers D, Wörtche H J
Institut für Strahlenbiologie, Westfälischen Wilhelms-Universität, Münster, Germany.
Z Naturforsch C J Biosci. 1997 May-Jun;52(5-6):364-72. doi: 10.1515/znc-1997-5-615.
The yield of single-strand breaks (ssb) and double-strand breaks (dsb) produced by alpha-particles at the end of their track in DNA-films was determined experimentally. Helium nuclei were accelerated to 600 keV in the 400 kV ion accelerator and scattered at a carbon target. The elastically scattered alpha-particles with energies of 344 keV and 485 keV were used to irradiate supercircular plasmid DNA in vacuo. For the dosimetry of the alpha-particles a surface barrier detector was used and the energy distribution of the alpha-particles determined. The energy loss of the particles in the DNA-layer was calculated. DNA samples were separated into the three conformational isomers using agarose gel electrophoresis. After fluorochromation the number of ssb and dsb per plasmid DNA molecule was established from the band intensities assuming the validity of Poisson statistics. Linear dose effect correlations were found for ssb and dsb per plasmid molecule. In the case of 344 keV-alpha-particles the yield of dsb was (8.6 +/- 0.9) x 10(-11) breaks/Gy x dalton. The ratio of ssb/dsb was 0.5 +/- 0.2. This is at least a factor of six larger than the ratio found in experiments with higher energy alpha-particles and from model calculations. Similar experiments with protons yielded a relative biological effectiveness (rbe) value of 2.8 for the induction of double-strand breaks by track end alpha-particles.
通过实验确定了α粒子在DNA薄膜中径迹末端产生的单链断裂（ssb）和双链断裂（dsb）的产额。在400 kV离子加速器中将氦核加速到600 keV，并使其在碳靶上散射。将能量为344 keV和485 keV的弹性散射α粒子用于在真空中辐照超螺旋质粒DNA。使用表面势垒探测器对α粒子进行剂量测定，并确定α粒子的能量分布。计算了粒子在DNA层中的能量损失。使用琼脂糖凝胶电泳将DNA样品分离为三种构象异构体。荧光染色后，假设泊松统计有效，根据条带强度确定每个质粒DNA分子的ssb和dsb数量。发现每个质粒分子的ssb和dsb存在线性剂量效应相关性。对于344 keV的α粒子，dsb的产额为（8.6±0.9）×10⁻¹¹ 断裂/戈瑞×道尔顿。ssb/dsb的比值为0.5±0.2。这至少比在高能α粒子实验和模型计算中发现的比值大六倍。用质子进行的类似实验得出，径迹末端α粒子诱导双链断裂的相对生物效应（rbe）值为2.8。
