【作者】 臧黎慧；

【导师】 童建； 魏志勇；

【作者基本信息】 苏州大学 ， 卫生毒理学， 2005， 硕士

【摘要】 目的 本研究旨在通过对⁶⁰Coγ射线诱导的DNA双链断裂（DSB）进行定量测量和观察其碎片的分布,探讨DNA双链断裂后碎片分布的统计碎裂模型的适用条件并将拟合的结果与实验结果进行比较,研究DNA双链断裂过程的机制。 方法 主要包括两个方面:一是以人正常成纤维细胞（GM0639）为研究对象,通过脉冲场凝胶电泳分离DSB碎片,扣除本底碎片分布的贡献,对⁶⁰Coγ射线不同辐射剂量诱导的DSB在比较宽的片段长度范围内进行定量和观察其碎片分布。二是推导出统计碎裂模型的公式,根据统计碎裂模型的计算结果与实验结果进行比较,分析碎裂片段大小的分布中线性关系和二次函数关系两种成分的贡献。 结果 在20～100Gy的照射剂量下,⁶⁰Coγ射线引起的GM0639细胞的DNA断裂片段释放的比例（FAR）从55%上升到85%,在剂量比较大时FAR趋于饱和;DNA断裂片段的平均长度从1.35Mbp下降到0.98Mbp;将断裂水平对剂量作图,可以由直线的斜率得到GM0639细胞的DSB断裂产额:（6.00±0.6）×10^-9Dsb/Bp/Gy,该值介于文献报道的断裂产额之间。另外,体系熵值取极大的分布是最可能的分布,取近似值E≈E₀+E₁l+E₂l²得到了辐射导致DNA双链断裂后碎裂片段随其大小l的分布函数exp（αl+βl²）。 结论 1.脉冲场电泳是分析DNA双链断裂的敏感方法。2.随着γ射线剂量的升高,DNA断裂片段的释放比例和平均长度分别升高和降低。3.实验结果支持DNA双链断裂后碎裂片段分布的统计碎裂模型。更多还原

【Abstract】 Objective: The purpose of the research is to study the mechanism of DNA double- strand breaks （DSB） by determining the yields and the distribution of DSB induced by ⁶⁰Co γ ray, and exploring the condition of the statistical fragmentation model based in comparison of the experimental data.Methods: The research was divided into two parts. 1. Normal human fibroblast cells GM0639 were irradiated by Gamma ray emitted from source ⁶⁰Co. The yields and distribution of double- strand breaks （DSB） were measured by the method of pulsed-field gel electrophoresis （PFGE） by subtracting the contributions of the background. 2. The formula of the statistical fragmentation model was established to analyze the contributions of linear and exponential function based on the experimental data with the model.Results: The results showed that the fractions of the activity released （FAR） of GM0639 cell’s DNA fragmentations increased from 55% to 85% as the dose increased from 20 to 100Gy and reached to a threshold （～85% ） at higher doses. The mean sizes of DNA fragments decreased from 1.35Mbp to 0.98Mbp as the dose increased. When plotted the breakage levels with the doses, a yield of DSB of GM0639: （0.600 ± 0.06） × 10^-9Dsb/Bp/Gy was obtained. The distribution pattern of the fragments was derived under the condition in which the entropy was at maximum. With the approximation E ≈ E₀ + E₁l + E₂l², the distribution functions were resulted as exp（αl + βl²）.Conclusions: 1. PFGE is a sensitive method in analyzing fragmentations of DNA double strand breaks. 2. With the increase of dose of γ-ray, the FAR of DNAincreases and the mean sizes of DNA fragments decrease respectively. 3. The experimental data support the radiation-induced DNA DSB statistical fragmentation model.更多还原