水环境中铜离子有害性的DNA表征方法

利用琼脂糖凝胶电泳法研究了铜离子对超螺旋X174 RF DNA结构的影响. 铜离子浓度为10^-3 mol/L 和10^-4 mol/L 时,与DNA作用24h后,可直接使质粒DNA的超螺旋结构完全转化为其它结构. 低浓度铜溶液(10^-6 mol/L) 与DNA作用24h后,52%的超螺旋结构发生了转化. 48h时,69%的超螺旋结构转化为其它结构. 在铜离子浓度一定的条件下,随着二者相互作用时间的延长,DNA超螺旋结构逐渐开环,断裂直至完全消失. 作用时间一定的条件下,铜离子浓度越高,越容易开环断裂,形成其它结构. 铜离子浓度、铜离子与DNA作用的时间以及DNA各种结构百分含量之间具有一定的剂量-效应关系. 通过测定DNA超螺旋结构的这种变化有可能发展一种相对于同一标准的比较污染物环境有害性的方法.

Evaluating the Harmfulness of Copper in Aquatic Environment by Measuring the Supercoiled Structure Change of Plasmid DNA

The interaction of cupric ions with supercoiled DNA was investigated by agarose gel electrophoresis. Experimental results indicate that cupric ions could convert DNA structure from supercoiled to relaxed forms outside the cells in distilled water medium. At the levels of 10^-3 mol/L and 10^-4 mol/L copper, supercoiled DNA was totally converted into other forms of DNA after 24 hours. At a lower cupric level of 10^-6 mol/L, 52% supercoiled DNA was converted to other forms after 24 h and the relaxed form increased by 17% at 48h. Supercoiled form of DNA relaxed and gradually disappeared with the increase of incubation period of copper ions with the plasmid DNA. Supercoiled DNA degraded into other forms more rapidly at higher copper concentration. The percentages of different forms of DNA were related to copper concentration and incubation time. These results suggested that changes in supercoiled DNA structure may provide a rapid and sensitive method to assess the harmfulness of copper in aquatic environment.