光谱法研究百草枯与小牛胸腺DNA的相互作用  

Study on the Interaction between Paraquat and Calf Thymus DNA by Spectral Methods

作　　者：童裳伦[1] 胡洲[1] 刘维屏[1] 

机构地区：[1]浙江大学环境与资源学院污染环境修复与生态健康教育部重点实验室,杭州310029

出　　处：《化学学报》2010年第14期1404-1410,共7页Acta Chimica Sinica

基　　金：国家自然科学基金(No20577039);浙江省自然科学基金杰出青年团队(NoR507212)资助项目

摘　　要：以亚甲基蓝(MB)为分子探针,用紫外-可见光谱、荧光光谱、荧光偏振和圆二色光谱研究了百草枯与小牛胸腺(ctDNA)的相互作用.MB分子主要以嵌插方式结合到ctDNA双螺旋结构上,而百草枯则以非竞争方式抑制MB与ctDNA的结合;百草枯对MB-ctDNA体系的荧光偏振以及百草枯对ctDNA圆二色光谱的影响,结果均表明百草枯与ctDNA主要作用方式为非嵌插结合.NaCl对百草枯与ctDNA的结合具有显著的抑制作用,因此可以推断带正电荷的百草枯离子可能通过与ctDNA链上带负电荷的磷酸基以静电相吸的方式结合而堆积在ctDNA双螺旋表面,引起ctDNA收缩,减弱了结合位点附近MB与ctDNA的静电作用;这可能由于钠离子中和了ctDNA磷酸基上的负电荷,从而削弱了百草枯与ctDNA间的静电作用.通过Scatchard方程计算,获得了百草枯与ctDNA的结合常数为1.80×104L·mol-1.The interaction of paraquat with calf thymus DNA（ctDNA） has been performed using methylene blue（MB） as a molecular probe by absorption spectra,fluorescence spectra,fluorescence polarization and circular dichroism spectra.MB primarily bound to double helical of ctDNA via the intercalative mode.Scatchard curves indicated the non-competitive inhibition of MB binding to ctDNA in the presence of paraquat.The results of fluorescence polarization and circular dichroism spectra all showed that the intercalative binding between paraquat and ctDNA was excluded.The results of the effect of sodium chloride on the binding of paraquat with ctDNA showed that sodium ions could remarkably constrain the above interaction.It was suggested that positively charged paraquat ions could interact with the negatively charged phosphate moieties of ctDNA through electrostatic attraction and stacked on the surface of double-stranded ctDNA,which might cause ctDNA shrinked and reduce the binding affinity of MB to ctDNA in the surrounding sites.Maybe this is because sodium ions may neutralize the negatively charged phosphate backbone of ctDNA,and then weaken the electrostatic attraction between paraquat and ctDNA.The binding constant of paraquat to ctDNA was 1.80×10^4 L·mol^-1 obtained by Scatchard equation.

关 键 词：百草枯 小牛胸腺DNA 亚甲基蓝 荧光偏振 圆二色光谱 相互作用 

分 类 号：R285[医药卫生—中药学]