Gemini表面活性剂(12-6-12)和DNA的相互作用

Interaction between the Gemini Surfactant (12-6-12) and DNA

应用紫外光谱、荧光探针、zeta电位、动态光散射和凝胶电泳等方法探讨了阳离子gemini表面活性剂C12H25N+(CH3)2―(CH2)6―(CH3)2N+C12H25·2Br- (12-6-12)与DNA之间的相互作用. 研究结果表明, 与传统表面活性剂相比, 偶联表面活性剂特殊的分子结构使其与DNA的作用更强烈. DNA引导表面活性剂在其链周围形成类胶束结构, 开始形成类胶束时对应的表面活性剂临界聚集浓度(CAC)比纯表面活性剂临界胶束浓度(CMC)低两个数量级. CAC与DNA的浓度无关, 而与表面活性剂之间的疏水作用以及表面活性剂与DNA之间的静电吸引作用密切相关. Zeta电位和凝胶电泳结果显示了DNA链所带负电荷逐渐被阳离子表面活性剂中和的过程. 借助原子力显微镜(AFM)成功观察到了松散的线团状DNA, 球状体随机地分散在DNA链上形成类似于串珠的结构、尺寸较大的球形复合物以及其由于吸附多余的表面活性剂重新带正电而被溶解得到的较小DNA/12-6-12聚集体. 圆二色(CD)光谱结果显示, 12-6-12可以诱导DNA的构象发生改变.

Interactions between DNA and the cationic gemini surfactant hexamethylene-1,3-bis（dodecy-dimethylammonium bromide）（12-6-12） in an aqueous solution were investigated using UV-Vis spectro-scopy,zeta potential,fluorescence emission spectroscopy,dynamic light scattering,and agarose gel electrophoresis.It could be found that interactions between DNA and the cationic gemini surfactant were stronger than interactions between DNA and traditional surfactant due to the special structure of gemini surfactant.The cationic gemini surfactant can interact with DNA at very low concentrations and micelle-like structures form around the DNA chains.The micelle-like structure of 12-6-12 that is induced by DNA appears at the critical aggregation concentration（CAC）.The CAC is two orders of magnitude lower than the critical micelle concentration（CMC） of 12-6-12 in a DNA-free solution.The CAC is independent of DNA concentration but it is dependent on the hydrophobic interaction between surfactant molecules and the electrostatic attractive interaction between the surfactant and DNA.Zeta potential and gel electrophoresis show that the negative charges of DNA are neutralized effectively and the zeta potential of the complex changes from negative to positive values.Atomic force microscopy（AFM） images show loose structures,beadlike structures（nucleosomes）,and globe structures.Circular dichroism（CD） spectra show that the secondary structure conformation of DNA changes because of its interaction with 12-6-12.