电解质和乙醇对DNA与Gemini表面活性剂相互作用的影响

Effect of Electrolytes and Ethanol on the Interaction between DNA and the Gemini Surfactant

应用荧光探针和zeta电位方法研究了电解质NaBr、NaCl、KCl和有机溶剂乙醇对DNA与Gemini表面活性剂相互作用的影响.DNA诱导的表面活性剂类胶束在较低浓度即可生成,这一浓度称为临界聚集浓度(CAC).Gemini表面活性剂比具有相同烷烃链长的单体表面活性剂更易聚集,对应的CAC较低.实验结果表明,盐(NaBr)浓度对DNA/表面活性剂体系的CAC影响不大,阴、阳离子的种类则对该体系有不同程度的影响.阴离子(Br-、Cl-)对体系的CAC有显著的影响,但阳离子(Na+、K+)的差异对CAC影响不大.极性溶剂乙醇对DNA与表面活性剂相互作用的影响比较复杂.乙醇浓度较低时有利于表面活性剂的聚集,使得CAC减小;而浓度较高时,则不利于表面活性剂聚集,从而使CAC变大.乙醇可显著改变DNA/表面活性剂复合物的zeta电位.

The effect of electrolytes NaBr, NaCl, KCl and ethanol on the interaction between DNA and the Gemini surfactant has been investigated with a fluorescence probe and the zeta potential. The micelle-like structure of the surfactant induced by DNA appears at a much lower surfactant concentration, which is defined as the critical aggregation concentration （CAC）. The Gemini surfactant is much more likely to aggregate than the monomer surfactant that contains the same alkyl chain, and so the corresponding CAC value is much smaller. Experimental results show that the CAC is almost independent of NaBr concentration and that the effect of ion species on the interaction between DNA and surfactant is different. The type of anion （Br^-, Cl^-） has an obvious effect on CAC, but the type of cation （Na^＋, K^＋） does not. The polar solvent ethanol can affect the interaction between DNA and the surfactant. A lower ethanol concentration facilitates surfactant aggregation, which leads to a decrease in CAC. The CAC value increases as the ethanol concentration is increased. The zeta potential of the DNA/surfactant complexes can also be changed by ethanol.