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

Abstract

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.