Interaction between the gemini surfactant (12-6-12) and DNA

Abstract

Interactions between DNA and the cationic gemini surfactant hexamethylene-1,3-bis(dodecydimethylammonium bromide) (12-6-12) in an aqueous solution were investigated using UV-Vis spectroscopy, 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 micellelike 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. © Editorial office of Acta Physico-Chimica Sinica.