Interactions Between DNA And Gemini Surfactant

As Genetic material, the most important physiological function of DNA is that self-propagating and guiding protein synthesis. The key to the success of gene therapy is that how to carry exogenous DNA into the cells in the body effectively and bring less side effects. In terms of cell phospholipids structure have some similarities with the structure of the surfactants, and cationic Gemini surfactant has potential advantages in the area of gene transfection, the study of interactions between DNA and surfactants would provide a theoretical basis for gene therapy.We use sonication method to obtain target DNA fragments, and study their interactions with the cationic Gemini surfactant at the interface and in the bulk phase. We found DNA fragments show rigidity while long-chain DNA show flexibility. There is a strong interaction between Gemini Surfactant12-S-12and DNA fragment, which lead to the appearance of different complexs with various surfactant concentrations. Though Gemini surfactant has different linker group (s=2,3,4), the interactions of12-s-12(s=2,3,4) and DNA fragments are similar. During the study of interation behavior between DNA and12-3-12in simulated body fluid(SBF) we found high anti-ion concentration is not only shielding electrostatic the attraction between DNA and12-3-12but also promote the emergence and growth of12-3-12surfactant aggregates, leading to precipitate was not dissolved which usual appear in low salt conditions. Surfactant molecules12-3-12aggregate around the DNA chains with the addition of surfactant and correspondingly the DNA network structures turn into necklace-like structures of complexes. Subsequently, the bigger spherical complexes and the coexistence of bigger complexes and smaller surfactant aggregates are observed in the present system, and circular dichroism (CD) spectra shows that DNA structure was changed from typical B conformation into condensed Ψ phase. Molecular dynamics simulation show that interaction process and model between polyelectrolyte and surfactant which coincide well with the experimental results.