Association Behavior Of Nucleic Acid Base Chiral Surfactants And Their Interaction With DNA

Chiral surfactants can form chiral aggragates via its self-assemble behavior in aqueous solution, which have great potential in biochemical technology, such as the recognition of drugs and the preparation of targeting DNA nanocarriers. Due to the unique recognition of hydrogen bonding and chirality, nucleobase-type surfactants is sensitive to the surrounding environment. Thus, the investigation of self-assemble behavior and mechanism on this surfactant is of great importance, which not only broaden the applications of chiral surfactants, but also can be used to develop functional chiral self-assemble material. Based on the above goals, this study proceeded these researches as follows.Three chiral nucleobase-type surfactants T-Cn-TAB(n=8,10,16) are synthesized in this paper.All of these surfactants are characterized by FT-IR,1H NMR,LC-MS, elemental analysis. In addition, their aggregation behaviors are investigated by surface tension, electrical conductivity method. Results indicate that the synthesized surfactants are the targeting compounds with high purity in accord with experimental requirement. Furthermore, with increasing hydrophobic chain, the cmc of T-Cn-TAB decreases gradually and the lowest value of γcmc is 47.2 mN/m. Circular dichroism spectrum showes that these surfactants have large-negative absorbance band, suggesting the existence of chiral self-assembly.The micelle behaviors of T-Cn-TAB (n=8,10,12) are systematically investigated through conductivity, ITC,1H NMR,2D NOESY, DLS, negative staining TEM and DFT calculation. It is found that the association of Chiral nucleobase-type Surfactants is a entropy-driven process with the thermal effect being-10.7 kJ/mol. Moreover, the thermal effect increases with the increasing of temperature. DLS indicates that the hydrated radius of chiral aggregates is about 0.7 nm. What’s more, TEM is found that aggregrates are uniform with high-dispersed sphere aggragates. As proved by 1H NMR and 2D NOESY, pyimidine rings lie in colloidal nucleus, in which adjacenting thymine is located parallelly owing to π-π stacking, thus leading to the formation of dense aggragets. Also, temperature boosting can change the size and chiral signal of self-assembly, which is due to the breakage of hydrogen bonding resulting from the change of temperature, consequently altering configuration of self-assembly.The interaction and associating mechanism between nucleobase-type T-C12-TAB and DNA are fully investigated by conductivity, fluorescence spectra, DLS, negative staining TEM and CD spectra. Conductivity method showed that the conductivity of T-C12-TAB is much higher in the presence of DNA, indincating the interaction between T-C12-TAB and DNA. As confirmed by fluorescence spectra containing EtBr probe, increasing the concentration of T-C12-TAB will lead to strengthen fluorescence intensity, which is contrary to results of interaction between that ionic liquid surfactants or traditional surfactants and DNA. This indicates that nucleobase-type surfactant and DNA have unique association property. Furthermore, the hydrated radius of DNA/T-C12-TAB complex increase from 225 nm to 360 nm as proved by DLS, suggesting that chiral surfactant and DNA have unique association property due to charge attraction and that the fluorescence characteristic. CD spectra showes that the structure of B-type DNA can persist, consistent with above results. In some cases, owing to the strong H-bond brought by the thymine ring and DNA base pairs, the:surfactant molecules lie in the grooves of DNA, making its size bigger.