Anion-Driven Influence of Tetrabutylammonium-Based Ionic Liquids on DNA Stability and Interaction Mechanisms

Ionic liquids (ILs) have been widely used as alternative solvents for the stabilization, storage, and extraction of DNA. However, studies on the interaction between ammonium-based ILs and DNA, particularly focusing on the effect of anions, remain limited. Tetrabutylammonium (TBA) cation-based ILs with propanoate, bromide, glutamate, and threoninate anions were used to analyze IL-DNA interactions through UV-vis titrations, steady-state and time-resolved fluorescence, and molecular docking. The conformational stability and thermal stability of DNA in IL solutions were analyzed through circular dichroism spectroscopy and UV thermal studies, respectively. Viscosity measurements of the IL solutions were carried out to support the data obtained from UV thermal studies. The TBA cation displays multiple modes of interaction at the groove through electrostatic, hydrophobic, and hydrogen bonding. Among the studied anions, the propanoate anion exhibits significant hydrophobic interactions in addition to hydrogen bonding, whereas glutamate and threoninate primarily engage in hydrogen bonding. The difference in the effect of the ILs on DNA underscores the significant influence of the anions on IL-DNA interactions.