Interactions of ammonium based ionic liquids with DNA in aqueous medium through Volumetric, acoustic and viscometric properties

Abstract

Ionic liquids (ILs) have emerged as a promising alternative solvent for DNA based studies as most of the studied ILs enhance the stability of DNA and act as a media for extraction and storage. Investigation of IL-DNA interactions through spectroscopic and computational analysis have been carried out earlier and we here attempt to explore the interaction through physicochemical properties of IL-DNA mixture in water medium that provide fundamental knowledge of the solvation behaviour. Properties such as density, ρ, speed of sound, u and viscosity, η, of two ILs, Benzyltributylammonium chloride ([BTBA]Cl) and Tetrabutylammonium bromide ([TBA]Br) in water as well as in aqueous DNA solutions with varying concentrations were measured over a temperature range from 293.15 − 323.15 K and at atmospheric pressure. The derived volumetric properties were calculated to understand the strength and extent of the solute–solvent interactions prevail in the solution. The analysis of partial molar volume at infinite dilution, V2∞, helped in the comparison of the strength of the interactions in between the studied solutes. The second derivative of V2∞ with respect to temperature, (∂2V2∞/∂T2)P facilitated in identifying the influence of the solutes in water structure formation around the solute and it was interesting to note that, although both the ILs behaved similarly in water as structure makers, [TBA]Br showed variation in the presence of DNA by demonstrating water structure breaking effects. Similar results were obtained from the analysis of viscometric properties as well. Further, the capability of the ILs to stay solvated in the DNA aqueous solution was confirmed by the results from the solvation number calculations.