Spectroscopic and Molecular Docking Study of the Interaction of DNA with a Morpholinium Ionic Liquid.

The structural integrity of a nucleic acid under various conditions determines its utility in biocatalysis and biotechnology. Exploration of the ionic liquids (ILs) for extraction of DNA and other nucleic acid based applications requires an understanding of the nature of interaction between the IL and DNA. Considering these aspects, we have studied the interaction between calf-thymus DNA and a less toxic morpholinium IL, [Mor1,2][Br], employing fluorescence correlation spectroscopy (FCS), conventional steady state and time-resolved fluorescence, circular dichroism (CD) and molecular docking techniques. While the CD spectra indicate the stability of DNA and retention of its B-form in the presence of the morpholinium IL, the docking study reveals that [Mor1,2](+) binds to the minor groove of DNA with a binding energy of -4.57 kcal mol(-1). The groove binding of the cationic component of the IL is corroborated by the steady state fluorescence data, which indicated displacement of a known minor groove binder, DAPI, from its DNA-bound state on addition of [Mor1,2][Br]. The FCS measurements show that the hydrodynamic radius of DNA remains more or less constant in the presence of [Mor1,2][Br], thus suggesting that the structure of DNA is retained in the presence of the IL. DNA melting experiments show that the thermal stability of DNA is enhanced in the presence of morpholinium IL.