Effect of Dimerization on Nucleic Acid Binding and Sensing of a Styryl-quinolinium Molecular Rotor: Spectroscopic Insights to Aggregation

Abstract

In pursuit of a more detailed understanding of the interaction mechanism between styryl dyes and G-quadruplex DNA, three different bis(styryl)quinolinium dyes were synthesized. The interactions of these compounds with G-quadruplex DNA were studied using UV-vis, fluorescence, and circular dichroism (CD) based experiments. The findings established that the selectivity of the molecules for binding with G-quadruplex DNA was changed upon dimerization of the parent molecule. The monomer (compound 1) was reported to bind to an antiparallel G-quadruplex, human telomeric DNA, whereas the dimeric compound (compound 6b) showed selectivity towards a parallel G-quadruplex, Pu22. The CD studies confirmed that the interaction between the molecules with Pu22 involves dye aggregation in the DNA recognition process. The propensity of dye aggregation was further studied in the presence of external agents such as SLS and cetrimide in which the dimeric compounds indicated formation of both J and H aggregates at various concentrations. Since styryl quinoliniums are also known for metabisulfite ion sensing, we also probed if the aggregation properties of the dimeric compound caused any changes in their visual detection. The kinetical and visual change studies showed a clear role of dimerization/aggregation in altering the sensing properties of the parent compound 1.