“Turn on” fluorescence response of monomethine cyanines caused by noncovalent binding to ct-DNA

Monomethine cyanines have been extensively studied for their use as probes for nucleic acids among other biological systems. Four monomethine cyanine dyes were synthesized with various heterocyclic moieties including quinoline, benzoxazole, benzothiazole, and 3,3-dimethylindolenine adjoining benz[c,d]indol-1-ium, which was found to directly influence their optical and energy profiles. The dyes were characterized by 1H and 13C NMR and HRMS. In this study the twisted conformation unique to monomethine cyanines was exploited in DNA binding studies where the benzoxazole containing sensor displayed up to 700-fold increase in fluorescence when bound to the DNA compared to the unbound form.