Saccharin Sodium

Fluorescence, UV, CD, FT-IR, viscosity, melting, electrophoresis and docking data were combined with MCR-ALS chemometrics to elucidate the binding of sodium saccharin (SSA) to calf thymus DNA by Zhang et al. Through MCR-ALS, the fluorescence and UV spectra were resolved without overlap, and the binding was shown to occur at a 1:1 stoichiometry. The results of static fluorescence quenching revealed negative ΔH° and ΔS° values, which implied that complexation was driven by hydrogen-bonds/van der Waals interactions, and was exothermic. Because of the negligible change in ΔTm and constant viscosity, along with similarity in iodide-quenching between SSA and ethidium bromide, and strong quenching of ss-DNA overfolded-DNA, intercalation was ruled out in favor of minor-groove binding.
CD revealed a B→A-like transition while the FT-IR shift implicated guanine as being involved in binding. Molecular docking of SSA to DNA showed that it sits in the minor groove and forms two H-bonds with guanines. Calf thymus plasmid electrophoresis showed that there was no cutting of DNA.

Fig. 1 Binding of Sodium Saccharin with calf thymus DNA. (Zhang G.; et al. 2014)