Spectroscopic studies on the interaction of sodium benzoate, a food preservative, with calf thymus DNA

The interaction between sodium benzoate (SB) and calf thymus DNA in simulated physiological buffer (pH 7.4) using acridine orange (AO) dye as a fluorescence probe, was investigated by UV–Vis absorption, fluorescence and circular dichroism (CD) spectroscopy along with DNA melting studies and viscosity measurements. An expanded UV–Vis spectral data matrix was resolved by multivariate curve resolution-alternating least squares (MCR−ALS) approach. The equilibrium concentration profiles and the pure spectra for SB, DNA and DNA–SB complex from the high overlapping composite response were simultaneously obtained. The results indicated that SB could bind to DNA, and hydrophobic interactions and hydrogen bonds played a vital role in the binding process. Moreover, SB was able to quench the fluorescence of DNA−AO complex through a static procedure. The quenching observed was indicative of an intercalative mode of interaction between SB and DNA, which was supported by melting studies, viscosity measurements and CD analysis.