Groove Binding of Vanillin and Ethyl Vanillin to Calf Thymus DNA.

Vanillin (VAN) and ethyl vanillin (EVA) are widely used food additives as flavor enhancers, but may have a potential security risk. In this study, the properties of binding of VAN or EVA with calf thymus DNA (ctDNA) were characterized by multi-spectroscopic methods, multivariate curve resolution-alternating least-squares (MCR-ALS) algorithm and molecular simulation. The concentration profiles for the components (VAN or EVA, ctDNA and VAN-ctDNA or EVA-ctDNA complex) by the MCR-ALS analysis showed that VAN or EVA interacted with ctDNA and formed VAN-ctDNA or EVA-ctDNA complex. The groove binding of VAN or EVA to ctDNA was supported by the results from viscosity measurements, melting studies, denaturation experiments, and competitive binding investigations. Analysis of the Fourier transform infrared spectra corroborated the prediction by molecular docking that VAN and EVA preferentially bound to thymine bases region of ctDNA. The circular dichroism and DNA cleavage assays indicated that both VAN and EVA induced conformational change (from B - like DNA structure toward to A - like form), but didn't lead to a significant damage on DNA. The fluorescence quenching of Hoechst 33,258-ctDNA complex by VAN or EVA was a static quenching, and hydrogen bonding and van der Waals forces were main forces. This study has provided insights into the mechanism of interaction between VAN or EVA with ctDNA, and may also help better understand their potential toxicity with regard to food safety. Graphical Abstract VAN or EVA binds to A-T rich regions of ctDNA in the minor groove.

Deciphering the intercalative binding modes of benzoyl peroxide with calf thymus DNA.

The binding of benzoyl peroxide (BPO), a flour brightener, with calf thymus DNA (ctDNA) was predicted by molecular simulation, and this were confirmed using multi-spectroscopic techniques and a chemometrics algorithm. The molecular docking result showed that BPO could insert into the base pairs of ctDNA, and the adenine bases were the preferential binding sites which were validated by the analysis of Fourier transform infrared spectra. The mode of binding of BPO with ctDNA was an intercalation as supported by the results from ctDNA melting and viscosity measurements, iodide quenching effects and competitive binding investigations. The circular dichroism and DNA cleavage assays indicated that BPO induced a conformational change from B-like DNA structure towards to A-like form, but did not lead to significant damage in the DNA. The complexation was driven mainly by hydrogen bonds and hydrophobic interactions. Moreover, the ultraviolet-visible (UV-vis) spectroscopic data matrix was resolved by a multivariate curve resolution-alternating least-squares algorithm. The equilibrium concentration profiles for the components (BPO, ctDNA and BPO-ctDNA complex) were extracted from the highly overlapping composite response to quantitatively monitor the BPO-ctDNA interaction. This study has provided insights into the mechanism of the interaction of BPO with ctDNA and potential hazards of the food additive.