Kinetic and thermodynamic studies on the interaction between calf thymus DNA and food additive vanillin - electrochemical methods

Abstract

• First electroanalytical method for interaction of vanillin with calf thymus-DNA in aqueous medium. • Vanillin can bind to ds-DNA via intercalative and electrostatic binding modes. • Kinetic and thermodynamic parameters were studied for free vanillin and vanillin bounded in DNA complex and discussed. This work describes a voltammetric study on the interaction of double-stranded calf thymus DNA (ds-DNA) and the food additive vanillin. To this end, a disposable pencil graphite electrode (PGE) was used as a voltammetric probe in aqueous media. The free vanillin has an irreversible oxidation signal in acetate buffer solution, pH 4.8. The changes in this signal in the presence of ds-DNA were followed by differential pulse voltammetry (DPV). Using the data obtained by Cyclic Voltammetry (CV), the kinetic parameters, diffusion coefficient (D), heterogeneous rate constant (k s ), and electrode surface concentration ( Γ) of free vanillin was evaluated. The values of these parameters found before and after complex formation between vanillin and DNA were compared to judge the interactions. The binding constant (K) and Gibbs free energy change (ΔG°) of the interaction were found as 1.78 × 10 4 M −1 and −24.25 kJ mol −1 , respectively. The effect of ionic strength on the interaction of vanillin and ds-DNA was also investigated. The results obtained indicate the existence of an interaction between vanillin and ds-DNA. Vanillin binds to DNA both through intercalation and electrostatic attraction. The binding constant related to the vanillin-DNA interaction was comparable to the literature values found by UV–Vis studies.