Development of a multifunctional biomimicking l-cysteine based oxovanadium(iv) complex: synthesis, DFT calculations, bromo-peroxidation and nuclease activity

Abstract

An oxovanadium complex [VO(sal-L-cys)(phen)] (sal-L-cys = Schiff base derived from salicylaldehyde and L-cysteine; phen = 1,10-phenanthroline) has been synthesized and characterized by spectroscopic studies (IR, UV-vis, ESI-MS and EPR studies). The structure of the complex has been optimized by density functional theory (DFT) calculations. Time-dependent DFT (B3LYP) calculations were used to establish and understand the nature of the electronic transitions observed in UV-vis spectra of the ligand and the complex. The multifunctionality of this oxovanadium complex has been exhibited by the application of it as a catalyst in peroxidative bromination of phenol red to demonstrate vanadium dependent bromoperoxidase activity, whereas nuclease activity has been established by DNA cleavage. The interaction of DNA with this structurally characterized oxovanadium complex has been studied by various physicochemical tools like UV-vis, fluorescence, and viscosity measurement studies. The intrinsic binding constant of the complex with DNA has been determined by electronic absorption studies and calculated to be (3.51 ± 0.02) × 10⁴ M⁻¹. The spectroscopic studies and the viscosity measurements indicate that the complex binds CT DNA by an intercalative mode. The ability of the complex to induce DNA cleavage was studied by gel electrophoresis techniques. The complex has been found to promote cleavage of pUC19 plasmid DNA from the super coiled (SC) form I to nicked coiled (NC) relaxed form II.