DNA/BSA binding of a new oxovanadium (IV) complex of glycylglycine derivative Schiff base ligand

In this study, a new oxovanadium (IV) Schiff base complex was synthesized by the reaction of {[5(triethylammoniummethyl)salicylaldehyde]chloride}triethylammonium and vanadyl sulfate. The complex was characterized by elemental analysis, FT-IR and UV-Vis spectroscopy. The interaction between the complex and bovine serum albumin (BSA) was studied by absorption and emission titration methods. The quality of the spectral changes and the large calculated value of both the binding constant (Kb = 7.53 x 10(4) M-1) and the Stern-Volmer quenching constant (KSV = 7.65 x 10(4) M-1) proved the strong affinity of the complex to BSA. The static quenching mechanism was confirmed by comparing the calculated Kb values at four different temperatures. The negative changes in enthalpy and Gibbs free energy, proved that the BSA-complex binding is exothermic and spontaneous. The fluorescence data also indicated 1:1 binding stoichiometry of the complex on one binding site of BSA. Competitive experiments with site markers (phenylbutazone and ibuprofen) and synchronous measurements identified site I of BSA as the main binding site. Molecular docking results confirmed the binding pocket of site I (sub domain IIA) as the binding site. In the second part of the work, the binding of the complex to fish sperm DNA (FS-DNA) was investigated by UV-Vis absorption spectroscopy, fluorescence spectroscopy, viscosity measurement and cyclic voltammetry. The Stern-Volmer quenching and bimolecular quenching rate constants (KSV = 6.13 x 10(2) M-1, kq = 6.13 x 10(10) M-1S-1) were calculated. Absorption and emission studies could present types of interactions for example groove binding and electrostatic. A minor changes in viscosity showed a groove binding mode. In cyclic voltammogram study, decrease in current and also shift of peak potentials positively after adding DNA supported a partial intercalation mode. Theoretical docking study proposed the minor groove as the main part for DNA-complex binding. (C) 2020 Elsevier B.V. All rights reserved.