Studies on DNA binding properties of new Schiff base ligands using spectroscopic, electrochemical and computational methods: Influence of substitutions on DNA-binding

Abstract

In this work, five new Schiff base ligands were synthesized and characterized by 1H NMR, 13C NMR, FT-IR, UV–Vis and elemental analysis (CHN). L1, L2 and L3, were derived from condensation of 2-Hydroxy-5-bromobenzaldehyde with 4-aminobenzoic acid, 3-aminobenzoic acid and 3-amino-4-methylbenzoic acid with 1:1 M ratio, respectively. While, L4 and L5 were prepared from condensation of 4-aminobenzoate with 3-ethoxy-2-hydroxybenzaldehyde and 3-methoxy-2-hydroxybenzaldehyd with 1:1 M ratio, respectively. Furthermore, the crystal structure of L4 and L5 were determined by single crystal X-ray analysis. The interaction of Schiff base ligands with fish sperm DNA (FS-DNA) was investigated under physiological conditions using fluorescence quenching, UV–Vis spectroscopy, molecular docking and molecular dynamics (MD) simulation methods. The estimated binding constants (kb) for the DNA-Ligands complexes were 8.9 × 104 M−1, 6.8 × 104 M−1, 1.2 × 105 M−1, 2.3 × 105 M−1, 1.7 × 105 M−1 for L1, L2, L3, L4 and L5, respectively. Based on similarity of the ligands structures and their Kb values, their affinity for binding to FS-DNA follow as: L3 > L1 > L2 and L4 > L5. The results revealed that ligands with stronger electron donating substituents, have higher DNA-binding ability than the others. Also, molecular docking results show that all of the synthesized ligands are minor groove binders and H-bond interactions have dominant role in the stability of ligand-DNA complexes. © 2018 Elsevier B.V.