K, Ca complexes with a sulfonic ligand: structure and DNA-binding properties

Abstract

A novel 4-(2,4-dihydroxybenzylideneamino)benzenesulfonic acid (HL), and its kalium(I), calcium(II) complexes [M(L)n]·2nH(2)O·Cl(n) (M=K(1) n=1, M=Ca(2) n=2), have been prepared and characterized. The crystal and molecular structures of 1 and 2 were determined by single-crystal X-ray diffraction. The interaction of 1, 2 and ligand (L) with calf thymus DNA was investigated by UV-visible (UV-vis), fluorescence and viscosity measurements. Experimental results indicate that 1, 2 and L could bind to DNA via the intercalation mode, and the binding affinity of 1 is stronger than that of 2 and L. The intrinsic binding constants of 1, 2 and L were 5.60×10(5), 6.53×10(5) and 1.44×10(5)M(-1), respectively. The cleavage reaction on plasmid DNA has been monitored by agarose gel electrophoresis. The results indicated that 1 and 2 could cleave pBR322 DNA.