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

A novel 4-(2,4-dihydroxybenzylideneamino)benzenesulfonic acid (HL), and its kalium(I), calcium(II) complexes [M(L)n]center dot 2nH(2)O center dot 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 X 10(5), 6.53 x 10(5) and 1.44 x 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. (C) 2012 Elsevier B.V. All rights reserved.