DNA binding, DNA cleavage and BSA interaction of a mixed-ligand copper(II) complex with taurine Schiff base and 1,10-phenanthroline

The DNA-binding properties and DNA-cleavage activities of a Cu(II) complex, [Cu(sal–tau(phen)]·1.5H2O (sal–tau = a Schiff base derived from salicylaldehyde and taurine, phen = 1,10-phenanthroline), have been investigated by using UV–Vis absorption, fluorescence, circular dichroism (CD) spectra and agarose gel electrophoresis. Results indicated that this Cu(II) complex can bind to calf thymus DNA (CT-DNA) via an intercalative mode and shows efficient cleavage activity in the absence and presence of reducer. Its intrinsic binding constant Kb (1.66 × 104 M−1) was calculated by absorption spectra and its linear Stern–Volmer quenching constant Ksq (3.05) was obtained from florescence spectroscopy, as well as the cleaving reaction rate constant k1 (2.0 × 10−4 s−1) was acquired from agarose gel electrophoresis. Meanwhile, the interactions of the complex with BSA have also been studied by spectroscopy. Results showed that the complex could quench the intrinsic fluorescence of bovine serum albumin (BSA) remarkably through a static quenching process, and induce a conformational change with the loss of helical stability of protein.