Comparison of nuclease activities of redox active and inactive binuclear mixed-polypyridyl complexes: zinc(II)/H2O2 and cadmium(II)/H2O2 systems display efficient nuclease activities

摘要

Six binuclear complexes, [Cu2(1,4-tpbd)(bpy)2-(ClO4)2](ClO4)r2DMF (1); [Zn2(1,4-tpbd)(bpy)2(ClO4)2]-(ClO4)24H2O (2); [Ni2(1,4-tpbd)(phen)2(DMF)2](ClO4)4· 0.5H2O (3); [Cd2(1,4-tpbd)(phen)2(Cl)2](ClO4)2·6H2O (4); [Co2(1,4-tpbd)(DMF)6](ClO4)4 (5); and [Ni2(1,4-tpbd)(DM-SO)2(NCS)4] (6) (1,4-tpbd = N,N,N'N'-tetrakis(2-pyridyl-methyl)benzene-l,4-diamine), have been synthesized and investigated as artificial nucleases. Single crystal diffraction reveals that the metal atoms in these complexes are all in a distorted octahedral geometry. The interactions of the complexes with calf thymus DNA (CT-DNA) have been investigated by UV absorption, fluorescence spectroscopy, circular dichroism spectroscopy and viscosity measurements, and modes of CT-DNA binding for the complexes are proposed. Further experiments showed that these complexes can also induce DNA cleavage, and their activities are promoted by external agents. The Zn(II)/H2O2 and Cd(II)/H2O2 systems display efficient oxidative cleavage of supercoiled DNA, which is attributed to a peroxide ion coordinated to the metal center.