A Series Of DNA Cleavage System And Their Biological Activity

Thirty-five new zinc(II), copper(II), cobalt(II) and nickel(ll) complexes, utilizing five interrelated polypyridyl ligands and other coligands, have been synthesized and characterized by element analyses and IR. The structures of these complexes have been determined by X-ray crystallographic methods. The interactions of the complexes with DNA have been explored by absorption, emission, circular dichroic spectral and gel electrophoresis. The protein binding abilities and mechanisms have been monitored by quenching emission in the presence of complexes using BSA as model protein. In addition, the antitumor activities and mechanisms for some complexes are investigated through MTT assay, colony-forming assay, Hoechst33342staining assay, Cell cycle arrest, Annexin V/PI (or Annexin V/7-AAD) analysis, comet assay and ROS generation experiments. This is beneficial for the research and development of metal antitumor drugs.The main contributions in this work are below:1. Five novel polypyridyl ligands have been synthesized and characterized by1H NMR, element analyses, IR and X-ray crystallographic methods.2. Ten new zinc(II) complexes have been synthesized with five interrelated polypyridyl ligands. The structures have been determined by X-ray crystallographic methods. Zinc(II) complexes bind to CT-DNA by partial intercalation binding mode. The DNA cleavage mechanism for complexes1-4and6-7and anaerobic experiments indicated the noninvolvement of molecular oxygen in the cleavage, such fact implies that DNA cleavage could be attributed to hydrolytic mechanism. The protein binding abilities and mechanisms have been monitored by quenching emission in the presence of complexes1-4and6-7using BSA as model protein. The MTT assay was done to test the ability of complexes1-4and6-7to inhibit cell growth, all of the complexes exhibit significant cytotoxic activity toward HeLa cell lines. Again, relatively the most potent cytotoxic effects were observed in MCF-7cells for complex6and in RL952cells for complex7, which were more or less equal to cisplatin against the same cell lines. The antitumor activities and mechanisms for the complexes3on HeLa cells and6on MCF-7cells were also investigated through colony-forming assay, Hoechst33342staining assay, Cell cycle arrest and Annexin V/7-AAD analysis.3. Twelve new copper(II) complexes have been synthesized with five interrelated polypyridyl ligands. The structures have been determined by X-ray crystallographic methods. Copper(II) complexes bind to CT-DNA by partial intercalation binding mode. Complex11exhibits prominent DNA cleavage without any external agents. In the presence of H2O2or GSH (glutathione), the DNA cleavage efficiencies of complexes12-22exhibit remarkable increases and the oxidation mechanisms have been discussed. The protein binding abilities and mechanisms have been monitored by quenching emission in the presence of complexes11-19using BSA as model protein. The MTT assay was done to test the ability of complexes12-19to inhibit cell growth, all of the complexes exhibit significant cytotoxic activity toward the three cell lines. Again, relatively the most potent cytotoxic effects were observed for dinuclear complex14, which were almost equal or even better to cisplatin against the same cell lines. The antitumor activities and mechanisms for the complexes12and14on HeLa cells were also investigated through colony-forming assay, Hoechst33342staining assay, Cell cycle arrest, Annexin V/PI analysis, comet assay and ROS generation experiments.4. Five new cobalt(II) complexes have been synthesized with five interrelated polypyridyl ligands. The structures have been determined by X-ray crystallographic methods. Cobalt(Ⅱ) complexes bind to CT-DNA by partial intercalation binding mode. They show obvious DNA cleavage activity without any external agents, which vary as27>23-25>26. The hydrolytic DNA cleavage mechanism for complexes23-25,27and the oxidation mechanisms of26have been discussed. The protein binding abilities and mechanisms have been monitored by quenching emission in the presence of complexes23-25using BSA as model protein.5. Eight new nickel(II) complexes have been synthesized with polypyridyl ligands and mixed-ligands (31-34). The structures have been determined by X-ray crystallographic methods. Nickel(Ⅱ) complexes30-34bind to CT-DNA by partial intercalation binding mode. The DNA cleavage efficiencies of30-34exhibit remarkably different with change of external conditions, such as no additive agents, with the presence of GSH (glutathione) or on the photoirradiation at365nm. The oxidation mechanisms also have been discussed. The protein binding abilities and mechanisms have been monitored by quenching emission in the presence of complexes30-34using BSA as model protein. The MTT assay was done to test the ability of complexes30-34to inhibit cell growth, and the most potent cytotoxic effect was observed for complex34, which was more or less equal to cisplatin against the same cell lines. The antitumor mechanism for the complex34was also investigated through Hoechst33342staining assay.In this paper, we have mainly investigated the chemical nuclease activities of transition metal complexes with polypyridyl ligands. Some quantitative parameters are calculated, and we also summarized the structure of transition metal complexes associated with the biological activity. All of these will be beneficial for designing efficient and simple chemical nuclease and understanding the mechanism on the metal antitumor drug.