Studies On The Nuclease Activities Of Transition Metal Complexes With Nitrogen-Containing Multidentate Ligands

The design and synthesis of chemical nuclease are the most attractive fields in the chemistry and biology over the last few decades due to its theory research and practice application on the structure probe of DNA, molecule light switch of DNA, DNA cleavage agent and antitumor drug. Focused on the topic of chemical nuclease acting as DNA cleavage agent, polypyridine and 1,2,4,-triazole have been used to design and synthesize thirty-two new complexes in this thesis. The structures of these complexes have been determined by X-ray crystallographic methods and characterized by element analyses, IR and MS. We also investigated the nuclease activity of these complexes by UV-Vis spectra, fluorescent spectra, circular dichronism spectra, electrochemistry, viscosity and gel electrophoresis. The antitumor activities for some complexes are investigated through MTT assay, AO/EB staining assay, FCM assay and cell colony-forming assay. This is beneficial for the research and development of metal antitumor drugs. Moreover, the magnetism of polynuclear complexes has also been investigated.The main contributions in this work are below:1. We have synthesized twenty transition metal complexes with 1,4-tpbd ligand. In vitro DNA cleavage experiments show that these complexes exhibit chemical nuclease activities in the presence or the absence of oxidant/reductant. The cleavage mechanism shows that complexes 1-4 cleave DNA through hydrolytic and oxidative processes, while other complexes 5-20 through oxidative process. The obtained hydrolysis rate constants are 2.94 h-1,4.23 h-1,2.97 h-1 and 2.95 h-1 for complexes 1-4 in the absence of external agents at pH=7.2 and 37℃. The antitumor activities show that complexes 5-7 exhibit significant cytotoxic activities in a concentration-dependent manner, and the IC50 values are 14.75,13.67 and 16.58μM, indicating that they have the potential to act as effective anticancer drugs;The assays of AO/EB staining adopting fluorescent microscopic analysis and Annexin V-PI flow cytometry show that the complexes induce apoptosis of cells;we also investigated the inhibition of complexes on tumor cell colony-forming ability, and found that the tumor cell colony-forming ability was inhibited by complexes 5-7 in a dose-dependent manner, indicating the complexes exhibit the ability of antitumor metastasis to a certain extent.2.We have synthesized seven transition metal complexes with 1,3-tpbd ligand and investigated their nuclease activities. The results show that complexes exhibit chemical nuclease activities in the presence or the absence of oxidant/reductant. The cleavage mechanism shows that complexes 21-24 cleavage DNA through hydrolytic and oxidative processes, the obtained hydrolysis rate constants are 3.47 h-1,5.16 h-1, 4.64 h-1 and 2.13 h-1 for complexes 21-24 in the absence of external agents at pH= 7.2 and 37℃. While nickel complexes 25-27 may be capable of promoting DNA cleavage through oxidative DNA damage pathway involved 1O2 and·OH as reactive oxygen species.3. We have synthesized five transition metal complexes with 1,2,4,-triazole-based ligands and investigated their nuclease activities. The DNA cleavage results indicate that complexes exhibit chemical nuclease activities in the presence or the absence of oxidant/reductant. The cleavage mechanism shows that complexes 28 cleave DNA through hydrolytic process with the obtained hydrolysis rate constant is 2.58 h-1, while other complexes 29-32 may be capable of promoting DNA cleavage through oxidative DNA damage pathway. Interestingly, polynuclear complexes 31-32 could cleave DNA effectively in the presence of oxidant/reductant. This fact indicates it is of paramount importance for reasonable designs of polynuclear complexes to be as efficient DNA cleavage agents. Moreover, the magnetic property studies indicate that the existence of antiferromagnetic coupling between the nickel(II) ions in complex 31, while 32 is a wheel-shaped octanuclear copper(II) complex, we think that it should be a hidden weak ferromagnet, due to spin canting.In our paper, we have mainly investigated the chemical nuclease activities of transition metal complexes with polypyridine and 1,2,4,-triazole-based ligands. Some quantitative paraments 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.