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New ternary copper complexes of pyridine Synthesis, Crystal Structure and DNA Interactions

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Tutor: ZhouJianLiang
School: Central South University
Course: Inorganic Chemistry
Keywords: polypyridine copper(¢ò) complex,L-Gly,DNA binding,DNA cleavage
CLC: O627.12
Type: Master's thesis
Year:  2010
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Abstract:
Transition metal complexes capable of binding and cleaving DNA under physiological conditions have been attracted much in the few decades due to their potential use due as structure probes in nucleic chemistry and as therapeutic agents.We first synthesized the ternary copper(¢ò) complex [Cu(dpq)(L-Gly)(H2O)]¡¤NO3¡¤1.5H2O (dpq=dipyrido[3,2-d;2¡¯3¡¯-f] quinoxaline, L-Gly=L-glycine). The structures of the complex have been characterized by various methods including infrared spectrum, elemental analysis X-ray crystallography. It has been found the complex is five-coordinate distorted square pyramid, and it crystallized in a triclinic system with space group P-1. Absorption spectra, fluorescence spectra and CD spectra were used to study the interactions between the complex and DNA, It suggested that the complex binds to CT-DNA via groove mode. The gel electrophoresis experiment showed that the complex exhibits efficient cleavage activity in the presence of ascorbate, and cleavage activity enhanced with the increase of concentration of the copper complex. When the concentration of the complex was 16.0¦ÌM, the supercoiled DNA was finally converted completely to nicked and linear DNA, and the amount of Form¢óreached 30.1%. The preliminary cleavage mechanism of the complex was also studied, the result showed that the complex may first interact with DNA to form Cu¢ò-DNA species, which then be reduced to Cu¢ñ-DNA intermediate by H2A. The Cu¢ñspecies then reacts with O2 to generate hydroxyl radicals, and the reactive oxygen species in this case then leads to the DNA strands scission.In the second part, we synthesized the ternary copper(¢ò) complex [Cu(dppz)(Gly)(H2O)]¡¤NO3¡¤H2O(dppz=dipyrido[3,2-a:2¡¯,3¡¯-c]phenazene, L-Gly= L-glycine). The structures of the complex have been characterized systematically by various methods including X-ray crystallography, elemental analysis, infrared spectrum. It has been found the complex is also five-coordinate distorted square pyramid, and it crystallized in a monoclinic system with space group P21/c. Absorption spectra, fluorescence spectra were used to study the interaction of the complex with DNA, the result is that this complex binds to DNA through intercalative mode; Because the ligand dppz has bigger planne than dpq, so complex [Cu(dppz)(Gly)(H2O)]¡¤NO3¡¤H2O binds to DNA through intercalative mode more easily than complex [Cu(dpq)(L-Gly)(H2O)]¡¤NO3¡¤1.5H2O. The gel electrophoresis experiment suggests that the complex exhibits efficient DNA cleavage activity in the presence of ascorbate, and cleavage activity become higher with the increasing concentration of the complex.Finally, we synthesized a new phenyl-bridged plypyridine ligand, and the preparation of the binuclear copper(II) complex of this ligand was also studied preliminarily.
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