二(吡啶-2-羧酸)钴配合物与DNA相互作用的电化学研究

Electrochemical Studies on the DNA Binding Property of a Pyridines Cobalt Complex Containing Pyridine-2-carboxylate

本文采用电化学方法(循环伏安法、常规脉冲伏安法和计时库仑法)研究了一种吡啶类钴配合物[Co(PC)2(H2O)2](PC=吡啶-2-羧酸)与DNA在水溶液中相互作用,探讨了该钴配合物与DNA二者之间结合模式、结合机理及结合参数等.循环伏安法发现该配合物在循环伏安图上呈现一对明显的氧化还原峰,经数值分析可知配合物的氧化还原峰电流比值Ipa/Ipc=0.5,且峰电位差ΔEp=72 mV,表明该配合物在金电极上的氧化还原过程为准可逆过程.随着DNA的加入,配合物的氧化还原峰电位发生了显著的减小,且式电位发生正移,表明二者之间通过嵌插方式发生了相互作用.配合物还原态与氧化态与DNA结合平衡常数比K2+/K3+=2.6,表明还原态的配合物与DNA之间结合能力是氧化态的2.6倍,符合嵌入模式的特征.常规脉冲伏安法考察了不同浓度DNA对配合物电化学响应的影响,结果表明[Co(PC)2(H2O)2]与DNA的结合常数K为9.4×104L/mol,显示出了中等强度的结合能力.计时库仑法进一步显示,当配合物与DNA作用后形成高分子量的复合物后扩散系数明显降低.

In this paper, a kind of pyridines cobalt complex [Co（PC）2（H2O）2] （PC=pyridine-2-carboxylate） was synthesized and the interaction with DNA was investigated by electrochemical methods. The cyclic voltammetry experiment showed that this cobalt complex had a well-identified pair of redox peaks, with the ratio of oxidation to reduction current value Ipa/Ipc=0.5 and potential difference △Ep=72 my, demonstrating a quasi-reversible redox process of complex on the gold electrode. After interaction with DNA, peak current of complex decreased remarkably accompanied by the positive shift of formal potentials, indicating a probable intercalation mode between the complex and DNA. Meanwhile, we observed the binding equilibrium constant between oxidation and reducing state of complex with DNA （K2＋/K3＋ was obtained to be 2.6） according to the formal potential difference value, proving the binding capability of complex in reduction state with DNA was 2.6 times over the oxidation state, which was in accord with the characteristic of intercalation based on Normal pulse voltammetry. The binding constant between reducing state of complex with DNA was determined to be 9.4×10^4 L/mol, presenting an moderate binding strength. Chronocoulometry assays revealed that the diffusion rate of the complex was decreased obviously after interaction with DNA.