溶液pH对硫堇与DNA相互作用方式的影响

用电化学和光谱方法研究了溶液pH对硫堇(TH)与小牛胸腺脱氧核糖核酸(CT-DNA)相互作用方式的影响.电化学测量结果表明，在pH 7.2的磷酸盐缓冲溶液中, TH与CT-DNA之间的作用方式以嵌入结合为主，在pH 6.5的磷酸盐缓冲溶液中， TH与CT-DNA之间的作用方式既存在嵌入结合也存在静电作用.荧光光谱测量结果表明，TH与DNA结合后其荧光发生猝灭，通过Stern-Volmer方程计算得到pH 6.5时TH-DNA体系的猝灭常数高于pH 7.2时的值，表明在pH 6.5的溶液中两者相互作用更强.圆二色谱(CD)实验结果也证实了这一结论.

Effect of pH on the Interaction Mode between TH and CT-DNA

The effect of pH of solution on the interaction between TH(thionine) and CT-DNA was studied using electrochemical and spectroscopic methods. The electrochemical results indicated that the interaction between TH and CT-DNA is in the intercalative mode in the pH 7. 2 phosphate buffer solution, but both inter-calative and electrostatic modes exist in the pH 6. 5 phosphate buffer solution. Fluorescence spectroscopic results showed that the fluorescence intensity of TH is efficiently quenched by CT-DNA bases. The quenching constant, Ksv obtained from the Stern-Volmer equation for the pH 6. 5 solution is larger than that for the pH 7. 2 solution indicating that the interaction between TH and CT-DNA in the pH 6. 5 solution is stronger than that in the pH 7. 2 solution. The conclusion is confirmed by the results of CD spectroscopic measurements.