硫堇与DNA分子作用机理的光谱研究

Spectral Study on the Interaction Mechanism between Thionine and Calf Thymus DNA

用紫外可见吸收光谱、荧光光谱、圆二色谱和光电子能谱等光谱方法研究了硫堇(TH)与小牛胸腺DNA(CTDNA)的作用机理。实验结果表明,在pH7.2的磷酸盐缓冲溶液中,TH与CTDNA之间的作用方式以嵌入作用为主,嵌入作用使TH的紫外最大吸收峰强度减小,且峰位发生红移。由紫外光谱实验结果线性拟合求得TH与CTDNA的表观结合常数K=1.45×104L·mol-1。荧光光谱实验结果表明:TH与CTDNA的嵌入作用使TH的荧光发生强烈猝灭,猝灭常数KSV为1.01×104L·mol-1。嵌入作用位点主要发生在CTDNA的鸟嘌呤(G)胞嘧啶(C)碱基序列富集区。通过对TH的光电子能谱中N,S原子的结合能变化分析,TH分子以杂环上S原子端与CTDNA的GC碱基对结合,两者的相互作用对CTDNA的二级结构构象产生影响。

The interaction mechanism of thionine （TH） and calf thymus DNA （CT-DNA） was studied with UV-Vis absorption spectroscopy, fluorescence spectroscopy, circular dichroism （CD）, and X-ray photoelectron spectroscopy （XPS）. It was demonstrated that in the pH 7.2 phosphate buffer solution, the interaction of TH and CT-DNA is in the intercalative mode. The absorbence of the absorption peak of TH decreases and the peak position shifts to the red direction. The binding constant （K） of TH with CT-DNA is 1.45× 10^4 mol· L^-1. The fluorescence intensities of TH decrease drastically with increasing the concentration of CT-DNA. The Stern-Volmer quenching constant （Ksv） was calculated to be 1.01 × 10^4 mol· L^-1. The intercalative sites are mainly located at the G-C sequences of the CT-DNA molecule through the S atom in the TH molecule according to the experimental data obtained from the fluorescence spectra and XPS analysis. The secondary structure conformation of CT-DNA is changed due to its interaction with TH.