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中文摘要：
在pH 7.4 的Tris-HCl的缓冲溶液中，采用紫外及荧光光谱法研究了荷叶中紫云英苷（AST）与DNA之间的相互作用，探讨了离子强度和阴离子猝灭剂KI对紫云英苷及紫云英苷-DNA体系荧光强度的影响，同时考察了紫云英苷和中性红与DNA结合的竞争性。结果表明DNA通过静态猝灭作用机制猝灭紫云英苷的荧光，并测得其在298及308 K时的猝灭速率常数（Kq）分别为3.120 ×1012和2.630×1012 L·mol-1·s-1，结合常数（Kd）分别为3.412×104和1.762×104 L·mol-1，结合位点数（n）分别为1.007和0.962;DNA的存在使紫云英苷的紫外吸收光谱发生减色效应且吸收波长产生红移;发现离子强度的改变对紫云英苷及紫云英苷-DNA体系的荧光强度影响不大;KI对结合形式存在的紫云英苷的荧光猝灭效率明显小于自由形式存在的紫云英苷的荧光猝灭效率;紫云英苷可插入DNA中置换出与DNA结合的中性红。这些结果说明荷叶中紫云英苷以嵌插模式与DNA进行结合。
英文摘要：
The interaction between astragalin （AST） from lotus leaf and deoxyribonucleic acid （DNA） in Tris-HC1 buffer （pH= 7.4） was investigated by the application of fluorescence spectroscopy and ultraviolet absorption spectroscopy, the effects of ionic strength and anion quencher KI on the fluorescence intensity of AST from lotus leaf and the system of AST-DNA were explored, and the competitive binding to DNA between AST from lotus leaf and Neutral Red（NR）dye was also studied. The results dem- onstrated that AST could bind to DNA and the formed complex quenched the intrinsic fluorescence of AST from lotus leaf through static quenching mechanism. The quenching rate constants of biomolecule（Kq）of the reaction of DNA with AST from lotus leaf were calculated to be 3. 120 ×10^12 and 2. 630 ×10^12 L·mol-1·s-1 by Stern-Volumer equation, the corresponding binding constants（Kd）were computed to be 3. 412 ×10^4 and 1. 762 ×10^12 L·mol-1·s-1 and the number of binding sites（n） was coun- ted to be 1. 007 and 0. 962 between AST from lotus leaf and DNA at 298 and 308 K, respectively. When bound to DNA, the AST from lotus leaf showed hypochromic effect and red shift in the absorption spectra. It was also found that different ionic strength had little or no effect on the fluorescence intensity of AST and AST-DNA, but the fluorescence intensity of AST-DNA qtienched by anionic quencher KI was much less than that of free AST. AST could be intercalated into DNA and displaced the NR from the NR-DNA complex. It was showed that AST from lotus leaf could combine with DNA in the mode of intercalation.
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