单宁酸（tannic acid，TA）具有抑菌性、抗氧化性性能，镁离子具有重要的生理调节作用，通过络合反应将单宁酸和氯化镁制备成单宁酸络合镁（tannic acid complexing magnesium，T-Mg）。为了进一步了解T-Mg的一些功能，本文利用紫外光谱法、荧光光谱法、黏度法和热变性等方法在体外模拟体内环境研究了单宁酸络合镁与脱氧核糖核酸（DNA）的相互作用方式并进行分析。T-Mg与DNA相互作用后，随着DNA浓度的增加，T-Mg-DNA体系紫外吸收峰呈现先减色效应和微弱的红移，最大减色率为1.82%，后增色效应，增色率为5.2%；采用摩尔比法，在pH=7.4的缓冲溶液中，25 ℃时，最大吸收波长222 nm处，求得T-Mg与DNA结合比为n(T-Mg) : n(DNA)=5.88:1，结合常数为6.20×107 L/mol；由于T-Mg嵌入到DNA碱基对之间，使得T-Mg-DNA体系荧光吸收强度增强，最大增幅为2.14倍。黏度法和热变性法表明，T-Mg可使DNA的黏度降低、热变性温度升高，进一步证实了T-Mg与DNA之间作用方式为以T-Mg部分插入为主导，镁离子促进了T-Mg和DNA之间的作用。

Tannic acid (T-A) had the antimicrobial resistance and oxidation resistance. Magnesium ions played an important role in physiological regulation. Tannic acid complexing magnesium (T-Mg) was prepared by complexation reaction with tannic acid and magnesium chloride. In order to further understand some effects of T-Mg, the interactive effect between tannic acid complexing magnesium and DNA has been investigated by electronic absorption spectroscopy, fluorescence spectroscopy, viscosity and thermal denaturation methods in simulated in vivo environment. With the increasing concentration of DNA, the ultraviolet spectrum of T-Mg-DNA system showed a hypochromic effect and a little red shift, and the maximum hypochromism was 1.82%. When the concentration of DNA was increased to a certain value, the hyperchromic effect was observed and the maximum hyperchromism was 5.2%. In an aqueous buffer solution (pH=7.4, at 25 ℃), the maximum absorption wavelength of T-Mg-DNA system was 222 nm. The binding ratio of T-Mg and DNA was n (T-Mg): n (DNA)=5.88:1, and the corresponding binding constant was 6.20×107 L/mol. An increasing fluorescence was observed in T-Mg-DNA system, and the intensity of fluorescence increased 2.14 times, which resulted from that T-Mg inserted into the base pairs of DNA. The results of viscosity and thermal denaturation indicated that addition of T-Mg can reduce the relative viscosity of DNA and increase thermal denaturation temperature. These findings further confirmed that T-Mg can bind with DNA mainly by partial insertion, and the presence of magnesium ions can promote the interaction between T-Mg and DNA.

国家自然科学基金项目(51174144)