Study of Interaction Mechanism between Tannic Acid Complexing Magnesium and DNA
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Abstract:
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.
