光谱法及分子模拟研究青蒿素与小牛胸腺DNA的相互作用

在pH 7.4的Tris-HCl缓冲溶液中，采用紫外吸收光谱、荧光光谱结合溴化乙锭（EB）荧光探针、共振散射光谱以及DNA熔点（T_m）实验和分子模拟等技术，研究了青蒿素（QHS）与小牛胸腺DNA（ctDNA）分子间结合位点与结合机制。光谱实验结果显示，QHS与DNA发生减色效应，QHS的加入使EB-DNA体系发生静态荧光猝灭，QHS与DNA作用后其467 nm处共振散射峰锐增，与QHS作用引起DNA的T_m值升高5℃，说明QHS竞争性地嵌插入DNA的碱基对中。通过计算获得QHS与DNA间结合常数K_a为1.43×10³ L/mol（298 K）、0.99×10³ L/mol（304 K）。分子模拟结果表明，QHS吡喃环部分结构嵌插到DNA小沟区域GA碱基对间，氢键和范德华力是两者间结合的主要非共价作用方式，该结论与光谱法和热力学所得结果一致。

Binding Interaction of Artemisinin and DNA: Spectroscopic Methodologies and Molecular Docking

In a Tris-HCl buffer solution at pH 7.4, ultraviolet spectroscopy, fluorescence spectrometry combined with ethidium bromide(EB) fluorescence probes, resonance scattering spectroscopy, and DNA melting point(T_m) experiments and molecular simulation techniques were used to investigate the binding site and binding mechanism between the artemisinin(QHS) and calf thymus DNA (ctDNA). Spectral results showed that QHS and DNA had a color-reducing effect, and the addition of QHS caused the static fluorescence quenching of EB-DNA system. When QHS interacted with DNA, its resonance scattering peak at 467 nm sharply increased, and the T_m value of DNA increased by 5℃. This showed that QHS was competitively inserted into the base pair of DNA. The calculated binding constants of QHS and DNA were 1.43×10³ L/mol(298 K) and 0.99×10³ L/mol(304 K). The molecular simulation results showed that the structure of the QHS pyran ring was intercalated between the GA base pairs in the DNA minor groove region. Hydrogen bonds and van der Waals forces were the main noncovalent interactions between them. This conclusion was consistent with the results obtained by spectroscopy and thermodynamics.