光谱法及分子模拟法研究杨梅素与ct-DNA的相互作用

Spectroscopic Studies and Molecular Docking of the Interaction between Myricetin and Calf Thymus DNA

采用紫外光谱、荧光光谱结合亚甲基蓝荧光探针(MB)、圆二色谱(CD)以及分子模拟等技术研究了生理条件下杨梅素与小牛胸腺DNA(ct-DNA)的相互作用,探索了其可能的结合位点与作用机制。热力学参数显示ΔH<0、ΔS<0,说明杨梅素与ct-DNA通过氢键和范德华力发生相互作用。光谱研究显示,ct-DNA能够猝灭杨梅素的内源荧光,猝灭方式为静态猝灭,两者的结合常数为1.86×103mol-1,结合位点数为1。在竞争性实验中杨梅素未能将MB从MB-DNA复合体系中游离出来,说明其与ct-DNA的作用方式为沟槽结合。圆二色光谱研究表明,杨梅素的加入未能破坏ct-DNA的双螺旋结构,两者的作用方式为沟槽结合。进一步通过分子模拟研究得到杨梅素与DNA结合的最低能量构象,杨梅素A环7-O和B环3’-O分别与DNA的碱基DA18和DA6在边缘小沟处通过氢键结合,周围富含碱基A和T,与光谱学研究结果一致,结合距离分别为2.061和1.918。

The interaction between myricetin and calf thymus DNA（ ct-DNA） at physiologic p H was investigated by ultraviolet and fluorescence spectroscopy in conjunction with fluorescent probe methylene blue（ MB）,circular dichroism（ CD） and molecular modeling methods. Thermodynamic parameters（ ΔH 0 and ΔS 0） indicated that hydrogen bond and van der Waals play main roles in the binding of myricetin to ct-DNA. The results of spectroscopic experiments suggested that the intrinsic fluorescence of myricetin was quenched in the presence of ct-DNA by static quenching mechanism.The binding constant and the corresponding number of binding sites（ n） were calculated to be 1. 86 ×103mol- 1and 1,respectively. In competition experiments,myricetin was unable to replace MB（ an intercalator） from MB- DNA complex, which is indicative of groove binding. Circular dichroism spectra of DNA showed that the attendance of myricetin was not able to change the formation of DNA,which is in agreement with groove binding mode of interaction. Moreover,from molecular modeling methods,a docked structure with minimum energy was obtained,in which myricetin was located in minor grooves preferentially surrounding with A and T rich regions. The results of docking showed that 7-O in A ring and 3＇-O in B ring of myricetin were bound with DA18 and DA6 of DNA double helix by hydrogen,respectively. The binding distances were 2. 061A and 1. 918A,respectively.