Wei Chunying, Jia Guoqing, Yuan Jingli, Feng Zhaochi, Li Can
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
Biochemistry. 2006 May 30;45(21):6681-91. doi: 10.1021/bi052356z.
Free-base porphyrin (5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H,23H-porphine) (H(2)TMPyP4) has been shown to be an effective telomerase inhibitor by an in vitro assay. Here, we examined the interactions of the H(2)TMPyP4 with three distinct G-quadruplex DNAs, the parallel-stranded (TG(4)T)4, dimer-hairpin-folded (G(4)T(4)G(4))2, and monomer-folded AG(3)(T(2)AG(3))(3), by ultraviolet resonance Raman spectroscopy (UVRR), UV-vis absorption spectroscopy, fluorescence spectroscopy, and surface-enhanced Raman spectroscopy (SERS). The data obtained by the continuous variation titration method show that the binding stoichiometry of H(2)TMPyP4/G-quadruplex is 2:1 for (TG(4)T)4 and 4:1 for (G(4)T(4)G(4))2 or AG(3)(T(2)AG(3))(3). The results of SERS spectra, UV-vis absorption titration, and fluorescence emission spectra together with the binding stoichiometries reveal that two H(2)TMPyP4 molecules are externally stacked at two ends of the parallel (TG(4)T)4 G-quadruplex, whereas H(2)TMPyP4 molecules can intercalate within their diagonal or lateral loop regions and intervals between two G-tetrads for (G(4)T(4)G(4))2 and AG(3)(T(2)AG(3))(3) G-quadruplexes. The binding of H(2)TMPyP4 to (TG(4)T)4 G-quadruplex results in the hypochromicity of the UV Raman signal of (TG(4)T)4, indicating that the stacking effects between H(2)TMPyP4 and DNA bases are significant. The Raman hyperchromicities and shifts are observed after the binding of H(2)TMPyP4 to both (G(4)T(4)G(4))2 and AG(3)(T(2)AG(3))(3) G-quadruplexes. This indicates that the intercalative H(2)TMPyP4 can lengthen the vertical distance between adjacent G-tetrads of (G(4)T(4)G(4))2 and AG(3)(T(2)AG(3))(3) and change their conformations. The present study provides new insights into the effect of H(2)TMPyP4 binding on the structures of G-quadruplexes and also demonstrates that Raman spectroscopy is an ideal method for examining the interaction between drugs and G-quadruplexes.
游离碱卟啉（5,10,15,20-四（1-甲基-4-吡啶基）-21H,23H-卟吩）（H(2)TMPyP4）已通过体外试验证明是一种有效的端粒酶抑制剂。在此，我们通过紫外共振拉曼光谱（UVRR）、紫外-可见吸收光谱、荧光光谱和表面增强拉曼光谱（SERS）研究了H(2)TMPyP4与三种不同的G-四链体DNA，即平行链（TG(4)T）4、二聚体-发夹折叠（G(4)T(4)G(4)）2和单体折叠AG(3)（T(2)AG(3)）(3)之间的相互作用。通过连续变化滴定法获得的数据表明，H(2)TMPyP4/G-四链体的结合化学计量比对于（TG(4)T）4为2:1，对于（G(4)T(4)G(4)）2或AG(3)（T(2)AG(3)）(3)为4:1。SERS光谱、紫外-可见吸收滴定和荧光发射光谱的结果以及结合化学计量比表明，两个H(2)TMPyP4分子在平行的（TG(4)T）4 G-四链体的两端外部堆叠，而H(2)TMPyP4分子可以插入（G(4)T(4)G(4)）2和AG(3)（T(2)AG(3)）(3) G-四链体的对角或侧向环区域以及两个G-四联体之间的间隔内。H(2)TMPyP4与（TG(4)T）4 G-四链体的结合导致（TG(4)T）4的紫外拉曼信号发生减色，表明H(2)TMPyP4与DNA碱基之间的堆叠效应显著。在H(2)TMPyP4与（G(4)T(4)G(4)）2和AG(3)（T(2)AG(3)）(3) G-四链体结合后观察到拉曼增色和位移。这表明插入的H(2)TMPyP4可以延长（G(4)T(4)G(4)）2和AG(3)（T(2)AG(3)）(3)相邻G-四联体之间的垂直距离并改变它们的构象。本研究为H(2)TMPyP4结合对G-四链体结构的影响提供了新的见解，并且还证明拉曼光谱是研究药物与G-四链体之间相互作用的理想方法。
