Institute of Molecular Science, Shanxi University, Taiyuan 030006, China.
Biophys Chem. 2010 May;148(1-3):51-5. doi: 10.1016/j.bpc.2010.02.009. Epub 2010 Feb 16.
The binding mode and stoichiometry of the cationic porphyrin TMPyP4 to G-quadruplex structure are still controversial to date, mainly due to the intricate polymorphism of G-rich sequences in the different conditions of solution. Here in the presence of the molecular crowding agent PEG, the binding interaction of TMPyP4 and another porphyrin derivative TPrPyP4 with four-stranded parallel (G(4)T(4)G(4))4 G-quadruplex was studied systematically using circular dichroism, visible absorption titration, and steady-state and time-resolved fluorescence spectroscopies. The results show that each (G(4)T(4)G(4))4 molecule is able to bind four TMPyP4 or TPrPyP4 molecules. Two types of independent and nonequivalent binding sites with the higher and lower binding affinity are confirmed, and the stronger and weaker binding constants are 2.74 x 10(8) and 8.21 x 10(5)M(-1) for (G(4)T(4)G(4))4-TMPyP4, 2.05 x 10(8) and 1.05 x 10(6)M(-1) for (G(4)T(4)G(4))4-TPrPyP4, respectively. The two porphyrin molecules stack on the two ends of G-quadruplex with the higher binding affinity, another two porphyrins bind weakly to the two external grooves.
阳离子卟啉 TMPyP4 与 G-四链体结构的结合模式和化学计量比至今仍存在争议，主要是由于在不同溶液条件下，富含 G 的序列存在复杂的多态性。在分子拥挤剂 PEG 的存在下，系统研究了 TMPyP4 和另一种卟啉衍生物 TPrPyP4 与四链平行（G(4)T(4)G(4))4 G-四链体的结合相互作用，使用圆二色性、可见吸收滴定、稳态和时间分辨荧光光谱法。结果表明，每个（G(4)T(4)G(4))4 分子能够结合四个 TMPyP4 或 TPrPyP4 分子。证实了两种具有不同结合亲和力的独立且非等效结合位点，较强和较弱的结合常数分别为（G(4)T(4)G(4))4-TMPyP4 的 2.74 x 10(8) 和 8.21 x 10(5)M(-1)，（G(4)T(4)G(4))4-TPrPyP4 的 2.05 x 10(8) 和 1.05 x 10(6)M(-1)。两个卟啉分子在具有较高结合亲和力的 G-四链体的两端堆积，另外两个卟啉较弱地结合到两个外部沟槽。
