Le Vu H, Nagesh Narayana, Lewis Edwin A
Department of Chemistry, Mississippi State University, Mississippi State, Mississippi, United States of America.
PLoS One. 2013 Aug 20;8(8):e72462. doi: 10.1371/journal.pone.0072462. eCollection 2013.
The interactions of three related cationic porphyrins, TMPyP4, TMPyP3 and TMPyP2, with a WT 39-mer Bcl-2 promoter sequence G-quadruplex were studied using Circular Dichroism, ESI mass spectrometry, Isothermal Titration Calorimetry, and Fluorescence spectroscopy. The planar cationic porphyrin TMPyP4 (5, 10, 15, 20-meso-tetra (N-methyl-4-pyridyl) porphine) is shown to bind to a WT Bcl-2 G-quadruplex via two different binding modes, an end binding mode and a weaker mode attributed to intercalation. The related non-planar ligands, TMPyP3 and TMPyP2, are shown to bind to the Bcl-2 G-quadruplex by a single mode. ESI mass spectrometry experiments confirmed that the saturation stoichiometry is 4:1 for the TMPyP4 complex and 2:1 for the TMPyP2 and TMPyP3 complexes. ITC experiments determined that the equilibrium constant for formation of the (TMPyP4)1/DNA complex (K1 = 3.7 × 10(6)) is approximately two orders of magnitude greater than the equilibrium constant for the formation of the (TMPyP2)1/DNA complex, (K1 = 7.0 × 10(4)). Porphyrin fluorescence is consistent with intercalation in the case of the (TMPyP4)3/DNA and (TMPyP4)4/DNA complexes. The non-planar shape of the TMPyP2 and TMPyP3 molecules results in both a reduced affinity for the end binding interaction and the elimination of the intercalation binding mode.
利用圆二色性、电喷雾电离质谱、等温滴定量热法和荧光光谱法，研究了三种相关的阳离子卟啉TMPyP4、TMPyP3和TMPyP2与野生型39聚体Bcl - 2启动子序列G - 四链体的相互作用。平面阳离子卟啉TMPyP4（5,10,15,20 - 中位 - 四（N - 甲基 - 4 - 吡啶基）卟啉）通过两种不同的结合模式与野生型Bcl - 2 G - 四链体结合，一种是末端结合模式，另一种较弱的模式归因于嵌入。相关的非平面配体TMPyP3和TMPyP2通过单一模式与Bcl - 2 G - 四链体结合。电喷雾电离质谱实验证实，TMPyP4复合物的饱和化学计量比为4:1，TMPyP2和TMPyP3复合物的饱和化学计量比为2:1。等温滴定量热实验确定，(TMPyP4)1/DNA复合物形成的平衡常数（K1 = 3.7 × 10(6)）比(TMPyP2)1/DNA复合物形成的平衡常数（K1 = 7.0 × 10(4)）大约大两个数量级。在(TMPyP4)3/DNA和(TMPyP4)4/DNA复合物的情况下，卟啉荧光与嵌入一致。TMPyP2和TMPyP3分子的非平面形状导致对末端结合相互作用的亲和力降低，并且消除了嵌入结合模式。
