INTERACTION OF DELTA-[RU(PHEN)(2)DPPZ](2+) AND LAMBDA-[RU(PHEN)(2)DPPZ](2+) WITH DNA - A CALORIMETRIC AND EQUILIBRIUM BINDING STUDY
INTERACTION OF DELTA-[RU(PHEN)(2)DPPZ](2+) AND LAMBDA-[RU(PHEN)(2)DPPZ](2+) WITH DNA - A CALORIMETRIC AND EQUILIBRIUM BINDING STUDY
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DOI：
10.1021/ja00122a008
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发表时间：
1995-05-03
影响因子：
15
通讯作者：
CHAIRES, JB
中科院分区：
文献类型：
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作者：
HAQ, I;LINCOLN, P;CHAIRES, JB
荧光和吸收光谱、等温滴定量热法和粘度测量已用于表征 Delta 和 Lambda [Ru(phen)(2)DPPZ](2+) 与小牛胸腺 DNA 的相互作用。连续变化的方法揭示了 Delta-和 Lambda-DPPZ 的两种不同的结合化学计量，分别对应于 0.7 和 3 mol 碱基对/mol 配体。获得了两种对映体的结合等温线，这两种对映体都显示出与 DNA 的强结合，在 25 ℃、含有 50 mM NaCl 的溶液中，Delta 和 Lambda 异构体的 K 值分别为 3.2 x 10(6) M(-1) bp 和 1.7 x 10(6) M(-1) bp。由于与 DNA 的相互作用，滴定量热法得出 Delta-DPPZ 的 Delta H 值为+0.3 kcal mol(-1)，而 Lambda-DPPZ 的 Delta H 值为+2.9 kcal mol(-1)。这些小的正焓经热差光谱证实，表明这些化合物与 DNA 的结合是熵驱动的。母体化合物三(菲咯啉)-Ru(II) 与DNA 的结合热值为+2.5 kcal mol(-1)。将所有三种化合物滴定到缓冲液中产生不可忽略的稀释热。检查了两种异构体的结合常数的盐依赖性。发现 Delta 和 Lambda 异构体的斜率 SK = (delta logK/delta log[Na+]) 分别为 1.9 和 2.1。通过使用聚电解质理论来解释观察到的平衡常数的盐依赖性，可以表明对结合常数有显着的非静电贡献。相对粘度实验表明，Delta-和 Lambda-DPPZ 都会增加棒状 DNA 的长度，其方式与经典嵌入的结合一致。荧光能量转移实验为 Delta- 和 Lambda-[Ru(phen)(2)DPPZ](2+) 嵌入 DNA 提供了额外的证据。
Fluorescence and absorption spectroscopy, isothermal titration calorimetry, and viscosity measurements have been used to characterize the interaction of Delta and Lambda [Ru(phen)(2)DPPZ](2+) with calf thymus DNA. The method of continuous variations revealed two distinct binding stoichiometries for both Delta- and Lambda-DPPZ, corresponding to 0.7 and 3 mol of base pair/mol of ligand. Binding isotherms were obtained for the two enantiomers, both of which show strong binding to DNA, with K = 3.2 x 10(6) M(-1) bp and 1.7 x 10(6) M(-1) bp for the Delta and Lambda isomers, respectively, at 25 degrees C in solutions containing 50 mM NaCl. Titration calorimetry gave Delta H values of +0.3 kcal mol(-1) for Delta-DPPZ and +2.9 kcal mol(-1) for Lambda-DPPZ for their interaction with DNA. These small positive enthalpies, which were confirmed using thermal difference spectroscopy, indicated that the binding of these compounds to DNA is entropically driven. An enthalpy of +2.5 kcal mol(-1) was obtained for the binding of the parent compound, tris(phenanthroline)-Ru(II), to DNA. Titration of all three compounds into buffer gave a nonnegligible heat of dilution. The salt dependence of the binding constant was examined for both isomers. The slope SK = (delta logK/delta log[Na+]) was found to be 1.9 and 2.1 for the Delta and Lambda isomers, respectively. By using polyelectrolyte theory to interpret the observed salt dependence of the equilibrium constant, it can be shown that there is a significant nonelectrostatic contribution to the binding constant. Relative viscosity experiments showed that both Delta- and Lambda-DPPZ increase the length of rod-like DNA, in a manner consistent with binding by classical intercalation. Fluorescence energy transfer experiments provided additional evidence for the intercalation of Delta- and Lambda-[Ru(phen)(2)DPPZ](2+) into DNA.