Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-41296 Gothenburg, Sweden.
Phys Chem Chem Phys. 2018 Apr 25;20(16):11336-11341. doi: 10.1039/c8cp01151f.
Isothermal titration calorimetry (ITC) has been utilized to investigate the effect of methyl substituents on the intercalating dppz ligand of the enantiomers of the parent complex Ru(phen)2dppz2+ (phen = 1,10-phenanthroline; dppz = dipyrido[3,2-a:2',3'-c]phenazine) on DNA binding thermodynamics. The methylated complexes (10-methyl-dppz and 11,12-dimethyl-dppz) have large, concentration-dependent, positive heats of dilution, and a strong endothermic background is also apparent in the ITC-profiles from titration of methylated complexes into poly(dAdT)2, which make direct comparison between complexes difficult. By augmenting a simple cooperative binding model with one equilibrium for complex self-aggregation in solution and one equilibrium for complex aggregation on saturated DNA, it was possible to find an excellent global fit to the experimental data with DNA affinity parameters restricted to be equal for all Δ-enantiomers as well as for all Λ-enantiomers. In general, enthalpic differences, compared to the unsubstituted complex, were small and less than 4 kJ mol-1, except for the heat of intercalation of Δ-10-methyl-dppz (-11,6 kJ mol-1) and Λ-11,12-dimethyl-dppz (+4.3 kJ mol-1).
等温热滴定法 (ITC) 已被用于研究取代基甲基对顺反式异构体母体配合物 Ru(phen)2dppz2+（phen = 1,10-邻菲啰啉；dppz = 二吡啶并[3,2-a:2',3'-c]吩嗪）中插层 dppz 配体与 DNA 结合热力学的影响。甲基化配合物（10-甲基-dppz 和 11,12-二甲基-dppz）具有较大的、浓度依赖性的正稀释热，并且在甲基化配合物滴定到 poly(dAdT)2 时，ITC 图谱中也明显出现强吸热背景，这使得直接比较各配合物变得困难。通过在简单的协同结合模型中加入一个平衡，用于溶液中配合物自聚集，以及一个平衡用于饱和 DNA 上的配合物聚集，可以找到与实验数据的极好的全局拟合，其中 DNA 亲和力参数限制为所有 Δ-对映异构体以及所有 Λ-对映异构体相等。一般来说，与未取代的配合物相比，焓变差异较小，小于 4 kJ mol-1，除了 Δ-10-甲基-dppz 的插入焓（-11.6 kJ mol-1）和 Λ-11,12-二甲基-dppz 的插入焓（+4.3 kJ mol-1）。
