Issue 16, 2018

Effects of methyl substitution on DNA binding enthalpies of enantiopure Ru(phenanthroline)2dipyridophenazine2+ complexes

Abstract

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).

Graphical abstract: Effects of methyl substitution on DNA binding enthalpies of enantiopure Ru(phenanthroline)2dipyridophenazine2+ complexes

Supplementary files

Article information

Article type
Paper
Submitted
20 Feb 2018
Accepted
01 Apr 2018
First published
03 Apr 2018
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2018,20, 11336-11341

Effects of methyl substitution on DNA binding enthalpies of enantiopure Ru(phenanthroline)2dipyridophenazine2+ complexes

A. K. F. Mårtensson and P. Lincoln, Phys. Chem. Chem. Phys., 2018, 20, 11336 DOI: 10.1039/C8CP01151F

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