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. Author manuscript; available in PMC: 2013 Nov 21.
Published in final edited form as: J Am Chem Soc. 2012 Nov 8;134(46):19223–19233. doi: 10.1021/ja3090687

Figure 1.

Figure 1

Chemical structures, binding affinities for CC mismatches, and approximated nuclear concentration of all compounds studied. Note all compounds are shown with both immines fully protonated; pKa’s of the immine protons vary among complexes and thus the protonation state of the inserting ligand will vary at physiological pH among the complexes. Binding affinities for [Rh(DIP)2(chrysi)]3+, [Rh(HDPA)2(chrysi)]3+, [Rh(bpy)2(chrysi)]3+, [Rh(DPAE)2(chrysi)]3+, and [Rh(PrDPA)2(chrysi)]3+ are previously reported.10,22,36 All other compounds’ DNA binding affinities were measured on the 29mer hairpin 5′-GGCAGGCATGGCTTTTTGCCATCCCTGCC-3′ (underline denotes the mismatch) in a competition assay through photocleavage by [Rh(bpy)2chrysi]3+. Samples were irradiated and electrophoresed through a 20% denaturing PAGE gel, and the percent of DNA cleavaged at each concentration was plotted as a function of log [Rh]. The data were fitted to a sigmoidal curve, and KB values were determined by calculating the concentration of rhodium at the inflection points of the curve and solving simultaneous equilibria. To determine nuclear rhodium concentrations, HCT116O cells were incubated in media containing 10 μM of each rhodium complex (except [Rh(DIP)2(chrysi)]3+, which was administered at 2 μM) for 24 h. The cells were harvested by trypsinization and the nuclei isolated. Rhodium content was quantified by ICP-MS first normalized to number of nuclei, then divided by the volume of the nucleus of a HCT116O cell, which was approximated as a sphere with radius 4 μm.46 It is important to note that while the structures all illustrate the Δ isomers, all experiments were done with racemic mixtures.