Adduct-induced DNA damage can affect transcription efficiency and DNA replication and repair. We previously investigated the effects of the 3′-next flanking base (G*CT vs G*CA; G*, FABP, N-(2′-deoxyguanosin-8-yl)-4′-fluoro-4-aminobiphenyl; FAF, N-(2′-deoxyguanosin-8-yl)-7-fluoro-2-aminofluorene) on the conformation of arylamine-DNA lesions in relation to E. coli nucleotide excision repair (JainV.HiltonB.LinB.PatnaikS.LiangF.DarianE.ZouY.MackerellA. D.Jr.ChoB. P.JainV.HiltonB.LinB.PatnaikS.LiangF.DarianE.ZouY.MackerellA. D.Jr.ChoB. P.23180767Nucleic Acids Res.201341869880). Here, we report the differential effects of the same pair of sequences on DNA replication in vitro by the polymerases exofree Klenow fragment (Kf-exo–) and Dpo4. We obtained dynamic 19F NMR spectra for two 19-mer modified templates during primer elongation: G*CA [d(5′-CTTACCATCG*CAACCATTC-3′)] and G*CT [d(5′-CTTACCATCG*CTACCATTC-3′)]. We found that lesion stacking is favored in the G*CT sequence compared to the G*CA counterpart. Surface plasmon resonance binding results showed consistently weaker affinities for the modified DNA with the binding strength in the order of FABP > FAF and G*CA > G*CT. Primer extension was stalled at (n) and near (n – 1 and n + 1) the lesion site, and the extent of blockage and the extension rates across the lesion were influenced by not only the DNA sequences but also the nature of the adduct’s chemical structure (FAF vs FABP) and the polymerase employed (Kf-exo– vs Dpo4). Steady-state kinetics analysis with Kf-exo– revealed the most dramatic sequence and lesion effects at the lesion (n) and postinsertion (n + 1) sites, respectively. Taken together, these results provide insights into the important role of lesion-induced conformational heterogeneity in modulating translesion DNA synthesis.

The platinum(II) complex [Pt(bzimpy)Cl]+ (1) [bzimpy = 2,6‐bis(benzimidazo‐2‐yl)pyridine] has been synthesized and characterized by FAB mass spectrometry and UV/Vis, NMR, and emission spectroscopy. Complex 1 emits weakly from its 3MLCT state in aqueous solution but strongly in nonaqueous media. Complex 1 exhibits a molecular light switch effect with a drastic enhancement in its emission intensity and a 72‐nm blue shift in the emission maxima in the presence of bovine serum albumin (BSA). Denaturation of BSA in the presence of 6 M urea leads to a decrease in the emission intensity of the complex, which suggests its binding to the hydrophobic pockets of the protein. In the presence of hemoglobin, however, quenching of the emission of the complex is observed due to its binding to Cys104 in subunit C and the resultant fluorescence resonance energy transfer from the platinum(II) complex to the heme. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Two platinum(II) complexes containing imidazolyl terpyridine (1) and benzimidazolyl terpyridine (2) were synthesized and characterized by ESI-MS, 1 H NMR, UV-Visible and fluorescence spectroscopy. Pt(II) complex 1 emits weakly in an aqueous solution but not complex 2. On addition of DNA, a 21-fold increase in the emission intensity of complex 1 was observed. Both complexes did not exhibit any change in emission maxima with serum albumin. No uptake of the complexes by live cells was observed.In dead cells, complex 1 stains the nuclear DNA specifically without addition of any external fluorophore.The apoptotic pathway of the cells induced by plumbagin was monitored using complex 1. Application of complex 1 as a DNA staining dye was tested in agarose gel electrophoresis. Taken together, the results from this study presents a new platinum(II) complex as a DNA staining agent, an alternative to highly mutagenic ethidium bromide in gel electrophoresis as well as in dead cells at a non-toxic concentration.