title: Copper-activated DNA photocleavage by a pyridine-linked bis-acridine intercalator.
abstract: We report the synthesis of new photonuclease 4 consisting of two acridine rings joined by a pyridine-based copper binding linker. We have shown that photocleavage of plasmid DNA is markedly enhanced when this ligand is irradiated in the presence of copper(II) (419 nm, 22 degrees C, pH 7.0). Viscometric data indicate that 4 binds to DNA by monofunctional intercalation, and equilibrium dialysis provides an estimated binding constant of 1.13 x 105 M-1 for its association with calf thymus DNA. In competition dialysis experiments, 4 exhibits preferential binding to GC-rich DNA sequences. When Cu(II) is added at a ligand to metal ratio of 1:1, electrospray ionization mass spectrometry demonstrates that compound 4 undergoes complex formation, while thermal melting studies show a 10 degrees C increase in the Tm of calf thymus DNA. Groove binding and intercalation are suggested by viscometric data. Finally, colorimetric and scavenger experiments indicate that the generation of Cu(I), H2O2, and superoxide contributes to the production of DNA frank strand breaks by the Cu(II) complex of 4. Whereas the strand breaks are distributed in a relatively uniform fashion over the four DNA bases, subsequent piperidine treatment of the photolysis reactions shows that alkaline labile lesions occur predominantly at guanine.
authors.affiliation: Departamento de Química OrgAnica and Departamento de Química-Física, Universidad de AlcalA, 28871-AlcalA de Henares, Madrid, Spain.
authors.forename: María-José
authors.initials: MJ
authors.lastname: Fernandez
authors.forename: Beth
authors.initials: B
authors.lastname: Wilson
authors.forename: Marta
authors.initials: M
authors.lastname: Palacios
authors.forename: María-Melia
authors.initials: MM
authors.lastname: Rodrigo
authors.forename: Kathryn B
authors.initials: KB
authors.lastname: Grant
authors.forename: Antonio
authors.initials: A
authors.lastname: Lorente
mesh_terms: D000166:Acridines / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D003300:Copper / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D007364:Intercalating Agents / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D009691:Nucleic Acid Denaturation; D010777:Photochemistry; D010957:Plasmids / Q000235:genetics; D011725:Pyridines / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013057:Spectrum Analysis; D044366:Transition Temperature; D014783:Viscosity
chemical_list: D000166:Acridines; D007364:Intercalating Agents; D008024:Ligands; D011725:Pyridines; C484811:bis-acridine; D003300:Copper; D004247:DNA; C427203:calf thymus DNA; C023666:pyridine