[Ru(TAP)₃]²⁺‐Photosensitized DNA Cleavage Studied by Atomic Force Microscopy and Gel Electrophoresis: A Comparative Study

Abstract

Topological modifications of plasmid DNA adsorbed on a variety of surfaces were investigated by using atomic force microscopy (AFM). On mica modified with 3-aminopropyltriethoxysilane (APS) or poly-L-lysine, the interaction between the plasmid DNA and the surface "freezes" the plasmid DNA conformation deposited from solution, and the AFM images resemble the projection of the three-dimensional conformation of the plasmid DNA in solution. Modified mica with low concentrations of Mg(2+) leads to a decrease in the interaction strength between plasmid DNA and the substrate, and the AFM images reflect the relaxed or equilibrium conformation of the adsorbed plasmid DNA. Under these optimized deposition conditions, topological modifications of plasmid DNA were produced under irradiation in the presence of [Ru(TAP)(3)](2+) (TAP = 1,4,5,8-tetraazaphenanthrene), which is a non-intercalating complex, and were followed as a function of illumination time. The observed structural changes correlate well with the conversion of the supercoiled covalently closed circular form (ccc form) into the open circular form (oc form), induced by a single-strand photocleavage. The AFM results obtained after fine-tuning of the plasmid DNA-substrate interaction compare well with those observed from gel electrophoresis, indicating that under the appropriate deposition conditions, AFM is a reliable technique to investigate irradiation-induced topological changes in plasmid DNA.

Synthesis, GC selective DNA binding and topoisomerase II inhibition activities of ruthenium(II) polypyridyl complex containing 11-aminopteridino[6,7-f][1,10]phenanthrolin-13(12H)-one

“…Considering the structure of the complex, the most possible binding mode is the hydrogen bonds formed between the guanine residue on the intercalative ligand appo and GC base pairs of DNA. [53,[56][57][58].…”

Oligonucleotide Duplexes with Tethered Photoreactive Ruthenium(II) Complexes: Influence of the Ligands and Their Linker on the Photoinduced Electron Transfer and Crosslinking Processes of the Two Strands

“…We previously demonstrated that Ru II complexes containing at least two π-deficient polyazaaromatic ligands such as tap (1,4,5,8-tetraazaphenanthrene) are able to form a photoadduct on the guanine (G) base of DNA or ODN and can also photocleave plasmidic DNA. [13,14] These reactions are induced by a photoelectron transfer process from the G base to the excited complex. [15] We have shown that formation of the photoadduct could be targeted towards a G residue of a specific sequence by using ODNs conjugated with the [Ru(tap) 2 …”

Ru–TAP complexes and DNA: from photo-induced electron transfer to gene photo-silencing in living cells

“…For this, longer DNA sequences have to be used; therefore, 500-base-pair DNA restriction fragments and plasmid DNA pUC19 have been examined. It was shown a long time ago that the illumination of Ru-TAP complexes in the presence of plasmids (figure 8) induces cleavages, as revealed by the occurrence of open circular and linear forms of the plasmid from agarose electrophoresis analysis [53] and from atomic force microscopy detections [54]. It is well known that the coiled circular plasmid is transformed, just by one single nick, into its open circular form.…”