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Synthesis, Characterization, DNA Binding, and Photocleavage Activity of Oxorhenium (V) Complexes with alpha-Diimine and Quinoxaline Ligands.

Mitsopoulou CA, Dagas C - Bioinorg Chem Appl (2010)

Bottom Line: Experimental data suggest that complex 1 intercalates into the DNA base pairs.Upon irradiation, complex 1 was found to promote the cleavage of plasmid pBR 322 DNA from supercoiled form I to nicked form II.The mechanism of the DNA cleavage by complex 1 was also investigated.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Inorganic Chemistry, Department of Chemistry, University of Athens, Panepistimiopolis, Zografou, Athens 157 71, Greece.

ABSTRACT
The complex [ReOCl(3)pq] (1) (where pq = 2-(2'pyridyl)quinoxaline) has been synthesized and fully characterized by UV-Vis, FTIR, 1 and 2D NMR, and cyclic voltammetry (CV). The DNA-binding properties of the complex 1 as well as of the compounds [ReOCl(3)bpy] (2), [ReOCl(3)phen] (3), and pq (4) were investigated by UV-spectrophotometric (melting curves), CV (cyclic voltammetry), and viscosity measurements. Experimental data suggest that complex 1 intercalates into the DNA base pairs. Upon irradiation, complex 1 was found to promote the cleavage of plasmid pBR 322 DNA from supercoiled form I to nicked form II. The mechanism of the DNA cleavage by complex 1 was also investigated.

No MeSH data available.


Photoactivated cleavage of pBR 322 DNA in the presence of 20 μM of complex 1 and different inhibitors after irradiation at λ > 400 nm for 60 minutes. Lane 0, DNA control; lane 1, no inhibitor; lanes 2–6: (2) histidine (5 mM), (3) DMSO (0.2 M), (4) ethanol (0.2 M), (5) sodium formate (5 mM).
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fig7: Photoactivated cleavage of pBR 322 DNA in the presence of 20 μM of complex 1 and different inhibitors after irradiation at λ > 400 nm for 60 minutes. Lane 0, DNA control; lane 1, no inhibitor; lanes 2–6: (2) histidine (5 mM), (3) DMSO (0.2 M), (4) ethanol (0.2 M), (5) sodium formate (5 mM).

Mentions: The ability of complex 1 to cleave DNA upon irradiation was determined by agarose gel electrophoresis [38]. When circular plasmid DNA in the presence of an inorganic molecule is subject to electrophoresis, relatively fast migration will be observed for the intact supercoil form (Form I). If scission occurs on one strand (nicking), the supercoil will relax to generate a slower-moving open circular form (Form II). If both strands are cleaved, a linear form (Form III) that migrates between Forms I and II will be generated [38]. Figure 6 shows gel electrophoresis separation of pBR 322 DNA after incubation with complex 1 and irradiation by visible light (λ > 400 nm) for 1 hour. Complex 1 exhibited concentration-dependent single-strand cleavage of supercoiled Form I into nicked Form II. Control experiment (lane 0) suggests that untreated DNA does not show any cleavage upon irradiation, with increasing concentration of 1 (lanes 1–3); the amount of Form I of pBR322 DNA diminishes gradually, whereas that of Form II increases. Under comparable experimental conditions, complex 2 exhibits more effective DNA cleavage activity than complex 1. In order to identify the nature of the reactive species that are responsible for the photo-activated cleavage of the plasmid DNA, we further investigated the influence of different potentially inhibiting agents. In the case of complex 1 (Figure 7), studies with the single oxygen quencher histidine were carried out and the plasmid cleavage was inhibited (lane 2), which confirmed that the singlet oxygen was involved in the cleavage. At the same time, in the presence of different hydroxyl radical scavengers such as DMSO (lane 3), ethanol (lane 4) and sodium formate (lane 5), different degrees of inhibition in the photo-induced cleavage of the plasmid by complex 1 were also observed. This indicates that hydroxyl radical also plays a significant role in the photocleavage mechanism for 1, and the photoreduction of ReO complexes with concomitant hydroxide oxidation is an important step in the DNA cleavage reaction [38].


Synthesis, Characterization, DNA Binding, and Photocleavage Activity of Oxorhenium (V) Complexes with alpha-Diimine and Quinoxaline Ligands.

Mitsopoulou CA, Dagas C - Bioinorg Chem Appl (2010)

Photoactivated cleavage of pBR 322 DNA in the presence of 20 μM of complex 1 and different inhibitors after irradiation at λ > 400 nm for 60 minutes. Lane 0, DNA control; lane 1, no inhibitor; lanes 2–6: (2) histidine (5 mM), (3) DMSO (0.2 M), (4) ethanol (0.2 M), (5) sodium formate (5 mM).
© Copyright Policy - open-access
Related In: Results  -  Collection

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fig7: Photoactivated cleavage of pBR 322 DNA in the presence of 20 μM of complex 1 and different inhibitors after irradiation at λ > 400 nm for 60 minutes. Lane 0, DNA control; lane 1, no inhibitor; lanes 2–6: (2) histidine (5 mM), (3) DMSO (0.2 M), (4) ethanol (0.2 M), (5) sodium formate (5 mM).
Mentions: The ability of complex 1 to cleave DNA upon irradiation was determined by agarose gel electrophoresis [38]. When circular plasmid DNA in the presence of an inorganic molecule is subject to electrophoresis, relatively fast migration will be observed for the intact supercoil form (Form I). If scission occurs on one strand (nicking), the supercoil will relax to generate a slower-moving open circular form (Form II). If both strands are cleaved, a linear form (Form III) that migrates between Forms I and II will be generated [38]. Figure 6 shows gel electrophoresis separation of pBR 322 DNA after incubation with complex 1 and irradiation by visible light (λ > 400 nm) for 1 hour. Complex 1 exhibited concentration-dependent single-strand cleavage of supercoiled Form I into nicked Form II. Control experiment (lane 0) suggests that untreated DNA does not show any cleavage upon irradiation, with increasing concentration of 1 (lanes 1–3); the amount of Form I of pBR322 DNA diminishes gradually, whereas that of Form II increases. Under comparable experimental conditions, complex 2 exhibits more effective DNA cleavage activity than complex 1. In order to identify the nature of the reactive species that are responsible for the photo-activated cleavage of the plasmid DNA, we further investigated the influence of different potentially inhibiting agents. In the case of complex 1 (Figure 7), studies with the single oxygen quencher histidine were carried out and the plasmid cleavage was inhibited (lane 2), which confirmed that the singlet oxygen was involved in the cleavage. At the same time, in the presence of different hydroxyl radical scavengers such as DMSO (lane 3), ethanol (lane 4) and sodium formate (lane 5), different degrees of inhibition in the photo-induced cleavage of the plasmid by complex 1 were also observed. This indicates that hydroxyl radical also plays a significant role in the photocleavage mechanism for 1, and the photoreduction of ReO complexes with concomitant hydroxide oxidation is an important step in the DNA cleavage reaction [38].

Bottom Line: Experimental data suggest that complex 1 intercalates into the DNA base pairs.Upon irradiation, complex 1 was found to promote the cleavage of plasmid pBR 322 DNA from supercoiled form I to nicked form II.The mechanism of the DNA cleavage by complex 1 was also investigated.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Inorganic Chemistry, Department of Chemistry, University of Athens, Panepistimiopolis, Zografou, Athens 157 71, Greece.

ABSTRACT
The complex [ReOCl(3)pq] (1) (where pq = 2-(2'pyridyl)quinoxaline) has been synthesized and fully characterized by UV-Vis, FTIR, 1 and 2D NMR, and cyclic voltammetry (CV). The DNA-binding properties of the complex 1 as well as of the compounds [ReOCl(3)bpy] (2), [ReOCl(3)phen] (3), and pq (4) were investigated by UV-spectrophotometric (melting curves), CV (cyclic voltammetry), and viscosity measurements. Experimental data suggest that complex 1 intercalates into the DNA base pairs. Upon irradiation, complex 1 was found to promote the cleavage of plasmid pBR 322 DNA from supercoiled form I to nicked form II. The mechanism of the DNA cleavage by complex 1 was also investigated.

No MeSH data available.