Limits...
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.


Thermal denaturation curves of C.T.-DNA in the presence of the complex ReOCl3pq before and after irradiation at increasing molar ratios r,  pH = 7.0.
© Copyright Policy - open-access
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2902146&req=5

fig3: Thermal denaturation curves of C.T.-DNA in the presence of the complex ReOCl3pq before and after irradiation at increasing molar ratios r, pH = 7.0.

Mentions: The study of the melting curves of C.T.-DNA indicates that the interaction of DNA with the oxorhenium (V) complexes 1 and 2, leads to the stabilization of the double helix in proportion to the ratio r = [ReOCl3(α-diimine)]/[CT-DNA] (Table 2). The stabilization can be assumed by the raising of the Tm which is finally observed in analogy with r, reaching at +10.85°C for 1 at r = 0.05 and pH = 7.0 (Figure 3). In the presence of all three complexes (1–3) the thermal stabilization of CT-DNA is observed in the series 1 > 2 > 3. Moreover, the reduction of the final hyperchromicity and the decrease of the slope of melting curves (increase of the transition) provide a strong evidence of the interaction which leads to DNA helix stabilization [33]. “Premelting effects” of the double helix which could be caused by the binding of oxorhenium (V) complexes, probably via allosteric effects, are rather not taking place since they would result in DNA helix destabilization [34]. The reversibility measurements of the 1 and 3 binding to CT-DNA (cooling the samples and reheating them) showed completely super-imposable results onto the first heating scans. This suggests that the species present in the solution of 1 or 3, do not alone inhibit reannealing, associating irreversibly with the single strand which is similar to the results obtained for the free ligands. Although the complex [ReOCl3phen] is isostructural to the complexes [ReOCl3pq] and [ReOCl3bpy], it presents different behaviour when interacts with CT-DNA. In both buffered pH 7.0 and pH 5.0 solutions, at all ratios, the melting points of CT-DNA are almost the same with free CT-DNA. Identical results have been obtained when CT-DNA was treated with all free ligands under investigation. So we can conclude that there is almost no interaction between the complex [ReOCl3phen] and CT DNA. No observable changes are measured after irradiation.


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)

Thermal denaturation curves of C.T.-DNA in the presence of the complex ReOCl3pq before and after irradiation at increasing molar ratios r,  pH = 7.0.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2902146&req=5

fig3: Thermal denaturation curves of C.T.-DNA in the presence of the complex ReOCl3pq before and after irradiation at increasing molar ratios r, pH = 7.0.
Mentions: The study of the melting curves of C.T.-DNA indicates that the interaction of DNA with the oxorhenium (V) complexes 1 and 2, leads to the stabilization of the double helix in proportion to the ratio r = [ReOCl3(α-diimine)]/[CT-DNA] (Table 2). The stabilization can be assumed by the raising of the Tm which is finally observed in analogy with r, reaching at +10.85°C for 1 at r = 0.05 and pH = 7.0 (Figure 3). In the presence of all three complexes (1–3) the thermal stabilization of CT-DNA is observed in the series 1 > 2 > 3. Moreover, the reduction of the final hyperchromicity and the decrease of the slope of melting curves (increase of the transition) provide a strong evidence of the interaction which leads to DNA helix stabilization [33]. “Premelting effects” of the double helix which could be caused by the binding of oxorhenium (V) complexes, probably via allosteric effects, are rather not taking place since they would result in DNA helix destabilization [34]. The reversibility measurements of the 1 and 3 binding to CT-DNA (cooling the samples and reheating them) showed completely super-imposable results onto the first heating scans. This suggests that the species present in the solution of 1 or 3, do not alone inhibit reannealing, associating irreversibly with the single strand which is similar to the results obtained for the free ligands. Although the complex [ReOCl3phen] is isostructural to the complexes [ReOCl3pq] and [ReOCl3bpy], it presents different behaviour when interacts with CT-DNA. In both buffered pH 7.0 and pH 5.0 solutions, at all ratios, the melting points of CT-DNA are almost the same with free CT-DNA. Identical results have been obtained when CT-DNA was treated with all free ligands under investigation. So we can conclude that there is almost no interaction between the complex [ReOCl3phen] and CT DNA. No observable changes are measured after irradiation.

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.