Synthesis and copper-mediated nuclease activity of a tetracationic tris(2,2'-bipyridine) ligand.
We report herein the synthesis of a novel tetracationic tris(2,2'-bipyridine) ligand 4. We show that this ligand metalated with copper(II), and in the presence of ascorbate as a reducing agent, strongly damages pUC18 plasmid DNA. Copper complex formation was demonstrated by ESI-MS (electrospray ionization-mass spectrum) at a 1:3 ligand to metal ratio. Binding of both 4 and its copper(II) complex to CT-DNA (calf thymus DNA) was characterized by viscosimetry, thermal denaturation and fluorescence-based competition assays. The viscosimetric data indicated that 4 and its copper(II) complex bind DNA through partial intercalation and thermal denaturation studies revealed a significant increase of duplex DNA stability in the presence of these species (DeltaT(m)=16.4 and 18.3 degrees C, respectively). Moreover, 4 and its copper(II) complex were found to effectively compete with ethidium bromide for the intercalative binding sites of DNA. Overall, the copper(II)-4 complex constitutes a very efficient DNA cleaving agent in the presence of ascorbate. Experiments with scavengers further suggest that the generation of Cu(I), hydrogen peroxide, superoxide, hydroxyl radical and singlet oxygen-like species contributes to the DNA breakage induced by the Cu(II) complex of 4.
Arias
María-Selma
MS
Departamento de Química Orgánica, Universidad de Alcalá, Madrid, Spain.
González-Alvarez
Marta
M
Fernández
María-José
MJ
Lorente
Antonio
A
Alzuet
Gloria
G
Borrás
Joaquín
J
D015082:2,2'-Dipyridyl / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D000818:Animals; D003300:Copper / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D053837:DNA Cleavage; D003851:Deoxyribonucleases / Q000138:chemical synthesis / Q000737:chemistry*; D008024:Ligands; D021241:Spectrometry, Mass, Electrospray Ionization
C544131:5,5'-bis((dimethyl(2-(dimethyl((5'-methyl-2,2'-bipyridin-5-yl)methyl)ammonio)ammonio)methyl)-2,2'-bipyridinyl tetrabromide); D008024:Ligands; D015082:2,2'-Dipyridyl; D003300:Copper; D004247:DNA; C427203:calf thymus DNA; D003851:Deoxyribonucleases