DNA binding and cleavage properties of certain tetrammine ruthenium(II) complexes of modified 1,10-phenanthrolines - effect of hydrogen-bonding on DNA-binding affinity

Maheswari, P. Uma ; Palaniandavar, M. (2004) DNA binding and cleavage properties of certain tetrammine ruthenium(II) complexes of modified 1,10-phenanthrolines - effect of hydrogen-bonding on DNA-binding affinity Journal of Inorganic Biochemistry, 98 (2). pp. 219-230. ISSN 0162-0134

Full text not available from this repository.

Official URL: http://linkinghub.elsevier.com/retrieve/pii/S01620...

Related URL: http://dx.doi.org/10.1016/j.jinorgbio.2003.09.003

Abstract

A series of ruthenium(II) mixed ligand complexes of the type [Ru(NH3)4(L)]2+, where L=imidazo[4,5-f][1,10]phenanthroline (ip), 2-phenylimidazo[4,5-f][1,10]phenanthroline (pip), 2-(2-hydroxyphenyl)imidazo[4,5-f][1,10]phenanthroline (hpip), 4,7-diphenyl-1,10-phenanthroline (dip), naphtha[2,3-a]dipyrido[3,2-h:2',3'-f]phenazine-5,18-dione (qdppz), 5,18-dihydroxynaphtho[2,3-a]dipyrido[3,2-h:2',3'-f]phenazine (hqdppz), have been isolated and characterized. The interaction of these complexes with calf thymus DNA (CT DNA) has been explored by using absorption, emission, and circular dichroic spectral methods, thermal denaturation studies and viscometry. All these studies suggest the involvement of the modified phenanthroline 'face' rather than the ammonia 'face' of the complexes in DNA binding. An intercalative mode of DNA binding, which involves the insertion of the modified phenanthroline ligands in between the base pairs, is suggested. The results from absorption spectral titration and circular dichroism (CD), thermal denaturation and viscosity experiments indicate that the qdppz and hqdppz complexes (Kb~106 and ΔTm=11-13 ° C) bind more avidly than the ip, pip and hpip complexes (Kb~105, ΔTm=6-8 ° C). Intramolecular hydrogen bonding in the hpip and hqdppz complexes increases the surface area of the intercalating diimines and enhances the DNA binding affinity substantially. The ammonia co-ligands of the complexes are possibly involved in hydrogen bonding with the intrastrand nucleobases to favour intercalation of the extended aromatic ligands. Circular dichroism spectral studies reveal that all the complexes effect certain structural changes on DNA duplex; [Ru(NH3)4(ip)]2+ induces a B to A transition while [Ru(NH3)4(qdppz)]2+ a B to ψ conformational change on CT DNA. Cleavage efficiency of the complexes were determined using pBR322 supercoiled plasmid DNA. All the complexes, except hqdppz complex, promote the cleavage of supercoiled plasmid (form I) to relaxed circular form (form II).

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:DNA Binding; Mixed Ligand Ru(II) Complexes; Extended Planar Aromatic Diimines; A Form of CT DNA; Intercalation
ID Code:30872
Deposited On:27 Dec 2010 08:03
Last Modified:09 Jun 2011 10:21

Repository Staff Only: item control page