title: Structures, spectra, and DNA-binding properties of mixed ligand copper(II) complexes of iminodiacetic acid: the novel role of diimine co-ligands on DNA conformation and hydrolytic and oxidative double strand DNA cleavage.
abstract: The coordination geometry around copper(II) in [Cu(imda)(phen)(H2O)] (1) (H2imda = iminodiacetic acid, phen = 1,10-phenanthroline) is described as distorted octahedral while those in [Cu(imda)(5,6-dmp)] (2) (5,6-dmp = 5,6-dimethyl-1,10-phenanthroline) and [Cu(imda)(dpq)] (3) (dpq = dipyrido-[3,2-d:2',3'-f]-quinoxaline) as trigonal bipyramidal distorted square-based pyramidal with the imda anion facially coordinated to copper(II). Absorption spectral (Kb: 1, 0.60+/-0.04x10(3); 2, 3.9+/-0.3x10(3); 3, 1.7+/-0.5x10(4) M(-1)) and thermal denaturation studies (deltaTm: 1, 5.70+/-0.05; 2, 5.5+/-10; 3, 10.6+/-10 degrees C) and viscosity measurements indicate that 3 interacts with calf thymus DNA more strongly than 1 and 2. The relative viscosities of DNA bound to 1 and 3 increase while that of DNA bound to 2 decreases indicating formation of kinks or bends and/or conversion of B to A conformation as revealed by the decrease in intensity of the helicity band in the circular dichroism spectrum of DNA. While 1 and 3 are bound to DNA through partial intercalation, respectively, of phen ring and the extended planar ring of dpq with DNA base stack, the complex 2 is involved in groove binding. All the complexes show cleavage of pBR322 supercoiled DNA in the presence of ascorbic acid with the cleavage efficiency varying in the order 3 > 1 > 2. The highest oxidative DNA cleavage of dpq complex is ascribed to its highest Cu(II)/Cu(I) redox potential. Oxidative cleavage studies using distamycin reveal minor groove binding for the dpq complex but a major groove binding for the phen and 5,6-dmp complexes. Also, all the complexes show hydrolytic DNA cleavage activity in the absence of light or a reducing agent with cleavage efficiency varying in the order 1 > 3 > 2.
authors.affiliation: School of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, Tamilnadu, India.
authors.forename: Balaraman
authors.initials: B
authors.lastname: Selvakumar
authors.forename: Venugopal
authors.initials: V
authors.lastname: Rajendiran
authors.forename: Palanisamy
authors.initials: P
authors.lastname: Uma Maheswari
authors.forename: Helen
authors.initials: H
authors.lastname: Stoeckli-Evans
authors.forename: Mallayan
authors.initials: M
authors.lastname: Palaniandavar
mesh_terms: D001667:Binding, Competitive; D002614:Chelating Agents / Q000737:chemistry; D002942:Circular Dichroism; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004249:DNA Damage; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D006868:Hydrolysis; D007098:Imino Acids / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D009942:Organometallic Compounds / Q000737:chemistry; D010084:Oxidation-Reduction; D010618:Phenanthrolines / Q000737:chemistry; D011810:Quinoxalines / Q000737:chemistry; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D044366:Transition Temperature; D014783:Viscosity
chemical_list: D002614:Chelating Agents; D007098:Imino Acids; D009942:Organometallic Compounds; D010618:Phenanthrolines; D011810:Quinoxalines; C460959:dipyridoquinoxaline copper(II) complex; D003300:Copper; D004247:DNA; C025205:1,10-phenanthroline; C008109:iminodiacetic acid