A Trinuclear Copper(II) Complex of 2,4,6-Tris(di-2-pyridylamine)-1,3,5-triazine Shows Prominent DNA Cleavage Activity

DNA binding studies of new valine derived chiral complexes of tin(IV) and zirconium(IV)

Valine derived chiral complexes of SnCl4 (1) and ZrCl4 (2) were designed as potent antitumor agents. These complexes were characterized by elemental analysis, IR, 1H NMR, 119Sn NMR and ESI mass spectroscopy. In vitro binding studies of complexes 1 and 2 under physiological conditions at room temperature with CT-DNA were carried out employing UV-vis absorption titration, fluorescence studies and viscosity measurements. The extent of binding was quantified by Kb values of complexes 1 and 2 which were found to be 1.97×10(4) and 1.17×10(3) M(-1), respectively, suggesting that complex 1 has significantly greater DNA binding propensity in contrast to the complex 2. The mode of action at the molecular level was ascertained by the interaction of complex 1 with 5'GMP and 5'TMP which revealed that complex 1 binds via electrostatic mode with the oxygen of the negatively charged surface phosphate group of the DNA helix. The supercoiled pBR322 plasmid DNA cleavage activity of complex 1 was ascertained by gel electrophoresis assay.

A mechanistic approach for the DNA binding of chiral enantiomeric L- and D-tryptophan-derived metal complexes of 1,2-DACH: cleavage and antitumor activity

A new chiral series of potential antitumor metal-based complexes 1-3(a and b) of L- and D-tryptophan have been synthesized and thoroughly characterized. Both enantiomers of 1-3 bind DNA noncovalently via phosphate interaction with slight preference of metal center for covalent coordination to nucleobases. The K(b) values of L-enantiomer, however, possess higher propensity for DNA binding in comparison with the D-enantiomeric analogs. The relative trend in K(b) values is as follows: 2(a) > 2(b) > 3(a) > 1(a) > 3(b) > 1(b). These observations together with the findings of circular dichoric and fluorescence studies reveal maximal potential of L-enantiomeric form of copper complex to bind DNA, thereby exerting its therapeutic effect. The complex 2a exhibits a remarkable DNA cleavage activity with pBR322DNA in the presence of different activators such as H(2) O(2) , ascorbic acid, 3-mercaptopropionic acid, and glutathione, suggesting the involvement of active oxygen species for the DNA scission. In vitro anticancer activity of complexes 1-3(a) were screened against 14 different human carcinoma cell lines of different histological origin, and the results reveal that 2a shows significant antitumor activity in comparison with both 1a and 3a and is particularly selective for MIAPACA2 (pancreatic cancer cell line).

Evaluation of a Schiff base copper complex compound as potent anticancer molecule with multiple targets of action

Copper is a biologically relevant metal as it is associated with various biomolecules related to essential physiological activities. Anticancer compounds with copper as a metal center is hypothesized to be less toxic and more potent. In the present study we have tested the efficacy of a family of Schiff base copper complexes of which the best compound was [Cu(Pyimpy)Cl(2)] where Pyimpy is a tridentate ligand containing two pyridine and one imine nitrogen donor. [Cu(Pyimpy)Cl(2)], represented as CuP1, was checked for its anticancer potential. The IC(50) value of CuP1 was found to be 4.29±0.42, 6.34±0.58 and 5.32±0.38 μM in MCF-7, PC3 and HEK 293 cells respectively. It was found to cause in vitro DNA fragmentation in comet assays and acridine orange staining of MCF 7 cells. CuP1 was further tested on rat breast tumor models and was found to inhibit tumor growth. It caused apoptosis within the tumor by the up regulation of caspase pathway and inhibition of the Akt, matrix metalloproteinase 9 and α-methyl acyl CoA racemase. Antioxidant enzymes which in general results in drug resistant condition in tumor tissues were significantly inhibited by this copper compound (P<0.05). Further, CuP1 did not show any prominent systemic toxicity. These results indicate that CuP1 can be a potential anticancer agent and further investigation will reveal more about its mode of action.

Synthesis and characterization of glucose-bis(pyrazole)-Cu(II)/Ni(II) complexes and their in vitro DNA binding studies

The D-glucose-bis pyrazolyl complexes of Cu(II) 1 and Ni(II) 2 were synthesized and characterized by elemental analysis, molar conductance measurements and spectroscopic methods. The solution structures of the complex have been assessed to square pyramidal using electronic absorption and electronic paramagnetic resonance (EPR) spectroscopy. The interaction of 1 and 2 with calf thymus DNA (CT DNA) has been carried out by absorption, emission, viscometric and electrochemical methods. The intrinsic binding constant K(b) was determined as 13.4x10(5) M(-1), 4.5x10(5) M(-1) for 1 and 2, respectively suggestive of strong binding of complexes with DNA. Furthermore, higher value of K(b) for 1 implies that this complex interacts more strongly with CT DNA in comparison to 2. The quenching constant "K" of 1 and 2 obtained from emission spectral methods was 1.33, 0.55, respectively. Complex 1 hydrolytically cleaved pBR322 supercoiled DNA in absence of an activating agent. The enhanced cleavage of pBR322 DNA was observed in presence of ascorbic acid as a reducing agent, 1 also displays efficient photonuclease activity through double strand DNA breaks when irradiated at 365 nm through mechanistic pathway involving hydroxyl radicals. In addition to the above binding studies, an in vitro binding study of complex 1 with protein human serum albumin (HSA), tyrptophan and mixtures of HSA, L-tryptophan with CT DNA was carried out. The in vitro "binding study" also supports that 1 shows higher binding affinity towards CT DNA.

Synthesis and biophysical studies of bis-macrocyclic cobalt/copper(II) complexes having a pyridine spacer with CT DNA and 5'-GMP

New bis-macrocyclic complexes of Co(III), 1, Ni(II), 2, and Cu(II), 3, containing pyridyl bridges between 13-membered macrocyclic subunits, have been synthesized via an in situ one-pot template condensation reaction (IOPTCR). The proposed structures of these new dinuclear complexes are consistent with the data obtained from elemental analysis, molar conductance, IR, EPR, UV/VIS, (1)H- and 13C-NMR, and ESI-MS. The complexes 2 and 3 possess square-planar geometry with four secondary N-atoms coordinated to the metal ion, while complex 1 reveals octahedral geometry in solution due to coordinated H(2)O molecules. DNA-Binding properties of the complexes 1 and 3 were investigated by absorption and emission titrations, cyclic voltammetry, and viscosity measurements. Complexes 1 and 3 are strong DNA binders with binding constants, K(b), of 1.64 x 10(5) and 2.05 x 10(5) M(-1), respectively. Hyperchromism, decrease in emission intensity of DNA-bound ethidium bromide (EB), and changes observed in the viscosity and cyclic voltammograms in the presence of added metal complexes reveals that the complexes bind to DNA predominantly by electrostatic attraction, substantiated by absorption titration with 5'-GMP.

Molecular oxygen and sulfur reactivity of a cyclotriveratrylene derived trinuclear copper(I) complex

Our continuing efforts into developing copper coordination chemistry relevant to dioxygen-processing copper proteins has led us to design and synthesize a cyclotriveratrylene (CTV)-based trinucleating ligand, CTV-TMPA, which employs tetradentate tris(2-pyridylmethyl)-amine chelates (TMPA) for their copper ion binding sites. Binding of three copper ions per CTV-TMPA unit was established by various chemical and spectroscopic methods such as UV-vis and resonance Raman (rR) spectroscopies. The following complexes were observed: A tricopper(I) complex [(CTV-TMPA)Cu(I)(3)](3+) (1), a CO adduct [(CTV-TMPA)Cu(I)(3)(CO)(3)](3+) (1-CO; nu(C=O) = 2094 cm(-1)), a triphenylphosphine adduct [(CTV-TMPA)Cu(I)(3)(PPh(3))(3)](3+) (1-PPh(3)), a tricopper(II) complex [(CTV-TMPA)Cu(II)(3)](3+) (1-Ox), and its tris-monochloride or tris-monobromide adducts. Also, introduction of dioxygen to the -80 degrees C solutions of 1 leads to O(2)-adducts, the first example of a synthetic copper complex which can stabilize a mononuclear Cu(II)-superoxo and dinuclear peroxo species simultaneously within one complex {[Cu] = 1.53 mM in THF: (mu-1,2-peroxo complex, lambda(max) = 543 (epsilon 9650) nm): nu(O-O) = 825 ((Delta(18)O(2)) = -47) cm(-1); nu(Cu-O) = 506 ((Delta(18)O(2)) = -26) cm(-1): (superoxo complex, lambda(max) = 427 (epsilon 3150) nm): nu(O-O) = 1129 ((Delta(18)O(2)) = -60) cm(-1); nu(Cu-O) = 463 ((Delta(18)O(2)) = -27) cm(-1)}. Elemental sulfur reacts reversibly with 1 leading to a (proposed) hexanuclear species [{(CTV-TMPA)Cu(II)(3)}(2)(mu-1,2-S(2)(2-))(3)](6+) (1-S) {lambda(max) = 544 (epsilon 7270) nm}, possessing one dicopper(II)-disulfide structural type: {THF solvent) nu(S-S) = 489 ((Delta(34)S) = -10) cm(-1); nu(Cu-S) = 307 ((Delta(34)S) = -5) cm(-1)}. Derivation of spectroscopic, structural, and chemical conclusions were aided by the study of a close mononuclear analogue with one pyridyl group of the TMPA parent possessing a 6-CH(2)OCH(3) substituent, this being part of the CTV-TMPA architecture.

Synthesis, X-ray crystal structures, magnetism, and DNA cleavage properties of copper(II) complexes with 1,4-tpbd ligand

Four new copper(II) complexes, [Cu(1,4-tpbd)Br(2)] (), [Cu(2)(1,4-tpbd)(H(2)O)(4)](ClO(4))(4) (), [Cu(2)(1,4-tpbd)(1,10-phen)(2)(DMF)(2)](ClO(4))(4) () and [Cu(2)(1,4-tpbd)(2,2'-bpy)(2)(ClO(4))(2)](ClO(4))(2) (), [1,4-tpbd = N,N,N',N'-tetrakis(2-pyridylmethyl)benzene-1,4-diamine], have been synthesized to serve as artificial nucleases. Single crystal X-ray diffraction reveals that the copper(II) atom has a distorted intermediate between square pyramidal and trigonal bipyramidal configuration for and a distorted square pyramidal geometry for , while a distorted octahedral environment for and . Variable-temperature magnetic susceptibility studies (2-300 K) indicate the existence of antiferromagnetic coupling between the copper(II) ions in complex . The interactions of the four complexes with calf thymus DNA (CT-DNA) have been investigated by UV absorption, fluorescent spectroscopy and cyclic voltammetry, and the modes of CT-DNA binding for the complexes have been proposed. In the absence of external agents, supercoiled plasmid DNA cleavage by the complexes was performed under aerobic conditions, the influence on the DNA cleavage process of different complex concentrations, reaction times was also studied. The DNA cleavage mechanisms were demonstrated with radical scavengers and anaerobic conditions, indicating all complexes cleaved pBR322 DNA in 50 mM Tris-HCl/18 mM NaCl buffer (pH = 7.2) at 37 degrees C through a hydrolytic process. In the four copper(II) complexes, complex showed highest cleavage activity with the pseudo-Michaelis-Menten kinetic parameters k(cat) = 4.23 h(-1) and K(m) = 2.4 x 10(-5) M.

Metallohelical triangles for selective detection of adenosine triphosphate in aqueous media

Metallohelical triangles consisting of chromophore units and hydrogen-bonding trigger sites were prepared by modulating two tridentate N(2)O units containing amide groups within a central benzene ring at the meta sites, for the selective detection of adenosine trisphosphate in aqueous media over other ribonucleotides.

Interaction of rac-[Cu(diimine)3]2+ and rac-[Zn(diimine)3]2+ complexes with CT DNA: effect of fluxional Cu(II) geometry on DNA binding, ligand-promoted exciton coupling and prominent DNA cleavage

The complexes [Cu(phen)(3)](ClO(4))(2) 1, [Cu(5,6-dmp)(3)](ClO(4))(2) 2, [Cu(dpq)(3)](ClO(4))(2) 3, [Zn(phen)(3)](ClO(4))(2) 4, [Zn(5,6-dmp)(3)](ClO(4))(2) 5 and [Zn(dpq)(3)](ClO(4))(2) 6, where phen = 1,10-phenanthroline, 5,6-dmp = 5,6-dimethyl-1,10-phenanthroline and dpq = dipyrido[3,2-d:2',3'-f]quinoxaline, have been isolated, characterized and their interaction with calf thymus DNA studied by using a host of physical methods. The X-ray crystal structures of rac-[Cu(5,6-dmp)(3)](ClO(4))(2) and rac-[Zn(5,6-dmp)(3)](ClO(4))(2) have been determined. While 2 possesses a regular elongated octahedral coordination geometry (REO), 5 possesses a distorted octahedral geometry. Absorption spectral titrations of the Cu(II) complexes with CT DNA reveal that the red-shift (12 nm) and DNA binding affinity of 3 (K(b), 7.5 x 10(4) M(-1)) are higher than those of 1 (red-shift, 6 nm; K(b), 9.6 x 10(3) M(-1)) indicating that the partial insertion of the extended phen ring of dpq ligand in between the DNA base pairs is deeper than that of phen ring. Also, 2 with a fluxional Cu(II) geometry interacts with DNA (K(b), 3.8 x 10(4) M(-1)) more strongly than 1 suggesting that the hydrophobic forces of interaction of 5,6 methyl groups on the phen ring is more pronounced than the partial intercalation of phen ring in the latter with a static geometry. The DNA binding affinity of 1 is lower than that of its Zn(ii) analogue 4, and, interestingly, the DNA binding affinity 2 of with a fluxional geometry is higher than that of its Zn(II) analogue 5 with a spherical geometry. It is remarkable that upon binding to DNA 3 shows an increase in viscosity higher than that the intercalator EthBr does, which is consistent with the above DNA binding affinities. The CD spectra show only one induced CD band on the characteristic positive band of CT DNA upon interaction with the phen (1,4) and dpq (3,6) complexes. In contrast, the 5,6-dmp complexes 2 and 5 bound to CT DNA show exciton-coupled biphasic CD signals with 2 showing CD signals more intense than 5. The Delta-enantiomer of rac-[Cu(5,6-dmp)(3)](2+) 2 binds specifically to the right-handed B-form of CT DNA at lower ionic strength (0.05 M NaCl) while the Lambda-enantiomer binds specifically to the left-handed Z-form of CT DNA generated by treating the B-form with 5 M NaCl. The complex 2 is stabilized in the higher oxidation state of Cu(II) more than its phen analogue 1 upon binding to DNA suggesting the involvement of electrostatic forces in DNA interaction of the former. In contrast, 3 bound to DNA is stabilized as Cu(I) rather than the Cu(II) oxidation state due to partial intercalative interaction of the dpq ligand. The efficiencies of the complexes to oxidatively cleave pUC19 DNA vary in the order, 3> 1 >> 2 with 3 effecting 100% cleavage even at 10 microM complex concentration. However, interestingly, this order is reversed when the DNA cleavage is performed using H(2)O(2) as an activator and the highest cleavage efficiency of 2 is ascribed to its electrostatic interaction with the exterior phosphates of DNA.