Interactions with herring sperm DNA and biological studies of sparfloxacin drug‐based copper(II) compounds

Copper(II) complexes of the type [Cu(SPF)(Lⁿ)Cl] (where SPF is sparfloxacin and Lⁿ = substituted terpyridines) were synthesized and found to have a distorted octahedral geometry. Superoxide dismutase‐like activity of the complexes was measured using a nitroblue tetrazolium/reduced nicotinamide adenine dinucleotide/phenazine methosulfate system and expressed in terms of the concentration of complex which terminates the formation of formazan by 50% (IC₅₀ value), which was found to range from 0.572 to 1.522 µm . Interactions of the complexes with herring sperm DNA were studied by absorption titration, viscosity measurement and gel electrophoresis under physiological conditions. The antimicrobial efficiency of the complexes was tested against five different microorganisms and showed good biological activity. All the complexes showed good cytotoxic activity, with LC₅₀ values ranging from 4.01 to 9.64 µg ml^?1. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthetic and antimicrobial studies on new gold(I) complexes of imidazolidin‐2‐ylidenes

Six new 1,3‐diorganylimidazolidin‐2‐ylidene (NHC) gold(I) complexes of the type [Au(NHC)₂]⁺ (1–6), were synthesized by reacting [AuCl(PPh)₃] with 1,3‐dimesitylimidazolidin‐2‐ylidene or bis(1,3‐dialkylimidazolidin‐2‐ylidene). The complexes 1–6 were fully characterized by elemental analyses and spectroscopic data. The placement of mesityl or para‐substituted benzyl groups on the nitrogen atoms of the ring of the complexes leads to the particularly active antibacterial agents evaluated in this work. It is worth noting that the p‐methoxybenzyl derivative (2) inhibited the growth of Pseudomona aeruginosa, Staphylococcus epidermidis, Staphylococcus aureus and Enterococcus faecalis with minimum inhibitory concentration (MIC) values of 3.12 µg ml^?1, 6.25 µg ml^?1, 3.12 µg ml^?1 and 3.12 µg ml^?1 respectively. In contrast, the analogous p‐dimethylaminobenzyl derivative (3) is effective only against Escherichia coli (MIC = 3.12 µg ml^?1). Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis,structural characterization and DNA binding affinity of new bioactive nano‐sized transition metal complexes with sulfathiazole azo dye for therapeutic applications

The azo dye ligand 4‐(5‐chloro‐2‐hydroxyphenylazo)‐N‐thiazol‐2‐ylbenzenesulfonamide (H₂L) formed by the coupling reaction of sulfathiazole and p‐chlorophenol was synthesized and characterized using elemental analysis and Fourier transform infrared (FT‐IR) as well as UV–visible spectra. Nano‐sized divalent Cu, Co, Ni, Mn and Zn complexes of the synthesized azo dye ligand were prepared and investigated using various spectroscopic and analytical techniques. Elemental and thermal analyses indicated the formation of the Cu(II), Ni(II) and Mn(II) complexes in a molar ratio of 1:2 (L:M) while Co(II) and Zn(II) complexes exhibited a 1:1 (M:L) ratio. FT‐IR spectral studies confirmed the coordination of the ligand to the metal ions through the phenolic hydroxyl oxygen, azo nitrogen, sulfonamide oxygen and/or thiazole nitrogen. The geometric arrangements around the central metal ions were investigated applying UV–visible and electron spin resonance spectra, thermogravimetric analysis and molar conductance measurements. X‐ray diffraction patterns revealed crystalline nature of H₂L and amorphous nature of all synthesized complexes. Transmission electron microscopy images confirmed nano‐sized particles and their homogeneous distribution over the complex surface. Antibacterial, antifungal and antitumour activities of the investigated complexes were screened compared with familiar standard drugs to confirm their potential therapeutic applications. The Cu(II) complex showed IC₅₀ of 3.47 μg ml^?1 (5.53 μM) against hepatocellular carcinoma cells, which means that it is a more potent anticancer drug compared with the standard cisplatin (IC₅₀ = 3.67 μg ml^?1 (12.23 μM)). Furthermore, the Co(II), Ni(II), Cu(II) and Zn(II) complexes displayed IC₅₀ greater than that of an applied standard anticancer agent (5‐flurouracil) towards breast carcinoma cells. Hence, these complexes can be considered as promising anticancer drugs. The mode of binding of the complexes with salmon serum DNA was determined through electronic absorption titration and viscosity studies.     

Cytotoxic activity of two polyaspartamide‐ based monoamineplatinum(II) conjugates against the HeLa cancer cell line

In this screening study in vitro, two polymer‐conjugated, square‐planar platinum(II) complexes bound to the carrier via a single primary amine ligand were tested for antineoplastic activity against the HeLa human cervical epithelioid carcinoma cell line. In the first of these conjugates, 1‐Pt , the spacer connecting the metal complex with the carrier backbone is a short oligo(ethylene oxide) segment, whereas a long poly(ethylene oxide) chain represents the spacer unit in the second conjugate, 2‐Pt . IC₅₀ data, expressed as conjugate concentration at 50% cell growth inhibition, are 48 µg Pt ml⁻¹ for 1‐Pt and 120 µg Pt ml⁻¹ (estimated) for 2‐Pt , the long tether in the latter conjugate presumably causing retarded enzymic release and lysosomal membrane crossing of the monomeric complex. The IC₅₀ value of 1‐Pt is close to that (44 µg Pt ml⁻¹) of a similar conjugate of an earlier investigation, 3‐Pt , in which the metal is chelated by two carrier‐attached, cis‐oriented amino groups in conformance with the ligand arrangement in cisplatin. It thus appears that, in the carrier‐bound state, both monoamine‐ and cis‐diamine‐coordinated platinum(II) complexes of suitable structures may well show similar biological performance patterns. Copyright­© 1999 John Wiley & Sons, Ltd.     

Synthesis,spectral characterization,electrochemistry and catalytic activities of Cu(II) complexes of bifunctional tridentate Schiff bases containing O?N?O donors

Paramagnetic copper(II) complexes of the type [Cu(PPh₃)(L)] (where L = bifunctional tridentate Schiff bases) were synthesized from the reaction of anthranillic acid with salicylaldehyde (H₂L¹), 2‐hydroxy‐1‐naphthaldehyde (H₂L²), o‐hydroxyacetophenone (H₂L³) and o‐vanillin (H₂L⁴) with monomeric metal precursor [CuCl₂(PPh₃)₂]. The obtained complexes were characterized by elemental analysis, magnetic susceptility and spectroscopic methods (FT‐IR, UV–vis and EPR and cyclic voltammetry). EPR and redox potential studies have been carried out to elucidate the electronic structure, nature of metal–ligand bonding and electrochemical features. EPR spectra exhibit a four line pattern with nitrogen super‐hyperfine couplings originating from imine nitrogen atom. These planar complexes possess a significant amount of tetrahedral distortion leading to a pseudo‐square planar geometry, as is evidenced from EPR properties. Cyclic voltammograms of all the complexes display quasireversible oxidations, Cu(III)? Cu(II), in the range 0.31–0.45 V and reduction peaks, Cu(II)? Cu(I),in the range ?0.29 to ?0.36 V, involving a large geometrical change and irreversible. The observed redox potentials vary with respect to the size of the chelate ring of the Schiff base ligands. Further, the catalytic activity of all the complexes has been found to be high towards the oxidation of alcohols into aldehydes and ketones in the presence of N‐methylmorpholine‐N‐oxide as co‐oxidant. The formation of high valent Cu^IV?O oxo species as a catalytic intermediate is proposed for the catalytic process. Copyright © 2008 John Wiley & Sons, Ltd.     

Application of Multivariate Calibration Methods for the Simultaneous Multiwavelength Spectrophotometric Determination of Fe(II), Cu(II), Zn(II), and Mn(II) in Mixtures

Abstract

A sensitive method for the simultaneous spectrophotometric determination of Fe(II), Cu(II), Zn(II), and Mn(II) in mixtures has been developed with the aid of multivariate calibration methods, such as classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS). The method is based on the spectral differences of the analytes in their complexation reaction with 4‐(2‐pyridylazo)‐resorcinol (PAR) and the use of full spectra with wavelengths in the range of 300–600 nm. It was found that both the spectral positive and negative bands obtained against the PAR blank, are proportional to the concentration for each metal complex. The obtained linear calibration concentration ranges are 0.025–0.6, 0.05–0.8, 0.025–0.8, and 0.05–0.8 µg ml^?1 for Fe(II), Cu(II), Zn(II), and Mn(II), respectively, and the LODs for the four metal ions were found to be approximately 1–3×10^?2 µg ml^?1. The proposed method was applied to a verification set of synthetic mixtures of these four metal ions, with models built in three different wavelength ranges, i.e., 300–450, 450–600, and 300–600 nm, corresponding to the positive, negative bands and their combinations, respectively. It was shown that the PLS model for the 300–600 nm range gave the best results (RPE_T=6.9% and average recovery ～100%; cf. PCR: RPE_T=9.5% and average Recovery ～110%). This method was also successfully applied for the determination of the four metal ions in pharmaceutical preparations, chicken feedstuff, and water samples.     

In vitro biomolecular interaction studies and cytotoxic activities of copper(II) and zinc(II) complexes bearing ONS donor thiosemicarbazones

Among all the bio‐metals, zinc and copper derivatives of ONS donor thiosemicarbazone have aroused great interest because of their potential biological applications. Multisubstituted thiosemicarbazone ligand H₂dspt (3,5‐dichlorosalicylaldehyde‐N⁴‐phenylthiosemicarbazone) derived new ternary complexes like [Zn(dspt)(phen)]?DMF ( 1 ) and [Cu(dspt)(phen)]?DMF ( 2 ), and another thiosemicarbazone, H₂dsct (3,5‐dichlorosalicylaldehyde‐N⁴‐cyclohexylthiosemicarbazone), derived [Cu(dsct)(bipy)]?DMF ( 3 ). These complexes have been characterized by elemental analysis (CHNS), Fourier transform infrared (FT‐IR), ultraviolet–visible (UV–Vis) and proton nuclear magnetic resonance (¹H‐NMR) spectra. The structures of the complexes were obtained by single‐crystal X‐ray diffraction analysis. Compounds 1 and 2 got crystallized in the monoclinic P2₁/c space group. The complexes showed interesting supramolecular interaction, which in turn stabilizes the complexes. The ground state electronic configurations of the complexes were studied using the B3LYP/LANL2DZ basis set, and ESP plots of complexes were investigated. The interaction of the complexes with calf thymus DNA (CT‐DNA) was studied using absorption and fluorescence spectroscopic methods. A UV study of the interaction of the complexes with calf thymus DNA (CT‐DNA) has shown that the complexes can effectively bind to CT‐DNA, and [Cu(dspt)(phen)]·DMF ( 2 ) exhibited the highest binding constant to CT‐DNA (K_b = 3.7 × 10⁴). Fluorescence spectral studies also indicated that Complex 2 binds relatively stronger with CT DNA through intercalative mode, exhibiting higher binding constant (K_q = 4.7 × 10⁵). The DNA cleavage result showed that the complexes are capable of cleaving the DNA without the help of any external agent. Molecular docking studies were carried out to understand the binding of complexes with the molecular target DNA. Complex 2 exhibited the highest cytotoxicity against human breast cancer cell line MD‐MBA‐231 (IC₅₀ = 23.93 μg/mL) as compared to Complex 1 (IC₅₀ = 44.40 μg/mL) .     

Synthesis,spectroscopic, and biological activities of two binuclear complexes [Cu(II)(1-phenylamidino-O-methylurea)2(H2O)]2(Cl2)2 and [Cu(II)(1-phenylamidino-O-i-butylurea)tmen]2(Cl2)2·2H2O

EPR spectra of two copper(II) binuclear complexes, [Cu(II)(1-phenylamidino-O-methylurea)₂(H₂O)]₂(Cl₂)₂ (1) and [Cu(II)(1-phenylamidino-O-i-butylurea)tmen]₂(Cl₂)₂?·?2H₂O (2), at room temperature showed fine structure transitions (ΔM _s?=?±1) and a very weak half-field signal corresponding to forbidden transitions (ΔM _s?=?±2). The spectrum of 1 showed disappearance of normal and half-field transitions when cooled to 77?K, suggesting antiferromagnetical coupling dicopper complex which is also supported by the low magnetic moments (µ _eff?=?1.64?B.M.). The isotropic exchange interaction constant J (41?cm^?1) for 2 indicated that interaction between the two spins of the binuclear complex is ferromagnetic, confirmed from the high magnetic moment value (µ _eff?=?2.25?B.M.). The binding of these complexes with calf thymus DNA suggested that these complexes interact with DNA by electrostatic or groove binding, not by intercalation. The two complexes have good antibacterial activity against tested bacteria responsible for urinary tract infection.     

Synthesis,characterization, DNA binding,photo-induced DNA cleavage,and antimicrobial activity of metal complexes of a Schiff base derived from bis(3-aminophenyl)malonamide

The peptide linkage Schiff base (H₂L) and its complexes have been synthesized and fully characterized by elemental analysis, UV–Vis, FTIR, ¹H-NMR, ¹³C-NMR, EPR, and FAB-mass spectra. The stoichiometry of the complexes is [ML] (where M = Cu(II), Co(II), Ni(II), Zn(II), and VO(IV)). All the complexes exhibit square-planar geometry except the vanadyl complex which has square-pyramidal geometry. Interactions of the complexes and free ligand with double-stranded calf thymus DNA (CT-DNA) are studied by UV-spectrophotometric, electrochemical, and viscosity measurements. The data suggest that all the complexes form adducts with DNA and distort the double helix by changing the base stacking. Vanadyl complex forms a weaker adduct to CT-DNA than other complexes, probably due to the square-pyramidal geometry. CT-DNA induces extensive distortion in the planarity of vanadyl complex as EPR spectral calculations reveal. The intrinsic binding constants (K _b) of [ZnL], [CuL], [CoL], and [NiL] are 1.1 × 10⁵, 1.4 × 10⁵, 0.8 × 10⁵, and 0.6 × 10⁵ M^?1, respectively. Photo-induced DNA cleavage indicates that all complexes cleave DNA effectively. Control DNA cleavage experiments using pUC19 supercoiled (SC) DNA and minor groove binder distamycin suggest major groove binding for the synthesized complexes. The antimicrobial results indicate that the complexes inhibit the growth of bacteria and fungi more than the free ligand.     

Antibacterial and Superoxide Dismutase Activity as Well as DNA Interactions of Ciprofloxacin‐Based Ternary Copper(II) Phenanthroline Complexes

. Five neutral mixed‐ligand mononuclear square‐pyramidal copper(II) complexes of the type [Cu(cpf)(Lⁿ)Cl] (cpf = ciprofloxacin and Lⁿ = phenanthroline derivatives) ( 1 – 5 ) were synthesized and characterized. The complexes were screened for their antibacterial activity and bactericidal activity against two Gram^(+ve) and three Gram^(–ve) microorganisms and the results showed that all complexes studied are more potent than the quinolone standard drug ciprofloxacin. Absorption titration, viscosity, and thermal denaturation measurement studies revealed that each of these square‐pyramidal complexes moderately interacts with calf thymus DNA. The binding constants for mixed ligand complexes are in order of 1.5 × 10⁴–3.0 × 10⁴ M^–1. Based on the data obtained in the DNA binding studies an intercalative mode of binding is suggested for these complexes. The nucleolytic cleavage activity of adducts and gyrase inhibition assay were studied on double stranded pUC19 DNA by gel electrophoresis experiments. From the SOD mimic study; the concentration of complexes ranging from 0.45 μM to 1.45 μM are enough to inhibit the reduction rate of NBT by 50 % (IC₅₀) in NADH/PMS system.     

New less toxic zeolite‐encapsulated Cu(II) complex nanomaterial for dual applications in biomedical field and wastewater remediation

A new dual‐functional Cu(II) complex and its nanohybrid form encapsulated into NaY zeolite cavities were synthesized. The synthesized compounds were characterized using elemental analyses, X‐ray fluorescence, infrared, ¹H NMR, electronic, electron spin resonance and mass spectra, powder X‐ray diffraction, surface area and transmission electron microscopy in addition to conductivity and magnetic susceptibility measurements. The encapsulated Cu(II) complex was catalytically tested for degradation of industrial wastewater. The decolorization and mineralization results indicate that the Cu(II) complex encapsulated into zeolite host is an effective heterogeneous catalyst for real industrial wastewater remediation. In addition, both free and encapsulated Cu(II) complexes were tested as anti‐microbial and anti‐tumour agents. The results show that the Cu(II) complex encapsulated into zeolite has a high activity (IC₅₀ = 14.4 μg ml^?1). The results of in vivo toxicity experiments indicate that the Cu(II) complex encapsulated into zeolite is a less toxic biocompatible material (LD₅₀ = 1245 mg kg^?1). The catalytic properties, cytotoxicity and toxicity of the new nanohybrid Cu(II) complex encapsulated into zeolite make it a promising eco‐friendly and biocompatible material for water remediation and biomedical applications.     

Effect of metal complex formation on the antibacterial activity of nitazoxanide: Spectroscopic and density functional theory calculations

In the present work, experimental and theoretical structural studies of two new nitazoxanide (NTZ) complexes, [Co(NTZ)(NO₃)₂(OH₂)] ( 1 ) and [Ni(NTZ)(CH₃COO)(OH₂)]·CH₃COO ( 2 ) were reported. The susceptibility of Staphylococcus aureus and Escherichia coli towards NTZ and its complexes was assessed. NTZ behaves as a monodentate ligand via the thiazole N atom forming distorted octahedral and tetrahedral complexes with Co(II) and Ni(II) ions, respectively. The d‐d transitions were assigned by the aid of time‐dependent density functional theory calculations. The magnetic susceptibility value of 1 remains unchanged in the temperature range of 298–77K, while that of 2 decreases linearly with the temperature to attain 2.79 μ_B at 77K. Coordination of NTZ (0.084 μmol ml^?1) to Co(II) ( 1 ) (0.028 μmol ml^?1) and Ni(II) ions ( 2 ) (0.079 μmol ml^?1) leads to an improvement in the toxicity against S. aureus.     

Crystal Structures,Magnetic Properties and Catecholase‐Like Activities of μ‐Alkoxo‐μ‐Carboxylato Double Bridged Dinuclear and Tetranuclear Copper(II) Complexes

One μ‐alkoxo‐μ‐carboxylato bridged dinuclear copper(II) complex, [Cu₂(L¹)(μ‐C₆H₅CO₂)] ( 1 )(H₃L¹ = 1,3‐bis(salicylideneamino)‐2‐propanol)), and two μ‐alkoxo‐μ‐dicarboxylato doubly‐bridged tetranuclear copper(II) complexes, [Cu₄(L¹)₂(μ‐C₈H₁₀O₄)(DMF)₂]·H₂O ( 2 ) and [Cu₄(L²)₂(μ‐C₅H₆O₄]·2H₂O·2CH₃CN ( 3 ) (H₃L² = 1,3‐bis(5‐bromo‐salicylideneamino)‐2‐propanol)) have been prepared and characterized. The single crystal X‐ray analysis shows that the structure of complex 1 is dimeric with two adjacent copper(II) atoms bridged by μ‐alkoxo‐μ‐carboxylato ligands where the Cu···Cu distances and Cu‐O(alkoxo)‐Cu angles are 3.5 11 Å and 132.8°, respectively. Complexes 2 and 3 consist of a μ‐alkoxo‐μ‐dicarboxylato doubly‐bridged tetranuclear Cu(II) complex with mean Cu‐Cu distances and Cu‐O‐Cu angles of 3.092 Å and 104.2° for 2 and 3.486 Å and 129.9° for 3 , respectively. Magnetic measurements reveal that 1 is strong antiferromagnetically coupled with 2J =‐210 cm^?1 while 2 and 3 exhibit ferromagnetic coupling with 2J = 126 cm^?1 and 82 cm^?1 (averaged), respectively. The 2J values of 1–3 are correlated to dihedral angles and the Cu‐O‐Cu angles. Dependence of the pH at 25 °C on the reaction rate of oxidation of 3,5‐di‐tert‐butylcatechol (3,5‐DTBC) to the corresponding quinone (3,5‐DTBQ) catalyzed by 1–3 was studied. Complexes 1–3 exhibit catecholase‐like active at above pH 8 and 25 °C for oxidation of 3,5‐di‐tert‐butylcatechol.     

Hexanuclear Zn(II) and Mononuclear Cu(II) Complexes containing imino phenol ligands: Exploitation of their Catalytic and Biological Perspectives

A unique hexanuclear zinc(II) ( 1 ) and two mononuclear copper(II) ( 2 and 3 ) complexes anchored with imino phenol ligand HL ¹ and HL ² were synthesized with good yield and purity (where HL ¹  = 4‐tert‐butyl‐2,6‐bis((mesitylimino)methylphenol and HL ²   =  5‐tert‐butyl‐2‐hydroxy‐3‐((mesitylimino)methyl)benzaldehyde). These complexes were characterized by utilizing various spectroscopic protocols like NMR, FTIR, UV as well as ESI‐Mass spectrometry, elemental analysis and single crystal X‐ray diffraction studies. Their potential to bind calf thymus DNA (CT‐DNA) was tested utilizing different techniques such as UV–visible and fluorescence spectroscopy. The experiment implies that they interact with CT‐DNA via non‐intercalative mode with moderate capabilities (K_b ~ 10⁴ M^?1). On the other hand, these complexes have high capabilities to quench the fluorescence of bovine serum albumin (BSA) following the static pathway. In addition, they are active catalysts for the oxidation reaction of 3,5‐di‐tert‐butylcatechol (3,5‐DTBC) to 3,5‐di‐tert‐butylquinone (3,5‐DTBQ) under aerobic condition. From the recorded EPR signals of all complexes, it has been concluded that the oxidation reaction proceeds via ligand oriented radical pathway instead of metal based redox participation. Kinetic studies using 1 – 3 indicate that it follows Michaelis–Menten type of equation with moderate to high turnover number (k_cat). Apart from these aspects, complexes 1 – 3 were screened for their cytotoxic behavior towards HeLa cells (human cervical carcinoma) and found quite active with comparable IC₅₀ values to cisplatin.     

Syntheses,toxicity and biodistribution of CO‐releasing molecules containing M(CO)5 (M = Mo,W and Cr)

A series of CO‐releasing molecules M(CO)₅ L (M = Mo, W and Cr), ( 1 , 2 , 3 , L = glycine methyl ester; 4 , 5 , 6 , N‐methylimidazole; 7 , 8 , 9 , 2‐aminopyridine; 10 , 11 , 12 , 3‐aminopyridine; 13 , 14 , 15 , 4‐aminopyridine), were synthesized. All complexes have been characterized by NMR, IR and electrospray ionization mass spectroscopy; the octahedral structures of 14 and 15 were also established by X‐ray crystallography. Furthermore, all complexes were evaluated for toxicity, pharmacokinetics and metabolic processes. Cytotoxic effects on the proliferation of fibroblast cell line were assayed by MTT. Among the complexes, Mo complex 1 showed the lowest cytotoxicity (IC₅₀ = 597 µmol l^?1) and W complex 2 showed a remarkable toxic effect, with IC₅₀ = 52 µmol l^?1. With the same ligand, the toxic effects of the complexes increase in the order of metal element W < Cr < Mo. For the same central metal element, the complexes containing imidazole showed lower toxic effects than those containing amino acid ester or aminopyridine. In accordance with the results from cytotoxicity, the complexes also showed corresponding toxic effects in animal models. The biodistributions of the complexes were established by inductively coupled plasma–atomic emission spectroscopy, measuring metal in tissues and organs. The results show that the complexes were gradually absorbed and unevenly distributed in vivo. The complexes containing imidazole entered tissues and organs faster than those containing amino acid ester. The complexes containing W atom were absorbed and distributed more slowly than those containing Mo or Cr atoms. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis,characterization, and DNA damaging of bivalent metal complexes incorporating tetradentate dinitrogen–dioxygen ligand as potential biocidal agents

A new symmetrical tetradentate Schiff base was prepared by the condensation of 5-nitro-o-vanillin and diaminoethane. Its complexes were synthesized and characterized by elemental analysis, magnetic moment, molar conductance, UV-Vis, IR, ¹H NMR, ESI-mass, and EPR spectra. The DNA-binding behavior of these complexes was investigated by absorption spectra, cyclic voltammetry, and viscosity measurements. The DNA-binding constants for Co(II), Ni(II), Cu(II), and Zn(II) complexes were 1.58?×?10⁴, 1.65?×?10⁴, 2.71?×?10⁴, and 1.83?×?10⁴ (mol?L^?1)^?1, respectively. The results suggest that the complexes intercalate between DNA base pairs. Further, all these complexes exhibit moderate to high ability to cleave pUC19 DNA. The ligand and its complexes have been screened for antimicrobial activities using the disc diffusion method against selected bacteria and fungi. Antibacterial activity was greater against Gram-positive than Gram-negative bacteria for Cu(II) complex and antifungal activity was greater against Aspergillus niger and Candida albicans for the Cu(II) complex.     

Antibacterial,SOD mimic and nuclease activities of copper(II) complexes containing ofloxacin and neutral bidentate ligands

Drug‐based mixed‐ligand copper(II) complexes of type [Cu(OFL)(Aⁿ)Cl]·5H₂O (OFL = ofloxacin, A¹ = pyridine‐2‐carbaldehyde, A² = 2,2′‐bipyridylamine, A³ = thiophene‐2‐carbaldehyde, A⁴ = 2,9‐dimethyl‐1,10‐phenanthroline, A⁵ = 2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline, A⁶ = 4,5‐diazafluoren‐9‐one, A⁷ = 1,10‐phenanthroline‐5,6‐dione and A⁸ = 5‐nitro‐1,10‐phenanthroline) were synthesized and characterized. Spectral investigations of complexes revealed square pyramidal geometry. Viscosity measurement and absorption titration were employed to determine the mode of binding of complexes with DNA. DNA cleavage study showed better cleaving ability of the complexes compared with metal salt and standard drug by conversion of a supercoiled form of pUC19 DNA to linear via circular. From the SOD mimic study, concentration of complexes ranging from 0.415 to 1.305 µM is enough to inhibit the reduction rate of NBT by 50% (IC₅₀) in the NADH‐PMS system. Antibacterial activity was assayed against selective Gram‐negative and Gram‐positive microorganisms using the doubling dilution technique. Copyright © 2010 John Wiley & Sons, Ltd.     

Immunoassay for the detection of lead ions in environmental water samples

A rapid, simple, and reliable competitive immunoassay was developed for measurement of lead ions Pb(II) in environmental samples. Avian antibodies were produced against Pb(II). Since lead ions are too small to elicit an immune response, the metal was coupled to protein carrier Bovine serum albumin (BSA) using a bifunctional chelator 1-(4-isothiocyanobenzyl) ethylenediamine N,N,N′,N′-tetra acetic acid (ITCBE). Poultry birds (layers) were immunised with this Pb(II)–ITCBE–BSA immunoconjugate and the avian antibodies (IgY) isolated from egg yolk recognised Pb(II)-ITCBE complexes as capture reagent and a Pb(II)–ITCBE conjugate of Alkaline phosphatase as an enzyme label. Antibody reaction was optimised for different concentrations of antigen and antibody dilutions. Cross reactivity with other metals were below 1% in competitive ELISA. The IC₅₀ value of this avian antibody was 0.19?µg?mL^?1. The detection range and the detection limit were 0.02–1000?µg?mL^?1and 0.2?µg?mL^?1, respectively.     

Synthesis,Characterization and Nuclease Activity of Ternary Copper(Ⅱ) Complexes Containing Dipyrido[3,2-a:2',3'-c]phenazine and L-α-Amino Acids

Two new complexes: [Cu(dppz)(L‐val)(H₂O)]ClO₄ ( 1 ) and [Cu(dppz)(L‐tyr)(H₂O)]ClO₄·1.5H₂O ( 2 ) (dppz=dipyrido[3,2‐a:2′,3′‐c]phenazine, L‐val=L‐valinate, L‐tyr=L‐tyrosinate) have been synthesized and investigated by elemental analysis, molar conductivity, UV‐Vis and IR spectroscopies. Complex 1 has been structurally characterized by the single‐crystal X‐ray diffraction method, which crystallizes in the triclinic space group P‐1 in a unit cell of a=0.9095(2) nm, b=1.3301(3) nm, c=1.3552(3) nm, α =93.518(3) °, β=97.192(3) °, γ=106.361(3) °, V=1.5526(6) nm³, Z=2, D_c=1.598 g·cm^?3, µ=0.849 mm^?1. The DNA binding and cleavage properties of the complexes have been studied by UV spectroscopy, fluorescence spectroscopy, viscosity measurement and agarose gel electrophoresis. The results show that the complexes can bind DNA by intercalation and cleave pBR322 DNA by free hydroxyl radical induced by the complexes in the presence of ascorbate, giving the order of the binding abilities and cleavage activity of the complexes to DNA: complex 2 > 1 .     

Synthesis and structural and DNA binding studies of mono‐ and dinuclear copper(II) complexes constructed with ─O and ─N donor ligands: Potential anti‐skin cancer drugs

Mononuclear and dinuclear copper(II) complexes with thiophenecarboxylic acid, [Cu(3‐TCA)₂(2,2′‐bpy)] ( 1 ), [Cu(3‐Me‐2‐TCA)₂(H₂O)(2,2′‐bpy)] ( 2 ), [Cu(5‐Me‐2‐TCA)₂(H₂O)(2,2′‐bpy)] ( 3 ) and [Cu₂(2,5‐TDCA)(DMF)₂(H₂O)₂(2,2′‐bpy)₂](ClO₄)₂ ( 4 ) (where 3‐TCA = 3‐thiophenecarboxylic acid; 3‐Me‐2‐TCA = 3‐methyl‐2‐thiophenecarboxylic acid; 5‐Me‐2‐TCA = 5‐methyl‐2‐thiophenecarboxylic acid; 2,5‐TDCA = thiophene‐2,5‐dicarboxylic acid; 2,2′‐bpy = 2,2′‐bipyridyl; DMF = N,N‐dimethylformamide), were synthesized. Compounds 1 – 4 were extensively characterized using both analytical and spectroscopic methods. Additionally, the solid‐state structures of 1 and 4 were unambiguously established from single‐crystal X‐ray diffraction studies. The hexacoordinated Cu(II) centre in 1 (CuO₄N₂) is a distorted octahedral geometry whereas the pentacoodinated 4 (CuO₃N₂) has distorted square pyramidal geometry. Compounds 1 and 4 exhibit intermolecular hydrogen bonding which leads to the formation of two‐ and three‐dimensional supramolecular architectures, respectively. Spectrophotometric and computational investigations suggest that these compounds bind with DNA in minor groove binding such that K_b = 4.9 × 10⁵ M^?1 and K_sv = 3.4 × 10⁵ M^?1, and binding score of ?5.26 kcal mol^?1. The binding affinity of these complexes to calf thymus DNA is in the order 2 > 3 > 4 > 1 . Methyl‐substituted thiophene ring increases the DNA binding affinity whereas unsubstituted thiophene ring DNA binding rate is reduced. The methyl group on the thiophene ring would sterically hinder π–π stacking of the ring with DNA base pairs, and subsequently they are involved in hydrophobic interaction with the DNA surface rather than partial intercalative interaction. Compounds 1 – 4 show pronounced activity against B16 mouse melanoma skin cancer cell lines as measured by MTT assay yielding IC₅₀ values in the micromolar concentration range. The compounds could prove to be efficient anti‐cancer agents, since at a concentration as low as 2.1 μg ml^?1 they exerted a significant cytotoxic effect in cancer cells whereas cell viability was not affected in normal cells.