Ternary copper(II) complexes of thiosemicarbazones and heterocyclic bases showing N3OS coordination as models for the type-2 centers of copper monooxygenases

Six ternary copper(II) complexes of general formulation [CuLB] (1-6), where L is dianionic ONS-donor thiosemicarbazones derived from the condensation of salicylaldehyde with thiosemicarbazides and B is NN-donor heterocyclic bases like 2,2'-bipyridine, 1,10-phenanthroline and 2,9-dimethyl-1,10-phenanthroline, are prepared from a reaction of copper(II) acetate hydrate with the heterocyclic base (B) and the thiosemicarbazone (H2L) in MeOH, and structurally characterized by X-ray diffraction technique. Crystal structures of the complexes display a distorted square-pyramidal (4 + 1) coordination geometry having the ONS-donor thiosemicarbazone bonded at the basal plane. The chelating heterocyclic bases exhibit axial-equatorial mode of bonding. The complexes are one-electron paramagnetic and they show axial X-band EPR spectra in DMF-toluene glass at 77 K giving g(parallel to)(A(parallel to)) and g(perpendicular to) values of similar to2.2 (175 x 10(-4) cm(-1)) and similar to2.0 indicating a {d(x2-y2)}(1) ground state. The complexes show a d-d band near 570 nm and a charge transfer band near 400 nm in DMF. The complexes are redox active and exhibit a quasireversible Cu(II)-Cu(I) couple in DMF-0.1 M tetrabutylammonium perchlorate near 0.1 V vs. SCE. They are catalytically active in the oxidation of ascorbic acid in presence of dioxygen. The complexes with a CuN3OS coordination model the ascorbate oxidation property of dopamine beta-hydroxylase and peptidylglycine a-hydroxylating monooxygeanase. (C) 2003 Elsevier Science B.V. All rights reserved.

Synthesis, biological studies of linear and branched arabinofuranoside-containing glycolipids and their interaction with surfactant protein A

Oligoarabinofuranoside-containing glycolipids relevant to mycobacterial cell wall components were synthesized in order to understand the functional roles of such glycolipids. A series of linear tetra-, hexa-, octa-and a branched heptasaccharide oligoarabinofuranosides, with 1 -> 2 and 1 -> 5 a-linkages between the furanoside residues, were synthesized by chemical methods from readily available monomer building blocks. Upon the synthesis of glycolipids, constituted with a double alkyl chain-substituted sn-glycerol core and oligosaccharide fragments, biological studies were performed to identify the effect of synthetic glycolipids on the biofilm formation and sliding motilities of Mycobacterium smegmatis. Synthetic glycolipids and arabinofuranosides displayed an inhibitory effect on the growth profile, but mostly on the biofilm formation and maturation. Similarly, synthetic compounds also influenced the sliding motility of the bacteria. Further, biophysical studies were undertaken, so as to identify the interactions of the glycolipids with a pulmonary surfactant protein, namely surfactant protein A (SP-A), with the aid of the surface plasmon resonance technique. Specificities of each glycolipid interacting with SP-A were thus evaluated. From this study, glycolipids were found to exhibit higher apparent association constants than the corresponding oligosaccharide portion alone, without the double alkyl group-substituted glycerol core.

Dicopper(II) complexes showing DNA hydrolase activity and monomeric adduct formation with bis(4-nitrophenyl)phosphate

Ferromagnetic dicopper(II) complexes [Cu(2)(mu-O(2)CCH(3))(mu-OH)(L)(2)(mu-L(1))](PF(6))(2), where L = 1,10-phenanthroline (phen), L(1) = H(2)O in 1 and L = dipyrido[3,2-d:2',3'-f]quinoxaline (dpq), L(1) = CH(3)CN in 2, are prepared and structurally characterized. Crystals of 1 and 2 belong to the monoclinic space group of P2(1)/n and P2(1)/m, respectively. The copper(II) centers display distorted square-pyramidal geometry having a phenanthroline base and two oxygen atoms of the bridging hydroxo and acetate group in the basal plane. The fifth coordination site has weak axially bound bridging solvent molecule H(2)O in 1 and CH(3)CN in 2. The Cu center dot center dot center dot Cu distances are 3.034 and 3.046 angstrom in 1 and 2, respectively. The complexes show efficient hydrolytic cleavage of supercoiled pUC19 DNA as evidenced from the mechanistic studies that include T4 DNA ligase experiments. The binuclear complexes form monomeric copper(II) adducts [Cu(L)(2)(BNPP)](PF(6)) (L = phen, 3; dpq, 4) with bis(4-nitrophenyl)phosphate (BNPP) as a model phosphodiester. The crystal structures of 3 and 4 reveal distorted trigonal bipyramidal geometry in which BNPP binds through the oxygen atom of the phosphate. The kinetic data of the DNA cleavage reactions of the binuclear complexes under pseudo- and true-Michaelis-Menten conditions indicate remarkable enhancement in the DNA hydrolysis rate in comparison to the control data. (C) 2011 Elsevier B.V. All rights reserved.

The selection of a sugar for transport and storage of carbon in plants

Sugars perform two vital functions in plants: as compatible solutes protecting the cell against osmotic stress and as mobile source of immediate and long-term energy requirement for growth and development. The two sugars that occur commonly in nature are sucrose and trehalose. Sucrose comprises one glucose and one fructose molecule; trehalose comprises two glucose molecules. Trehalose occurs in significant amounts in insects and fungi which greatly outnumber the plants. Surprisingly, in plants trehalose has been found in barely detectable amounts, if at all, raising the question `why did nature select sucrose instead of trehalose as the mobile energy source and as storage sugar for the plants'? Modelling revealed that when attached to the ribbon-shaped beta-1,4 glucan a trehalose molecule is shaped like a hook. This suggests that the beta-1,4 glucan chains with attached trehalose will fail to align to form inter-chain hydrogen bonds and coalesce into a cellulose microfibril, as a result of which in trehalose-accumulating plant cells, the cell wall will tend to become leaky. Thus in plants an evolutionary selection was made in favour of sucrose as the mobile energy source. Genetic engineering of plant cells for combating abiotic stresses through microbial trehalose-producing genes is fraught with risk of damage to plant cell walls.

An eight-connected metal organic framework based on Cu(5) clusters: Synthesis, structure, magnetic and catalytic properties

A reaction of copper acetate, 5-nitroisophthalic acid in a water-methanol mixture under solvothermal condition results in a new metal-organic framework compound, [Cu(5)(mu(3)-OH)(2)(H(2)O)(6){(NO(2))-C(6)H(3)-(COO)(2)}(4)]center dot 5H(2)O, (1). The compound contains Cu5 pentameric cluster units connected by 5-nitro isophthalate (NIPA) moieties forming a CdCl(2)-like layer, which are further connected by another NIPA moiety forming the three-dimensional structure. The water molecules in (1) can be reversibly adsorbed. The removal of water accompanies a change in the colour as well as a structural re-organization. Magnetic studies suggest strong antiferromagnetie correlations between the Cu5 cluster units. The compound (1) exhibits heterogeneous Lewis acid catalysis for the cyanosilylation of imines with more than 95 % selectivity. Compound (1) has been characterized by IR, UV-vis, TGA, powder XRD studies.

Selective biodissolution of calcium and iron from bauxite in the presence of Bacillus polymyxa

A bacterium Bacillus polymyxa was found to be capable of selective removal of calcium and iron from bauxite. The bioleached residue was found to be enriched in its alumina content with insignificant amounts of iron and calcium as impurities. The developed bio- process was found to be capable of producing a bauxite product which meets the specifica- tions as a raw material for the manufacture of alumina based ceramics and refractories. The role of bacterial cells and metabolic products in the selective dissolution of calcium (present as calcite) and iron (present as hematite and goethite) from bauxite was assessed and possi- ble mechanisms illustrated. The effect of different parameters such as sucrose concentra- tion, pH, pulp density and time on selective biodissolution was studied. It was observed that periodic decantation and replenishment of the leach medium was beneficial in improving the dissolution kinetics. Calcium removal involves chelation with bacterial exopolysaccha- tides and acidolysis by organic acid generation. Hematite could be solubilized through a reductive dissolution mechanism.

Composition of Extrafloral Nectar Influences Interactions between the Myrmecophyte Humboldtia brunonis and its Ant Associates

Ant-plant interactions often are mediated by extrafloral nectar (EFN) composition that may influence plant visitation by ants. Over a 300 km range in the Indian Western Ghats, we investigated the correlation between the EFN composition of the myrmecophytic ant-plant Humboldtia brunonis (Fabaceae) and the number and species of ants visiting EFN. EFN composition varied among H. brunonis populations and between plant organs (floral bud vs. young leaf EFN). In general, EFN was rich in sugars with small quantities of amino acids, especially essential amino acids, and had moderate invertase activity. In experiments at the study sites with sugar and amino acid solutions and with leaf or floral bud EFN mimics, dominant EFN-feeding ants differentiated between solutions as well as between mimics. The castration parasite Crematogaster dohrni (northern study site) was the least selective and did not exhibit any clear feeding preferences, while the largely trophobiont-tending non-protective Myrmicaria brunnea (middle study site) preferred higher sucrose concentrations and certain essential/non-essential amino acid mixtures. The mutualistic Technomyrmex albipes (southern study site) preferred sucrose over glucose or fructose solutions and consumed the leaf EFN mimic to a greater extent than the floral bud EFN mimic. This young leaf EFN mimic had low sugar concentrations, the lowest viscosity and sugar: amino acid ratio, was rich in essential amino acids, and appeared ideally suited to the digestive physiology of T. albipes. This preference for young leaf EFN may explain the greater protection afforded to young leaves than to floral buds by T. albipes, and may also help to resolve ant-pollinator conflicts. The differential response of dominant ants to sugar, amino acids, or solution viscosity suggests that plants can fine-tune their interactions with local ants via EFN composition. Thus, EFN can mediate local partner-choice mechanisms in ant-plant interactions.

Anticancer property of Bryophyllum pinnata (Lam.) Oken. leaf on human cervical cancer cells

Background: Bryophyllum pinnata (B. pinnata) is a common medicinal plant used in traditional medicine of India and of other countries for curing various infections, bowel diseases, healing wounds and other ailments. However, its anticancer properties are poorly defined. In view of broad spectrum therapeutic potential of B. pinnata we designed a study to examine anti-cancer and anti-Human Papillomavirus (HPV) activities in its leaf extracts and tried to isolate its active principle. Methods: A chloroform extract derived from a bulk of botanically well-characterized pulverized B. pinnata leaves was separated using column chromatography with step-gradient of petroleum ether and ethyl acetate. Fractions were characterized for phyto-chemical compounds by TLC, HPTLC and NMR and Biological activity of the fractions were examined by MTT-based cell viability assay, Electrophoretic Mobility Shift Assay, Northern blotting and assay of apoptosis related proteins by immunoblotting in human cervical cancer cells. Results: Results showed presence of growth inhibitory activity in the crude leaf extracts with IC50 at 552 mu g/ml which resolved to fraction F4 (Petroleum Ether: Ethyl Acetate:: 50: 50) and showed IC50 at 91 mu g/ml. Investigations of anti-viral activity of the extract and its fraction revealed a specific anti-HPV activity on cervical cancer cells as evidenced by downregulation of constitutively active AP1 specific DNA binding activity and suppression of oncogenic c-Fos and c-Jun expression which was accompanied by inhibition of HPV18 transcription. In addition to inhibiting growth, fraction F4 strongly induced apoptosis as evidenced by an increased expression of the pro-apoptotic protein Bax, suppression of the anti-apoptotic molecules Bcl-2, and activation of caspase-3 and cleavage of PARP-1. Phytochemical analysis of fraction F4 by HPTLC and NMR indicated presence of activity that resembled Bryophyllin A. Conclusions: Our study therefore demonstrates presence of anticancer and anti-HPV an activity in B. pinnata leaves that can be further exploited as a potential anticancer, anti-HPV therapeutic for treatment of HPV infection and cervical cancer.

Sensitive Liquid Chromatography-Tandem Mass Spectrometry Method for the Determination of Olanzapine in Human Urine

A sensitive and selective liquid chromatographic-tandem mass spectrometric (LC-MS-MS) method was developed to determine olanzapine (OLZ) in human urine. After solid-phase extraction with SPE cartridge, the urine sample was analysed on a C-18 column (Symmetry 3.5 mu m, 50 x 4.6 mm i.d) interfaced with a triple quadrupole tandem mass spectrometer. Positive electrospray ionization was employed as the ionization source. The mobile phase consisted of ammonium acetate (pH 7.8)-acetonitrile (10:90, v/v). The method was linear over a concentration range of 1-100 ngml(-1). The lower limit of quantitation was 1 ngml(-1). The intra-day and inter-day relative standard deviation across three validation runs over the entire concentration range was < 11.5 %. The accuracy determined at three concentrations (8.0, 50.0 and 85.0 ngml(-1) OLZ) was within +/- 1.21 % in terms of relative errors.

Influence of Sn doping on structural, optical and electrical properties of ZnO thin films prepared by cost effective sol-gel process

Tin (Sn) doped zinc oxide (ZnO) thin films were synthesized by sol-gel spin coating method using zinc acetate di-hydrate and tin chloride di-hydrate as the precursor materials. The films were deposited on glass and silicon substrates and annealed at different temperatures in air ambient. The agglomeration of grains was observed by the addition of Sn in ZnO film with an average grain size of 60 nm. The optical properties of the films were studied using UV-VIS-NIR spectrophotometer. The optical band gap energies were estimated at different concentrations of Sn. The MOS capacitors were fabricated using Sn doped ZnO films. The capacitance-voltage (C-V), dissipation vs. voltage (D-V) and current-voltage (I-V) characteristics were studied and the electrical resistivity and dielectric constant were estimated. The porosity and surface area of the films were increased with the doping of Sn which makes these films suitable for opto-electronic applications. (C) 2012 Elsevier B.V. All rights reserved.

A Rare Phenoxido/Acetato/Azido Bridged Trinuclear and an Unprecedented Phenoxido/Azido Bridged One-Dimensional Polynuclear Nickel(II) Complexes: Synthesis, Crystal Structure, and Magnetic Properties with Theoretical Investigations on the Exchange Mechanism

The reaction of a tridentate Schiff base ligand HL (2-(3-dimethylaminopropylimino)-methyl]-phenol) with Ni(II) acetate or perchlorate salts in the presence of azide as coligand has led to two new Ni(II) complexes of formulas Ni3L2(OAc)(2)(mu(1,1)-N-3)(2)(H2O)(2)]center dot 2H(2)O (1) and Ni2L2(mu(1,1)-N-3) (mu(1,3)-N-3)](n)(2). Single crystal X-ray structures show that complex 1 is a linear trinuclear Ni(II) compound containing a mu(2)-phenwddo, an end-on (EO) azido and a syn-syn acetato bridge between the terminal and the central Ni(II) ions. Complex 2 can be viewed as a one-dimensional (1D) chain in which the triply bridged (di-mu(2)-phenoxido and EO azido) dimeric Ni-2 units are linked to each other in a zigzag pattern by a single end-to-end (EE) azido bridge. Variable-temperature magnetic susceptibility studies indicate the presence of moderate ferromagnetic exchange coupling in complex 1 with J value of 16.51(6) cm(-1). The magnetic behavior of 2 can be fitted in an alternating ferro- and antiferromagnetic model J(FM) = +34.2(2.8) cm(-1) and J(AF) = -21.6(1.1) cm(-1)] corresponding to the triple bridged dinuclear core and EE azido bridge respectively. Density functional theory (DFT) calculations were performed to corroborate the magnetic results of 1 and 2. The contributions of the different bridges toward magnetic interactions in both compounds have also been calculated.

Approaches to alpha-amino acids via rearrangement to electron-deficient nitrogen: Beckmann and Hofmann rearrangements of appropriate carboxyl-protected substrates

The titled approaches were effected with various 2-substituted benzoylacetic acid oximes 3 (Beckmann) and 2-substituted malonamic acids 9 (Hofmann), their carboxyl groups being masked as a 2,4,10-trioxaadamantane unit (an orthoacetate). The oxime mesylates have been rearranged with basic Al2O3 in refluxing CHCl3, and the malonamic acids with phenyliodoso acetate and KOH/MeOH. Both routes are characterized by excellent overall yields. Structure confirmation of final products was conducted with X-ray diffraction in selected cases. The final N-benzoyl and N-(methoxycarbonyl) products are alpha-amino acids with both carboxyl and amino protection; hence, they are of great interest in peptide synthesis.

Effect of doping concentration on the structural and optical properties of pure and tin doped zinc oxide thin films by nebulizer spray pyrolysis (NSP) technique

Pure and tin doped zinc oxide (Sn:ZnO) thin films were prepared for the first time by NSP technique using aqueous solutions of zinc acetate dehydrate, tin (IV) chloride fendahydrate and methanol. X-ray diffraction patterns confirm that the films are polycrystalline in nature exhibiting hexagonal wurtzite type, with (0 0 2) as preferred orientation. The structural parameters such as lattice constant ('a' and `c'), crystallite size, dislocation density, micro strain, stress and texture coefficient were calculated from X-ray diffraction studies. Surface morphology was found to be modified with increasing Sn doping concentration. The ZnO films have high transmittance 85% in the visible region, and the transmittance is found to be decreased with the increase of Sn doping concentration. The corresponding optical band gap decreases from 3.25 to 3.08 eV. Room temperature photoluminescence reveals the sharp emission of strong UV peak at 400 nm (3.10 eV) and a strong sharp green luminescence at 528 nm (2.34 eV) in the Sn doped ZnO films. The electrical resistivity is found to be 10(6) Omega-cm at higher temperature and 10(5) Omega-cm at lower temperature. (C) 2012 Elsevier Ltd. All rights reserved.

Efficient field emission properties of ZnO (core)/graphite (shell) nanowires

In this work the field emission studies of a new type of field emitter, zinc oxide (ZnO) core/graphitic (g-C) shell nanowires are presented. The nanowires are synthesized by chemical vapor deposition of zinc acetate at 1300 degrees C Scanning and transmission electron microscopy characterization confirm high aspect ratio and novel core-shell morphology of the nanowires. Raman spectrum of the nanowires mat represents the characteristic Raman modes from g-C shell as well as from the ZnO core. A low turn on field of 2.75 V/mu m and a high current density of 1.0 mA/cm(2) at 4.5 V/mu m for ZnO/g-C nanowires ensure the superior field emission behavior compared to the bare ZnO nanowires. (C) 2012 Elsevier B.V. All rights reserved.

Zn-nicotinate complex - a precursor for ZnO nanoparticles

A zinc-nicotinate complex has been prepared by direct reaction of zinc acetate and nicotinic acid in the presence of template tetramethylethylenediamine and is characterized by elemental analysis, FTIR, and TGA/DTA. The Zn complex was a precursor for the synthesis of ZnO nanoparticles. A correlation of the thermal and spectral properties of the precursor complex with its structure has been discussed. Thermolysis under air was studied by thermogravimetry, and the resulting ZnO product was characterized by XRD and TEM, showing compact particles with a diameter of about 1750nm.