Sm(III)nitrate-catalyzed one-pot synthesis of furano3,2c]-1,2,3,4-tetrahydroquinolines and DNA photocleavage studies

The synthesis and DNA photocleavage studies of furano3,2-c]-1,2,3,4-tetrahydroquinolines have been reported. Sm(III)nitrate was found to be an efficient for the Diels-Alder reaction of aryl amines with 2,3-dihydrofuran to offer the corresponding furano3,2-c]-1,2,3,4-tetrahydroquinolines derivatives as a mixture of cis/trans stereoisomers in moderate yields. The aqueous solubility of acid catalyst can be recycled without significant loss of activity. The DNA photocleavage studies shows that, the cis/trans stereoisomers are good DNA cleavage mimic in terms of molecular structure. (C) 2012 Elsevier B.V. All rights reserved.

Non-neutral evolution in non-LEE-encoded type III effectors of attaching and effacing Escherichia coli

Attaching and effacing Escherichia coli (AEEC) employ type III secretion system (T3SS) to secrete effector proteins into host cells and regulate their function. Here we have investigated T3SS genes of AEEC for non-neutral evolution. Our analysis revealed non-neutral evolution in three genes (nleE1, nleB2 and nleD) which encode effector proteins. These genes are located outside the locus of enterocyte effacement (LEE). In general, non-LEE effector genes show greater deviation from neutral evolution than LEE effector genes. These results suggest that effector genes located outside LEE are under greater selection pressure than those present in LEE. (C) 2012 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

Synthesis, antimicrobial, DNA-binding and photonuclease studies of Cobalt(III) and Nickel(II) Schiff base complexes

New metal complexes of the type M(nih)(L)](PF6)(n)center dot xAH(2)O and M(nih)(2)](PF6)center dot xH(2)O (where M = Co(III) or Ni(II), L = 1,10-phenanthroline (phen)/or 2,2' bipyridine (bpy), nih = 2-hydroxy-1-naphthaldehyde isonicotinoyl hydrazone, n = 2 or 1 and x = 3 or 2) have been synthesized and characterized by elemental analysis, magnetic, IR and H-1 NMR spectral data. The electronic and magnetic moment 2.97-3.07 B.M. data infers octahedral geometry for all the complexes. The IR data reveals that Schiff base (nih) form coordination bond with the metal ion through azomethine-nitrogen, phenolic-oxygen and carbonyl-oxygen in a tridentate fashion. In addition, DNA-binding properties of these six metal complexes were investigated using absorption spectroscopy, viscosity measurements and thermal denaturation methods. The results indicated that the nickel(II) complex strongly bind with calf-thymus DNA with intrinsic DNA binding constant K-b value of 4.9 x 10(4) M-1 for (3), 4.2 x 10(4) M-1 for (4), presumably via an intercalation mechanism compared to cobalt(III) complex with K-b value of 4.6 x 10(4) M-1 (1) and 4.1 x 10(4) M-1 (2). The DNA Photoclevage experiment shows that, the complexes act as effective DNA cleavage agent. (C) 2012 Elsevier B.V. All rights reserved.

Performance analysis of boron nitride embedded armchair graphene nanoribbon metal-oxide-semiconductor field effect transistor with Stone Wales defects

We study the performance of a hybrid Graphene-Boron Nitride armchair nanoribbon (a-GNR-BN) n-MOSFET at its ballistic transport limit. We consider three geometric configurations 3p, 3p + 1, and 3p + 2 of a-GNR-BN with BN atoms embedded on either side (2, 4, and 6 BN) on the GNR. Material properties like band gap, effective mass, and density of states of these H-passivated structures are evaluated using the Density Functional Theory. Using these material parameters, self-consistent Poisson-Schrodinger simulations are carried out under the Non Equilibrium Green's Function formalism to calculate the ballistic n-MOSFET device characteristics. For a hybrid nanoribbon of width similar to 5 nm, the simulated ON current is found to be in the range of 265 mu A-280 mu A with an ON/OFF ratio 7.1 x 10(6)-7.4 x 10(6) for a V-DD = 0.68 V corresponding to 10 nm technology node. We further study the impact of randomly distributed Stone Wales (SW) defects in these hybrid structures and only 2.5% degradation of ON current is observed for SW defect density of 3.18%. (C) 2014 AIP Publishing LLC.

Carbohydrate-Appended Tumor Targeting Iron(III) Complexes Showing Photocytotoxicity in Red Light

Glucose-appended photocytotoxic iron(III) complexes of a tridentate Schiff base phenolate ligand Fe(bpyag) (L)] (NO3) (1-3), where bpyag is N,N-bis(2- pyridylmethyl)-2-aminoethyl-beta-D-glucopyranoside and H2L is 3-(2-hydroxyphenylimino)-1-phenylbutan-1-one (H(2)phap) in 1, 3-(2-hydroxyphenylimino)-9-anthrylbutan-1-one (H(2)anap) 2, and 3- (2-hydroxyphenylimino)-1-pyrenylbutan-1-one (H(2)pyap) in 3, were synthesized and characterized. The complex Fe(dpma)(anapn(NO3) (4), having bis-(2-pyridylmethyl)benzylamine (dpma), in which the glucose moiety of bpyag is substituted by a phenyl group, was used as a control, and the complex Fe(dpma)(anap)](PF6) (4a) was structurally characterized by X-ray crystallography. The structure shows a FeN4O2 core in a distorted octahedral geometry. The high-spin iron(III) complexes with magnetic moment value of similar to 5.9 mu(B) showed a low-energy phenolate-to-Fe(III) charge-transfer (CT) absorption band as a shoulder near 500 nm with a tail extending to 700 nm and an irreversible Fe(III)-Fe(II) redox couple near -0.6 V versus saturated calomel electrode. The complexes are avid binders to calf thymus DNA and showed photocleavage of supercoiled pUC19 DNA in red (647 nm) and green (532 nm) light. Complexes 2 and 3 displayed significant photocytotoxicity in red light, with an IC50 value of similar to 20 mu M in HeLa and HaCaT cells, and no significant toxicity in dark. The cell death is via an apoptotic pathway, by generation of reactive oxygen species. Preferential internalization of the carbohydrate-appended complexes 2 and 3 was evidenced in HeLa cells as compared to the control complex 4. A 5-fold increase in the cellular uptake was observed for the active complexes in HeLa cells. The photophysical properties of the complexes are rationalized from the density functional theory calculations.

Titanium nitride thin film anode: chemical and microstructural evaluation during electrochemical studies

TIN thin films with (200) fibre texture are deposited on Cu substrate at room temperature using reactive magnetron sputtering. They exhibit a discharge capacity of 172 mu Ah cm(-2) mu m(-1) (300 mAh g(-1)) in a non-aqueous electrolyte containing a Li salt. There is a graded decrease in discharge capacity when cycled between 0.01 and 3.0 V. Electron microscopy investigations indicate significant changes in surface morphology of the cycled TiN electrodes in comparison with the as deposited TiN films. From XPS depth profile analysis, it is inferred that Li intercalated TIN films consist of lithium compounds, hydroxyl groups, titanium sub oxides and TiN. Lithium diffusivity and reactivity decrease with increase in depth and the major reaction with lithium takes place at film surface and grain boundaries. (C) 2014 Elsevier Ltd. All rights reserved.

Azide/thiocyanate incorporated cobalt(III)-Schiff base complexes: Characterizations and catalytic activity in aerobic epoxidation of olefins

Reaction of cobalt(II) perchlorate hexahydrate with a potentially tetradentate Schiff base ligand, HL (2-methoxy-6-(2-diethylaminoethylimino)methyl]phenol) in presence of sodium azide and sodium thiocyanate yields two complexes Co( L)( HL)(N-3)]center dot ClO4 ( 1) and Co( L)( HL)(NCS)] center dot ClO4 ( 2); both being characterized by different physicochemical methods. Crystal structure of 1 was determined by single crystal X-ray diffraction while that of 2 was reported earlier. In 1, the central cobalt(III) adopts slightly distorted octahedral geometry with same donor set to that of 2. Catalytic efficacy of the complexes towards epoxidation of different alkenes under aerobic condition were investigated in homogeneous medium which reveals that 1 is better catalyst than 2 with respect to alkene oxidation, reflected from the turn over frequencies (TOF) measured at an optimum temperature of 60 degrees C in acetonitrile. (C) 2014 Published by Elsevier B.V.

A napthelene-pyrazol conjugate: Al(III) ion-selective blue shifting chemosensor applicable as biomarker in aqueous solution

A newly synthesized and crystalographically characterized napthelene-pyrazol conjugate, 1-(5-phenyl-1H-pyrazole-3-ylimino)-methyl]-naphthalen-2-ol (HL) behaves as an Al(III) ion-selective chemosensor through internal charge transfer (ICT)-chelation-enhanced fluorescence (CHEF) processes in 100 mM HEPES buffer (water-DMSO 5 : 1, v/v) at biological pH with almost no interference of other competitive ions. This mechanism is readily studied from electronic, fluorimetric and H-1 NMR titration. The probe (HL) behaved as a highly selective fluorescent sensor for Al(III) ions as low as 31.78 nM within a very short response time (15-20 s). The sensor (HL), which has no cytotoxicity, is also efficient in detecting the distribution of Al(III) ions in HeLa cells via image development under fluorescence microscope.

Iron(III) Catecholates for Cellular Imaging and Photocytotoxicity in Red Light

Iron(III) complexes Fe(L)(L') (NO3)]-in which L is phenyl-N, N-bis(pyridin-2-yl) methyl]methanamine (1), (anthracen-9-yl)N, N-bis(pyridin-2-yl) methyl] methanamine (2), (pyreny-1-yl)-N, N-bis(pyridin- 2-yl) methyl] methanamine (3-5), and L' is catecholate (1-3), 4-tert-butyl catecholate (4), and 4-(2-aminoethyl)benzene- 1,2-diolate (5)-were synthesized and their photocytotoxic proper-ties examined. The five electron-paramagnetic complexes displayed a FeIII/ Fe-II redox couple near similar to 0.4 V versus a saturated calomel electrode (SCE) in DMF/0.1m tetrabutylammonium perchlorate (TBAP). They showed unpre-cedented photocytotoxicity in red light (600-720 nm) to give IC50-15 mm in various cell lines by means of apoptosis to generate reactive oxygen species. They were ingested in the nucleus of HeLa and HaCaT cells in 4 h, thereby interacting favorably with calf thymus (ct)-DNA and photocleaving pUC19 DNA in red light of 785 nm to form hydroxyl radicals.

Iron(III) Complexes of a Pyridoxal Schiff Base for Enhanced Cellular Uptake with Selectivity and Remarkable Photocytotoxicity

Iron(III) complexes of pyridoxal (vitamin B6, VB6) or salicylaldehyde Schiff bases and modified dipicolylamines, namely, Fe(B)(L)](NO3) (15), where B is phenyl-N,N-bis((pyridin-2-yl)methyl)methanamine (phbpa in 1), (anthracen-9-yl)-N,N-bis((pyridin-2-yl)methyl)methanamine (anbpa in 2, 4) and (pyren-1-yl)-N,N-bis((pyridin-2-yl)methyl)methanamine (pybpa in 3, 5) (H2L1 is 3-hydroxy-5-(hydroxymethyl)-4-(((2-hydroxyphenyl)imino)methyl)-2-methylp yridine (13) and H2L2 is 2-(2-hydroxyphenyl-imino)methyl]phenol), were prepared and their uptake in cancer cells and photocytotoxicity were studied. Complexes 4 and 5, having a non-pyridoxal Schiff base, were prepared to probe the role of the pyridoxal group in tumor targeting and cellular uptake. The PF6 salt (1a) of complex 1 is structurally characterized. The complexes have a distorted six-coordinate FeN4O2 core where the metal is in the +3 oxidation state with five unpaired electrons. The complexes display a ligand to metal charge transfer band near 520 and 420 nm from phenolate to the iron(III) center. The photophysical properties of the complexes are explained from the time dependent density functional theory calculations. The redox active complexes show a quasi-reversible Fe(III)/Fe(II) response near -0.3 V vs saturated calomel electrode. Complexes 2 and 3 exhibit remarkable photocytotoxicity in various cancer cells with IC50 values ranging from 0.4 to 5 mu M with 10-fold lower dark toxicity. The cell death proceeded by the apoptotic pathway due to generation of reactive oxygen species upon light exposure. The nonvitamin complexes 4 and 5 display 3-fold lower photocytotoxicity compared to their VB6 analogues, possibly due to preferential and faster uptake of the vitamin complexes in the cancer cells. Complexes 2 and 3 show significant uptake in the endoplasmic reticulum, while complexes 4 and 5 are distributed throughout the cells without any specific localization pattern.

Nonlinear Optical Properties and Temperature-Dependent UV-Vis Absorption and Photoluminescence Emission in 2D Hexagonal Boron Nitride Nanosheets

Recently, a lot of interest has been centred on the optical properties of hexagonal boron nitride (h-BN), which has a similar lattice structure to graphene. Interestingly, h-BN has a wide bandgap and is biocompatible, so it has potential applications in multiphoton bioimaging, if it can exhibit large nonlinear optical (NLO) properties. However, extensive investigation into the NLO properties of h-BN have not been done so far. Here, NLO properties of 2D h-BN nanosheets (BNNS) are reported for the first time, using 1064-nm NIR laser radiation with a pulse duration of 10 ns using the Z-scan technique. The reverse saturable absorption occurs in aqueous colloidal solutions of BNNS with a very large two-photon absorption cross section (sigma(2PA)) of approximate to 57 x 10(-46) cm(4) s(-1) photon(-1). Also, by using UV-Vis absorption spectroscopy, the temperature coefficient of the bandgap (dE(g)/dT) of BNNS is determined to be 5.9 meV K-1. Further defect-induced photoluminescence emission in the UV region is obtained in the 283-303 K temperature range, under excitations of different wavelengths. The present report of large sigma(2PA) combined with stability and biocompatibility could open up new possibilities for the application of BNNS as a potential optical material for multiphoton bioimaging and advanced photonic devices.

Visible light-induced cytotoxicity of a dinuclear iron(III) complex of curcumin with low-micromolar IC50 value in cancer cells

Photoactive metal complexes have emerged as potential candidates in the photodynamic therapy (PDT) of cancer. We present here the synthesis, characterization and visible light-triggered anticancer activity of two novel mixed-ligand oxo-bridged iron(III) complexes, viz., {Fe(L)(acac)}(2)(mu-O)](ClO4)(2) (1) and {Fe (L)(cur)}(2)(mu-O)](ClO4)(2) (2) where L is bis-(2-pyridylmethyl)-benzylamine, acac is acetylacetonate and cur is the monoanion of curcumin (bis(4-hydroxy-3-methoxyphenyl)-1,6-diene-3,5-dione). The crystal structure of complex 1 (as PF6 salt, 1a) shows distorted octahedral geometry of each iron(III) centre formed by the FeN3O3 core. The 1: 2 electrolytic complexes are stable in solution and retain their oxo-bridged identity in aqueous medium. Complex 2 has a strong absorption band in the visible region and shows promising photocytotoxicity in HeLa and MCF-7 cancer cells in visible light giving respective IC50 values of 3.1 +/- 0.4 lM and 4.9 +/- 0.5 lM while remains non-toxic in the dark (IC50 > 50 lM). The control complex 1 is inactive both in the light and dark. Complex 2 accumulates in cytoplasm of HeLa and MCF-7 cells as evidenced from fluorescence microscopy and triggers apoptotic cell death via light-assisted generation of reactive oxygen species (ROS). Taken together, complex 2 with its promising photocytotoxicity but negligible dark toxicity in cancer cells has significant photochemotherapeutic potential for applications in PDT. (C) 2015 Elsevier B.V. All rights reserved.

Mitochondria-Targeting Iron(III) Catecholates for Photoactivated Anticancer Activity under Red Light

Iron(III) catecholates Fe(R-bpa)(R-dopa)Cl] (1, 2) with a triphenylphosphonium (TPP) moiety, where R-bpa is 2-(TPP-N,N-bis((pyridin-2-yl)methyl)ethanamine) chloride (TPPbpa) and R-dopa is 4-{2-(anthracen-9-yl)methylamino]ethyl}benzene-1,2-diol (andopa, 1) or 4-{2-(pyren-1-yl)-methylamino]ethyl}benzene-1,2-diol (pydopa, 2), were synthesized and their photocytotoxicity studied. Complexes 3 and 4 with phenyl-N,N-bis(pyridin-2-yl)methyl]methanamine (phbpa) were used as controls. The catecholate complexes showed an absorption band near 720 nm. The 5e(-) paramagnetic complexes showed a Fe-III/Fe-II irreversible response near -0.45 V and a quasi-reversible catechol/semiquinone couple near 0.5 V versus saturated calomel electrode (SCE) in DMF/0.1 M tetrabutylammonium perchlorate. They showed photocytotoxicity in red/visible light in HeLa, HaCaT, MCF-7, and A549 cells. Complexes 1 and 2 displayed mitochondrial localization, reactive oxygen species (ROS) generation under red light, and apoptotic cell death. Control complexes 3 and 4 exhibited uniform distribution throughout the cell. The complexes showed DNA photocleavage under red light (785 nm), forming hydroxyl radicals as the ROS.