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1

Crystal structure of 8-quinolinol-7-sulfonic acid monohydrate  

Microsoft Academic Search

The structure of monohydrated 8-quinolinol-7-sulfonic acid has been determined from 1156 x-ray intensities obtained by counter methods at room temperature and refined by full-matrix least squares toR = 0.054. The space group isP21\\/c and the cell constants area = 7.08(1),b = 9.485(10),c = 16.407(10) Å,ß = 115.5(5) °. The zwitterionic compound occurs in infinite sheets connected by hydrogen bonds through

J. C. A. Boeyens

1976-01-01

2

THE THERMAL DECOMPOSITION OF THE 5,7-DIHALO-8QUINOLINOL RARE EARTH METAL CHELATES  

Microsoft Academic Search

S>The thermal decomposition of the 5,7-dichloro-, 5,7dibromo- and 5,7-; diiodo-8-quinolinol chelates of La, Ce, Pr, Nd, Sm, and Y was investigated on the ; thermobalance. The chelates decomposed in the temperature range from 65 to 125 ; deg C while the oxide levels were obtained from 395 to 805 deg C. Although the ; chelate thermal stability temperatures varied little

W Wendlandt

1957-01-01

3

8-Quinolinolate complexes of yttrium and ytterbium: molecular arrangement and fragmentation under laser impact.  

PubMed

New 8-quinolinolate (Q) complexes of yttrium () and ytterbium () were synthesized by the reactions of Cp3Y and Yb[N(SiMe3)2]3 with 3 equiv. of 8-hydroxyquinoline in a DME solution. Single crystal X-ray analysis revealed the trinuclear molecular structure of the compounds Ln3Q9. The LDI-TOFMS investigation displayed that under the laser impact the compounds split off Q(-) anions to give Ln3Q8(+), Ln2Q5(+) and LnQ3(+) moieties. In the negative mode spectra the anions Q(-) and LnQ4(-) were observed. The DFT calculations showed the decreased stability of cationic Ln-quinolinolate as compared with their anionic counterparts. Complex which is used as an emitter in a three-layer OLED displayed a metal-centered emission at 979 nm and an intensity of 50 ?W cm(-2) at 15.5 V. PMID:24048370

Baranov, Evgeny V; Fukin, Georgy K; Balashova, Tatyana V; Pushkarev, Anatoly P; Grishin, Ivan D; Bochkarev, Mikhail N

2013-10-22

4

Fluorometric determination of serum and urinary aluminium with 8-quinolinol by kinetic-differentiation-mode micellar chromatography.  

PubMed

A new fluorometric method has been developed for the determination of aluminium with 8-quinolinol by kinetic-differentiation-mode micellar chromatography. The proposed method enabled the determination of aluminium down to 1 microgram/l in human serum and urine without preliminary deproteinization. The most remarkable point of this method is that only aluminium ion selectively responds among metal ions. The complex formation of aluminium in serum with 8-quinolinol was completed within a few minutes at room temperature. The serum matrix and aluminium chelate were separated on a reversed-phase column with an eluent containing acetonitrile, sodium dodecylsulfate, and Triton X-100, and aluminium chelate was detected at Ex 370 nm, Em 504 nm. The values obtained by this method were in good agreement with those of Zeeman graphite-furnace atomic absorption spectrometry. The proposed method will provide a simple and rapid technique for the determination aluminium in medical fields. PMID:9440292

Sato, M; Yoshimura, H; Shimmura, T; Obi, H; Hatakeyama, S; Kaneko, E; Hoshino, H; Yotsuyanagi, T

1997-11-21

5

Fluorometric determination of serum and urinary aluminium with 8-quinolinol by kinetic-differentiation-mode micellar chromatography  

Microsoft Academic Search

A new fluorometric method has been developed for the determination of aluminium with 8-quinolinol by kinetic-differentiation-mode micellar chromatography. The proposed method enabled the determination of aluminium down to 1 ?g\\/l in human serum and urine without preliminary deproteinization. The most remarkable point of this method is that only aluminium ion selectively responds among metal ions. The complex formation of aluminium

Makoto Sato; Hajime Yoshimura; Tetsuo Shimmura; Hideki Obi; Shin-ichi Hatakeyama; Emiko Kaneko; Hitoshi Hoshino; Takao Yotsuyanagi

1997-01-01

6

Molecular optical switches based on [Ru(OAc)(2cqn)2NO](H2cqn=2-chloro-8-quinolinol)  

NASA Astrophysics Data System (ADS)

Photoisomerization from cis-2 [Ru(OAc)(2cqn)2NO] (H2cqn=2-chloro-8-quinolinol) to cis-1 isomer was studied quantitatively and the effect of wavelength on isomerization was investigated. The main absorption band in UV-Vis region for cis-1 and cis-2 isomer was observed from 350 nm to 500 nm, and the kinetic study showed that the photoisomerization from cis-2 to cis-1 isomer was first-order and the rate constant (k) is 0.00022 (s-1) at 420 nm, 0.00018 (s-1) at 475 nm, 0.00011 (s-1) at 550 nm, respectively. Density functional theory (DFT) calculation suggested that the electronic transition from a ligand based orbital to an antibonding overlap of the Ru(d) and ?* NO(p) orbitals control the photo induced reactivity of [Ru(OAc)(2cqn)2NO] complexes. The study provides basic information to design the molecular optical switches and advance optoelectronic materials based on nitrosylruthenium(II) complexes.

Wang, Hongfei; Jin, Xiaowei; Wang, Jianru; Qiao, Xiaoyan

2011-11-01

7

Extractive photometric determination of gallium with 8-quinolinol in layered crystals of bismuth telluride-estimation of the determination limit.  

PubMed

A method for determining microgram amounts of gallium in milligram samples of layered monocrystals of the type A(V)(2)B(VI)(3) is described. For the separation of 1-5 mug of gallium(III) from a large excess of bismuth in a single extraction the recommended conditions are pH 3.6-4.2 (acetate buffer, V(aq) 40 ml), an adequate excess of 8-quinolinol for complete extraction and of thiosulphate for masking bismuth. The absorbance of a chloroform extract (V(org) = 10 ml) is measured at 392.5 nm in a 50-mm cell against a blank extract concurrently obtained with a solution of pure Bi(2)Te(3). Reference polycrystalline materials are used to check the precision and accuracy of the method. In routine analysis of layered monocrystals a relative standard deviation of 4-8% is to be expected for about 1 mug of gallium in the extraction system. Estimation of the limit of determination, based on two statistical models, is discussed with respect to the error of the method and the fluctuation of the blank. PMID:18964630

Srámková, J; Kotrlý, S

1988-11-01

8

Determination of ultra-trace amounts of cobalt in seawater by graphite furnace atomic absorption spectrometry after pre-concentration with Ni\\/8-quinolinol\\/1-nitroso-2-naphthol complex  

Microsoft Academic Search

A sensitive and accurate method for the determination of ultra-trace amounts of cobalt in seawater is described. Ultra-trace amounts of cobalt were pre-concentrated by co-precipitation with a combination of 8-quinolinol and nickel as a carrier element and 1-nitroso-2-naphtol as an auxiliary complexing agent. The co-precipitates obtained were directly measured by graphite furnace atomic absorption spectrometry using the solid-sampling technique. The

Qiangbin Zhang; Hirotsugu Minami; Sadanobu Inoue; Ikuo Atsuya

2000-01-01

9

Studies of the degradation mechanism of organic light-emitting diodes based on tris(8-quinolinolate)aluminum Alq and 2-tert-butyl-9,10-di(2-naphthyl)anthracene TBADN  

NASA Astrophysics Data System (ADS)

Previously, radical cation of tris(8-quinolinolate)aluminum (Alq•+) has been associated with the instability of Alq films subjected to holes-only electrical current. Yet, the questions remain (i) whether Alq•+ is the primary source of the intrinsic degradation of bipolar organic light-emitting diodes (OLEDs) based on Alq, (ii) whether Alq•+ reactions result in deep charge traps in holes-only devices as found in bipolar counterparts, and (iii) whether radical cations can be a common source of degradation of OLEDs irrespective of materials. With regards to generality of hole-current-related degradation, it is interesting to examine the behavior of 9,10-diarylanthracenes (DAAs)-the practically important class of blue-fluorescing light-emitting-layer hosts. These questions prompted our comparative study of the effects of unipolar currents in Alq and 2-t-butyl-9,10-di(2-naphthyl)anthracene (TBADN), which was chosen as a representative material of the DAA class. First, we identified device structures allowing for rigorous and stable unipolar conduction. Interestingly, even in pristine holes-only devices, our voltammetric measurements indicated that Alq contains a substantial density of deep hole traps (far deeper than what can be explained by energetic disorder), which can be charged by passing holes-only current and seemingly discharged by exposure to white light. As for aged holes-only Alq devices, they exhibited symptoms qualitatively matching those of aged bipolar Alq devices, viz., photoluminescence (PL) loss, transition voltage (V0) rise, and drive voltage (Vd) rise. Notably, PL and V0 are linearly correlated in both holes-only and bipolar devices, which reinforces the supposed link between Alq•+ and the degradation in both types of devices. Yet, there are indications the Alq•+ instability may not be the only degradation pathway in bipolar devices. Even though our observations for holes-only Alq devices agree qualitatively with previously reported ones, we observe far slower degradation rates [Alq PL fades up to ~500 times slower in holes-only devices, while Alq electroluminescence (EL) fades ~50 times slower in bipolar control devices]. It is possible that impurities play a significant, perhaps crucial role in the degradation mechanism of both bipolar and holes-only devices, especially the relatively shorter-lived ones. In sharp contrast to Alq, all three observables (PL, V0, and Vd) indicate that holes-only current in TBADN (neat or doped with a perylene-based blue dopant) does not result in degradation in the time that is sufficient for the corresponding bipolar control devices to lose 60%-80% of EL and 20%-30% of PL. We find that the electrons-only current in Alq or TBADN does not result in degradation either. Thus, the degradation of Alq and DAA bipolar devices may be caused by fundamentally dissimilar mechanisms: while hole current may damage the former, it does not appear to affect the latter, suggesting that the initiation step is different.

Jarikov, Viktor V.; Kondakov, Denis Y.

2009-02-01

10

Antimicrobial Activity of 8-Quinolinols, Salicylic Acids, Hydroxynaphthoic Acids, and Salts of Selected Quinolinols with Selected Hydroxy-Acids  

PubMed Central

Seventy-seven compounds were screened by the disc-plate method against strains of five bacteria and five fungi. A new constant was proposed to describe the antimicrobial activity of a compound in a defined system of organisms. This constant includes not only the inhibitory level of activity of the material but also the number of organisms inhibited. This constant, the antimicrobial spectrum index, was compared with the antimicrobial index of Albert.

Gershon, Herman; Parmegiani, Raulo

1962-01-01

11

Cancer stem\\/progenitor cell active compound 8-quinolinol in combination with paclitaxel achieves an improved cure of breast cancer in the mouse model  

Microsoft Academic Search

Increasing evidence suggests that breast cancer is caused by cancer stem cells and the cure of breast cancer requires eradication\\u000a of breast cancer stem cells. In this study, we established and characterized a sphere culture model derived from side population\\u000a cells from the human breast cancer cell line MCF7. The sphere culture could be maintained long term and was enriched

Jiangbing Zhou; Hao Zhang; Peihua Gu; Joseph B. Margolick; Deling Yin; Ying Zhang

2009-01-01

12

Hollow fiber cartridges for removal of particulate matter from natural waters prior to matrix isolation and trace metal enrichment using an 8-quinolinol chelating ion exchanger in a flow system  

Microsoft Academic Search

Natural water samples are normally filtered through a 0.45 ?m membrane filter before analysis. Such filters clog rapidly, however, when the content of humic acids is high. An alternative approach for natural water filtration is reported in this paper. Sample solutions are pumped into tubing containing a coaxial hollow fiber and a needle valve restrictor at the outlet. One end

Nii-Kotey Djane; Fredrik Malcus; Eduardo Martins; Gerald Sawula; Gillis Johansson

1995-01-01

13

Effect of the Organic Ligand on the Flame-Emission Response for Vanadium.  

National Technical Information Service (NTIS)

Flame emission intensities from vanadium in the forms of chelates of N-nitrosophenyl hydroxylamine and 8-quinolinol in methylisobutyl ketone were measured. Although differences in atomic absorption characteristics for vanadium bound by different ligands h...

B. J. Wood J. A. Galobardes L. B. Rogers

1981-01-01

14

76 FR 54230 - Product Cancellation Order for Certain Pesticide Registrations  

Federal Register 2010, 2011, 2012, 2013

...Borax. Copper naphthenate. 001448-00149...Copper 8- Copper, bis(8- Quinolinolate...Microbiocide 56.... 1-(Alkyl...Suite 200, Burr Ridge, IL 60527. 961...Pool & Spa (An Arch Chemicals, Inc. Business...Drexel Chemical Company, 1700...

2011-08-31

15

76 FR 3138 - Notice of Receipt of Requests To Voluntarily Cancel Certain Pesticide Registrations  

Federal Register 2010, 2011, 2012, 2013

...Copper 8- Copper, bis(8- Quinolinolate...Microbiocide 56.. 1-(Alkyl...Pear Wrap III.... Copper carbonate, basic...Suite 200, Burr Ridge, IL 60527. 961...Pool & Spa, (An Arch Chemicals, Inc. Business...Drexel Chemical Company, 1700...

2011-01-19

16

Supramolecular synthon pattern in solid clioquinol and cloxiquine (APIs of antibacterial, antifungal, antiaging and antituberculosis drugs) studied by 35 Cl NQR, 1 H- 17 O and 1 H- 14 N NQDR and DFT\\/QTAIM  

Microsoft Academic Search

The quinolinol derivatives clioquinol (5-chloro-7-iodo-8-quinolinol, Quinoform) and cloxiquine (5-chloro-8-quinolinol) were\\u000a studied experimentally in the solid state via 35Cl NQR, 1H-17O and 1H-14N NQDR spectroscopies, and theoretically by density functional theory (DFT). The supramolecular synthon pattern of O–H···N\\u000a hydrogen bonds linking dimers and ?–? stacking interactions were described within the QTAIM (quantum theory of atoms in molecules)\\u000a \\/DFT (density functional theory)

Jolanta Natalia Latosi?ska; Magdalena Latosi?ska; Marzena Agnieszka Tomczak; Janez Seliger; Veselko Žagar

17

The blue aluminum and gallium chelates for OLEDs  

Microsoft Academic Search

Pentacoordinate Al and Ga complexes of the type ML2OR, where L is a 2-methyl-8-quinolinolate and OR is a monodentate, anionic O donor ligand, were optimized for robust use in vapor-deposited OLEDs. Photophysical, thermal, and crystallographic properties relevant to OLEDs are reported. The utility of the complexes is illustrated in new formulations for blue fluorescent and red phosphorescent OLEDs.

Joseph C. Deaton; Christopher T. Brown; Manju Rajeswaran; Marina E. Kondakova

2008-01-01

18

Effects of subinhibitory concentrations of nitroxoline on the surface properties of Escherichia coli  

Microsoft Academic Search

Nitroxoline (5-nitro-8-quinolinol; NIQ) at subinhibitory concentrations (sub-MIC) decreased the adherence of uropathogenicEscherichia coli to catheter surface and significantly enhanced cell surface hydrophobicity. The surface hydrophobicity increased in the presence\\u000a of sub-MIC of NIQ and also in an excess of Mg2+. The effect of NIQ on the cell surface was not related to the bacteriostatic effect of this agent. The increase

H. Latrache; P. Bourlioux; M. Karroua; H. Zahir; A. Hakkou

2000-01-01

19

Flow-injection column preconcentration directly coupled with electrothermal atomization atomic absorption spectrometry for the determination of aluminium. Comparison of column packing materials  

Microsoft Academic Search

A method has been developed for the determination of endogenous levels of aluminium (>1 ?l?1) in water samples using an automated on-line preconcentration system with flow injection coupled directly to an electrothermal atomic absorption spectrometer. Two preconcentration materials, 8-quinolinol immobilized on controlled-pore glass (8-Q-CPG) and Amberlite XAD-2, poly(styrene\\/divinyl benzene) copolymer (XAD-2) were investigated and compared. Both systems were found to

Dongxing Yuan; Ian L. Shuttler

1995-01-01

20

Displacement of the bandedges of GaInP{sub 2} in aqueous electrolytes induced by surface modification  

SciTech Connect

Photoelectrolysis of water at ambient temperature (25 C) into hydrogen and oxygen thermodynamically requires a free energy of 1.23 eV. GaInP{sub 2} was identified as a promising material since its bandgap (1.8 to 1.9 eV) is ideal for this reaction. However, previous work determining the flatband potential of p-GaInP{sub 2} has revealed that the position of the bandedges are from 100 to 400 meV too negative for water splitting. The surface of epi layer p-GaInP{sub 2} electrodes was treated using 8-quinolinol, cupferron, and ferrocyanide, producing a modified surface directed at varying the Helmholtz layer charge. Mott-Schottky and photocurrent-voltage measurements were carried out to determine if there was any shift in the flatband potential or change in the onset of photocurrent due to the altered surface charge. Treatments with 8-quinolinol and cupferron were found to shift the flatband to more positive potentials; treatments with ferrocyanide produced a negative shift. The quinolate-modified interface had flatband potentials that were pH independent in the range 5 through 8. Photoluminescence studies on electrodes that were etched, treated with 8-quinolinol, and exposed to air for long periods showed no degradation of the luminescence intensity or photoluminescence decay time, in contrast to untreated electrodes.

Kocha, S.S.; Turner, J.A. [National Renewable Energy Lab., Golden, CO (United States). Photoconversion Branch

1995-08-01

21

Studies on technetium complexes containing nitrogen heterocyclic ligands  

SciTech Connect

Two classes of low valent technetium complexes containing polypyridyl ligands have been prepared and characterized by spectrophotometric, mass spectroscopic, electrochemical and single crystal x-ray structure techniques. The first class, of the general form cis(X),trans(P)-(Tc/sup III/II/X/sub 2/ (PR/sub 2/R')L)/sup +/0/ (X = Cl or Br, L = 2,2'-bipyridine, 1,10-phenanthroline or 4,4'-dimethyl-2,2'-bipyridine), can be prepared in either the Tc(III) or Tc(II) form. The second class, of the general form trans (P)-TcX(PR/sub 2/R')terpy/sup +/, can be prepared only in the Tc(II) form. A series of Tc(V) complexes containing 8-quinolinolate ligands has been synthesized and characterized. The complexes are of the general form TcO(L)/sub 2/X, where L is a bidentate 8-quinolinolate ligand and X is Cl or Br. The complexes have been characterized by elemental analysis, UV-visible and IR spectroscopy and by single crystal x-ray structural analysis of TcO (oxMe)Cl (oxMe = 2-methyl-8-quinolinolate). Single crystal x-ray structural analysis of a new complex chlorobis(2-(2-hydroxyphenyl)benzothialoato)-oxotechnetium(V), TcO(hbt)/sub 2/Cl, is presented. This complex results from the oxidative intramolecular ring closure reaction of a tridentate O,N,S Schiff base molecule N-(2-mercaptophenyl)salicylideneimine to form the bidentate 2-(2-hydroxyphenyl)benzothiazole moiety.

Wilcox, B.E.

1987-01-01

22

Selective Precipitation of Thorium lodate from a Tartaric Acid-Hydrogen Peroxide Medium Application to Rapid Spectrophotometric Determination of Thorium in Silicate Rocks and in Ores  

USGS Publications Warehouse

This paper presents a selective iodate separation of thorium from nitric acid medium containing d-tartaric acid and hydrogen peroxide. The catalytic decomposition of hydrogen peroxide is prevented by the use of 8quinolinol. A few micrograms of thorium are separated sufficiently clean from 30 mg. of such oxides as cerium, zirconium, titanium, niobium, tantalum, scandium, or iron with one iodate precipitation to allow an accurate determination of thorium with the thoronmesotartaric acid spectrophotometric method. The method is successful for the determination of 0.001% or more of thorium dioxide in silicate rocks and for 0.01% or more in black sand, monazite, thorite, thorianite, eschynite, euxenite, and zircon.

Grimaldi, F. S.

1957-01-01

23

Effects of subinhibitory concentrations of nitroxoline on the surface properties of Escherichia coli.  

PubMed

Nitroxoline (5-nitro-8-quinolinol; NIQ) at subinhibitory concentrations (sub-MIC) decreased the adherence of uropathogenic Escherichia coli to catheter surface and significantly enhanced cell surface hydrophobicity. The surface hydrophobicity increased in the presence of sub-MIC of NIQ and also in an excess of Mg2+. The effect of NIQ on the cell surface was not related to the bacteriostatic effect of this agent. The increase in nitrogen and decrease in phosphate content in the cell surface was found in the presence of NIQ. NIQ did not inhibit the expression of fimbriae. PMID:11501411

Latrache, H; Bourlioux, P; Karroua, M; Zahir, H; Hakkou, A

2000-01-01

24

Reactions of the cationic diruthenium carbonyl complex [Ru 2(?-dppm) 2(CO) 4(?,? 2-O 2CMe)] + with bidentate ligands; intramolecularly assisted stereospecific synthesis via the second-sphere face-to-face ?–? stacking interactions  

Microsoft Academic Search

The reactions of the diruthenium carbonyl complexes [Ru2(?-dppm)2(CO)4(?,?2-O2CMe)]X (X=BF4? (1a) or PF6? (1b)) with neutral or anionic bidentate ligands (L,L) afford a series of the diruthenium bridging carbonyl complexes [Ru2(?-dppm)2(?-CO)2(?2-(L,L))2]Xn ((L,L)=acetate (O2CMe), 2,2?-bipyridine (bpy), acetylacetonate (acac), 8-quinolinolate (quin); n=0, 1, 2). Apparently with coordination of the bidentate ligands, the bound acetate ligand of [Ru2(?-dppm)2(CO)4(?,?2-O2CMe)]+ either migrates within the same complex

Kom-Bei Shiu; Shih-Wei Jean; Yu Wang; Gene-Hsiang Lee

2002-01-01

25

Bicyclic compounds repress membrane vesicle production and Pseudomonas quinolone signal synthesis in Pseudomonas aeruginosa.  

PubMed

Pseudomonas aeruginosa secretes membrane vesicles (MVs) that deliver several virulence factors as a cargo. We found that indole and its derivative compounds, including 4-hydroxyindole, 5-hydroxyindole, 6-hydroxyindole and isatin, repress MV production significantly. These compounds also repressed the synthesis of Pseudomonas quinolone signal (PQS), which is one of the quorum-sensing signals that upregulate virulence gene expression and positively control MV production. Moreover, we showed that other bicyclic compounds, including 1-naphthol, 2-naphthol, 2,3-dihydroxynaphthalene, 1-aminonaphthalene and 8-quinolinol, significantly repress MV production and PQS synthesis. In conclusion, we provide new information about the chemical structures that inhibit P. aeruginosa virulence. PMID:20146747

Tashiro, Yosuke; Toyofuku, Masanori; Nakajima-Kambe, Toshiaki; Uchiyama, Hiroo; Nomura, Nobuhiko

2010-01-11

26

Tetra-kis(8-quinolinolato-?2 N,O)hafnium(IV) dimethyl-formamide solvate monohydrate  

PubMed Central

In the title compound, [Hf(C9H6NO)]·C3H7NO·H2O, the hafnium(IV) atom is coordinated by four 8-quinolinolate (Ox) ligands, forming a slightly distorted square-anti­prismatic coordination polyhedron. The crystal packing is controlled by O—H?O and C—H?O hydrogen-bonding inter­actions and ?–? inter­actions between quinoline ligands of neighbouring mol­ecules. The inter­planar distances vary between 3.150?(1) and 3.251?(2)?Å, while centroid–centroid distances vary from 3.589?(1) to 4.1531?(1)?Å.

Viljoen, Johannes A.; Visser, Hendrik G.; Roodt, Andreas

2010-01-01

27

Potentiometric responses of polymeric liquid membranes based on hydrophobic chelating agents to metal ions.  

PubMed

The effect of hydrophobicity of acidic chelating agents as sensing materials on the potentiometric responses of polymeric liquid membranes was investigated. The chelating agents tested were 8-quinolinol (HOx), dithizone (HDz), 1-(2-pyridylazo)-2-naphthol (PAN) and their alkylated analogues, 5-octyloxymethyl-8-quinolinol (HO8Q), di(phexylphenyl)thiocarbazone (C6HDz), 7-pentadecyloxy-1-(2-pyridylazo)-2-naphthol (C15PAN) and a series of N-alkylcarbonyl-N-phenylhydroxylamines (CnPHA, n = 3, 6, 9, 12). The distribution coefficients between membrane solvent and water were determined to evaluate the hydrophobicity of the agents. The potential-pH profiles of the membranes containing hydrophobic chelating agents demonstrated the generation of potentiometric responses, while less hydrophobic agents gave no response. A possible model for the generation of membrane potential is proposed. The charge separation is attained by the permselective uptake of metal cations by the chelating agent anion at membrane/solution interface, where the high hydrophobicity of the agent enables the anionic or deprotonated form of the agents to remain at the membrane/solution interface. PMID:11708143

Itoh, Y; Ueda, Y; Hirano, A; Sugawara, M; Tohda, K; Akaiwa, H; Umezawa, Y

2001-05-01

28

Homogeneous liquid-liquid solvent extraction. [Propylene carbonate-water system  

SciTech Connect

This investigation was undertaken to extend the technique of homogeneous liquid-liquid solvent extraction into propylene carbonate. The mutual solubilities of propylene carbonate in water and vice-versa are shown in the phase diagram. The extraction of a variety of monodentate and bidentate ligand complexes with Fe(III) as a function of ligand concentration and pH were investigated. The monodentate ligands studied include, thiocyanate, chloride, bromide, benzoate, and bathophenanthrolines. The bidentate ligands studied include the various ..beta..-diketones, 8-quinolinol, and also cupferron which was studied under normal conditions, i.e., not under conditions of homogeneous extraction. The homogeneous extraction proved effective for a variety of chelate complexes and ion association complexes of iron giving, in all cases, very rapid extraction as compared with the slow rate of conventional extraction methods.

Ting, C.S.; Williams, E.T.; Finston, H.L.

1980-01-01

29

Concentration method for the spectrochemical determination of seventeen minor elements in natural water  

USGS Publications Warehouse

A method for the quantitative spectrochemical determination of microgram amounts of 17 minor elements in water is given. The chelating reagents 8-quinolinol, tannic acid, and thionalide are utilized to concentrate traces (1 to 500 ??g.) of aluminum, cobalt, chromium, copper, iron, gallium, germanium, manganese, nickel, titanium, vanadium, bismuth, lead, molybdenum, cadmium, zinc, and beryllium. Indium is added as a buffer, and palladium is used as an internal standard. The ashed oxides of these 17 metals are subsequently subjected to direct current arcing conditions during spectrum analysis. The method can be used to analyze waters with dissolved solids ranging from less than 100 to more than 100,000 p.p.m. There is no limiting concentration range for the determination of the heavy metals since any volume of sample can be used that will contain a heavy metal concentration within the analytical range of the method. Both the chemical and spectrographic procedures are described, and precision and accuracy data are given.

Silvey, W. D.; Brennan, R.

1962-01-01

30

Pollutant-Induced Modulation in Conformation and ?-Lactamase Activity of Human Serum Albumin  

PubMed Central

Structural changes in human serum albumin (HSA) induced by the pollutants 1-naphthol, 2-naphthol and 8-quinolinol were analyzed by circular dichroism, fluorescence spectroscopy and dynamic light scattering. The alteration in protein conformational stability was determined by helical content induction (from 55 to 75%) upon protein-pollutant interactions. Domain plasticity is responsible for the temperature-mediated unfolding of HSA. These findings were compared to HSA-hydrolase activity. We found that though HSA is a monomeric protein, it shows heterotropic allostericity for ?-lactamase activity in the presence of pollutants, which act as K- and V-type non-essential activators. Pollutants cause conformational changes and catalytic modifications of the protein (increase in ?-lactamase activity from 100 to 200%). HSA-pollutant interactions mediate other protein-ligand interactions, such as HSA-nitrocefin. Therefore, this protein can exist in different conformations with different catalytic properties depending on activator binding. This is the first report to demonstrate the catalytic allostericity of HSA through a mechanistic approach. We also show a correlation with non-microbial drug resistance as HSA is capable of self-hydrolysis of ?-lactam drugs, which is further potentiated by pollutants due to conformational changes in HSA.

Ahmad, Ejaz; Rabbani, Gulam; Zaidi, Nida; Ahmad, Basir; Khan, Rizwan Hasan

2012-01-01

31

PROPERTIES OF PROTEINASE FROM STREPTOCOCCUS FAECALIS VAR. LIQUEFACIENS1  

PubMed Central

Bleiweis, Arnold S. (The Pennsylvania State University, University Park), and Leonard N. Zimmerman. Properties of proteinase from Streptococcus faecalis var. liquefaciens. J. Bacteriol. 88:653–659. 1964.—The extracellular group D streptococcal proteinase is inactivated by chelating agents [ethylenediamine-tetraacetate (EDTA), o-phenanthroline, and 8-quinolinol] and mercaptans (cysteine, mercaptoethanol, and thioglycolate). The optimal inhibitory concentrations of EDTA (4 × 10?4m) and cysteine (2.5 × 10?2m) promote rapid loss of activity with 50% inactivation after 4 to 5 min. Enzyme inactivated by either EDTA or cysteine is reactivated about 80% by 4 × 10?4m Zn++. Such reactivation of EDTA-treated enzyme is prevented completely by iodoacetate (5 × 10?2m) and of cysteine-treated enzyme by oxidizing conditions, which suggests that the zinc binding-site may be a thiol. High levels of zinc (10?3m) do not allow reactivation in either case, and actually inhibit native proteinase. Ca++, Mg++, Co++, Fe++, Cu++, and Ni++ do not reactivate cysteine-treated enzyme, but Mn++ (10?4 to 8 × 10?4m) allows 27% reversal. N2-held, cysteine-treated enzyme can be spontaneously reactivated if the substrate is flushed with O2 during the assay; leakage of air or O2 into the samples before assay leads to loss of reactivatability. Native proteinase does not lose activity after dialysis for 43 hr against 0.07 m phosphate buffer. It is concluded that the group D proteinase obtained from Streptococcus faecalis var. liquefaciens is probably a zinc metalloenzyme that is unlike the thiol-activated, group A streptococcal proteinase, but similar to the mammalian carboxypeptidase A.

Bleiweis, Arnold S.; Zimmerman, Leonard N.

1964-01-01

32

Stereo-Selectivity of Human Serum Albumin to Enantiomeric and Isoelectronic Pollutants Dissected by Spectroscopy, Calorimetry and Bioinformatics  

PubMed Central

1–naphthol (1N), 2–naphthol (2N) and 8quinolinol (8H) are general water pollutants. 1N and 2N are the configurational enantiomers and 8H is isoelectronic to 1N and 2N. These pollutants when ingested are transported in the blood by proteins like human serum albumin (HSA). Binding of these pollutants to HSA has been explored to elucidate the specific selectivity of molecular recognition by this multiligand binding protein. The association constants (Kb) of these pollutants to HSA were moderate (104–105 M?1). The proximity of the ligands to HSA is also revealed by their average binding distance, r, which is estimated to be in the range of 4.39–5.37 nm. The binding free energy (?G) in each case remains effectively the same for each site because of enthalpy–entropy compensation (EEC). The difference observed between ?Cpexp and ?Cpcalc are suggested to be caused by binding–induced flexibility changes in the HSA. Efforts are also made to elaborate the differences observed in binding isotherms obtained through multiple approaches of calorimetry, spectroscopy and bioinformatics. We suggest that difference in dissociation constants of pollutants by calorimetry, spectroscopic and computational approaches could correspond to occurrence of different set of populations of pollutants having different molecular characteristics in ground state and excited state. Furthermore, our observation of enhanced binding of pollutants (2N and 8H) in the presence of hemin signifies that ligands like hemin may enhance the storage period of these pollutants in blood that may even facilitate the ill effects of these pollutants.

Ahmad, Ejaz; Rabbani, Gulam; Zaidi, Nida; Singh, Saurabh; Rehan, Mohd; Khan, Mohd Moin; Rahman, Shah Kamranur; Quadri, Zainuddin; Shadab, Mohd.; Ashraf, Mohd Tashfeen; Subbarao, Naidu; Bhat, Rajiv; Khan, Rizwan Hasan

2011-01-01

33

Small-molecule quinolinol inhibitor identified provides protection against BoNT/A in mice.  

PubMed

Botulinum neurotoxins (BoNTs), etiological agents of the life threatening neuroparalytic disease botulism, are the most toxic substances currently known. The potential for the use as bioweapon makes the development of small-molecule inhibitor against these deadly toxins is a top priority. Currently, there are no approved pharmacological treatments for BoNT intoxication. Although an effective vaccine/immunotherapy is available for immuno-prophylaxis but this cannot reverse the effects of toxin inside neurons. A small-molecule pharmacological intervention, especially one that would be effective against the light chain protease, would be highly desirable. Similarity search was carried out from ChemBridge and NSC libraries to the hit (7-(phenyl(8-quinolinylamino)methyl)-8-quinolinol; NSC 84096) to mine its analogs. Several hits obtained were screened for in silico inhibition using AutoDock 4.1 and 19 new molecules selected based on binding energy and Ki. Among these, eleven quinolinol derivatives potently inhibited in vitro endopeptidase activity of botulinum neurotoxin type A light chain (rBoNT/A-LC) on synaptosomes isolated from rat brain which simulate the in vivo system. Five of these inhibitor molecules exhibited IC(50) values ranging from 3.0 nM to 10.0 µM. NSC 84087 is the most potent inhibitor reported so far, found to be a promising lead for therapeutic development, as it exhibits no toxicity, and is able to protect animals from pre and post challenge of botulinum neurotoxin type A (BoNT/A). PMID:23071727

Singh, Padma; Singh, Manglesh Kumar; Chaudhary, Dilip; Chauhan, Vinita; Bharadwaj, Pranay; Pandey, Apurva; Upadhyay, Nisha; Dhaked, Ram Kumar

2012-10-11

34

Small-Molecule Quinolinol Inhibitor Identified Provides Protection against BoNT/A in Mice  

PubMed Central

Botulinum neurotoxins (BoNTs), etiological agents of the life threatening neuroparalytic disease botulism, are the most toxic substances currently known. The potential for the use as bioweapon makes the development of small-molecule inhibitor against these deadly toxins is a top priority. Currently, there are no approved pharmacological treatments for BoNT intoxication. Although an effective vaccine/immunotherapy is available for immuno-prophylaxis but this cannot reverse the effects of toxin inside neurons. A small-molecule pharmacological intervention, especially one that would be effective against the light chain protease, would be highly desirable. Similarity search was carried out from ChemBridge and NSC libraries to the hit (7-(phenyl(8-quinolinylamino)methyl)-8-quinolinol; NSC 84096) to mine its analogs. Several hits obtained were screened for in silico inhibition using AutoDock 4.1 and 19 new molecules selected based on binding energy and Ki. Among these, eleven quinolinol derivatives potently inhibited in vitro endopeptidase activity of botulinum neurotoxin type A light chain (rBoNT/A-LC) on synaptosomes isolated from rat brain which simulate the in vivo system. Five of these inhibitor molecules exhibited IC50 values ranging from 3.0 nM to 10.0 µM. NSC 84087 is the most potent inhibitor reported so far, found to be a promising lead for therapeutic development, as it exhibits no toxicity, and is able to protect animals from pre and post challenge of botulinum neurotoxin type A (BoNT/A).

Singh, Padma; Singh, Manglesh Kumar; Chaudhary, Dilip; Chauhan, Vinita; Bharadwaj, Pranay; Pandey, Apurva; Upadhyay, Nisha; Dhaked, Ram Kumar

2012-01-01

35

Stereo-selectivity of human serum albumin to enantiomeric and isoelectronic pollutants dissected by spectroscopy, calorimetry and bioinformatics.  

PubMed

1-naphthol (1N), 2-naphthol (2N) and 8-quinolinol (8H) are general water pollutants. 1N and 2N are the configurational enantiomers and 8H is isoelectronic to 1N and 2N. These pollutants when ingested are transported in the blood by proteins like human serum albumin (HSA). Binding of these pollutants to HSA has been explored to elucidate the specific selectivity of molecular recognition by this multiligand binding protein. The association constants (K(b)) of these pollutants to HSA were moderate (10(4)-10(5) M(-1)). The proximity of the ligands to HSA is also revealed by their average binding distance, r, which is estimated to be in the range of 4.39-5.37 nm. The binding free energy (?G) in each case remains effectively the same for each site because of enthalpy-entropy compensation (EEC). The difference observed between ?C(p) (exp) and ?C(p) (calc) are suggested to be caused by binding-induced flexibility changes in the HSA. Efforts are also made to elaborate the differences observed in binding isotherms obtained through multiple approaches of calorimetry, spectroscopy and bioinformatics. We suggest that difference in dissociation constants of pollutants by calorimetry, spectroscopic and computational approaches could correspond to occurrence of different set of populations of pollutants having different molecular characteristics in ground state and excited state. Furthermore, our observation of enhanced binding of pollutants (2N and 8H) in the presence of hemin signifies that ligands like hemin may enhance the storage period of these pollutants in blood that may even facilitate the ill effects of these pollutants. PMID:22073150

Ahmad, Ejaz; Rabbani, Gulam; Zaidi, Nida; Singh, Saurabh; Rehan, Mohd; Khan, Mohd Moin; Rahman, Shah Kamranur; Quadri, Zainuddin; Shadab, Mohd; Ashraf, Mohd Tashfeen; Subbarao, Naidu; Bhat, Rajiv; Khan, Rizwan Hasan

2011-11-02

36

Clioquinol: review of its mechanisms of action and clinical uses in neurodegenerative disorders.  

PubMed

Clioquinol was produced as a topical antiseptic and marketed as an oral intestinal amebicide in 1934, being used to treat a wide range of intestinal diseases. In the early 1970s, it was withdrawn from the market as an oral agent because of its association with subacute myelo-optic neuropathy (SMON), a syndrome that involves sensory and motor disturbances in the lower limbs and visual changes. The first methods for determining plasma and tissue clioquinol (5-chloro-7-iodo-8-quinolinol) levels were set up in the 1970s and involved HPLC separation with UV detection, these were followed by a more sensitive GC method with electron capture detection and a gaschromatographic-massspectrometric (GC-MS) method. Finally, an HPLC method using electrochemical detection has proved to be as highly sensitive and specific as the GC-MS. In rats, mice, rabbits, and hamsters, clioquinol is rapidily absorbed and undergoes first-pass metabolization to glucuronate and sulfate conjugates; the concentrations of the metabolites are higher than those of free clioquinol. Bioavailabilty versus intraperitoneal dosing is about 12%. Dogs and monkeys form fewer conjugates. In man, single-dose concentrations are dose related, and the drug's half-life is 11-14 h. There is no accumulation, and the drug is much less metabolized to conjugates. Clioquinol acts as a zinc and copper chelator. Metal chelation is a potential therapeutic strategy for Alzheimer's disease (AD) because zinc and copper are involved in the deposition and stabilization of amyloid plaques, and chelating agents can dissolve amyloid deposits in vitro and in vivo. In general, the ability of clioquinol to chelate and redistribute metals plays an important role in diseases characterised by Zn, Cu, Fe dyshomeostasis, such as AD and Parkinson's disease, as it reduces oxidation and the amyloid burden. Zinc chelators may also act as anticancer agents. Animal toxicity studies have revealed species-specific differences in neurotoxic responses that are related to the serum levels of clioquinol and metabolites. This is also true in humans, who form fewer conjugates. The results of studies of Alzheimer patients are conflicting and need further confirmation. The potential therapeutic role of the two main effects of MPACs (the regulation of the distribution of metals and antioxidants) has not yet been fully explored. PMID:21199452

Bareggi, Silvio R; Cornelli, Umberto

2010-12-27