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991.
Mohammad?Asif?Iqbal Ki-Hyun?KimEmail author Jan?E.?Szulejko Jinwoo?Cho 《Analytical and bioanalytical chemistry》2014,406(2):643-655
The gas–liquid partitioning behavior of major odorants (acetic acid, propionic acid, isobutyric acid, n-butyric acid, i-valeric acid, n-valeric acid, hexanoic acid, phenol, p-cresol, indole, skatole, and toluene (as a reference)) commonly found in microbially digested wastewaters was investigated by two experimental approaches. Firstly, a simple vaporization method was applied to measure the target odorants dissolved in liquid samples with the aid of sorbent tube/thermal desorption/gas chromatography/mass spectrometry. As an alternative method, an impinger-based dynamic headspace sampling method was also explored to measure the partitioning of target odorants between the gas and liquid phases with the same detection system. The relative extraction efficiency (in percent) of the odorants by dynamic headspace sampling was estimated against the calibration results derived by the vaporization method. Finally, the concentrations of the major odorants in real digested wastewater samples were also analyzed using both analytical approaches. Through a parallel application of the two experimental methods, we intended to develop an experimental approach to be able to assess the liquid-to-gas phase partitioning behavior of major odorants in a complex wastewater system. The relative sensitivity of the two methods expressed in terms of response factor ratios (RFvap/RFimp) of liquid standard calibration between vaporization and impinger-based calibrations varied widely from 981 (skatole) to 6,022 (acetic acid). Comparison of this relative sensitivity thus highlights the rather low extraction efficiency of the highly soluble and more acidic odorants from wastewater samples in dynamic headspace sampling. 相似文献
992.
Mohammed?M?Hefnawy Atef?M?Homoda Mohammed?A?Abounassif Amer?M?Alanazi Abdulrahaman?Al-Majed Gamal?A?MostafaEmail author 《Chemistry Central journal》2014,8(1):59
Background
The construction and electrochemical response characteristics of Poly (vinyl chloride) membrane sensors for moxifloxacin HCl (MOX) are described. The sensing membranes incorporate ion association complexes of moxifloxacin cation and sodium tetraphenyl borate (NaTPB) (sensor 1), phosphomolybdic acid (PMA) (sensor 2) or phosphotungstic acid (PTA) (sensor 3) as electroactive materials.Results
The sensors display a fast, stable and near-Nernstian response over a relative wide moxifloxacin concentration range (1 × 10-2 - 4.0 × 10-6, 1 × 10-2 - 5.0 × 10-6, 1 × 10-2 - 5.0 × 10-6 M), with detection limits of 3 × 10-6, 4 × 10-6 and 4.0 × 10-6 M for sensor 1, 2 and 3, respectively over a pH range of 6.0 - 9.0. The sensors show good discrimination of moxifloxacin from several inorganic and organic compounds. The direct determination of 400 μg/ml of moxifloxacin show an average recovery of 98.5, 99.1 and 98.6% and a mean relative standard deviation of 1.8, 1.6 and 1.8% for sensors 1, 2 and 3 respectively.Conclusions
The proposed sensors have been applied for direct determination of moxifloxacin in some pharmaceutical preparations. The results obtained by determination of moxifloxacin in tablets using the proposed sensors are comparable favorably with those obtained using the US Pharmacopeia method. The sensors have been used as indicator electrodes for potentiometric titration of moxifloxacin.993.
Samson?Jegan?Jennifer Packianathan?Thomas MuthiahEmail author Duraiswamy?Tamilselvi 《Chemistry Central journal》2014,8(1):58
Background
Most of the benzyladenine and furfuryladenine derivatives inhibit tumor/cancer cell growth; their toxicity is lesser than the compounds used for the treatment of cancer now-a-days. Many cytokinin derivatives are tested for anticancer activity.Results
A series of transition metal complexes containing N6-benzyl/furfuryl aminopurines of formula [Mn(FAH)2(H2O)(Cl3)]2.Cl2(1), [Co(FAH)2(H2O)(Cl3)]2.Cl2(2), [Co(FAH)2(Cl4)]2 .[Co(FAH)2(H3O)(Cl3)].Cl2(3), [Ni(FAH)2(H2O)(Cl3)]2.Cl2. (H2O) (4), [Zn(BAH)Br3] (5) and [Cd2(BAH)2(μ-Br)4Br2]n(6) (where BAH and FAH benzyladeninium and furfuryladeninium cations respectively) have been synthesized and characterized. Crystal structures of (1-4) have similar distorted octahedral coordination geometry, while (5) and (6) have distorted tetrahedral geometry and octahedral geometries respectively. In (1-4) two halide ions and two cytokinin cations (BAH+/FAH+) are laterally coordinated to the metal ion. A water molecule and a halide ion are axially coordinated. But the coordination sphere of (5) consists of N7 coordinated benzyladeninium ion and three halide ions. The complex (6) is a coordination polymer bridged by bromide anions. A common notable feature in (1-4) is the presence of one or more lattice chloride anions. They help in a chain formation by N-H…Cl halide involving hydrogen bonding interactions in between the Hoogsteen site hydrogen.Conclusions
The observed crystal structures emphasize the role of the halide ions in developing the supramolecular architectures by halide involving hydrogen bonding interactions. Also most of the reported cobalt cytokinin complexes possess tetrahedral coordination geometry, but some cobalt complexes have distorted octahedral coordination geometry, which are discussed and compared.
994.
Sergiu?Sima Catinca?SecuianuEmail author Viorel?Feroiu Dan?Gean? 《Central European Journal of Chemistry》2014,12(9):893-900
New vapor-liquid equilibria (VLE) data at 323.15, 333.15, 343.15, and 353.15 K and pressures up to 112.9 bar are reported for the carbon dioxide + 2-methyl-2-propanol system. The experimental method used in this work was a static analytical method with liquid and vapor phases sampling using a rapid online sampler injector (ROLSI?) coupled to a gas chromatograph (GC) for analysis. Measured VLE data and literature data for carbon dioxide + 2-methyl-2-propanol system were modeled with the Soave-Redlich-Kwong (SRK) cubic equation of state with classical van der Waals (two-parameter conventional mixing rule, 2PCMR) mixing rules. A single set of interaction parameters that lead to a correct phase behavior was used in this work to model the new VLE data and critical points of the mixtures in a wide range of temperature and pressure. The SRK prediction results were compared to the new data measured in this study and to available literature data. 相似文献
995.
Adriana?SamideEmail author Bogdan?Tutunaru 《Central European Journal of Chemistry》2014,12(9):901-908
Quinine sulfate dihydrate (QNS), IUPAC name: (8S,9R)-6-methoxy-4-quinolenyl-5-vinyl-2-quinuclidinyl methanol sulfate dihydrate, was tested as corrosion inhibitor for carbon steel in 1.5 mol L?1 HCl solution using the potentiodynamic polarization and the electrochemical impedance spectroscopy (EIS) associated with UV-Vis spectrophotometry. The electrochemical results showed that, the inhibition efficiency (IE) increased with the increase in QNS concentration, reaching a maximum value of 93.35±0.25%. The polarization resistance (R p) followed the same trend, obtaining the highest value of 659.7 Ω cm2, while the corrosion current density (i corr) reached the lowest level of 195 µA cm?2. The action mechanism of QNS was proposed considering the ability of quinine (QN) to be adsorbed on the metal surface via the lone pairs of electrons from hydroxyl oxygen atom, and/or from quinoline and quinuclidinic nitrogens. The occurrence of the complexes between inhibitor and iron ions was considered an additional process, which may contribute to protective layer formation. The Temkin adsorption isotherm was found as the best fitting for the degree of surface coverage (θ) values. In order to elucidate the mechanism of protective layer formation, the free energy of adsorption (ΔG o ads) value was calculated. This indicates that the inhibitor acts by chemical adsorption on the steel surface. 相似文献
996.
Tomá? Sára Thomas C Schwarz Dennis Kurzbach Christoph H Wunderlich Christoph Kreutz Robert Konrat 《ChemistryOpen》2014,3(3):115-123
Protein–protein interactions are of utmost importance to an understanding of biological phenomena since non-covalent and therefore reversible couplings between basic proteins leads to the formation of complex regulatory and adaptive molecular systems. Such systems are capable of maintaining their integrity and respond to external stimuli, processes intimately related to living organisms. These interactions, however, span a wide range of dissociation constants, from sub-nanomolar affinities in tight complexes to high-micromolar or even millimolar affinities in weak, transiently formed protein complexes. Herein, we demonstrate how novel NMR and EPR techniques can be used for the characterization of weak protein–protein (ligand) complexes. Applications to intrinsically disordered proteins and transiently formed protein complexes illustrate the potential of these novel techniques to study hitherto unobserved (and unobservable) higher-order structures of proteins. 相似文献
997.
该文基于牛血清白蛋白模板金纳米簇(BSA@AuNCs)与羟基氧化钴(CoOOH)纳米片构建了一种激活型荧光纳米探针用于生物硫醇的检测。带负电的BSA@AuNCs能通过静电吸附作用组装到带正电的CoOOH纳米片表面,与此同时,BSA@AuNCs的荧光由于内滤效应(IFE)有效地被CoOOH纳米片猝灭,形成BSA@AuNCs-CoOOH纳米探针。当向纳米探针溶液加入生物硫醇(0.05~150 μmol/L)时,生物硫醇与纳米探针中的CoOOH纳米片发生氧化还原反应,CoOOH纳米片被降解生成Co2+,同时释放出BSA@AuNCs,BSA@AuNCs荧光信号恢复。结果表明,该纳米探针可以检测低浓度的生物硫醇,对生物硫醇(半胱氨酸、谷胱甘肽和高半胱氨酸)的检出限为30 nmol/L。相对于其他的氨基酸、金属离子及糖类化合物,该纳米探针对生物硫醇具有较高的选择性并成功应用于人血清样品中生物硫醇的检测。 相似文献
998.
999.
1000.
A Kondo-like effect, namely, the upturn of resistivity at low temperatures, is observed in perovskite manganite when nonmagnetic insulators are doped as secondary phase. In this paper, the low-temperature resistivity upturn effect has been argued to originate from interfacial magnetic phase reconstruction. Heisenberg spin lattices have been simulated using the Monte Carlo method to reveal phase competition around secondary phase boundary, namely, manganite-insulator boundary that behaves with a weak antiferromagnetic tendency. Moreover, the resistor network model based on double-exchange conductive mechanism reproduces the low-temperature resistivity upturn effect. Our work provides a reasonable physical mechanism to understand the novel transport behaviors in microstructures of correlated electron systems. 相似文献