bluuebunny/crossref_metadata_2025 huggingface dataset:
Light Scattering and Lateral Resolved Reflection Spectroscopy on Electrochemically Reacting Electrodes
Authors: Oelkrug D. , Reich S. , Specht M. , Stauch H.
Published: March 2014

The electrochemical formation and reduction of oxide films on rough and polished electrodes of iron, low‐carbon steel and copper is investigated by in situ reflection spectroscopy in the UV/VIS‐range with simultaneous detection of polarized specular reflection and depolarized scattering. The reflectivity of the electrodes can be scanned with a lateral resolution of < 10 μm, and a rapid diode array reflectometer allows the registration of a series of complete spectra in the millisecond range which help to analyze the kinetics of electrode processes. The conversion of homogeneous films into light‐scattering porous layers can be detected in the region of a few monolayers and the voltages and pH‐values at which these conversions take place are determined. The experimental change of reflectivity with film thickness is compared with model calculations. Lateral resolved measurements on copper prove that the cupric oxide film is reduced to the metal not uniformly but first on the front of the electrode and then on the rear beginning at the edges and ending in the centre.
Eine neue Methode zur Untersuchung der Elektrosorption reaktiver Verbindungen
Authors: Holze Rudolf , Schneider Jürgen , Hamann Carl Heinz
Published: March 2014

The determination of thermodynamic and kinetic data of reactive chemisorption of organic molecules on electrodes with a new procedure is described. It substitutes a rapid electrolyte exchange with potential control of the working electrode for an electrode transfer. A new measurement and evaluation procedure allows determination of degree of coverage, rate of adsorption and interaction between adsorbate molecules from cyclic voltamograms recorded after adsorption and electrolyte exchange. As an example the adsorption of aliphatic alcohols (C1 to C4) on a platinum electrode in contact with an acidic electrolyte solution is studied. The results show the power of the method as compared with other ones, in particular with respect to kinetic data on the process not accessible by other methods. The adsorption rate constant increases from C1 to C3 by an order of magnitude with every C‐atom; the actual rate of adsorption changes much less, since with increasing chain length repulsive interaction between adsorbate molecules increases. Sec‐propanol shows a greatly diminished rate of adsorption, t‐butanol is adsorbed only slightly.
A Molecular Dynamics Study on the Water/Metal Interfacial Potential
Authors: Spohr E. , Heinzinger K.
Published: March 2014

Several Molecular Dynamics simulations of water on the (100) plane of a platinum single crystal have been performed for different degrees of surface coverage. The orientation of the water molecules is mainly determined by the water‐water interactions which is even true at low coverage as the water molecules are not distributed uniformly on the surface. The calculated work function change is in good agreement with experimental results.
Studies of the Differential Double Layer Capacitance of the Copper (111) Face in Aqueous Solutions
Authors: Weidenauer Markus , Weil Konrad G.
Published: March 2014

The double layer capacitance of electropolished copper (111) faces was measured in aqueous solutions in the presence of inert supporting electrolyte and in the presence of chloride ions. In the absence of chloride, we find a capacitance maximum at the anodic scan. The corresponding maximum during the cathodic scan is shifted to more negative potentials. There remains a shift even when the scan rate is extrapolated to zero. The positions of the maxima vary with ≈ 30 mV/pH. In the presence of chloride ions, the same maxima are observed. Now they are nearly two times higher, but their position also varies with the pH and not with the concentration of Cl−‐ions. This indicates a correlation between oxide layer formation and reduction with the adsorption and desorption of chloride ions. – From the time dependence of the double layer capacitance after cathodic steps, we conclude that the reduction of the oxide layer is accompanied by a phase transition.
The Polymerisation of Aniline and Methylsubstituted Derivatives: Electrochemical and Spectroscopic Investigations
Authors: Hochfeld A. , Kessel R. , Schultze J. W. , Thyssen A.
Published: March 2014

During the potentiostatic polymerisation of aniline (ANI) and 2,6‐dimethylaniline (2,6‐DMA) we measured simultaneously the current densities i, the anodic charge qan, the redox charge qredox, the electrode capacity C, the average thickness d̄ of polymer and the absorption. ANI shows a delayed nucleation with a following autocatalytic polymerisation with hemispherical growth. The polymerisation of 2,6‐DMA takes place after a short period of nucleation. Then it grows homogeneously with a decreasing rate. Finally polymerisation is inhibited by termination reactions after a short period of nucleation. – The thickness of the interfacial double layer d′ is determined by capacity measurements to be d′PANI = 0.4 nm and d′P‐2,6‐DMA = 4 nm. – The Electrochemical Quartz Micro‐Balance (EQMB) yields the thickness d̄ of the total polymer layer, >400 nm in the case of PANI and about 40 nm for P‐2,6‐DMA after 3600 s. The number of electrons z exchanged during a redox cycle per monomer unit can be derived to about 0.1 for PANI and about 0.05 for P‐2,6‐DMA. – Because of a small torsion angle between the aniline rings the electronic conductivity of polyaniline (PANI) is high and the redox charge > 10% of the theoretical charge corresponding to 1 e‐/monomer. The torsion angle of poly‐2,6‐dimethylaniline (P‐2,6‐DMA) is high. Therefore the electronic conductivity is low and the redox charge < 5%. – The stoichiometric and other properties of the polymer films were investigated with XPS.
Temperature Dependence of the Proton‐Discharge Reaction at Gold and Silver Electrodes
Authors: Frese U. , Schmickler W.
Published: March 2014

The kinetics of the Volmer reaction, which is the first step in the hydrogen evolution reaction, have been investigated by means of potentiostatic pulses. Measurements were performed in liquid and frozen HClO4 · 5.5 H2O in the temperature range 180 to 300 K. The apparent transfer coefficient is found to depend strongly on temperature. Classical theories of heterogeneous charge transfer reactions are unable to explain this result. A new model for a “field assisted proton transfer” is presented, which results in a temperature dependent charge transfer coefficient.
Quo vadis, Elektrochemie?
Authors: Gerischer H.
Published: March 2014

After a brief historical introduction into the development of electrochemistry an outlook is given concerning the prospects of electrochemical research about basic problems of solid/electrolyte interfaces. Emphasis is given to developments providing an interpretation on the atomistic and molecular level.
The Application of Multi‐Photon Ionization Mass Spectrometry to the Study of the Reactions O + C2H4, F + C3H6, F + c‐C3H6, F + CH3OH, H + CH2OH and O + CH3O
Authors: Heinemann‐Fiedler P. , Hoyermann K.
Published: March 2014

The experimental arrangement of a time‐of‐flight mass spectrometer with multi‐photon ionization and electron impact ionization is described. This set up was combined with a discharge flow reactor and a molecular beam sampling device. The detection of the radicals CH3, C3H5, CH2OH and their deuterated analogs by the wave‐length selective multi‐photon ionization allowed the identification of primary products of elementary reactions in the gas‐phase (around 1 mbar). The branching ratios for the reactions

were determined as (0.5 ± 0.15), (0.5 ± 0.1), (0.95 ± 0.05), respectively. – For the reactions of the CH2OH and CH3O radicals with H and O atoms, the following reaction paths were established:
X‐Ray Characterization of Single Crystals of the Reaction Center I of Water Splitting Photosynthesis
Authors: Witt I. , Witt H. T. , Di Fiore D. , Rögner M. , Hinrichs W. , Saenger W. , Granzin J. , Betzel Ch. , Dauter Z.
Published: March 2014

A new type of crystals of the reaction center I complex, RC I, of water splitting photosynthesis has been prepared from the cyanobacterium Synechococcus sp. In contrast to our first crystals (11), the new ones have a length of up to 1 mm, a thickness of up to 50 μm and show X‐ray diffraction patterns with a resolution of about 4 Å. The space group of the hexagonal crystals is probably P6322. One RC I represents the asymmetric unit. The unit cell dimensions are a = b = 285 Å, c = 167 Å, α = β = 90° and γ = 120°. The building block of the crystal lattice is a trimer (diameter ˜19 nm, height ˜6 nm, and apparent mass ˜600 kDa). The trimer is composed of 3 identical RC I units so that the quaternary structure is α3. The unit cell harbors four trimers in two layers with two trimers each.
Excess Gibbs Energies of Some Liquid Mixtures With Polar Components, Effects of Local Polarizability
Authors: van Nhu Nguyen , Nowak G. , Svejda P.
Published: March 2014

Vapour pressures of binary liquid mixtures of 2‐chloro‐2‐methylpropane, 2‐butanone and ethanenitrile + 2,2,4‐trimethylpentane (isooctane) or + 2,4,4‐trimethyl‐1‐pentene (α‐diisobutylene) were determined by static measurements in an apparatus according to Marsh with an improved vapour pressure cell and a water ebulliometer for the pressure measurements. Also the excess volumes of some of the systems and the isothermal compressibility of 2,4,4‐trimethyl‐1‐pentene were measured by the vibrating tube method. From theses data molar excess Gibbs energies at 293.15 K were determined which could be discussed in terms of different polarizabilities of the structurally closely related compounds isooctane and α‐diisobutylene on mixing with liquids of increasing polarity.
Hydrogen Bonding and Phase Transitions of RbOH · H2O and CsOH · H2O Studied by IR and Raman Spectroscopy
Authors: Lutz H. D. , Henning J. , Jacobs H. , Harbrecht B.
Published: March 2014

The infrared and Raman spectra of RbOH · H2O and of trimorphic CsOH · H2O, LTM, RTM, and HTM, in the range of 95–401 K are presented and discussed in terms of hydrogen bonding, disorder of the hydrogen atoms, and phase transitions. The different behaviour of OH− ions and H2O molecules as hydrogen bond donor and acceptor groups results in strong hydrogen bonding for HOH···OH− linkages and only weak H‐bonds for OH−···OH2 groupings. This is, for example, shown from the very different OH stretching modes of OH− and H2O in CsOH · H2O RTM, viz., 3496 and 2800 cm−1, observed for the same O···O distance of 264 pm. The temperature shifting of the OH− stretching modes in the range 340–395 K of CsOH · H2O can be interpreted by a Landau type order‐disorder phase transition. The halfwidths of the OH− bands exhibit an Arrhenius type behaviour. The activation energies derived reflect the band energies of lattice and librational modes (vibrational dephasing) as well as the energy barriers of proton reorientation processes, i.e., 17 kJ/mol for CsOH · H2O HTM.
Evaluation of agomelatine stability under different stress conditions using an HPLC method with fluorescence detection: application to the analysis of tablets and human plasma
Authors: El‐Shaheny R. N.
Published: March 2014

A simple and highly sensitive stability‐indicating HPLC method was developed and validated for the determination of the new antidepressant agent, agomelatine (AGM). Separation of AGM from its stress‐induced degradation products was achieved on a BDS Hypersil phenyl column (250 mm × 4.6 mm i.d., 5 µm particle size) using methanol–0.05 M phosphate buffer of pH 2.5 (35: 65, v/v) as a mobile phase with fluorescence detection at 230/370 nm. Naproxen was used as an internal standard. The method satisfied all the validation requirements, as evidenced by good linearity (correlation coefficient of 0.9999, over the concentration range 0.4–40.0 ng/mL), accuracy (recovery average 99.55 ± 0.90%), precision (intra‐day RSD 0.54–1.35% and inter‐day RSD 0.93–1.26%), robustness and specificity. The stability of AGM was investigated under different ICH recommended stress conditions including acidic, alkaline, neutral, oxidative and photolytic. AGM was found to be labile to acidic and alkaline degradation and a kinetic study was conducted to explore its degradation behavior. First‐order degradation rate constants and half‐life times were calculated in each case. The proposed method was applied for the determination of AGM in tablets and spiked human plasma with mean percentage recoveries of 99.87 ± 0.31 (n = 3) and 102.09 ± 5.01 (n = 5), respectively. Hence, the proposed method was successfully applied for the determination of AGM in human volunteer plasma. The results were compared statistically with those obtained by a comparison HPLC method revealing no significant differences between the two methods regarding accuracy and precision. Copyright © 2014 John Wiley & Sons, Ltd.
Antioxidant defense parameters as predictive biomarkers for fermentative capacity of active dried wine yeast
Authors: Gamero‐Sandemetrio Esther , Gómez‐Pastor Rocío , Matallana Emilia
Published: March 2014

The production of active dried yeast (ADY) is a common practice in industry for the maintenance of yeast starters and as a means of long term storage. The process, however, causes multiple cell injuries, with oxidative damage being one of the most important stresses. Consequentially, dehydration tolerance is a highly appreciated property in yeast for ADY production. In this study we analyzed the cellular redox environment in three Saccharomyces cerevisiae wine strains, which show markedly different fermentative capacities after dehydration. To measure/quantify the effect of dehydration on the S. cerevisiae strains, we used: (i) fluorescent probes; (ii) antioxidant enzyme activities; (ii) intracellular damage; (iii) antioxidant metabolites; and (iv) gene expression, to select a minimal set of biochemical parameters capable of predicting desiccation tolerance in wine yeasts. Our results show that naturally enhanced antioxidant defenses prevent oxidative damage after wine yeast biomass dehydration and improve fermentative capacity. Based on these results we chose four easily assayable parameters/biomarkers for the selection of industrial yeast strains of interest for ADY production: trehalose and glutathione levels, and glutathione reductase and catalase enzymatic activities. Yeast strains selected in accordance with this process display high levels of trehalose, low levels of oxidized glutathione, a high induction of glutathione reductase activity, as well as a high basal level and sufficient induction of catalase activity, which are properties inherent in superior ADY strains.
Quality and antitumour activity evaluation of extract of Hypericum ascyron
Authors: Li Xiu‐Mei , Luo Xue‐Gang , Ma Ning , Li Kun , Li Wen , Ma De‐Yun , Zhang Tong‐Cun
Published: March 2014

Similarity assessment of complex chromatographic profiles is a potential tool for the identification and quality control of herbal medicinal products to guarantee the expected biological activity. In this paper, a high‐performance liquid chromatography method was established for controlling the quality of extract of Hypericum ascyron for the first time. With this method, the correlation coefficients of similarity of 10 batches extract of H. ascyron were >0.97. The extract of H. ascyron displayed steadily inhibitorty activities on the growth of human cervical cancer Hela cell lines. Therefore, the present study successfully set up a sensitive efficient method which might confirm stable biological activity of the extract of H. ascyron. Copyright © 2014 John Wiley & Sons, Ltd.
Liquid chromatography/quadrupole time‐of‐flight mass spectrometry in combination with online hydrogen/deuterium exchange technique for structural elucidation of phase I metabolites of iso‐phenylcyclopentylamine in rat bile
Authors: Liu Xiaoxue , Wang Suilou , Ding Li , Chen Xiaoping , Shen Wenbin , Dong Xin , Yun Changhong , Lin Hongda
Published: March 2014

MS/MS experiment and accurate mass measurement are powerful tools in metabolite identification. However, sometimes these data do not provide enough information to assign an unambiguous structure to a metabolite. In combination with MS techniques, hydrogen/deuterium (H/D) exchange can provide additional information for structural elucidation by determination of the number of exchangeable hydrogen atoms in a structure. In this study, the principal phase I metabolites of iso‐phenylcyclopentylamine in rat bile were identified by high‐performance liquid chromatography with electrospray ionization quadrupole time‐of‐flight mass spectrometry (ESI‐Q‐TOF‐MS). Since N‐oxidation may occur because of the existence of the primary amino group in the structure, it was difficult to differentiate the hydroxylated metabolites from N‐oxides by ESI‐Q‐TOF‐MS alone. Therefore, online H/D exchange technique was applied to solve this problem. Finally, 25 phase I metabolites were detected and structurally described, in which 11 were confirmed to be N‐oxides. This study demonstrated the effectiveness of high‐resolution mass spectrometry in combination with an online H/D exchange technique in rapid identification of drug metabolites, especially in discriminating hydroxylated metabolites from N‐oxides. Copyright © 2014 John Wiley & Sons, Ltd.
Nanosecond Dynamics of Calmodulin and Ribosome‐Bound Nascent Chains Studied by Time‐Resolved Fluorescence Anisotropy
Authors: Lamprou Paraskevas , Kempe Daryan , Katranidis Alexandros , Büldt Georg , Fitter Jörg
Published: March 2014

We report a time‐resolved fluorescence anisotropy study of ribosome‐bound nascent chains (RNCs) of calmodulin (CaM), a prototypical member of the EF‐hand family of calcium‐sensing proteins. As shown in numerous studies, in vitro protein refolding can differ substantially from biosynthetic protein folding, which takes place cotranslationally and depends on the rate of polypeptide chain elongation. A challenge in this respect is to characterize the adopted conformations of nascent chains before their release from the ribosome. CaM RNCs (full‐length, half‐length, and first EF‐hand only) were synthesized in vitro. All constructs contained a tetracysteine motif site‐specifically incorporated in the first N‐terminal helix; this motif is known to react with FlAsH, a biarsenic fluorescein derivative. As the dye is rotationally locked to this helix, we characterized the structural properties and folding states of polypeptide chains tethered to ribosomes and compared these with released chains. Importantly, we observed decelerated tumbling motions of ribosome‐tethered and partially folded nascent chains, compared to released chains. This indicates a pronounced interaction between nascent chains and the ribosome surface, and might reflect chaperone activity of the ribosome.
Characterization of a Fluidized Catalytic Cracking Catalyst on Ensemble and Individual Particle Level by X‐ray Micro‐ and Nanotomography, Micro‐X‐ray Fluorescence, and Micro‐X‐ray Diffraction
Authors: Bare Simon R. , Charochak Meghan E. , Kelly Shelly D. , Lai Barry , Wang Jun , Chen‐Wiegart Yu‐chen Karen
Published: March 2014

A combination of advanced characterization techniques: synchrotron X‐ray micro‐ and nanotomography, micro‐X‐ray fluorescence, and micro‐XRD have been used to characterize a commercial spent equilibrium fluid catalytic cracking catalyst (ECAT) at both the ensemble and individual particle level. At the ensemble level, X‐ray microtomography was used to determine the average size, shape, and respective distributions of over 1200 individual catalyst particles. This information is important to determine performance in commercial operation. It is shown that a large fraction of the particles contained large internal voids (5–80 μm diameter), and these voids likely aid the accessibility for large hydrocarbon molecules. At the individual particle level, by using X‐ray nanotomography, these voids were visualized at a much smaller scale (≈100 nm–12 μm in diameter). In addition, the individual phases that are present in the particle, for example, TiO2 and clay, are readily visualized in 3 D. Micro‐X‐ray fluorescence (XRF) was used to map, and semiquantitatively determine, both the contaminant (Ni, V, Fe) and inherent (La) catalyst elemental distributions. The distribution of zeolite Y in the ECAT particle was inferred from the La XRF map. Micro‐XRD determined the lattice constant of the zeolite Y at the individual catalyst particle level. This in‐depth characterization study at the ensemble and individual ECAT particle level presents a robust methodology that provides an understanding of the ECAT at both the micro‐ and nanometer scales.
Synthetic Control of Spectroscopic and Photophysical Properties of Triarylborane Derivatives Having Peripheral Electron‐Donating Groups
Authors: Ito Akitaka , Kawanishi Kazuyoshi , Sakuda Eri , Kitamura Noboru
Published: March 2014

The spectroscopic and photophysical properties of triarylborane derivatives were controlled by the nature of the triarylborane core (trixylyl‐ or trianthrylborane) and peripheral electron‐donating groups (N,N‐diphenylamino or 9H‐carbazolyl groups). The triarylborane derivatives with and without the electron‐donating groups showed intramolecular charge‐transfer absorption/fluorescence transitions between the π orbital of the aryl group (π(aryl)) and the vacant p orbital on the boron atom (p(B), π(aryl)–p(B) CT), and the fluorescence color was tunable from blue to red by the combination of peripheral electron‐donating groups and a triarylborane core. Detailed electrochemical, spectroscopic, and photophysical studies of the derivatives, including solvent dependences of the spectroscopic and photophysical properties, demonstrated that the HOMO and LUMO of each derivative were determined primarily by the nature of the peripheral electron‐donating group and the triarylborane core, respectively. The effects of solvent polarity on the fluorescence quantum yield and lifetime of the derivatives were also tunable by the choice of the triarylborane core.
Access to Optically Active 3‐Substituted Piperidines by Ring Expansion of Prolinols and Derivatives
Authors: Gomez Pardo Domingo , Cossy Janine
Published: March 2014

The ring expansion of prolinols via an aziridinium intermediate gives C3‐substituted piperidines in good yields and enantiomeric excess, the substituent at the C3 position being derived from the most reactive nucleophile in the reaction mixture. Depending on the nucleophile, the reaction proceeds under thermodynamic or kinetic control. The regioselectivity of attack of nucleophiles on the aziridinium intermediate depends on the nature of the substituents on the nitrogen atom and the C4 position of the starting prolinols.
Aromatic Superhalogens
Authors: Child Brandon Z. , Giri Santanab , Gronert Scott , Jena Puru
Published: March 2014

No organic molecules with electron affinities near or above those of halogens are known. We show for the first time that aromaticity rules can be used to design molecules with electron affinities far exceeding those of halogen atoms either by tailoring the ligands of cyclopentadienyl or by multiple benzoannulations of cyclopentadienyl in conjunction with the substitution of CH groups with isoelectronic N atoms. Results based on density functional theory revealed that the electron affinities of some of these organic molecules can reach as high as 5.59 eV, thus opening the door to new class of superhalogens that contain neither a metal nor a halogen atom.
Amine‐Catalyzed Enantioselective 1,3‐Dipolar Cycloadditions of Aldehydes to C,N‐Cyclic Azomethine Imines
Authors: Li Wenjun , Jia Qianfa , Du Zhiyun , Zhang Kun , Wang Jian
Published: March 2014

Amine‐catalyzed enantioselective 1,3‐dipolar cycloadditions of aldehydes to C,N‐cyclic azomethine imines were developed. The reactions between diversely substituted C,N‐cyclic azomethine imines and aldehydes proceeded smoothly in the presence of chiral prolinol silyl ether catalyst and gave the C‐1‐substituted tetrahydroisoquinolines in a highly stereoselective manner. These tetrahydroisoquinolines could be efficiently transformed to several other useful polycyclic frameworks.
A Practical and Stereoselective Organocatalytic Alkylation of Aldehydes with Benzodithiolylium Tetrafluoroborate
Authors: Gualandi Andrea , Mengozzi Luca , Giacoboni Jessica , Saulnier Steve , Ciardi Moira , Cozzi Pier Giorgio
Published: March 2014

Recently, the direct substitution of allylic, benzylic, and tertiary alcohols has been achieved via SN1‐type reactions with catalytic amounts of Brønsted or Lewis acids. When a new stereogenic center is formed most of these transformations produce the desired product as a racemate, as these reactions proceed through carbenium ions. The arsenal of activation modes available in organocatalysis can be used to set up suitable reaction conditions in which chiral nucleophiles (enamine catalysis) or chiral electrophiles (iminium catalysis, chiral counterion catalysis) can easily be generated. Recently, we have used stabilized carbenium ions, directly available or obtained from the corresponding alcohols, in new organocatalytic stereoselective SN1‐type reactions. The commercially available carbenium ion benzodithiolylium tetrafluoroborate 1 can be used for the straightforward organocatalytic stereoselective alkylation of aldehydes. In this account we will illustrate the application of this methodology in the total synthesis of natural products and the preparation of valuable starting materials. Chirality 26:607–613, 2014. © 2014 Wiley Periodicals, Inc.
Synthetic and Biological Studies of Tubulin Targeting C2‐Substituted 7‐Deazahypoxanthines Derived from Marine Alkaloid Rigidins
Authors: Scott Robert , Karki Menuka , Reisenauer Mary R. , Rodrigues Roberta , Dasari Ramesh , Smith W. Ross , Pelly Stephen C. , van Otterlo Willem A. L. , Shuster Charles B. , Rogelj Snezna , Magedov Igor V. , Frolova Liliya V. , Kornienko Alexander
Published: March 2014

C2‐aryl‐ and C2‐alkyl‐7‐deazahypoxanthines as analogues of marine alkaloid rigidins were prepared utilizing novel synthetic methods developed for the construction of the pyrrolo[2,3‐d]pyrimidine ring system. The new compounds exhibited sub‐micromolar to nanomolar antiproliferative potencies against a panel of cell lines including in vitro models for drug‐resistant tumors, such as glioblastoma, melanoma and non‐small‐cell lung cancer. A selected representative C2‐methyl‐7‐deazahypoxanthine was found to inhibit microtubule dynamics in cancer cells, lending evidence for tubulin targeting as a mode of action for these compounds in cancer cells. The results of the docking studies utilizing the colchicine site on β‐tubulin were consistent with the observed structure–activity relationship data, including an important finding that derivatization at C2 with linear alkyl groups leads to the retention of activity, thus permitting the attachment of a biotin‐containing linker for the subsequent proteomics assays. Because many microtubule‐targeting compounds are successfully used to fight cancer in the clinic, the reported antitubulin rigidin analogues have significant potential as new anticancer agents.
3‐Phenylpropanoic Acid‐Based Phosphotyrosine (pTyr) Mimetics: Hit Evolution to a Novel Orally Active Protein Tyrosine Phosphatase 1B (PTP1B) Inhibitor
Authors: Tang Yan‐Bo , Liu Jun‐Zheng , Zhang Shu‐En , Du Xin , Nie Feilin , Tian Jin‐Ying , Ye Fei , Huang Kai , Hu Jin‐Ping , Li Yan , Xiao Zhiyan
Published: March 2014

Protein tyrosine phosphatase 1B (PTP1B) is a promising therapeutic target for type 2 diabetes. Herein, we report the evolution of a previously identified 3‐phenylpropanoic acid‐based PTP1B inhibitor to an orally active lead compound. A series of 3‐phenylpropanoic acid‐based PTP1B inhibitors were synthesized, and three of them, 3‐(4‐(9H‐carbazol‐9‐yl)phenyl)‐5‐(3,5‐di‐tert‐butyl‐4‐methoxyphenyl)‐5‐oxopentanoic acid (9), 3‐(4‐(9H‐carbazol‐9‐yl)phenyl)‐5‐(4′‐bromo‐[1,1′‐biphenyl]‐4‐yl)‐5‐oxopentanoic acid (10) and 3‐(4‐(9H‐carbazol‐9‐yl)‐2‐fluorophenyl)‐5‐(4‐cyclohexylphenyl)‐5‐oxopentanoic acid (16), showed IC50 values at sub‐micromolar level. Further in vivo evaluation indicated the sodium salt of 9 not only exhibited significant insulin‐sensitizing and hypoglycemia effects, but also decreased the serum levels of triglyceride and total cholesterol in high‐fat‐diet‐induced insulin resistance model mice. Preliminary in vivo pharmacokinetic studies on the sodium salt of 9 revealed its pharmacokinetic profile after oral administration in rats. These results provide proof‐of‐concept for the dual effects of PTP1B inhibitors on both glucose and lipid metabolisms.
Computational Insight into p21‐Activated Kinase 4 Inhibition: A Combined Ligand‐ and Structure‐Based Approach
Authors: Li Rui‐Juan , Wang Jian , Xu Zhen , Huang Wan‐Xu , Li Jia , Jin Sheng‐Fei , Zhao Dong‐Mei , Cheng Mao‐Sheng
Published: March 2014

p21‐Activated kinase 4 (PAK4) is a serine/threonine protein kinase that plays important roles in a wide variety of human diseases including cancer. Targeting this kinase with specific inhibitors is of great interest in the treatment of cancer. In this study, PAK4 and its interaction with ATP‐competitive inhibitors was investigated by a combined ligand‐ and structure‐based approach. First, a ligand‐based pharmacophore model was generated, consisting of five chemical features: a positive ionizable center, two hydrophobic groups, a hydrogen bond donor, and a hydrogen bond acceptor, which is consistent with available SAR information. The characteristics of the active site were then described as a topological region and used in docking of nine selected inhibitors. Combination of the pharmacophore model and results from the docking studies allowed us to weigh the various pharmacophore features and to identify the positive ionizable center as a spacer rather than an essential point. This research led to the proposal of an interaction model inside the PAK4 active site and provided guidance for the design of more potent PAK4 inhibitors.
Lateral habenula and the rostromedial tegmental nucleus innervate neurochemically distinct subdivisions of the dorsal raphe nucleus in the rat
Authors: Sego Chemutai , Gonçalves Luciano , Lima Leandro , Furigo Isadora C. , Donato Jose , Metzger Martin
Published: March 2014

The lateral habenula (LHb) is an epithalamic structure differentiated in a medial (LHbM) and a lateral division (LHbL). Together with the rostromedial tegmental nucleus (RMTg), the LHb has been implicated in the processing of aversive stimuli and inhibitory control of monoamine nuclei. The inhibitory LHb influence on midbrain dopamine neurons has been shown to be mainly mediated by the RMTg, a mostly GABAergic nucleus that receives a dominant input from the LHbL. Interestingly, the RMTg also projects to the dorsal raphe nucleus (DR), which also receives direct LHb projections. To compare the organization and transmitter phenotype of LHb projections to the DR, direct and indirect via the RMTg, we first placed injections of the anterograde tracer Phaseolus vulgaris leucoagglutinin into the LHb or the RMTg. We then confirmed our findings by retrograde tracing and investigated a possible GABAergic phenotype of DR‐projecting RMTg neurons by combining retrograde tracing with in situ hybridization for GAD67. We found only moderate direct LHb projections to the DR, which mainly emerged from the LHbM and were predominantly directed to the serotonin‐rich caudal DR. In contrast, RMTg projections to the DR were more robust, emerged from RMTg neurons enriched in GAD67 mRNA, and were focally directed to a distinctive DR subdivision immunohistochemically characterized as poor in serotonin and enriched in presumptive glutamatergic neurons. Thus, besides its well‐acknowledged role as a GABAergic control center for the ventral tegmental area (VTA)–nigra complex, our findings indicate that the RMTg is also a major GABAergic relay between the LHb and the DR. J. Comp. Neurol. 522:1454–1484, 2014. © 2013 Wiley Periodicals, Inc.
A residual modified transformation formula from munsell to sRGB color system
Authors: Hsiao Shih‐Wen , Tsai Cheng‐Ju
Published: March 2014

A residual modified transformation formula from Munsell to sRGB color system is presented in this article. The development of the transformation formula is based on the 1625 Munsell color chips in the Munsell Renotation Data that could be displayed on the sRGB monitor. The developed transformation formula consists of two models, one is named as the corresponding matrix model and the other is the residual modified model. The corresponding matrix model was obtained using numerical analysis methods to map each chip color attribute values from Munsell to sRGB and then its corresponding matrix for each Hue was constructed. The residual modified model was obtained using the discrete cosine transform to construct a residual modified function, which was used to modify the transformation error of each chip after applying the corresponding matrix model. The transformed accuracy rate for the corresponding matrix model is 88.4% and for the residual modified model can be enhanced to 96.6% for all of the chips. The developed transformation formula can be applied to research in which Munsell colors are presented on the sRGB monitor. With the aid of these formulas, designers can show the advanced real‐time results on a sRGB monitor for the product's color planning based on Munsell color system. Therefore, this research has a great contribution on the practical application for color planning in product design. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 243–255, 2015
Perovskite Solar Cells Based on Nanocolumnar Plasma‐Deposited ZnO Thin Films
Authors: Ramos F. Javier , López‐Santos Maria C. , Guillén Elena , Nazeeruddin Mohammad Khaja , Grätzel Michael , Gonzalez‐Elipe Agustin R. , Ahmad Shahzada
Published: March 2014

ZnO thin films having a nanocolumnar microstructure are grown by plasma‐enhanced chemical vapor deposition at 423 K on pre‐treated fluorine‐doped tin oxide (FTO) substrates. The films consist of c‐axis‐oriented wurtzite ZnO nanocolumns with well‐defined microstructure and crystallinity. By sensitizing CH3NH3PbI3 on these photoanodes a power conversion of 4.8 % is obtained for solid‐state solar cells. Poly(triarylamine) is found to be less effective when used as the hole‐transport material, compared to 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (spiro‐OMeTAD), while the higher annealing temperature of the perovskite leads to a better infiltration in the nanocolumnar structure and an enhancement of the cell efficiency.
One‐Dimensional [Ni(O2CR)2(NN)x] Polymers: Structural, Magnetic, and Density Functional Theory Studies
Authors: Cortijo Miguel , Herrero Santiago , Jerez Belén , Jiménez‐Aparicio Reyes , Perles Josefina , Priego José L. , Torroba Javier , Tortajada José
Published: March 2014

Five nickel complexes, [Ni2(3,4,5‐tmb)4(4,4′‐bpy)] (1), [Ni2(2‐ntc)4(4,4′‐bpy)] (2), [Ni(9‐atc)2(4,4′‐bpy)] (3), [Ni(3,4,5‐tmb)2(t‐bpee)] (4), and [Ni2(2‐ntc)4(t‐bpee)2] (5) (3,4,5‐tmb=3,4,5‐trimethoxybenzoate; 2‐ntc=2‐naphthalenecarboxylate; 9‐atc=9‐anthracenecarboxylate; 4,4′‐bpy=4,4′‐bipyridine; t‐bpee=trans‐1,2‐bis(4‐pyridyl)ethylene), are prepared. They are characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, and single‐crystal and powder X‐ray diffraction. 1 and 2 form linear chains of paddlewheel units joined by 4,4′‐bpy ligands; 3 and 4 display zigzag chains formed by cis‐bis(chelate) Ni(O2CR)2 units joined by 4,4′‐bpy and t‐bpee, respectively; and the structure of 5 consists of double chains. The magnetic behavior of the compounds is also studied, and DFT calculations using the broken‐symmetry approximation are performed to gain a better understanding of the strong antiferromagnetism found in 1.
Biphasic Catalytic Conversion of Fructose by Continuous Hydrogenation of HMF over a Hydrophobic Ruthenium Catalyst
Authors: Yang Yanliang , Du Zhongtian , Ma Jiping , Lu Fang , Zhang Junjie , Xu Jie
Published: March 2014

The production of chemicals directly from sugars is an important step in biomass conversion. Herein, tetrahydro‐2,5‐furandimethanol (THFDM), obtained from fructose, is formed by using a combination of acid and hydrophobic Ru/SiO2 in a water/cyclohexane biphasic system. Two key factors enable the high selectivity towards THFDM: modifying the hydrogenation catalyst so that it has hydrophobic properties, and the continuous hydrogenation of generated 5‐(hydroxymethyl)furfural in the cyclohexane phase. Moreover, the selectivity towards THFDM is found to depend strongly on the acid catalyst used.
Early gestational weight gains within current recommendations result in increased risk of gestational diabetes mellitus among Korean women
Authors: Park Sunmin , Kim Min‐Hyoung , Kim Sung‐Hoon
Published: March 2014

Background

We prospectively assessed whether maternal weight gain at 24–28 weeks of gestation (MWG24) influences the risk of developing gestational complications, such as gestational diabetes mellitus (GDM) and other adverse pregnancy outcomes, in pregnant Korean women.

Methods

Maternal weight gain from self‐reported pre‐pregnancy weight until 24–28 weeks of gestation was measured in 731 pregnant women, and an expected MWG24 was determined using the Institute of Medicine 2009 guidelines. Glucose tolerance, insulin resistance, insulin secretory capacity, anthropometric measurements, lipid profiles, nutrient intakes and pregnancy outcomes were evaluated at 24–28 weeks of gestation. The adjusted odds ratios (ORs) for GDM, large‐for‐gestational‐age infants, small‐for‐gestational‐age infants and preterm delivery were determined according to maternal weight gain by logistic regression analysis after adjusting for covariates.

Results

Compared with a normal MWG24, an inadequate MWG24 reduced the OR (0.565) for GDM, but an excessive MWG24 did not affect the OR (0.854). However, ORs for preterm delivery were significantly higher in both inadequate and excessive MWG24 groups in comparison with the normal MWG24. There were no other adverse pregnancy outcomes due to the inadequate MWG24. MWG24 was not associated with a significant increase in ORs for delivering large‐for‐gestational‐age or small‐for‐gestational‐age infants or delivery by caesarean section. Although energy intake was less than the estimated energy requirement in all groups, MWG24 was linearly associated with energy intake such that energy balance was positive in the excessive MWG24 group.

Conclusions

This study suggests that both target weight gain and energy intake recommendations for early pregnancy may not be optimal for Korean women and that race‐specific recommendations are needed to decrease the risk of GDM without increasing adverse pregnancy outcomes. Copyright © 2014 John Wiley & Sons, Ltd.
Defining conservation units in a stocking‐induced genetic melting pot: unraveling native and multiple exotic genetic imprints of recent and historical secondary contact inAdriatic grayling
Authors: Meraner Andreas , Cornetti Luca , Gandolfi Andrea
Published: March 2014

The definition of conservation units is crucial for the sustainable management of endangered species, though particularly challenging when recent and past anthropogenic and natural gene flow might have played a role. The conservation of the European grayling,Thymallus thymallus, is particularly complex in its southern distribution area, where the Adriatic evolutionary lineage is endangered by a long history of anthropogenic disturbance, intensive stocking and potentially widespread genetic introgression. We provide mtDNAsequence and microsatellite data of 683 grayling from 30 sites of Adriatic as well as Danubian and Atlantic origin. We apply Bayesian clustering and Approximate Bayesian Computation (ABC) to detect microgeographic population structure and to infer the demographic history of the Adriatic populations, to define appropriate conservation units. Varying frequencies of indigenous genetic signatures of the Adriatic grayling were revealed, spanning from marginal genetic introgression to the collapse of native gene pools. Genetic introgression involved multiple exotic source populations of Danubian and Atlantic origin, thus evidencing the negative impact of few decades of stocking. Within the Adige River system, a contact zone of western Adriatic and eastern Danubian populations was detected, withABCanalyses suggesting a historical anthropogenic origin of eastern Adige populations, most likely founded by medieval translocations. Substantial river‐specific population substructure within the Adriatic grayling Evolutionary Significant Unit points to the definition of different conservation units. We finally propose a catalog of management measures, including the legal prohibition of stocking exotic grayling and the use of molecular markers in supportive‐ and captive‐breeding programs.
Metal‐Catalyzed and Metal‐Free Alkyne Hydrothiolation: Synthetic Aspects and Application Trends
Authors: Dondoni Alessandro , Marra Alberto
Published: March 2014

Alkyne hydrothiolation – that is, the addition of the SH bond of a thiol across the carbon‐carbon triple bond of an unactivated alkyne – belongs to the ample class of hydrofunctionalization reactions whose main feature is their occurrence with total atom economy. Hence this reaction is emerging as a valuable tool for the preparation of sulfur‐containing compounds such as vinyl thioethers, which are of interest for their own biological properties and for their use as intermediates in total synthesis. Thus, the first part of this review deals with the various efforts directed towards the preparation of vinyl thioethers in a regio‐ and diastereoselective manner by metal‐catalyzed approaches in recent years. The number of methods employed, with use of a variety of catalysts and reaction conditions, allow the synthesis of vinyl thioethers to be carried out with high efficiency and selectivity. The second part of the article is based on the use of the photoinduced free‐radical approach to hydrothiolation, which allows the introduction of two thiol fragments across the carbon‐carbon triple bond, thereby leading to the formation of dithioethers. This approach turned out to be especially useful as a ligation tool for the installation of densely functionalized arrays on various scaffolds and complex biomolecular systems. Concluding remarks emphasize the role of the photoinduced free‐radical strategy as a complementary tool to copper‐catalyzed azide‐alkyne cycloaddition.
CdSe Quantum Dots Based Electrochemiluminescence Immunosensor with Simple Structure for Ultrasensitive Detection of Salbutamol
Authors: Zhang Jing , Cai Fudong , Deng Anping , Li Jianguo
Published: March 2014

A rapid and ultrasensitive electrochemiluminescence (ECL) competitive immunoassay based on CdSe quantum dots (QDs) and the shorter chain as possible (cysteamine and glutaraldehyde) has been designed for the detection of salbutamol (SAL). Cysteamine and glutaraldehyde made coating antigen immobilize well on the gold electrode surface through the reaction between functional groups, which brought about the simplicity of the immunosensor to some extent. Transmission electron microscopy image, dynamic light scattering, photoluminescence, ultraviolet‐visible absorption and electrochemical impedance spectra were used to characterize the prepared CdSe QDs and the cysteamine/glutaraldehyde/Ovalbumin‐SAL/anti‐SAL‐QDs immunosensor. In the air‐saturated PBS buffer containing 0.1 M K2S2O8 and 0.1 M KCl (pH 9.0), a strong ECL emission of QDs can be observed which depended linearly on the logarithm of the salbutamol concentration with a wide range from 0.05 ng mL−1 to 100 ng mL−1, and a detection limit of 0.0056 ng mL−1. The sensitivity, repeatability, and specificity of the ECL immunosensor have been evaluated. The sensor has been applied to real samples with satisfactory results. This work will open new ways of detecting food additive residue based on QDs ECL in immunoassays.
Experimental and Theoretical Study of the Energy Savings from Wet Ethanol Production and Utilization
Authors: López‐Plaza Emilio Luis , Hernández Salvador , Barroso‐Muñoz Fabricio Omar , Segovia‐Hernández Juan Gabriel , Aceves Salvador M. , Martínez‐Frías Joel , Saxena Samveg , Dibble Robert
Published: March 2014

As a result of the energy crisis in recent decades, biofuels have gained importance as an option to diminish the oil dependence of automotive industry. Ethanol is one of these biofuels for which demand around the world has increased in recent years. However, to be used as a fuel, the ethanol must be dehydrated to avoid problems in actual engines, and this step has a high energy cost. To overcome this drawback, some studies have demonstrated the use of wet ethanol in homogeneous charge compression ignition (HCCI) engines. In this work, the production of wet ethanol, using conventional distillation, was studied using rigorous simulation studies and experimental tests in a distillation column. The simulation analysis and experimental validation of the energy requirements to obtain wet ethanol were achieved. The results showed that wet ethanol can be produced by using a distillation column with a small number of stages and low reflux ratios, which results in energy savings. Also, the results indicated that for low purities of the distilled ethanol (wet ethanol), the ratios between the energy required during the distillation process and the energy produced by ethanol during the combustion were low. This result implies that the use of wet ethanol can be considered as realistic option in HCCI engines.
Non‐stationary conditional extremes of northern North Sea storm characteristics
Authors: Jonathan P. , Ewans K. , Randell D.
Published: March 2014

Characterising the joint structure of extremes of environmental variables is important for improved understanding of those environments. Yet, many applications of multivariate extreme value analysis adopt models that assume a particular form of extremal dependence between variables without justification, or restrict attention to regions in which all variables are extreme. The conditional extremes model of Heffernan and Tawn provides one approach to avoiding these particular restrictions.

Extremal marginal and dependence characteristics of environmental variables typically vary with covariates. Reliable descriptions of extreme environments should also therefore characterise any non‐stationarity. A recent article by the current authors extends the conditional extremes model of Heffernan and Tawn to include covariate effects, using Fourier representations of model parameters for single periodic covariates.

Here, we further extend our recent work, introducing a general purpose spline representation for model parameters as functions of multidimensional covariates, common to all inference steps. We use a non‐crossing quantile regression to estimate appropriate non‐stationary marginal quantiles simultaneously as functions of covariate; these are necessary as thresholds for extreme value modelling and for standardisation of marginal distributions prior to application of the conditional extremes model. Then, we perform marginal extreme value and conditional extremes modelling within a roughness‐penalised likelihood framework, with cross‐validation to estimate suitable model parameter roughness. Finally, we use a bootstrap re‐sampling procedure, encompassing all inference steps, to quantify uncertainties in, and dependence structure of, parameter estimates and estimates of conditional extremes of one variate given large values of another.

We validate the approach using simulations from known joint distributions, the extremal dependence structures of which change with covariate. We apply the approach to joint modelling of storm peak significant wave height and associated storm peak period for extra‐tropical storms at a northern North Sea location, with storm direction as covariate. We evaluate the impact of incorporating directional effects on estimates for conditional return values. Copyright © 2014 John Wiley & Sons, Ltd.