bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of realgar on extracellular amino acid neurotransmitters in hippocampal CA1 region determined by online microdialysis–dansyl chloride derivatization–high‐performance liquid chromatography and fluorescence detection
Authors: Huo Taoguang , Zhang Yinghua , Li Weikai , Yang Huilei , Jiang Hong , Sun Guifan 
Published: February 2014

ABSTRACTAn online microdialysis (MD)–dansyl chloride (Dns) derivatization–high‐performance liquid chromatography (HPLC) and fluorescence detection (FD) system was developed for simultaneous determination of eight extracellular amino acid neurotransmitters in hippocampus. The MD probe was implanted in hippocampal CA1 region. Dialysate and Dns were online mixed and derivatized. The derivatives were separated on an ODS column and detected by FD. The developed online system showed good linearity, precision, accuracy and recovery. This online MD‐HPLC system was applied to monitor amino acid neurotransmitters levels in rats exposed to realgar (0.3, 0.9 and 2.7 g/kg body weight). The result shows that glutamate concentrations were significantly increased (p < 0.05) in hippocampal CA1 region of rats exposed to three doses of realgar. A decrease in γ‐aminobutyric acid concentrations was found in rats exposed to medium and high doses of realgar (p < 0.05). Elevation of excitotoxic index (EI) values in hippocampal CA1 region of realgar‐exposed rats was observed (p < 0.05). Positive correlation was found between EI values and arsenic contents in hippocampus of realgar‐exposed rats, which indicates that the change in extracellular EI values is associated with arsenic accumulation in hippocampus. The developed online MD–Dns derivatization–HPLC–FD system provides a new experimental method for studying the effect of toxic Chinese medicines on amino acid neurotransmitters. Copyright © 2014 John Wiley & Sons, Ltd.
Simultaneous determination of cotinine and trans‐3‐hydroxycotinine in urine by automated solid‐phase extraction using gas chromatography–mass spectrometry
Authors: Chiadmi Fouad , Schlatter Joël 
Published: February 2014

ABSTRACTA gas chromatography–mass spectrometry method was developed and validated for the simultaneous automated solid‐phase extraction and quantification of cotinine and trans‐3‐hydroxycotinine in human urine. Good linearity was observed over the concentration ranges studied (R2 > 0.99). The limit of quantification was 10 ng/mL for both analytes. The limits of detection were 0.06 ng/mL for cotinine (COT) and 0.02 ng/mL for trans‐3‐hydroxycotinine (OH‐COT). Accuracy for COT ranged from 0.98 to 5.28% and the precision ranged from 1.24 to 8.78%. Accuracy for OH‐COT ranged from −2.66 to 3.72% and the precision ranged from 3.15 to 7.07%. Mean recoveries for cotinine and trans‐3‐hydroxycotinine ranged from 77.7 to 89.1%, and from 75.4 to 90.2%, respectively. This analytical method for the simultaneous measurement of cotinine and trans‐3‐hydroxycotinine in urine will be used to monitor tobacco smoking in pregnant women and will permit the usefulness of trans‐3‐hydroxycotinine as a specific biomarker of tobacco exposure to be determined. © 2014 The Authors. Biomedical Chromatography published by John Wiley & Sons Ltd.
The Fairness of National Decision‐making Procedures: The Views of Adolescents in 18 European Countries
Authors: Ellenbroek Moniek , Verkuyten Maykel , Thijs Jochem , Poppe Edwin 
Published: February 2014

ABSTRACTThis study examines adolescents' evaluation of the fairness of three forms of democratic decision‐making procedures (direct democracy, representative democracy and group representation) and one non‐democratic procedure (oligarchy). Social dominance orientation‐Egalitarianism (SDO‐E), religious group identification and the countries' level of democracy are examined as predictors. The 2008 Europroject dataset was used, which contained 4441 native majority adolescents (mean age = 16.1 years) in 18 European countries. Adolescents evaluated direct democracy as most fair, followed by group representation, representative democracy and oligarchy. This rank order was found independent of the issue under consideration (moral or social), and of SDO‐E and religious identification, and across the countries. In addition, adolescents scoring higher on SDO‐E and on religious identification found group representation and non‐democratic oligarchy fairer. Copyright © 2014 John Wiley & Sons, Ltd.
Macromolecular Uptake of Alkyl‐Chain‐Modified Guanidinoglycoside Molecular Transporters
Authors: Inoue Makoto , Wexselblatt Ezequiel , Esko Jeffrey D. , Tor Yitzhak 
Published: February 2014

AbstractGuanidinoglycosides, a family of cellular transporters capable of delivering high Mw biopolymers, have previously been shown to display high selectivity for cell‐surface heparan sulfate proteoglycans and promote their clustering. Herein, the internalization mechanism of amphiphilic guanidinoglycoside derivatives was investigated by cell‐surface FRET analysis. Unexpectedly, although the heparan sulfate selectivity is maintained, the cellular uptake of these derivatives does not appear to involve clustering of the proteoglycans on the cell surface. This suggests a distinct uptake mechanism when compared to the parent guanidinoglycoside‐based carriers.
Biofragments: An Approach towards Predicting Protein Function Using Biologically Related Fragments and its Application to Mycobacterium tuberculosis CYP126
Authors: Hudson Sean A. , Mashalidis Ellene H. , Bender Andreas , McLean Kirsty J. , Munro Andrew W. , Abell Chris 
Published: February 2014

AbstractWe present a novel fragment‐based approach that tackles some of the challenges for chemical biology of predicting protein function. The general approach, which we have termed biofragments, comprises two key stages. First, a biologically relevant fragment library (biofragment library) can be designed and constructed from known sets of substrate‐like ligands for a protein class of interest. Second, the library can be screened for binding to a novel putative ligand‐binding protein from the same or similar class, and the characterization of hits provides insight into the basis of ligand recognition, selectivity, and function at the substrate level. As a proof‐of‐concept, we applied the biofragments approach to the functionally uncharacterized Mycobacterium tuberculosis (Mtb) cytochrome P450 isoform, CYP126. This led to the development of a tailored CYP biofragment library with notable 3D characteristics and a significantly higher screening hit rate (14 %) than standard drug‐like fragment libraries screened previously against Mtb CYP121 and 125 (4 % and 1 %, respectively). Biofragment hits were identified that make both substrate‐like type‐I and inhibitor‐like type‐II interactions with CYP126. A chemical‐fingerprint‐based substrate model was built from the hits and used to search a virtual TB metabolome, which led to the discovery that CYP126 has a strong preference for the recognition of aromatics and substrate‐like type‐I binding of chlorophenol moieties within the active site near the heme. Future catalytic analyses will be focused on assessing CYP126 for potential substrate oxidative dehalogenation.
A Simple Strategy for Glycosyltransferase‐Catalyzed Aminosugar Nucleotide Synthesis
Authors: Zhang Jianjun , Singh Shanteri , Hughes Ryan R. , Zhou Maoquan , Sunkara Manjula , Morris Andrew J. , Thorson Jon S. 
Published: February 2014

AbstractA set of 2‐chloro‐4‐nitrophenyl glucosamino‐/xylosaminosides were synthesized and assessed as potential substrates in the context of glycosyltransferase‐catalyzed formation of the corresponding UDP/TDP‐α‐D‐glucosamino‐/xylosaminosugars and in single‐vessel model transglycosylation reactions. This study highlights a robust platform for aminosugar nucleotide synthesis and reveals OleD Loki to be a proficient catalyst for U/TDP‐aminosugar synthesis and utilization.
Transfer Hydrogenation of Cellulose‐based Oligomers over Carbon‐supported Ruthenium Catalyst in a Fixed‐bed Reactor
Authors: Shrotri Abhijit , Kobayashi Hirokazu , Tanksale Akshat , Fukuoka Atsushi , Beltramini Jorge 
Published: February 2014

AbstractRu supported on activated carbon was found to be active for the transfer hydrogenation of cellulose oligomers, which were produced by the milling of acidulated microcrystalline cellulose. A C6 sugar alcohol yield of 85 % was obtained in less than 1 h reaction time in a batch reactor. Optimum reaction conditions for transfer hydrogenation were determined as 180 °C and a pH above 2.2 using glucose as a substrate. Use of deuterium as a marker established that direct transfer of hydride species from 2‐propanol to glucose occurs through the dihydride mechanism. Formation of molecular hydrogen from 2‐propanol dehydrogenation was found to be a side reaction, with little influence on the glucose hydrogenation step. Conversion of cellulose oligomers to hexitols was also achieved in a continuous flow fixed‐bed reactor with 36.4 % yield at a liquid hourly space velocity of 4.7 h−1. The catalytic activity did not decrease even after 12 h of the onstream reaction.
Redox‐Induced Spin‐State Switching and Mixed Valency in Quinonoid‐Bridged Dicobalt Complexes
Authors: Schweinfurth David , Rechkemmer Yvonne , Hohloch Stephan , Deibel Naina , Peremykin Irina , Fiedler Jan , Marx Raphael , Neugebauer Petr , van Slageren Joris , Sarkar Biprajit 
Published: February 2014

AbstractThe complexes [{(tmpa)CoII}2(μ‐L1)2−]2+ (12+) and [{(tmpa)CoII}2(μ‐L2)2−]2+ (22+), with tmpa=tris(2‐pyridylmethyl)amine, H2L1=2,5‐di‐[2‐(methoxy)‐anilino]‐1,4‐benzoquinone, and H2L2=2,5‐di‐[2‐(trifluoromethyl)‐anilino]‐1,4‐benzoquinone, were synthesized and characterized. Structural analysis of 22+ revealed a distorted octahedral coordination around the cobalt centers, and cobalt–ligand bond lengths that match with high‐spin CoII centers. Superconducting quantum interference device (SQUID) magnetometric studies on 12+ and 22+ are consistent with the presence of two weakly exchange‐coupled high‐spin cobalt(II) ions, for which the nature of the coupling appears to depend on the substituents on the bridging ligand, being antiferromagnetic for 12+ and ferromagnetic for 22+. Both complexes exhibit several one‐electron redox steps, and these were investigated with cyclic voltammetry and UV/Vis/near‐IR spectroelectrochemistry. For 12+, it was possible to chemically isolate the pure forms of both the one‐electron oxidized mixed‐valent 13+ and the two‐electron oxidized isovalent 14+ forms, and characterize them structurally as well as magnetically. This series thus provided an opportunity to investigate the effect of reversible electron transfers on the total spin‐state of the molecule. In contrast to 22+, for 14+ the metal–ligand distances and the distances within the quinonoid ligand point to the existence of two low‐spin CoIII centers, thus showing the innocence of the quintessential non‐innocent ligands L. Magnetic data corroborate these observations by showing the decrease of the magnetic moment by roughly half (neglecting spin exchange effects) on oxidizing the molecules with one electron, and the disappearance of a paramagnetic response upon two‐electron oxidation, which confirms the change in spin state associated with the electron‐transfer steps.
PdII‐Catalyzed Mild CH ortho Arylation and Intramolecular Amination Oriented by a Phosphinamide Group
Authors: Guan Jing , Wu Guo‐Jie , Han Fu‐She 
Published: February 2014

AbstractA novel protocol for the Pd‐catalyzed ortho‐arylation of aryl phosphinamide with boronic acid is reported. By using phosphinamide as a new directing group, the reaction proceeds efficiently under mild conditions at 40 °C. Mechanistic studies reveal that the reaction proceeds via a PdII to Pd0 cycle. The phosphinamide group is also shown to be an effective orienting group for direct CH amination.
Displacement Plating of a Mesoporous Pt Skin onto Co Nanochains in a Low‐Concentration Surfactant Solution
Authors: Li Cuiling , Imura Masataka , Yamauchi Yusuke 
Published: February 2014

AbstractMesoporous Pt skins on Co nanochains are successfully synthesized by a displacement reaction between Pt species and a Co support with the assistance of surfactant micelles. The assembly of surfactant micelles on Co nanochains plays a key role in the formation of mesoporous Pt layers. The evolution of the mesoporous Pt layers is carefully studied at different time intervals. As the reaction time increases, the mesoporous Pt layers become thicker, and well‐defined mesoporous structures gradually develop. The obtained mesoporous Pt skin exhibits high activity and superior CO tolerance in the electro‐oxidation reaction of methanol. The mesoporous Pt skin also shows very high durability, and only a 20.2 % loss of the Pt electrochemical surface area is found even after a harsh durability test.
Electrochemical Preparation of N‐Doped Cobalt Oxide Nanoparticles with High Electrocatalytic Activity for the Oxygen‐Reduction Reaction
Authors: Yu Hongtao , Li Yunchao , Li Xiaohong , Fan Louzhen , Yang Shihe 
Published: February 2014

AbstractNitrogen‐doped CoO (N‐CoO) nanoparticles with high electrocatalytic activity for the oxygen‐reduction reaction (ORR) were fabricated by electrochemical reduction of CoCl2 in acetonitrile solution at cathodic potentials. The initially generated, highly reactive nitrogen‐doped Co nanoparticles were readily oxidized to N‐CoO nanoparticles in air. In contrast to their N‐free counterparts (CoO or Co3O4), N‐CoO nanoparticles with a N content of about 4.6 % exhibit remarkable ORR electrocatalytic activity, stability, and immunity to methanol crossover in an alkaline medium. The CoNx active sites in the CoO nanoparticles are held responsible for the high ORR activity. This work opens a new path for the preparation of nitrogen‐doped transition metal oxide nanomaterials, which are promising electrocatalysts for fuel cells.
Metal‐to‐Ligand Alkyl Migration Inducing Carbon–Sulfur Bond Cleavage in Dialkyl Yttrium Complexes Supported by Thiazole‐Containing Amidopyridinate Ligands: Synthesis, Characterization, and Catalytic Activity in the Intramolecular Hydroamination Reaction
Authors: Lyubov Dmitry M. , Luconi Lapo , Rossin Andrea , Tuci Giulia , Cherkasov Anton V. , Fukin Georgy K. , Giambastiani Giuliano , Trifonov Alexander A. 
Published: February 2014

AbstractNeutral YIII dialkyl complexes supported by tridentate N−,N,N monoanionic methylthiazole– or benzothiazole–amidopyridinate ligands have been prepared and completely characterized. Studies on their stability in solution revealed progressive rearrangement of the coordination sphere in the benzothiazole‐containing system through an unprecedented metal‐to‐ligand alkyl migration and subsequent thiazole ring opening. Attempts to synthesize hydrido species from the dialkyl precursor led to the generation of a dimeric yttrium species stabilized by a trianionic N−,N,N−,S− ligand as the result of metal‐to‐ligand hydride migration with chemoselective thiazole ring opening and subsequent dimerization through intermolecular addition of the residual YH group to the imino fragment of a second equivalent of the ring‐opened intermediate. DFT calculations were used to elucidate the thermodynamics and kinetics of the process, in support of the experimental evidence. Finally, all isolated yttrium complexes, especially their cationic forms prepared by activation with the Lewis acid Ph3C+[B(C6F5)4]−, were found to be good candidate catalysts for intramolecular hydroamination/cyclization reactions. Their catalytic performance with a number of primary and secondary amino alkenes was assessed.
Ene‐ene‐yne Reactions: Activation Strain Analysis and the Role of Aromaticity
Authors: Fernández Israel , Bickelhaupt F. Matthias , Cossío Fernando P. 
Published: February 2014

AbstractThe trend in reactivity of the thermal cycloisomerization reactions of 1,3‐hexadien‐5‐ynes, ABCDEF, were explored and analyzed by using density functional theory at the M06‐2X/def2‐TZVPP level. These reactions proceed through formally aromatic transition states to form a bent‐allene intermediate with relatively high activation barriers. Activation‐strain analyses show that the major factor controlling this Hopf cyclization is the geometrical strain energy associated with the rotation of the terminal [A] group. This rotation is necessary for achieving a favorable HOMO–LUMO overlap with the yne‐moiety [F] associated with the formation of the new AF single bond. In addition, the relationship between the aromaticity of the corresponding cyclic transition states (all six‐membered rings) and the computed activation barriers were analyzed. The calculations also indicate that the aromatization of the bent‐allene structures takes place through two consecutive 1,2‐hydrogen shifts, the second one exhibiting negligible energy barriers.
Synthesis of Oxacyclic Scaffolds via Dual Ruthenium Hydride/Brønsted Acid‐Catalyzed Isomerization/Cyclization of Allylic Ethers
Authors: Ascic Erhad , Ohm Ragnhild G. , Petersen Rico , Hansen Mette R. , Hansen Casper L. , Madsen Daniel , Tanner David , Nielsen Thomas E. 
Published: February 2014

AbstractA ruthenium hydride/Brønsted acid‐catalyzed tandem sequence is reported for the synthesis of 1,3,4,9‐tetrahydropyrano[3,4‐b]indoles (THPIs) and related oxacyclic scaffolds. The process was designed on the premise that readily available allylic ethers would undergo sequential isomerization, first to enol ethers (Ru catalysis), then to oxocarbenium ions (Brønsted acid catalysis) amenable to endo cyclization with tethered nucleophiles. This methodology provides not only an attractive alternative to the traditional oxa‐Pictet–Spengler reaction for the synthesis of THPIs, but also convenient access to THPI congeners and other important oxacycles such as acetals.
The Significant Role of Carboxylated Carbonaceous Fragments in the Electrochemistry of Carbon Nanotubes
Authors: Ma Xiao , Jia Li , Zhang Lu , Zhu Liande 
Published: February 2014

AbstractCarbon nanotubes (CNTs) have been widely employed as electrode materials in diverse branches of electrochemistry, which are claimed to display dramatically improved electrochemical behaviour compared to the conventional carbon materials. But a series of recent publications have demonstrated that the electrocatalysis of CNTs might be due to the presence of some impurities, such as metallic catalysts, nanographitic particles and amorphous carbon. For this reason, CNTs are usually purified or treated with nitric acid or nitric and sulphuric acid prior to their versatile applications. However, the strong acidic and oxidative conditions are so aggressive that serious erosion of the tube structures has inevitably taken place, which creates defects on the sidewalls and gives rise to numerous molecular byproducts, commonly referred as carboxylated carbonaceous fragments (CCFs). The adsorption of CCFs on CNTs greatly alters the surface conditions of CNTs which may significantly impact on their electrochemical properties. To this end, we wish to disclose whether the electrocatalysis of the nitric acid purified CNTs is affected by the adsorption of the CCFs. Ascorbic acid (AA) and β‐nicotinamide adenine dinucleotide (NADH) as selected as the targeting benchmarks that are known to be insensitive to the presence of metallic impurities, which may guarantee the preclusion of the promoting contributions from the metallic catalysts resident in CNTs. We have demonstrated that the electrocatalytic activities of the CNTs are actually dominated by the adsorbed CCFs generated during the acidic pre‐treatment. After removal of the CCFs by base rinse, the electrocatalytic properties of CNTs are greatly deteriorated and degraded to the level similar to the conventional graphite powder. We believe this finding is particularly meaningful to uncover the mysterious electrocatalysis of CNTs.
Design of Amphiphilic Peptide Geometry towards Biomimetic Self‐Assembly of Chiral Mesoporous Silica
Authors: Huang Zhehao , Yao Yuan , Che Shunai 
Published: February 2014

AbstractIn nature, diatoms and sponges are exquisite examples of well‐defined structures produced by silica biomineralisation, in which proteins play an important role. However, the artificial peptide templating route for the silica mesostructure remains a formidable and unsolved challenge. Herein, we report our effort on the design of amphiphilic peptides for synthesising a highly ordered two‐dimensional (2D)‐hexagonal and lamellar chiral silica mesostructure using trimethoxysilylpropyl‐N,N,N‐trimethylammonium chloride as the co‐structure directing agent (CSDA). The geometry of the peptide was designed by adding proline residues into the hydrophobic chain of the peptide to break the β‐sheet conformation by weakening the intermolecular hydrogen bonds; this led to the mesophase transformation from the most general lamellar structure to the 2D hexagonal P6mm mesostructure by increasing the amphiphilic molecules packing parameter g. Enantiomerically pure chiral mesostructures were formed thanks to the intrinsic chirality and relatively strong intermolecular hydrogen bonds of peptides.
Light Harvesting and Amplification of Emission of Donor Perylene–Acceptor Perylene Aggregates in Aqueous Medium
Authors: Sukul Pradip K. , Datta Ayan , Malik Sudip 
Published: February 2014

AbstractWith the aid of rational design, we have synthesized a pair of water‐soluble donor‐ and acceptor‐type twisted perylene bisimide units, which together form aggregates upon lowering the pH of the medium, providing bright yellow fluorescence. The light‐harvesting efficiency of the co‐assembled system can be tuned by controlling the ratio of donor to acceptor and 98.1 % efficiency has been achieved.
A Novel Hybrid Metal–Organic Framework–Polymeric Monolith for Solid‐Phase Microextraction
Authors: Lin Chen‐Lan , Lirio Stephen , Chen Ya‐Ting , Lin Chia‐Her , Huang Hsi‐Ya 
Published: February 2014

AbstractThis study describes the fabrication of a novel hybrid metal–organic framework– organic polymer (MOF–polymer) for use as a stationary phase in fritless solid‐phase microextraction (SPME) for validating analytical methods. The MOF–polymer was prepared by using ethylene dimethacrylate (EDMA), butyl methacrylate (BMA), and an imidazolium‐based ionic liquid as porogenic solvent followed by microwave‐assisted polymerization with the addition of 25 % MOF. This novel hybrid MOF–polymer was used to extract penicillin (penicillin G, penicillin V, oxacillin, cloxacillin, nafcillin, dicloxacillin) under different conditions. Quantitative analysis of the extracted penicillin samples using the MOF–organic polymer for SPME was conducted by using capillary electrochromatography (CEC) coupled with UV analysis. The penicillin recovery was 63–96.2 % with high reproducibility, sensitivity, and reusability. The extraction time with the proposed fabricated SPME was only 34 min.