bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence for Kinetic Nucleation in Helical Nanofiber Formation Directed by Chiral Solvent for a Perylene Bisimide Organogelator
Authors: Stepanenko Vladimir , Li Xue‐Qing , Gershberg Jana , Würthner Frank 
Published: February 2013

AbstractThe self‐assembly behavior of an achiral perylene bisimide (PBI) organogelator that bears two 3,4,5‐tridodecyloxybenzoylaminoethyl substituents at the imide positions has been investigated in chiral solvents (R)‐ and (S)‐limonene in great detail by circular dichroism (CD) spectroscopy and atomic force microscopy (AFM). CD spectroscopic studies on dilute solutions revealed a preferential population of one‐handed helical assemblies in chiral solvent with an enantiomeric excess close to 100 %, whereas AFM images of more than 100 nanofibers of the organogel obtained from more concentrated solutions were found to consist of both handed helices with an enantiomeric excess of only 20 %. This discrepancy is attributed to the fast gelation process at high dye concentration that evidently proceeds through non‐equilibrated nuclei in a kinetic rather than thermodynamic self‐assembly process. Under these conditions the chiral induction from the homochiral solvent may not be adequate in effectively populating only one‐handed helices.
Copper‐Catalyzed Aerobic Oxidative CH and CC Functionalization of 1‐[2‐(Arylamino)aryl]ethanones Leading to Acridone Derivatives
Authors: Yu Jipan , Yang Haijun , Jiang Yuyang , Fu Hua 
Published: February 2013

AbstractEfficient copper‐catalyzed aerobic oxidative CH and CC functionalization of 1‐[2‐(arylamino)aryl]ethanones leading to acridones has been developed. The procedure involves cleavage of aromatic CH and acetyl CC bonds with intramolecular formation of a diarylketone bond. The protocol uses inexpensive Cu(O2CCF3)2 as catalyst, pyridine as additive, and economical and environmentally friendly oxygen as the oxidant, and the corresponding acridones with various functional groups were obtained in moderate to good yields.
Fast Reductive Amination by Transfer Hydrogenation “on Water”
Authors: Lei Qian , Wei Yawen , Talwar Dinesh , Wang Chao , Xue Dong , Xiao Jianliang 
Published: February 2013

AbstractReductive amination of various ketones and aldehydes by transfer hydrogenation under aqueous conditions has been developed, by using cyclometallated iridium complexes as catalysts and formate as hydrogen source. The pH value of the solution is shown to be critical for a high catalytic chemoselectivity and activity, with the best pH value being 4.8. In comparison with that in organic solvents, the reductive amination in an aqueous phase is faster, and the molar ratio of the substrate to the catalyst (S/C) can be set as high as 1×105, the highest S/C value ever reported in reductive amination reactions. The catalyst is easy to access and the reaction is operationally simple, allowing a wide range of ketones and aldehydes to react with various amines in high yields. The protocol provides a practical and environmental friendly new method for the synthesis of amine compounds.
Effect of Pumice and Sand on the Sustainability of Granular Iron Beds for the Aqueous Removal of CuII, NiII, and ZnII
Authors: Bilardi Stefania , Calabrò Paolo S. , Caré Sabine , Moraci Nicola , Noubactep Chicgoua 
Published: February 2013

AbstractCurrent knowledge of the basic principles underlying the design of Fe0 beds is weak. The volumetric expansive nature of iron corrosion was identified as the major factor determining the sustainability of Fe0 beds. This work attempts to systematically verify developed concepts. Pumice and sand were admixed to 200 g of Fe0 in column studies (50:50 volumetric proportion). Reference systems containing 100% of each material have been also investigated. The mean grain size of the used materials (in mm) were 0.28 (sand), 0.30 (pumice), and 0.50 (Fe0). The five studied systems were characterized (i) by the time dependent evolution of their hydraulic conductivity (permeability) and (ii) for their efficiency for aqueous removal of CuII, NiII, and ZnII (about 0.3 mM of each). Results showed unequivocally that (i) quantitative contaminant removal was coupled to the presence of Fe0, (ii) additive admixture lengthened the service life of Fe0 beds, and (iii) pumice was the best admixing agent for sustaining permeability while the Fe0/sand column was the most efficient for contaminant removal. The evolution of the permeability was well‐fitted by the approach that the inflowing solution contained dissolved O2. The achieved results are regarded as starting point for a systematic research to optimize/support Fe0 filter design.
Monitoring Binding of HIV‐1 Capsid Assembly Inhibitors Using 19F Ligand‐and 15N Protein‐Based NMR and X‐ray Crystallography: Early Hit Validation of a Benzodiazepine Series
Authors: Goudreau Nathalie , Coulombe René , Faucher Anne‐Marie , Grand‐Maître Chantal , Lacoste Jean‐Eric , Lemke Christopher T. , Malenfant Eric , Bousquet Yves , Fader Lee , Simoneau Bruno , Mercier Jean‐François , Titolo Steve , Mason Stephen W. 
Published: February 2013

AbstractThe emergence of resistance to existing classes of antiretroviral drugs underlines the need to find novel human immunodeficiency virus (HIV)‐1 targets for drug discovery. The viral capsid protein (CA) represents one such potential target. Recently, a series of benzodiazepine inhibitors was identified via high‐throughput screening using an in vitro capsid assembly assay (CAA). Here, we demonstrate how a combination of NMR and X‐ray co‐crystallography allowed for the rapid characterization of the early hits from this inhibitor series. Ligand‐based 19F NMR was used to confirm inhibitor binding specificity and reversibility as well as to identify the N‐terminal domain of the capsid (CANTD) as its molecular target. Protein‐based NMR (1H and 15N chemical shift perturbation analysis) identified key residues within the CANTD involved in inhibitor binding, while X‐ray co‐crystallography confirmed the inhibitor binding site and its binding mode. Based on these results, two conformationally restricted cyclic inhibitors were designed to further validate the possible binding modes. These studies were crucial to early hit confirmation and subsequent lead optimization.
Experimental and Theoretical Study of the n‐Doped Successive Polyanions of Oligocruciform Molecular Wires: Up to Five Units of Charge
Authors: Al Ouahabi Abdelaziz , Baxter Paul , Mathis Claude , Bernard Maxime , Vileno Bertrand , Gisselbrecht Jean‐Paul , Turek Philippe , Mouesca Jean‐Marie , Choua Sylvie 
Published: February 2013

AbstractThe electronic structure of polyanions of sterically encumbered triisopropylsilyl‐substituted linear and cyclic oligo(phenyleneethynylene)s (Monomer, Trimer, Pentamer, and Triangle) is investigated by electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), and UV/Vis–near‐infrared (NIR) spectroscopies, cyclic voltammetry, and theoretical calculations (DFT). Increasing anion orders are generated sequentially in vacuo at room temperature by chemical reaction with potassium metal up to the pentaanion. The relevance of these compounds acting as electron reservoirs is thus demonstrated. Even‐order anions are EPR silent, whereas the odd species exhibit different signatures, which are identified after comparison of the measured hyperfine couplings by ENDOR spectroscopy with those predicted by DFT calculations. With increasing size of the oligomers the electron spin density is first distributed over the backbone carbon atoms for the monoanions, and then further localized at the outer phenyl rings for the trianion species. Examination of the UV/Vis‐NIR spectra indicates that the monoanions (T.−, P.−) exhibit two transitions in the Vis‐NIR region, whereas a strong absorption in the IR region is solely observed for higher reduced states. Electronic transitions of the neutral monoanions and trianions are redshifted with increasing oligomer size, whereas for a given oligomer a blueshift is observed upon increasing the charge, which suggests a localization of the spin density.
Competitive Bond Rupture in the Photodissociation of Bromoacetyl Chloride and 2‐ and 3‐Bromopropionyl Chloride: Adiabatic versus Diabatic Dissociation
Authors: Hsu Ming‐Yi , Tsai Po‐Yu , Wei Zheng‐Rong , Chao Meng‐Hsuan , Zhang Bing , Kasai Toshio , Lin King‐Chuen 
Published: February 2013

AbstractCompetitive bond dissociation mechanisms for bromoacetyl chloride and 2‐ and 3‐bromopropionyl chloride following the 1[n(O)→π*(CO)] transition at 234–235 nm are investigated. Branching ratios for CBr/CCl bond fission are found by using the (2+1) resonance‐enhanced multiphoton ionization (REMPI) technique coupled with velocity ion imaging. The fragment branching ratios depend mainly on the dissociation pathways and the distances between the orbitals of Br and the CO chromophore. CCl bond fission is anticipated to follow an adiabatic potential surface for a strong diabatic coupling between the n(O)π*(CO) and np(Cl)σ*(CCl) bands. In contrast, CBr bond fission is subject to much weaker coupling between n(O)π*(CO) and np(Br)σ*(CBr). Thus, a diabatic pathway is preferred for bromoacetyl chloride and 2‐bromopropionyl chloride, which leads to excited‐state products. For 3‐bromopropionyl chloride, the available energy is not high enough to reach the excited‐state products such that CBr bond fission must proceed through an adiabatic pathway with severe suppression by nonadiabatic coupling. The fragment translational energies and anisotropy parameters for the three molecules are also analyzed and appropriately interpreted.
Triarylamine‐Substituted Imidazole‐ and Quinoxaline‐Fused Push–Pull Porphyrins for Dye‐Sensitized Solar Cells
Authors: Hayashi Hironobu , Touchy Abeda Sultana , Kinjo Yuriko , Kurotobi Kei , Toude Yuuki , Ito Seigo , Saarenpää Hanna , Tkachenko Nikolai V. , Lemmetyinen Helge , Imahori Hiroshi 
Published: February 2013

AbstractWe have prepared a push–pull porphyrin with an electron‐donating triarylamino group at the β,β′‐edge through a fused imidazole group and an electron‐withdrawing carboxyquinoxalino anchoring group at the opposite β,β′‐edge (ZnPQI) and evaluated the effects of the push–pull structure of ZnPQI on optical, electrochemical, and photovoltaic properties. ZnPQI showed red‐shifted Soret and Q bands relative to a reference porphyrin with only an electron‐withdrawing group (ZnPQ), thus demonstrating the improved light‐harvesting property of ZnPQI. The optical HOMO–LUMO gap was consistent with that estimated by DFT calculations. The ZnPQI‐sensitized solar cell exhibited a relatively high power conversion efficiency (η) of 6.8 %, which is larger than that of the ZnPQ‐sensitized solar cell (η=6.3 %) under optimized conditions. The short‐circuit current and fill factor of the ZnPQI‐sensitized solar cell are larger than those of the ZnPQ‐sensitized solar cell, whereas the open circuit potential of the ZnPQI‐sensitized cell is smaller than that of the ZnPQ‐sensitized cell, leading to an overall improved cell performance of ZnPQI. Such fundamental information provides a new tool for the rational molecular design of highly efficient dye‐sensitized solar cells based on push–pull porphyrins.
Ilexgenin A Obtained from Ilex hainanensis Merr. Improves Diet‐Induced Non‐Alcoholic Fatty Liver Disease in Rats
Authors: Cui Wei‐xi , Li Jing‐Jing , Chen Xiao‐qing , Mao Qian , Wei Xiang‐lan , Wen Xiao‐dong , Yang Jie , Wang Qiang 
Published: February 2013

Abstract

Preclinical Research

Nonalcoholic fatty liver disease (NAFLD) is a common aspect of metabolic syndrome, which includes a wide spectrum of liver damage and is closely associated with insulin resistance and lipid peroxidation. The current study aimed to evaluate the protective effect of Ilexgenin A (IA), obtained from Ilex hainanensis Merr., on NAFLD and investigate the underlying mechanisms. Sprague‐Dawley rats were fed a high‐fat (HF) diet for 3 weeks to induce NAFLD. They were divided into HF diet rats and HF‐IA‐treated rats, which were treated with IA (80 mg/kg p.o.) for 2 weeks. IA alleviated hepatic steatosis and insulin resistance and reduced plasma levels of alanine transaminase, aspartate aminotransferase, triglyceride, total cholesterol, low‐density lipoprotein‐cholesterol, malondialdehyde, interleukin 6, and tumor necrosis factor‐α, while increasing plasma levels of high‐density lipoprotein‐cholesterol and superoxide dismutase (SOD). IA decreased hepatic triglycerides, total cholesterol, malondialdehyde, and restored the abnormal down‐regulation of SOD. IA also decreased Cytochrome P450 2E1 expression and up‐regulated peroxisome proliferator‐activated receptor α (PPARα) expression in liver. These results suggested that IA had the potential to attenuate NAFLD by improving lipid metabolism, insulin resistance, inflammation, and oxidative stress, as well as adjusting the expression of Cytochrome P450 2E1 and PPARα.
Ecohydrology of street trees: design and irrigation requirements for sustainable water use
Authors: Vico Giulia , Revelli Roberto , Porporato Amilcare 
Published: February 2013

ABSTRACTWhereas the beneficial effects of urban vegetation have long been recognized, growing conditions in urban environments, especially for street trees, are typically harsh and limited by low water availability. Supplemental irrigation may be used to preserve aesthetic quality and ability to provide ecosystem services of urban vegetation but requires careful management of available economic and water resources to reduce urban water footprint. To this purpose, decision makers need quantitative tools, requiring few, physically based parameters and accounting for the uncertainties and future scenarios of the hydroclimatic forcing. Focusing on in‐row and isolated trees, a minimalist description of street tree water balance is proposed here, including rainfed and irrigated conditions, and explicitly accounting for tree water requirements, growing conditions (in terms of soil properties and extension of bare soil, permeable and impervious pavements surrounding the tree) and rainfall unpredictability. The proposed model allows the quantification of tree cooling capacity, water stress occurrence and irrigation requirements, as a function of soil, plant and climate characteristics, thus providing indications regarding the tree ability to provide ecosystem services and management costs. In particular, an analysis of different planting designs suggests that a balanced design consisting in bare soil and permeable pavement with size equal to the lateral canopy extension is optimal for water conservation, tree cooling capacity and health. The proposed model provides useful indications towards the definition of site‐specific guidelines for species selection and planting design, for sustainable urban vegetation. Copyright © 2013 John Wiley & Sons, Ltd.
The Prins Cascade Cyclization Reaction for the Synthesis of Angularly‐Fused Tetrahydropyran and Piperidine Derivatives
Authors: Subba Reddy B. V. , Kumar Harish , Borkar Prashant , Yadav J. S. , Sridhar B. 
Published: February 2013

Abstract2‐Arylethylbut‐3‐en‐1‐ol is found to undergo smooth Prins cascade reactions with various aldehydes in the presence of Sc(OTf)3 (10 mol‐%) and a stoichiometric amount of TsOH to afford the corresponding trans‐fused hexahydro‐1H‐benzo[f]isochromenes in good yields with excellent selectivity. Likewise, N‐tosyl‐2‐phenethylbut‐3‐en‐1‐amine gives trans‐fused octahydrobenzo[f]isoquinoline derivatives under similar conditions. This is the first example of the synthesis of hexahydro‐1H‐benzo[f]isochromene and octahydrobenzo‐[f]isoquinoline from 2‐arylethylbut‐3‐en‐1‐ol and N‐tosyl‐2‐phenethylbut‐3‐en‐1‐amine, respectively.
The First Enantioselective Approach to 13a‐Methyl‐14‐hydroxyphenanthroindolizidine Alkaloids – Synthetic Studies towards Hypoestestatin 2
Authors: Su Bo , Deng Meng , Wang Qingmin 
Published: February 2013

AbstractThe first enantioselective approach to 13a‐methyl‐14‐hydroxyphenanthroindolizidine alkaloids was achieved in six linear steps from phenanthryl alcohol and features a highly substrate‐dependent Parham cycloacylation and Seebach's enantioselective alkylation as the key steps. The route is concise, protecting‐group free, provides access to all stereoisomers, and works on a gram scale. In addition to the putative structure of hypoestestatin 2, the other three stereoisomers and two structurally related analogues were synthesized, none of which shows identical NMR spectra to those reported for natural hypoestestatin 2, which indicates that further structure revision is required.
Regio‐ and Stereoselective Olefination of Phenol Carbamates through C–H Bond Functionalization
Authors: Li Bin , Ma Jianfeng , Liang Yujie , Wang Nuancheng , Xu Shansheng , Song Haibin , Wang Baiquan 
Published: February 2013

AbstractTwo pathways that can be used to access ortho‐olefinated phenol carbamate, including a ruthenium(II)‐catalyzed oxidative olefination of phenol carbamate with acrylates and a rhodium(III)‐catalyzed alkyne hydroarylation of phenol carbamate with internal alkynes through direct C–H activation, are reported. Both reactions afford substituted alkenes in a highly regio‐ and stereoselective manner.
Reexamination of the Direct Electrochemical Reduction of S‐Nitrosothiols
Authors: Peng Bo , Meyerhoff Mark E. 
Published: February 2013

AbstractWe report here on the electrochemical reduction of S‐nitrosothiol species (RSNO). Nitric oxide (NO) is the reported common product from electrochemically reduced RSNOs at physiological pH. However, studies here at pH 7.4 show that during the reduction of RSNOs (−0.6 V to −0.9 V, vs. Ag/AgCl), no significant amount of NO is detected. Gas analysis suggests RSNO are reduced to nitrous oxide (N2O) at pH 7.4 and can only be converted back to NO at more oxidizing voltages. Interestingly, at pH 4.0, a direct one‐electron reduction of RSNOs appears to occur and generates significant amounts of NO from RSNO species.
MWCNT Modified Glassy Carbon Electrode: Probing Furazolidone‐DNA Interactions and DNA Determination
Authors: Fotouhi Lida , Bahmani Farzaneh 
Published: February 2013

AbstractThe interactions of furazolidone (Fu) with double‐stranded calf thymus DNA (dsDNA) on the multiwalled carbon nanotubes modified glassy carbon electrode (MWCNT/GCE) have been studied by voltammetry and UV‐vis spectroscopy. The binding constants of Fu with DNA and the stoichiometric coefficient according to the Hill’s model have been determined. A detailed analysis of cyclic voltammograms gave fundamental electrochemical parameters including the electroactive surface coverage (Γ), the transfer coefficient (α), and the heterogeneous rate constant (ks). Two linear calibration curves were obtained for DNA detection in the concentration ranges of 40–100 µ L−1 and 100–1000 µg L−1 with a detection limit of 25 µg L−1.
Validation of a New Analytical Method for the Measurement of Free Fatty Acids in Biodiesel
Authors: da Silva Figueiredo Elizabeth , de Castro Vieira Eduardo , de Siqueira Cavalcanti Eduardo Homem , D'Elia Eliane 
Published: February 2013

AbstractInternational and Brazilian standards have in common the acid number as the main qualification parameter for biodiesel. Free fatty acids lead to engine corrosion and contribute to the formation of gum. The analytical methods specified for analysis are based on colorimetric and potentiometric titrations, which are characterised by lack of selectivity. This article proposes a new method based on the electrochemical reduction of quinones in the presence of the free fatty acids found in biodiesel on the glassy carbon electrode surface in the range of 0.4 V to −0.65 V versus Ag/AgCl/Cl− (3 mol L−1). The proposed method was validated.
Facilitated Ion Transfers at the Micro‐Water/1,2‐Dichloroethane Interface by Crown Ether Derivatives
Authors: Qiao Yonghui , Zhang Ben , Zhu Xinyu , Ji Tianrong , Li Bo , Li Qing , Chen Erqiang , Shao Yuanhua 
Published: February 2013

AbstractThe transfers of potassium ion (K+) facilitated by 3,3′,6,6′‐tetrakis[p‐(n‐dodecyloxy)benzoyloxymethyl]dibenzo‐18‐crown‐6 (L1) and of sodium ion (Na+) facilitated by 3′,6′‐bis{3′′,4′′,5′′‐tris[p‐(n‐dodecyloxy)benzyloxy]benzoyloxymethyl}benzo‐15‐crown‐5 (L2) have been investigated at the micro‐water/1.2‐dichloroethane (micro‐W/DCE) interface supported at the tip of a micropipette by cyclic voltammetry and chronoamperometry. The experimental results demonstrate that the mechanisms of both facilitated ion transfer (FIT) processes correspond to the transfer by an interfacial complexation (TIC) and the transfer by an interfacial dissociation (TID) processes. Some thermodynamic parameters, such as, stoichiometry, diffusion coefficient and the association constants are evaluated by cyclic voltammetry. Furthermore, the chronoamperometry has been employed to explore the roughness of the interface supported at the micropipette by analysis of the current‐time curves based on the system of facilitated Na+ transfer by L2 at the water/DCE interface.
Preparation of Liposomal Progesterone and Its Application on the Measurement of Progesterone Interpreted via Electrochemical and Colorimetric Sensing Platforms
Authors: Tien Chia‐Ying , Jou Amily Fang‐ju , Fan Nien‐Chu , Chuang Min‐Chieh , Ho Ja‐an Annie 
Published: February 2013

AbstractWe herein demonstrate a successful synthesis of methylene blue (MB)‐encapsulated liposomal progesterone (LP) with an amplification merit beneficial for analytical applications. Both colormetric and electrochemical immunosensing strips for the leveling of progesterone, a hormone that helps to regulate the menstrual cycle of women, were achieved and characterized. Particular attention was given to the incorporation of an electrochemical screen‐printed electrode toward disposable and deployed diagnostics, enabling the reliable quantification of progesterone in connection to a LOD of 0.83 pg/mL. The novel, simple and specific amplification approach holds the promise to endorse a fast and high‐fidelity diagnostics required for immediate therapeutic attempts.
Interfacial Electron Transfer from CdSe/ZnS Quantum Dots to TiO2 Nanoparticles: Linker Dependence at Single Molecule Level
Authors: Chang Yu‐Pin , Tsai Po‐Yu , Lee Hsin‐Lung , Lin King‐Chuen 
Published: February 2013

AbstractWe utilize single molecule spectroscopy combined with time‐correlated single‐photon counting to probe electron transfer (ET) kinetics from CdSe/ZnS (core/shell) quantum dots (QDs) to TiO2 through various lengths of linker molecules. The QD‐linker‐TiO2 complexes with varied linker length, linker structure, and QD size are fabricated by a surface‐based stepwise method to show control of the rate and of the magnitude of fluctuations of photo‐induced ET at the single molecule level. The ET rate constants are determined to be 2.8×107, 1.9×107, and 3.5×106 s−1 for the chain length of 1.5, 6.2 and 13.8 Å, respectively. The electronic coupling strengths between QDs and TiO2 are further calculated to be 3.68, 3.60, and 1.59 cm−1 for the three different chain lengths by using the Marcus ET model.