bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimation of spatial covariance of log conductivity from particle size data
Authors: Riva Monica , Sanchez‐Vila Xavier , Guadagnini Alberto 
Published: May 2014

AbstractWe derive analytical relationships between the spatial covariance of the (natural) logarithm of hydraulic conductivity (K) and that of representative soil particle sizes and porosity. The latter quantities can be directly measured during routine sedimentological analyses of soil samples and provide a way of incorporating K estimates into groundwater flow models at a relatively modest experimental cost. Here we rely on widely used empirical formulations requiring measurements of representative particle diameters and, in some cases, of medium porosity. We derive exact formulations relating the spatial covariance of these quantities and K and present workable approximations on the basis of perturbation methods. Our formulations provide a direct link between key geostatistical descriptors of sedimentological and hydraulic parameters of heterogeneous aquifers which can be employed in classical estimation and simulation procedures. The approach and theoretical results are tested on an extensive data set comprising 411 particle size curves collected at 12 boreholes in a small‐scale alluvial aquifer.
Carbonsäureaktivierung in der asymmetrischen Organokatalyse
Authors: Monaco Mattia Riccardo , Poladura Belén , Diaz de Los Bernardos Miriam , Leutzsch Markus , Goddard Richard , List Benjamin 
Published: May 2014

AbstractOrganokatalyse hat sich zu einem allgemeinen Ansatz für die asymmetrische Katalyse entwickelt und ist sowohl zur Übergangsmetallkatalyse als auch zur Biokatalyse komplementär.1 Ihr Erfolg beruht besonders auf der Einführung neuer und universeller Aktivierungsmodi.2 Bemerkenswerterweise wurden Carbonsäuren zwar als Katalysator oder dirigierende Gruppe in der supramolekularen Übergangsmetallkatalyse verwendet,3 ein genereller und spezifischer Aktivierungsmodus für diese nützliche und weit verbreitete Substanzklasse fehlt aber bisher. Hier stellen wir die Heterodimerbildung von Carbonsäuren und chiralen Phosphorsäuren als neues Aktivierungsprinzip für die Organokatalyse vor. Diese Selbstorganisation erhöht sowohl die Acidität des Phosphorsäurekatalysators als auch die Reaktivität der Carbonsäure. Um dieses Prinzip zu Illustrieren, wenden wir es auf die generelle und hoch enantioselektive katalytische Aziridinöffnung mit Carbonsäuren als Nukleophilen an.
Substrate Profiling of Glutathione S‐transferase with Engineered Enzymes and Matched Glutathione Analogues
Authors: Feng Shan , Zhang Lei , Adilijiang Gulishana , Liu Jieyuan , Luo Minkui , Deng Haiteng 
Published: May 2014

AbstractThe identification of specific substrates of glutathione S‐transferases (GSTs) is important for understanding drug metabolism. A method termed bioorthogonal identification of GST substrates (BIGS) was developed, in which a reduced glutathione (GSH) analogue was developed for recognition by a rationally engineered GST to label the substrates of the corresponding native GST. A K44G‐W40A‐R41A mutant (GST‐KWR) of the mu‐class glutathione S‐transferases GSTM1 was shown to be active with a clickable GSH analogue (GSH‐R1) as the cosubstrate. The GSH‐R1 conjugation products can react with an azido‐based biotin probe for ready enrichment and MS identification. Proof‐of‐principle studies were carried to detect the products of GSH‐R1 conjugation to 1‐chloro‐2,4‐dinitrobenzene (CDNB) and dopamine quinone. The BIGS technology was then used to identify GSTM1 substrates in the Chinese herbal medicine Ganmaocongji.
Simultaneous Arrangement of up to Three Different Molecules on the Pore Surface of a Metal–Macrocycle Framework: Cooperation and Competition
Authors: Tashiro Shohei , Umeki Tsutomu , Kubota Ryou , Shionoya Mitsuhiko 
Published: May 2014

AbstractPorous crystals are excellent materials with potential spatial functions through molecular encapsulation within the pores. Co‐encapsulation of multiple different molecules further expands their usability and designability. Herein we report the simultaneous arrangement of up to three different guest molecules, TTF (tetrathiafulvalene), ferrocene, and fluorene, on the pore surfaces of a porous crystalline metal–macrocycle framework (MMF). The position and orientation of adsorbed molecules arranged in the pore were determined by single‐crystal X‐ray diffraction analysis. The anchoring effect of hydrogen bonds between the hydroxy groups of the guest molecules and inter‐guest cooperation and competition are significant factors in the adsorption behaviors of the guest molecules. This finding would serve as a design basis of multicomponent functionalized nanospaces for elaborate reactions that are realized in enzymes.
Hydrogenation of Esters to Alcohols with a Well‐Defined Iron Complex
Authors: Werkmeister Svenja , Junge Kathrin , Wendt Bianca , Alberico Elisabetta , Jiao Haijun , Baumann Wolfgang , Junge Henrik , Gallou Fabrice , Beller Matthias 
Published: May 2014

AbstractWe present the first base‐free Fe‐catalyzed ester reduction applying molecular hydrogen. Without any additives, a variety of carboxylic acid esters and lactones were hydrogenated with high efficiency. Computations reveal an outer‐sphere mechanism involving simultaneous hydrogen transfer from the iron center and the ligand. This assumption is supported by NMR experiments.
Helical DNA Origami Tubular Structures with Various Sizes and Arrangements
Authors: Endo Masayuki , Yamamoto Seigi , Emura Tomoko , Hidaka Kumi , Morone Nobuhiro , Heuser John E. , Sugiyama Hiroshi 
Published: May 2014

AbstractWe developed a novel method to design various helical tubular structures using the DNA origami method. The size‐controlled tubular structures which have 192, 256, and 320 base pairs for one turn of the tube were designed and prepared. We observed the formation of the expected short tubes and unexpected long ones. Detailed analyses of the surface patterns of the tubes showed that the short tubes had mainly a left‐handed helical structure. The long tubes mainly formed a right‐handed helical structure and extended to the directions of the double helical axes as structural isomers of the short tubes. The folding pathways of the tubes were estimated by analyzing the proportions of short and long tubes obtained at different annealing conditions. Depending on the number of base pairs involved in one turn of the tube, the population of left‐/right‐handed and short/long tubes changed. The bending stress caused by the stiffness of the bundled double helices and the non‐natural helical pitch determine the structural variety of the tubes.
Deactivation of Cationic CuI and AuI Catalysts for A3 Coupling by CH2Cl2: Mechanistic Implications of the Formation of Neutral CuI and AuI Chlorides
Authors: Grirrane Abdessamad , Álvarez Eleuterio , García Hermenegildo , Corma Avelino 
Published: May 2014

AbstractCare should be exercised when using CH2Cl2 as a solvent for reactions in which amines are a reagent, since undesirable deactivation of cationic copper(I) and gold(I) catalysts to form the corresponding inactive neutral chloride complexes [LMCl] (M=Cu or Au) can occur as a result of the generation of hydrogen chloride in the medium. CuI and AuI deactivation has been proved for the Mannich three‐component coupling reaction. A series of CuI and AuI complexes with potential mechanistic implications were isolated and characterized by X‐ray crystallography.
A facile method to prepare high‐purity magnetite nanoparticles by electrooxidation of iron in water using a pulsed direct current
Authors: Setyawan Heru , Fajaroh Fauziatul , Pusfitasari Memik Dian , Yuwana Minta , Affandi Samsudin 
Published: May 2014

ABSTRACTHigh‐purity magnetite (Fe3O4) nanoparticles were successfully synthesized via the electrooxidation of iron in an aqueous system using a pulsed direct current (pulsed DC). The pure iron to be electrooxidized was electroplated on a steel plate, which was then used as a sacrificial anode in the electrochemical system. The electrolyte used was demineralized water, either with or without added NaOH, which was used to vary the pH of the solution, between 7 and 10. We showed that the pulsed DC significantly enhanced the purity of the magnetite that was formed. The FeOOH impurities that are typically present when continuous DC is used were not observed. The particles produced using the proposed method were nearly spherical in shape. The size of the particles ranged from 7 to 23 nm depending on the conditions of synthesis, namely, the pulse frequency, duty cycle, and pH. The magnetite nanoparticles exhibited ferromagnetic properties, with values of saturation magnetization ranging from 18 to 55 emu/g. The results obtained from thermal gravimetric/differential thermal analysis revealed that magnetite was converted into maghemite at a temperature of approximately 200 °C and into hematite under further heating to 500 °C. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.
Chemoenzymatic Synthesis of Functional Sialyl LewisX Mimetics with a Heteroaromatic Core
Authors: Schlemmer Claudine , Wiebe Christine , Ferenc Dorota , Kowalczyk Danuta , Wedepohl Stefanie , Ziegelmüller Patrick , Dernedde Jens , Opatz Till 
Published: May 2014

AbstractFunctional mimetics of the sialyl LewisX tetrasaccharide were prepared by the enzymatic sialylation of a 1,3‐diglycosylated indole and a glycosyl azide, which was subsequently transformed into a 1,4‐diglycosylated 1,2,3‐triazole, by using the trans‐sialidase of Trypanosoma cruzi. These compounds inhibited the binding of E‐, L‐, and P‐selectin‐coated nanoparticles to polyacrylamide‐bound sialyl‐LewisX‐containing neighboring sulfated tyrosine residues (sTyr/sLeX‐PAA) at low or sub‐millimolar concentrations. Except for E‐selectin, the mimetics showed higher activities than the natural tetrasaccharide.
Optimized Plasmid Systems for the Incorporation of Multiple Different Unnatural Amino Acids by Evolved Orthogonal Ribosomes
Authors: Lammers Christoph , Hahn Liljan E. , Neumann Heinz 
Published: May 2014

AbstractIncorporation of multiple different unnatural amino acids into the same polypeptide remains a significant challenge. Orthogonal ribosomes, which are evolvable as they direct the translation of a single dedicated orthogonal mRNA, can provide an avenue to produce such polypeptides routinely. Recent advances in engineering orthogonal ribosomes have created a prototype system to enable genetically encoded introduction of two different functional groups, albeit with limited efficiency. Here, we systematically investigated the limiting factors of this system by using assays to measure the levels and activities of individual components; we identified Methanosarcina barkeri PylRS as a limiting factor for protein yield. Balancing the expression levels of individual components significantly improved growth rate and protein yield. This optimization of the system is likely to increase the scope of evolved orthogonal ribosome‐mediated incorporation of multiple different unnatural amino acids.
Activation of protease‐activated receptor‐2 disrupts vaginal epithelial barrier function
Authors: Li Yan , Feng Chong , Wei Xing , Zhang Jiyuan , Zan Ronghua , Zheng Guizhi , Yang Xiaoying , Zhai Jianjun 
Published: May 2014

AbstractThe epithelial cell barrier function is a critical factor in the maintenance of the homeostasis of the vaginal mucosa. This study elucidates one of the mast cell‐derived chemical mediators, tryptase, on compromising the vaginal epithelial barrier function. The results showed that human vaginal cell line, VK2, express PAR2. Activation of PAR2 increases the expression of ADAM10 in VK2 cells, interferes with the endosome/lysosome fusion, and compromises the epithelial barrier function. We conclude that the activation of PAR2 on VK2 cells increases the expression of ADAM10, and compromises the VK2 monolayer barrier function.
Development block of golden hamster ICSI embryos is associated with decreased expression of HDAC1, HSPA1A and MYC
Authors: Pan Xiaoyan , Kong Delong , Liu Limei , Gao Fei , Zhang Xueming , Tang Bo , Li Ziyi 
Published: May 2014

AbstractWe have investigated the mechanism for embryo development block in vitro and to improve the development rate of golden hamster embryos in vitro. Intracytoplasmic sperm injection (ICSI) technique was used to produce golden hamster ICSI embryos. The changes in the histone acetylation and the expression of histone deacetylase and related genes were analyzed by immunocytochemical staining and real‐time PCR both in golden hamster in vivo embryos and in ICSI embryos. Aged oocytes significantly increased the oocyte spontaneous activation rate. In vitro cultured ICSI embryos suffered from severe development block in M199TE medium. Expression of histone deacetylase 1 (HDAC1) was significantly decreased in the nuclei of the arrested ICSI 2‐cell embryos, and its nuclear and cytoplasmic expression pattern was also markedly altered. The acetylation level of H4K5, however, was not significantly changed between golden hamster in vivo embryos and ICSI embryos. HSPA1A and MYC, the marker genes for zygotic genome activation (ZGA), were transcriptionally decreased in arrested ICSI 2‐cell embryos. Transcription of HDAC1 was also downregulated in these embryos, whereas the mRNA expression of the proapoptotic gene, BAX, was not changed. These results indicate that the golden hamster ICSI embryo development block during ZGA is associated with decreased nuclear expression and altered expression of HDAC1. HSPA1A, MYC, and HDAC1 mRNA levels, which decrease, resulting in ZGA failure.
CYP3A4‐dependent cellular response does not relate to CYP3A4‐catalysed metabolites of C‐1748 and C‐1305 acridine antitumor agents in HepG2 cells
Authors: Augustin Ewa , Niemira Magdalena , Hołownia Adam , Mazerska Zofia 
Published: May 2014

AbstractHigh CYP3A4 expression sensitizes tumor cells to certain antitumor agents while for others it can lower their therapeutic efficacy. We have elucidated the influence of CYP3A4 overexpression on the cellular response induced by antitumor acridine derivatives, C‐1305 and C‐1748, in two hepatocellular carcinoma (HepG2) cell lines, Hep3A4 stably transfected with CYP3A4 isoenzyme, and HepC34 expressing empty vector. The compounds were selected considering their different chemical structures and different metabolic pathways seen earlier in human and rat liver microsomes C‐1748 was transformed to several metabolites at a higher rate in Hep3A4 than in HepC34 cells. In contrast, C‐1305 metabolism in Hep3A4 cells was unchanged compared to HepC34 cells, with each cell line producing a single metabolite of comparable concentration. C‐1748 resulted in a progressive appearance of sub‐G1 population to its high level in both cell lines. In turn, the sub‐G1 fraction was dominated in CYP3A4‐overexpressing cells following C‐1305 exposure. Both compounds induced necrosis and to a lesser extent apoptosis, which were more pronounced in Hep3A4 than in wild‐type cells. In conclusion, CYP3A4‐overexpressing cells produce higher levels of C‐1748 metabolites, but they do not affect the cellular responses to the drug. Conversely, cellular response was modulated following C‐1305 treatment in CYP3A4‐overexpressing cells, although metabolism of this drug was unaltered.
The Effect of Water on the Heterogeneously Catalyzed Selective Oxidation of Acrolein: An Isotope Study
Authors: Petzold Tina , Blickhan Nina , Drochner Alfons , Vogel Herbert 
Published: May 2014

AbstractThe effect of water on the selective gas phase oxidation of acrolein to acrylic acid on a Mo/V/W mixed oxide catalyst was studied by performing steady‐state isotopic transient kinetic analysis experiments with H218O. Experiments were performed in the temperature range of 90–345 °C at ambient pressure. It could be shown that acrolein exchanges its carbonylic oxygen with oxygen from water even at low temperatures (<200 °C), at which no acrolein oxidation occurs. At higher temperatures (>200 °C), the oxygen atoms of the water molecules incorporate into all oxidation products such as acrylic acid, carbon monoxide, and carbon dioxide.
Mn Oxide‐Silver Composite Nanowires for Improved Thermal Stability, SERS and Electrical Conductivity
Authors: Pradhan Mukul , Sinha Arun Kumar , Pal Tarasankar 
Published: May 2014

AbstractRedox transformation reaction between aqueous AgNO3 and Mn(CH3COO)2 at low temperature (∼80 °C) has been adopted for industrial‐scale production of uniform Ag–MnOOH composite nanowires for the first time. Varying amounts of incorporated Ag in the composite retain the 1D morphology of the composite. Nanowires upon annealing evolve Ag–MnO2 nanocomposites, once again with the retention of the parental morphology. Just 4 % of silver incorporation in the composite demonstrates metal‐like conducting performance from the corresponding semiconducting material. Transition of MnO2 to Mn2O3 to Mn3O4 takes place upon heat treatment in relation to successive increase in Ag concentrations in the nanowires. The composites offer resistance to the observed oxide transformation. This is evidenced from the progressive increase in transition temperature. In situ Raman, ex situ thermal and XRD analysis corroborate the fact. The composite with 12 % Ag offers resistance to the transformation of MnO2, which is also verified from laser heating. Importantly, Ag nanoparticle incorporation is proved to offer a thermally stable and better surface enhanced Raman scattering (SERS) platform than the individual components. Both the Ag–MnOOH and Ag–MnO2 nanocomposites with 8 atomic % Ag show the best SERS enhancement (enhancement factor ∼1010). The observed enhancement relates to charge transfer as well as electromagnetic effects.
A Supramolecular Tubular Nanoreactor
Authors: Li Zhi‐Qiang , Zhang Ying‐Ming , Chen Yong , Liu Yu 
Published: May 2014

AbstractThe extremely strong noncovalent complexation between the rigid host of phthalocyanine‐bridged β‐cyclodextrins and the amphiphilic guest carboxylated porphyrin is employed to construct a hollow tubular structure as a supramolecular nanoreactor. A representative coupling reaction occurs in the hydrophobic interlayers of the tubular walls in pure water at room temperature, leading to an enhancement of ten times higher reaction rate without any adverse effect on catalytic activity and conversion.
Halogen‐ and Hydrogen‐Bonding Catenanes for Halide‐Anion Recognition
Authors: Gilday Lydia C. , Beer Paul D. 
Published: May 2014

AbstractHalogen‐bonding (XB) interactions were exploited in the solution‐phase assembly of anion‐templated pseudorotaxanes between an isophthalamide‐containing macrocycle and bromo‐ or iodo‐functionalised pyridinium threading components. 1H NMR spectroscopic titration investigations demonstrated that such XB interpenetrated assemblies are more stable than analogous hydrogen bonding (HB) pseudorotaxanes. The stability of the anion‐templated halogen‐bonded pseudorotaxane architectures was exploited in the preparation of new halogen‐bonding interlocked catenane species through a Grubbs’ ring‐closing metathesis (RCM) clipping methodology. The catenanes’ anion recognition properties in the competitive CDCl3/CD3OD 1:1 solvent mixture revealed selectivity for the heavier halides iodide and bromide over chloride and acetate.
A New Strategy for Storage and Transportation of Sensitive High‐Energy Materials: Guest‐Dependent Energy and Sensitivity of 3D Metal–Organic‐Framework‐Based Energetic Compounds
Authors: Zhang Sheng , Liu Xiangyu , Yang Qi , Su Zhiyong , Gao Wenjuan , Wei Qing , Xie Gang , Chen Sanping , Gao Shengli 
Published: May 2014

AbstractReaction of Co(II) with the nitrogen‐rich ligand N,N‐bis(1H‐tetrazole‐5‐yl)‐amine (H2bta) leads to a mixed‐valence, 3D, porous, metal–organic framework (MOF)‐based, energetic material with the nitrogen content of 51.78%, [Co9(bta)10(Hbta)2(H2O)10]n⋅(22 H2O)n (1). Compound 1 was thermohydrated to produce a new, stable, energetic material with the nitrogen content of 59.85% and heat of denotation of 4.537 kcal cm−3, [Co9(bta)10(Hbta)2(H2O)10]n (2). Sensitivity tests show that 2 is more sensitivity to external stimuli than 1, reflecting guest‐dependent energy and sensitivity of 3D, MOF‐based, energetic materials. Less‐sensitive 1 can be regarded as a more safe form for storage and transformation to sensitive 2.
Two‐Step Synthesis of Multi‐Substituted Amines by Using an N‐Methoxy Group as a Reactivity Control Element
Authors: Yoritate Makoto , Meguro Tatsuhiko , Matsuo Naoya , Shirokane Kenji , Sato Takaaki , Chida Noritaka 
Published: May 2014

AbstractInvited for the cover of this issue is the group of Prof. Noritaka Chida and Dr. Takaaki Sato at Keio University, Japan. The cover illustrates the­ N‐methoxy group as the reactivity control element to allow for beautiful chemical transformations to blossom in organic synthesis. Read the full text of the article at 10.1002/chem.201402231.
Model‐Based Determination of the Optimal Reaction Route for Integrated Multiphase Processes
Authors: Hentschel Benjamin , Freund Hannsjörg , Sundmacher Kai 
Published: May 2014

AbstractGrundlage für eine optimale Reaktorauslegung ist die Kenntnis der optimalen Reaktionsführung. Modellbasierte Methoden sind dabei von besonderem Wert, da bei komplexen Systemen eine intuitive Erarbeitung der optimalen Reaktionsführung nicht mehr möglich ist. Am Beispiel der Hydroformulierung langkettiger Alkene wird hier eine auf modellbasierter Optimalsteuerung beruhende Methode beschrieben, die mögliche Stoffrückführungen bereits in einer frühen Phase der Prozessentwicklung berücksichtigt und damit neben der optimalen Reaktionsführung auch auf Anforderungen an die Trennoperationen schließen lässt.
Regulating the Interactions of Adsorbates on Surfaces by Scanning Tunneling Microscopy Manipulation
Authors: Sun Qiang , Xu Wei 
Published: May 2014

AbstractScanning tunneling microscopy (STM) manipulation has received wide attention in the surface science community since the pioneering work of Eigler to construct surface nanostructures in an atom by atom fashion. Lots of scientists have been inspired and devoted to study the surface issues with the help of STM manipulations and great achievements have been obtained. In this Minireview, we mainly describe the recent progress in applying STM manipulations to regulate the inter‐adsorbate and adsorbate–substrate interactions on solid surfaces. It was shown that this technique could not only differentiate intermolecular interactions but also construct molecular nanostructures by regulating different kinds of inter‐adsorbate interactions or adsorbate–substrate interactions.
Organic Nonlinear Optical Materials: The Mechanism of Intermolecular Covalent Bonding Interactions of Kekulé Hydrocarbons with Significant Singlet Biradical Character
Authors: Liu Jing , Xia Jiarui , Song Peng , Ding Yong , Cui Yanling , Liu Xuemei , Dai Yumei , Ma Fengcai 
Published: May 2014

AbstractThe ground‐ and excited‐state properties of benzene‐linked bisphenalenyl (B‐LBP), naphthaline‐linked bisphenalenyl (N‐LBP), and anthracene‐linked bisphenalenyl (A‐LBP) Kekulé molecules and their respective one‐dimensional (1D) stacks are investigated using time‐dependent density functional theory (TD‐DFT) and a range of extensive multidimensional visualization techniques. The results reveal a covalent π–π bonding interaction between overlapping phenalenyl radicals whose bond length is shorter than the van der Waals distance between carbon atoms. Increasing the linker length and/or number of molecules involved in the 1D stack decreases the HOMO–LUMO energy gap and increases the wavelength of the systems. The charge‐transfer mechanism and electron coherence both differ with changes in the linker length and/or number of molecules involved in the 1D stack.