bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Fluorine‐Iminium Ion Gauche Effect: Proof of Principle and Application to Asymmetric Organocatalysis
Authors: Sparr Christof , Schweizer W. Bernd , Senn Hans Martin , Gilmour Ryan 
Published: March 2009

AbstractDer gauche‐Effekt, der bei der reversiblen Bildung eines Iminiumions (siehe Struktur: F grün, N blau) auftritt, bietet eine nützliche Möglichkeit, die räumliche Ausrichtung von Intermediaten in durch sekundäre Amine katalysierten Reaktionen zu steuern. Dieses Phänomen wurde beim Entwurf eines neuartigen Organokatalysators genutzt und bei der stereoselektiven Epoxidierung von α,β‐ungesättigten Aldehyden angewendet.magnified image
Hohe elektrische Leitfähigkeit einzelner Moleküle – eine Herausforderung in der Reihe der konjugierten Oligomere
Authors: Meier Herbert 
Published: March 2009

AbstractAuf dem Weg zu molekularer Elektronik: Ausgedehnte konjugierte Oligomere sind wünschenswert für die molekulare Elektronik, ihre elektrische Leitfähigkeit sollte hierfür jedoch einen niedrigen Abklingfaktor aufweisen. Nun wurden die abgebildeten Zink‐komplexierten Oligo(ethinylenporphyrindiylethinylene) entwickelt, die sich durch ultraniedrige Abklingfaktoren der Einzelmolekül‐Leitfähigkeit auszeichnen.magnified image
Relative Orientation of Rigid Nitroxides by PELDOR: Beyond Distance Measurements in Nucleic Acids
Authors: Schiemann Olav , Cekan Pavol , Margraf Dominik , Prisner Thomas F. , Sigurdsson Snorri Th. 
Published: March 2009

AbstractShow me your angle: Incorporation of the rigid spin labelÇallows determination of both distance and orientation of two nitroxide spin labels in DNA by PELDOR experiments at common X‐band frequencies. The orientational information is obtained by varying the position of the detection pulses over the nitroxide spectrum. Simulation of the set of time traces yields very precise distances and angles.magnified image
A Dinuclear Nickel(I) Dinitrogen Complex and its Reduction in Single‐Electron Steps
Authors: Pfirrmann Stefan , Limberg Christian , Herwig Christian , Stößer Reinhard , Ziemer Burkhard 
Published: March 2009

AbstractElectron by electron: β‐Diketiminato nickel(I) complex fragments are capable of activating N2 through coordination. The resulting complex can be reduced in two single‐electron steps, which further activates the NN bond. The picture shows the structure of the singly reduced complex with μ‐η1:η1‐bound N2.magnified image
Complete Chiral Resolution Using Additive‐Induced Crystal Size Bifurcation During Grinding
Authors: Noorduin Wim L. , van der Asdonk Pim , Meekes Hugo , van Enckevort Willem J. P. , Kaptein Bernard , Leeman Michel , Kellogg Richard M. , Vlieg Elias 
Published: March 2009

AbstractGrinding them down: By using a tailor‐made additive, even in the absence of racemization in solution, abrasive grinding can yield an enantiopure solid state. This novel chiral resolution technique is based on an asymmetric bifurcation in the crystal size distribution as a result of stereoselective hampered crystal growth. R=o‐tolyl.magnified image
The Regio‐ and Stereoselective Synthesis of trans‐2,3‐Dihydropyridine N‐oxides and Piperidines
Authors: Andersson Hans , Gustafsson Magnus , Boström Dan , Olsson Roger , Almqvist Fredrik 
Published: March 2009

AbstractReactivity NOwn: Pyridine N‐oxides can be used for the complete regio‐ and stereoselective synthesis of trans‐substituted piperidines. The sequential addition of Grignard reagents and aldehydes or ketones to pyridine N‐oxides yields a complete regio‐ and stereoselective trans 2,3‐addition reaction in high yields, and the substituted 2,3‐dihydropyridine N‐oxide can be reduced to form 2,3‐trans‐substituted piperidines (see scheme).magnified image
Formation of Ammonia from an Iron Nitrido Complex
Authors: Scepaniak Jeremiah J. , Young Jessica A. , Bontchev Ranko P. , Smith Jeremy M. 
Published: March 2009

AbstractRadical ideas: Reaction of the iron(IV) nitrido complex [PhB(MesIm)3FeN] (see picture, Mes=2,4,6‐Me3C6H2) with TEMPO‐H (1‐hydroxy‐2,2,6,6‐tetramethylpiperidine) results in high yields of ammonia and quantitative formation of [PhB(MesIm)3Fe(tempo)]. The mechanism likely involves hydrogen‐atom transfer from TEMPO‐H to the nitrido complex. Similar reaction with the triphenylmethyl radical yields [PhB(MesIm)3FeNCPh3].magnified image
The Fluorine‐Iminium Ion Gauche Effect: Proof of Principle and Application to Asymmetric Organocatalysis
Authors: Sparr Christof , Schweizer W. Bernd , Senn Hans Martin , Gilmour Ryan 
Published: March 2009

AbstractThe gauche effect that is induced upon reversible formation of an iminium ion (see structure: green F, blue N) provides a powerful method for the preorganization of transient intermediates that are central to secondary amine catalyzed processes. This phenomenon has been exploited in the design of a novel organocatalyst and is showcased in the stereoselective epoxidation of α,β‐unsaturated aldehydes.magnified image
On the Function and Structure of Synthetically Modified Porins
Authors: Reitz Simon , Cebi Menekse , Reiß Philipp , Studnik Gregor , Linne Uwe , Koert Ulrich , Essen Lars‐Oliver 
Published: March 2009

AbstractThe attachment of modulators to a trimeric porin ion channel was investigated (see picture of the trimer with a crown ether modulator (orange)). The interplay of modulator and protein is essential for the conformational heterogeneity of the hybrid channel. Single‐site attachment in large pores is not sufficient to change the electrophysiological characteristics of the pores—such change requires additional noncovalent interactions or second‐site attachments.magnified image
Effect of air flow rate on the foam fractionation of a mixture of egg white and egg yolk
Authors: Stowers Chris C. , Makarov Viktor , Walker Andy , Edwards Ross A. , Tanner Robert D. 
Published: March 2009

AbstractFoam fractionation was previously shown to be an effective tool for the separation of the two visible phases in a chicken egg: egg white and the egg yolk.1 This study is a continuation of the previous study with the objective of determining the optimal separation condition in terms of air flow rate. Our results show that air flow rate is a critical operational parameter when separating these protein‐rich mixtures of egg white and egg yolk. The results show that respective concentrations of egg yolk and egg white phases change independently with respect to the air flow rate, leading to the observation that air flow rate could be exploited as a processing variable to selectively remove proteins from one section of the egg over the other section. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
An integrated analysis of prospects for advanced coal‐fired power technology in China
Authors: Li Aijun 
Published: March 2009

AbstractWith energy‐saving and pollution abatement policy becoming stricter and stronger, advanced coal‐fired power technology will undoubtedly play a significant role in China for the new style in industrialization of power industry. In order to forecast coal consumption for power generation from the view of Chinese economic development, firstly this paper simulates total energy consumption and loss during energy transformation in 2030 by computable general equilibrium model. Then power generation by various advanced coal‐fired power technologies such as air pollution controlling, green coal‐fired power and combined heat and power (CHP) in 2030 is estimated, thus their effects on abatement of air pollution emissions are assessed. Finally, some policy suggestions are given for developing highly efficient and super clean coal‐fired power technology in China. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Performance and characterization of irradiated poly(vinyl alcohol)/polyvinylpyrrolidone composite hydrogels used as cartilages replacement
Authors: Zheng Yudong , Huang Xiaoshan , Wang Yingjun , Xu Hong , Chen Xiaofeng 
Published: March 2009

AbstractIn this article, hydrogels were prepared by compounding polyvinylpyrrolidone (PVP) with poly(vinyl alcohol) (PVA), which is used as artificial cartilages, by means of repeating freezing and thawing and irradiation, for improving their mechanical and surface lubricative properties. The structures and properties, including gel content, crystallized degree, elastic modulus, and frictional coefficients of the compound hydrogels with different PVP contents and irradiative conditions, were examined and compared. The existence of PVP macromolecules interfered with the crystallization of PVA hydrogels resulted in the decrease of gel contents and elastic modulus, as well as the unstable external frictional coefficient in water. After irradiation treatment, these performances increased with irradiation intensity in lower dose ranges. The solubility and exudation of PVP in water were prevented and reduced because of the chemical crosslink of PVA and PVP, and the lubricative properties of PVA/PVP hydrogels in water were improved. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
A sophisticated library search strategy using folksonomies and similarity matching
Authors: Pera Maria Soledad , Lund William , Ng Yiu‐Kai 
Published: March 2009

AbstractLibraries, private and public, offer valuable resources to library patrons. As of today, the only way to locate information archived exclusively in libraries is through their catalogs. Library patrons, however, often find it difficult to formulate a proper query, which requires using specific keywords assigned to different fields of desired library catalog records, to obtain relevant results. These improperly formulated queries often yield irrelevant results or no results at all. This negative experience in dealing with existing library systems turns library patrons away from directly querying library catalogs; instead, they rely on Web search engines to perform their searches first, and upon obtaining the initial information (e.g., titles, subject headings, or authors) on the desired library materials, they query library catalogs. This searching strategy is an evidence of failure of today's library systems. In solving this problem, we propose an enhanced library system, which allows partial, similarity matching of (a) tags defined by ordinary users at a folksonomy site that describe the content of books and (b) unrestricted keywords specified by an ordinary library patron in a query to search for relevant library catalog records. The proposed library system allows patrons posting a query Q using commonly used words and ranks the retrieved results according to their degrees of resemblance with Q while maintaining the query processing time comparable with that achieved by current library search engines.
Tuning the Electronic Structure of Graphene by Molecular Charge Transfer: A Computational Study
Authors: Manna Arun K , Pati Swapan K 
Published: March 2009

AbstractInsulating semiconducting conductors? The electronic properties of graphene can be tuned through molecular charge transfer, induced by organic electron donor (acceptor), TTF (TCNE, TCNQ), molecules. Such molecular‐charge‐transfer process has significant effects on optical and transport properties, in particular the characteristic Raman spectra of graphene.magnified imageWe have studied the modification in the electronic structure, as well as optical and transport properties of graphene induced by molecular charge transfer using ab initio density functional theory. Our results from first‐principles spin‐polarized calculations are compared with those of the available data from Raman spectroscopic studies of modified graphene systems. We find that electron donor and acceptor molecules adsorbed onto the graphene surface exhibit effective molecular charge transfer, giving rise to mid‐gap molecular levels with tuning of the band gap region near the Dirac point. The molecular charge transfer causes the stiffening or softening of the Raman G‐band frequency in graphene, and we find that it also has a significant impact on the intensity ratio of the D‐ to G‐band, corroborating experimental findings. We suggest that these charge transfer mechanisms can be probed through the low‐frequency profile of the optical conductivity.
An improved high‐performance liquid chromatography method for quantification of methotrexate polyglutamates in red blood cells of children with juvenile idiopathic arthritis
Authors: Hroch Miloš , Tuková Jana , Doležalová Pavla , Chládek Jaroslav 
Published: March 2009

AbstractMethotrexate is used widely in the pharmacotherapy of juvenile idiopathic arthritis. Polyglutamates of methotrexate are active metabolites which accumulate in cells including erythrocytes. Their intracellular concentration may reflect methotrexate bioavailability and, at the same time, may serve as a bioindicator for optimization of methotrexate therapy and drug monitoring. Therefore, a simple and selective isocratic reversed phase chromatographic method with fluorescence detection (excitation/emission wavelengths of 370/463 nm) was developed which quantifies the sum of all methotrexate polyglutamates in erythrocytes as methotrexate after their enzymatic conversion with γ‐glutamylhydrolase. Separation was carried out on a Phenomenex GEMINI C18 column using a mobile phase flowing at a rate of 0.6 ml/min and consisting of a mixture (110:890:0.25 v/v) of acetonitrile, ammonium acetate buffer (0.05 m, pH=5.5) and hydrogen peroxide 30% (w/w). The method was found linear over the concentration range of 25–400 nmol/l. Its intra‐ and inter‐day precision and accuracy were characterized by coefficients of variation and relative errors less than 20%. The limits of detection and quantification achieved 10.9 and 32.9 nmol/l, respectively. The method was proved suitable for monitoring the concentration of methotrexate polyglutamates in erythrocytes of patients with juvenile idiopathic arthritis. Copyright © 2009 John Wiley & Sons, Ltd.
Stabwerke und Teilflächenbelastung nach DIN 1045‐1 und Eurocode 2 – Modelle und Anwendungen
Authors: Empelmann Martin , Wichers Marco 
Published: March 2009

AbstractStabwerkmodelle sind leistungsfähige Werkzeuge zur Beschreibung des Tragverhaltens und zur Bemessung von Stahl‐ und Spannbetonbauteilen. Ein wesentliches Anwendungsgebiet liegt in der Abbildung und Berechnung von so genannten Diskontinuitätsbereichen. Ein ebenso häufig auftretendes und mit den Stabwerkmodellen eng verknüpftes Problem ist das der Teilflächenbelastung. Im Vergleich zur Biege‐ oder Schubbemessung sind die Angaben der Normenwerke zur Anwendung von Stabwerkmodellen bzw. zum Nachweis von Teilflächenbelastungen begrenzt. Daher hat der planende Ingenieur in der Praxis die Aufgabe, auf Basis der Normenansätze geeignete Stabwerkmodelle zu finden. Der vorliegende Artikel vergleicht hierzu die wesentlichen Angaben der DIN 1045‐1 und des Eurocodes 2 (DIN EN 1992‐1‐1) bezüglich der Nutzung von Stabwerkmodellen sowie der Nachweisführung bei Teilflächenbelastungen und gibt zusätzliche Hinweise für ausgewählte Anwendungsfälle.
Der Skybarturm Neue Mitte Lehen West – Berechnung und Ausführung
Authors: Olipitz Michael , Holzleitner Regina 
Published: March 2009

AbstractDer Stadtteil Lehen zählt zu den am dichtest besiedelten Gebieten von Salzburg. Hier entstand in einer Bauzeit von ca. zwölf Monaten das derzeit größte multifunktionale Bauvorhaben. Herausragend mit den weit auskragenden Bibliotheksgeschossen und der Skybar ist das Westgebäude. “Schiefe Türme benötigen einen Rückhalt” ist das Motto der Entwurfsoptimierung am Skybarturm.Der folgende Aufsatz widmet sich den technischen Herausforderungen bei der Errichtung des Skybarturms, der zur Gänze in Stahlbeton hergestellt wurde. Mit einer Schiefstellung von 19.5° gegen die Vertikale und einer Gesamthöhe von 30 m mit einer außermittig aufgesetzten Skybar aus Stahl waren höchste Anforderungen gestellt. Die unterschiedlichen Maßnahmen zur Reduzierung der Turmverformung sowie dynamische Betrachtungen bilden den Schwerpunkt. Hybride Konstruktionen erfordern nicht nur das Zusammenspiel unterschiedlicher Materialien sondern auch der unterschiedlichen Gewerke, wie sie an Hand dieses Bauvorhabens beispielhaft vorgezeigt wurde.
Using goal setting, self‐monitoring, and feedback to increase calorie expenditure in obese adults
Authors: Donaldson Jeanne M. , Normand Matthew P. 
Published: March 2009

AbstractObesity has become a leading cause of health problems in America, many of which can be combated by increasing physical activity. As a result, interventions targeting increased physical activity are greatly needed. In this study, a package intervention consisting of goal setting, self‐monitoring, and feedback was evaluated across five participants in a multiple baseline design with a brief reversal for three of the five participants. The intervention package increased calorie expenditure for all five participants. Copyright © 2009 John Wiley & Sons, Ltd.
Effects of response blocking and competing stimuli on stereotypic behavior
Authors: Hagopian Louis P. , Toole Lisa M. 
Published: March 2009

AbstractThe effects of response blocking and competing stimuli on stereotypy and aggression were examined in an analysis conducted with a young girl diagnosed with autism and intellectual disability. A functional analysis of the stereotypic behavior revealed that blocking stereotypy increased aggression. The treatment analysis revealed that the provision of competing stimuli, without response blocking resulted in decreases in both topographies. Findings suggest that the provision of competing stimuli may be less likely to occasion other behaviors than blocking. Copyright © 2009 John Wiley & Sons, Ltd.
Signaling stimulus presentation during treatment with noncontingent reinforcement: Visual versus vocal signals
Authors: Schadler John J. , Wilder David A. , Blakely Elbert 
Published: March 2009

AbstractThe independent effects of two signals implemented during treatment with noncontingent reinforcement (NCR) were examined. First, functional analyses showed that problem behavior exhibited by two individuals with developmental disabilities was sensitive to social positive reinforcement. A reversal design was then used to compare the effectiveness of a timer (NCR‐visual) to a vocal statement (NCR‐vocal) indicating when the stimulus would be returned in the context of a NCR procedure. Results showed that NCR reduced problem behavior for both participants. In addition, for one participant, the NCR‐visual condition reduced problem behavior to a greater degree than the NCR‐vocal condition. Copyright © 2009 John Wiley & Sons, Ltd.
Protection of dystrophic muscle cells with polyphenols from green tea correlates with improved glutathione balance and increased expression of 67LR, a receptor for (−)‐epigallocatechin gallate
Authors: Dorchies Olivier M. , Wagner Stéphanie , Buetler Timo M. , Ruegg Urs T. 
Published: March 2009

AbstractDuchenne muscular dystrophy (DMD) is a fatal muscle wasting disease caused by the absence of the protein dystrophin. Because oxidative stress contributes to the pathogenesis of DMD, we investigated if a green tea polyphenol blend (GTP) and its major polyphenol (−)‐epigallocatechin gallate (EGCg), could protect muscle cell primary cultures from oxidative damage induced by hydrogen peroxide (H2O2) in the widely used mdx mouse model. On‐line fluorimetric measurements using an H2O2‐sensitive probe indicated that GTP and EGCg scavenged peroxide in a concentration‐dependent manner. A 48 h exposure to EGCg increased glutathione content but did not alter the expression of proteins involved in membrane stabilization and repair. Pretreatment of dystrophic cultures with GTP or EGCg 48 h before exposure to H2O2 improved cell survival. Normal cultures were protected by GTP but not by EGCg. 67LR, a receptor for EGCg, was seven times more abundant in dystrophic compared with normal cultures. Altogether our results demonstrate that GTP and EGCg protect muscle cells by scavenging H2O2 and by improving the glutathione balance. In addition, the higher levels of 67LR in dystrophic muscle cells compared with normal ones likely contribute to EGCg‐mediated survival. © 2009 International Union of Biochemistry and Molecular Biology, Inc.
Chaperone‐like activities of different molecular forms of β‐casein. Importance of polarity of N‐terminal hydrophilic domain
Authors: Yousefi Reza , Shchutskaya Yulia Y. , Zimny Jaroslaw , Gaudin Jean‐Charles , Moosavi‐Movahedi Ali A. , Muronetz Vladimir I. , Zuev Yuriy F. , Chobert Jean‐Marc , Haertlé Thomas 
Published: March 2009

AbstractAs a member of intrinsically unstructured protein family, β‐casein (β‐CN) contains relatively high amount of prolyl residues, adopts noncompact and flexible structure and exhibits chaperone‐like activity in vitro. Like many chaperones, native β‐CN does not contain cysteinyl residues and exhibits strong tendencies for self‐association. The chaperone‐like activities of three recombinant β‐CNs wild type (WT) β‐CN, C4 β‐CN (with cysteinyl residue in position 4) and C208 β‐CN (with cysteinyl residue in position 208), expressed and purified from E. coli, which, consequently, lack the phosphorylated residues, were examined and compared with that of native β‐CN using insulin and alcohol dehydrogenase as target/substrate proteins. The dimers (β‐CND) of C4‐β‐CN and C208 β‐CN were also studied and their chaperone‐like activities were compared with those of their monomeric forms. Lacking phosphorylation, WT β‐CN, C208 β‐CN, C4 β‐CN and C4 β‐CND exhibited significantly lower chaperone‐like activities than native β‐CN. Dimerization of C208 β‐CN with two distal hydrophilic domains considerably improved its chaperone‐like activity in comparison with its monomeric form. The obtained results demonstrate the significant role played by the polar contributions of phosphorylated residues and N‐terminal hydrophilic domain as important functional elements in enhancing the chaperone‐like activity of native β‐CN. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 623–632, 2009.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
From gene mutation to protein characterization
Authors: Moffet David A. 
Published: March 2009

AbstractA seven‐week “gene to protein” laboratory sequence is described for an undergraduate biochemistry laboratory course. Student pairs were given the task of introducing a point mutation of their choosing into the well studied protein, enhanced green fluorescent protein (EGFP). After conducting literature searches, each student group chose the mutation they wanted to introduce into EGFP. Students designed their sequence‐specific mutagenic primers and constructed their desired mutation. The resulting EGFP mutant proteins were expressed in E. coli, purified and characterized. This laboratory sequence connected the major concepts of molecular biology and biochemistry, while incorporating the thrill of novel discovery in an undergraduate‐level biochemistry laboratory course.