bluuebunny/crossref_metadata_2025_split huggingface dataset:
Der optimale Molekülsatz für Screening‐Anwendungen: eine Synthesestrategie
Authors: Nielsen Thomas E. , Schreiber Stuart L. 
Published: December 2007

AbstractDie Entwicklung von niedermolekularen Sonden und Wirkstoffen umfasst mindestens drei Phasen: 1) eine Auffindungsphase, die oft die Synthese und das Screening von Wirkstoffkandidaten erfordert, 2) eine Optimierungsphase, die die Synthese und Analyse von Strukturvarianten erfordert, und 3) eine Produktionsphase, die eine effiziente Synthese der optimierten molekularen Sonde oder des optimierten Wirkstoffs erfordert. Der Einsatz spezialisierter Projektgruppen hat oft zur Folge, dass die einzelnen Stufen ohne vorherige Koordination der Aktivitäten ausgeführt werden; so können z. B. vertraglich gebundene (“outgesourcte”) Chemiker in der ersten Stufe und unternehmensinterne Medizinal‐ und Prozesschemiker in den zweiten bzw. dritten Stufen eingesetzt werden. Eine koordinierte Planung im Vorfeld der ersten Screens findet oft nicht statt, und jede der Projektgruppen kann auf einen Flaschenhals stoßen, den man bei vorheriger Planung im Prinzip hätte vermeiden können. Die Herausforderung besteht deshalb darin, eine neue Art von Chemie zu entwickeln, die eine für ein Screening geeignete Sammlung biologisch aktiver Moleküle hervorbringt, die in allen drei Phasen der Sonden‐ oder Wirkstoffentwicklung eine erhöhte Erfolgswahrscheinlichkeit haben. Bis dahin ist es ein weiter Weg, erste Fortschritte sind aber zu verzeichnen. In diesem Kurzaufsatz fassen wir eine neuartige Strategie zur diversitätsorientierten Synthese niedermolekularer Verbindungen zusammen, die das Potenzial hat, diese Herausforderungen zu meistern.
Studies on the comprehensive performance of graphite and additives filled high density polyethylene composites
Authors: Sun Changzhi , Zhao Wenyuan , Chen Shigang 
Published: December 2007

AbstractThe comprehensive performance of graphite and additives filled high‐density polyethylene (HDPE) composites is studied in this article. Four graphites with different particle diameters are used as conductive fillers in HDPE/graphite. Plasticizer, nucleator, and certain particle diameter graphite are employed to prepare HDPE composite. The behavior of crystallization and the distribution of graphite are also studied by means of SEM. An orthogonal design experiment is taken to optimize the content of the filler. The experimental results indicate that the positive temperature coefficient (PTC) effect is related to the particle diameter of graphite. And the bending strength of HDPE/graphite composite with the plasticizer and nucleator is two times less than that of HDPE‐graphite blends. Meanwhile, the high PTC intensity (the ratio of peak resistivity to room temperature resistivity) is also preserved. An excellent comprehensive performance conductive composite is prepared. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Crosslinking reaction mechanism of diisopropyl xanthogen polysulfide accelerator in bromobutyl elastomer for medical device applications
Authors: Ohbi D. S. , Purewal T. S. , Shah T. , Siores E. 
Published: December 2007

AbstractThe use of an accelerator based on diisopropyl xanthogen polysulfide (DIXP) to formulate bromobutyl elastomer (BIIR‐DIXP) compositions for sealing medical devices was published in the Journal of Applied Polymer Science (Ohbi, D. S.; Pureval, T. S.; Shah, T.; Siores, E. 2007, 106, 526). In this publication, a reaction scheme for the DIXP accelerator in situ with BIIR is proposed. It is based on the evolved volatile chemical species determined during the curing reaction of BIIR‐DIXP composition, and is formulated in the light of generally accepted mechanism of crosslinking elastomers using sulfur‐based accelerators. The volatile chemical species were determined using coupled thermogravimetric infrared analysis (TGA‐IR) and head space gas chromatography mass spectroscopy (GC‐MS) analysis. The main volatiles evolved during the curing reaction were carbonyl sulfide, carbon disulfide, and isopropyl bromide. These are considered to be associated with the formation of the active rubber‐bound DIXP sulfurating species required for the crosslinking reaction. Analysis of the acetone extract of cured BIIR‐DIXP also showed that the DIXP is totally consumed during the cure reaction, and the formulation is largely free of cure reaction byproducts. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Structure and metal type effects on cure kinetics of DGEBA with benzil bisthiosemicarbazone complexes
Authors: Ghaemy Mousa , Behmadi Hossein 
Published: December 2007

AbstractThe curing reaction kinetics of the diglycidyl ether of bisphenol A‐ (DGEBA) based epoxy was investigated according to the change of curing agents. Complex curing agents based on Ni(II) and Cu(II) chelates with benzil bisthiosemicarbazone (LH6) as a ligand was studied using differential scanning calorimetry. The curing reaction was characterized by high‐activation energies (Ea), cure onset (Ti), and peak maximum (Tp) temperatures. Dynamic kinetic parameters were calculated by using Kissinger and Ozawa methods. For the NiLH6Cl2, CuLH6Cl2, and LH6 the average values of Ea were calculated to be 165.16, 165.92, and 115.75 kJ/mol, respectively. For the NiLH6Cl2 systems, their activation energies at 40 and 30 phr are equal. The Ti and Tp of the DGEBA/NiLH6Cl2 system are lower than those of DGEBA/CuLH6Cl2 system. These results indicate that NiLH6Cl2 has a higher reactivity toward epoxy resin at the beginning of the curing reaction. The effect of hardener concentration, heating rate, and type of metal ion on the cure kinetic parameters and the shape of DSC thermograms were investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and characterization of fullerene grafted poly(ε‐caprolactone)
Authors: Kai Weihua , Hua Lei , Dong Tungalag , Pan Pengju , Zhu Bo , Inoue Yoshio 
Published: December 2007

AbstractThe fullerene grafted poly(ε‐caprolactone) (PCL) was successfully synthesized with a graft efficiency of 80%. The fullerene moieties grafted onto the PCL chain aggregate into 1–2 μm particles so that a physical pseudo‐network is formed. Because of the existence of the network structure, the fullerene grafted PCL film can retain its shape at much higher temperatures than that of pure PCL film, as observed in dynamic mechanical tests. It shows a hydrophobic gelling behavior in chloroform solution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Organocatalytic Enantioselective One‐Pot Synthesis and Application of Substituted 1,4‐Dihydropyridines—Hantzsch Ester Analogues
Authors: Franke Patrick T. , Johansen Rasmus L. , Bertelsen Søren , Jørgensen Karl Anker 
Published: December 2007

AbstractAn easy and simple one‐pot approach for the formation of optically active substituted 1,4‐dihydropyridines by using asymmetric organocatalysis is presented. The one‐pot reaction of α,β‐unsaturated aldehydes with β‐diketones or β‐ketoesters and primary amines gives optically active 2,3‐substituted 1,4‐dihydropyridines in moderate yields and with enantioselectivities up to 95 % ee. It is also demonstrated that the optically active 1,4‐dihydropyridines can be used in situ for the direct enantioselective reduction of, for example, α‐ketoesters with high enantioselectivity.
Conformational Preference and Potential Templates ofN‐Methylated Cyclic Pentaalanine Peptides
Authors: Chatterjee Jayanta , Mierke Dale F. , Kessler Horst 
Published: December 2007

AbstractSystematicN‐methylation of all peptide bonds in the cyclic pentapeptide cyclo(‐D‐Ala‐Ala4‐) has been performed yielding 30 differentN‐methylated derivatives, of which only seven displayed a single conformation on the NMR time scale. The conformation of these differentiallyN‐methylated peptides was recently reported by us (J. Am. Chem. Soc.2006,128, 15 164–15 172). Here we present the conformational characterization of nine additionalN‐methylated peptides from the previous library which are not homogeneous but exist as a mixture in which at least one conformation is preferred by over 80 %. The structures of these peptides are investigated employing various 2D‐NMR techniques, distance geometry calculations and further refined by molecular dynamics simulations in explicit DMSO. The comparison of the conformation of these nine peptides and the seven conformationally homogeneous peptides allow us to draw conclusions regarding the influence ofN‐methylation on the peptide backbone of cyclic pentapeptide of the class cyclo(‐D‐Ala‐Ala4‐). Here we present the different conformational classes of the peptides arising from the definitive pattern ofN‐methylation which can eventually serve as templates for the design of bioactive peptides.
Pd PEPPSI‐IPr‐Mediated Reactions in Metal‐Coated Capillaries Under MACOS: The Synthesis of Indoles by Sequential Aryl Amination/ Heck Coupling
Authors: Shore Gjergji , Morin Sylvie , Mallik Debasis , Organ Michael G. 
Published: December 2007

AbstractA method has been devised for the microwave‐assisted, continuous‐flow preparation of indole alkaloids by a two‐step aryl amination/cross‐coupling sequence of bromoalkenes and 2‐bromoanilines. This process requires both the presence of a metal‐lined flow tube (a 1180 micron capillary) and the Pd PEPPSI‐IPr catalyst; without either, the catalyst or the film, there is zero turnover of this catalytic process. A silver film has been shown to provide some conversion (48–62 %), but optimal results (quantitative) across a variety of bromoalkenes and bromoanilines were achieved by using a highly porous palladium film. Possible roles for the Pd film are considered, as is the interplay of the catalyst and the film.
A class of methods and algorithms for the analysis of successive origination of holes in a pre‐stressed viscoelastic body. Finite strains
Authors: Levin V. A. , Zingerman K. M. 
Published: December 2007

AbstractA class of methods and algorithms for the solution of two‐dimensional quasi‐static problems of stress distribution near holes is considered for finite strains. It is assumed that the holes have originated successively in a previously loaded body made of incompressible viscoelastic material. The problem is formulated on the basis of the theory of repeated superposition of large deformations. The mechanical properties of the material are described by convolution integral relations with the kernel of weak singularity. The solution is obtained using the approximate analytical methods (Signorini's technique, Laplace transform, and Muskhelishvili's technique). A special‐purpose software for analytical calculations is used for the solution. Some numerical results are presented. Copyright © 2007 John Wiley & Sons, Ltd.
Self‐Assembling Nanoparticles at Surfaces and Interfaces
Authors: Kinge Sachin , Crego‐Calama Mercedes , Reinhoudt David N. 
Published: December 2007

AbstractNanoparticles are the focus of much attention due to their astonishing properties and numerous possibilities for applications in nanotechnology. For realising versatile functions, assembly of nanoparticles in regular patterns on surfaces and at interfaces is required. Assembling nanoparticles generates new nanostructures, which have unforeseen collective, intrinsic physical properties. These properties can be exploited for multipurpose applications in nanoelectronics, spintronics, sensors, etc. This review surveys different techniques, currently employed and being developed, for assembling nanoparticles in to ordered nanostructures. In this endeavour, the principles and methods involved in the development of assemblies are discussed. Subsequently, different possibilities of nanoparticle‐based nanostructures, obtained in multi‐dimensions, are presented.
Visualizing the Frontier Orbitals of a Conformationally Adapted Metalloporphyrin
Authors: Weber‐Bargioni Alexander , Auwärter Willi , Klappenberger Florian , Reichert Joachim , Lefrançois Simon , Strunskus Thomas , Wöll Christof , Schiffrin Agustin , Pennec Yan , Barth Johannes V. 
Published: December 2007

AbstractWe present a molecular‐level study of the geometric and electronic properties of CoII tetraphenylporphyrin molecules adsorbed on the Cu(111) surface. A combination of low‐temperature scanning tunneling microscopy and near‐edge X‐ray absorption fine structure observations reveals how the metal substrate induces a conformational adaptation into a distorted saddle‐shaped geometry. By scanning tunneling spectroscopy we identified the discrete energy levels of the molecule and mapped their spatial electron‐density distributions. These results, along with a simple theoretical description, provide a direct correlation between the shape of frontier molecular orbitals and intramolecular structural features.
Environmental quality and the cost of environmental regulation: a comparison of Scotland with the international community
Authors: Le Roux Jean , Williams Evan , Staines Andrew , Bergmann Ariel 
Published: December 2007

AbstractIn today's global economy, assessing costs of compliance is crucial to understand how environmental regulations influence firms' behaviour and in particular their ability to compete at an international level. A three step methodology is used to conduct a comparison of Scotland's industry with the international community. The first step compares environmental protection expenditures among the European Community. The second step uses the Environmental Regulatory Regime Index developed by Porter and Esty to compare regulatory quality among 71 nations. The final step compares Scotland's environmental quality with the international community based on three criteria: SO2, PM10 and energy efficiency. Relative to the countries used in this research, Scotland is found to have a high quality regulatory regime, low costs of compliance for industry and a mixture of moderate to high environmental quality. Because significant deficiencies exist in the data, some uncertainties remain in the results. Published in 2007 with the permission of the Controller of Her Majesty's Stationery Office and the Queen's Printer for Scotland.
A Chemoenzymatic, Preparative Synthesis of the Isomeric Forms of p‐Menth‐1‐en‐9‐ol: Application to the Synthesis of the Isomeric Forms of the Cooling Agent 1‐Hydroxy‐2,9‐cineole
Authors: Serra Stefano , Fuganti Claudio , Gatti Francesco G. 
Published: December 2007

AbstractA preparative‐scale synthesis of the four p‐menth‐1‐en‐9‐ol isomers 2a–5a has been achieved by means of two chemoenzymatic processes. Both synthetic pathways start from the enantiomeric forms of limonene that are converted into p‐mentha‐1,8‐dien‐9‐al isomers 12 and 15. The baker's yeast mediated reduction of the latter aldehydes afforded compounds 3a and 5a, respectively, with very high enantioselectivity. Moreover, chemical reduction of 12 and 15 gives the mixtures of enantiopure diastereoisomers 2a/3a and 4a/5a, respectively. PPL (Porcine pancreas lipase) mediated resolution of the latter mixtures followed by fractionating crystallization of derivatives 2b–5b allowed the enantio‐ and diastereoisomerically pure alcohols 2a–5a to be obtained. Compounds 2a–5a have then been used as starting materials for the preparation of four isomers of the cooling agent 1‐hydroxy‐2,9‐cineole (6–9). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Metrological Aspects of Activity Measurements in Mixed Electrolytes by Ion‐Selective Electrodes
Authors: Wunderli Samuel , Andres Hanspeter 
Published: December 2007

AbstractBased on the model equation for the measurand analyte activity, all significant sources of uncertainty are identified, their magnitude estimated from published and experimental data and finally combined to give the uncertainty in the reported value of the analyte activity. It is found that the combined uncertainty is dominated by the uncertainties in the diffusion potential EJ and the time‐dependent response behavior κ of the sensor. Using Henderson's approach EJ is calculated not to vary more than 150 μV for physiological analytes in contact with a 3 M KCl reference solution. The stability of the reference electrode as well as the flow characteristics in the vicinity of the sensing element greatly influence the response time of the sensor. By minimizing the mentioned contributions of EJ and κ in the uncertainty budget, combined uncertainties for activity values in the range of 2% are feasible for univalent ions.
Mathematical Model of Current‐Polarized Ionophore‐Based Ion‐Selective Membranes: Large Current Chronopotentiometry
Authors: Zook Justin M. , Buck Richard P. , Gyurcsányi Róbert E. , Lindner Ernő 
Published: December 2007

AbstractThe properties of ionophore‐based ion‐selective membranes were investigated theoretically and experimentally for the first time in large‐current chronopotentiometric experiments. In these experiments, when either the free ionophore or the ion‐ionophore complex concentration drops to zero at one of the membrane boundaries, a characteristic drop in voltage (breakpoint) appears in the chronopotentiometric transients at a transition time τ. Based on a mathematical model of current polarized membranes, theoretical equations were derived and tested. These equations describe the correlation between the transition time τ and the concentration of free ionophore, the concentration of ion‐ionophore complex, and the diffusion coefficients of species in the membrane. The simulated concentration profiles correlated well with concentration profiles recorded experimentally prior to the transition time using spectroelectrochemical microscopy (SpECM). Diffusion coefficients calculated from (i) the transition times, (ii) curve fitting, and (iii) the initial ohmic resistance of the studied membranes were also compared.
Amperometric Nitrosothiol Sensor Using Immobilized Organoditelluride Species as Selective Catalytic Layer
Authors: Hwang Sangyeul , Cha Wansik , Meyerhoff Mark E. 
Published: December 2007

AbstractA new amperometric sensor capable of responding to various biological S‐nitrosothiol species (RSNOs) is described. The sensor is prepared using an organoditelluride‐tethered poly(allyamine hydrochloride) (PAH) polymer crosslinked within a dialysis membrane support mounted at the distal surface of an amperometric NO probe. The surface immobilized organoditelluride layer serves as a selective catalyst to decompose various RSNO species to NO in the presence of a thiol reducing agent added to the sample. The proposed sensor responds directly and reversibly to various low molecular weight (LMW) RSNOs in the range of 0.1 μM to 10 μM with nearly equal sensitivity. The main advantage of this sensor over previously reported Cu(II/I) and organodiselenium‐based RSNO sensors is its long operational life‐time (at least one month). A discussion regarding solution phase transnitrosation reactions potentially allowing the measurement of higher molecular weight S‐nitrosoproteins is provided, along with data showing preliminary results in this direction. Further, the direct detection of endogenous RSNO species in diluted fresh whole sheep blood is also demonstrated using this new sensor.
Voltammetric (Micro)Electrodes for the In Situ Study of Fe2+ Oxidation Kinetics in Hot Springs and S2O$\rm{ _3^{2 - } }$ Production at Hydrothermal Vents
Authors: Mullaugh Katherine M. , Luther George W. , Ma Shufen , Moore Tommy S. , Yücel Mustafa , Becker Erin L. , Podowski Elizabeth L. , Fisher Charles R. , Trouwborst Robert E. , Pierson Beverly K. 
Published: December 2007

AbstractWe have used solid‐state Au/Hg voltammetric electrodes to understand redox and biogeochemical processes in hot spring and deep sea hydrothermal environments. These electrodes are non‐specific and have the capability of measuring simultaneously a suite of chemical species including several of the principal redox species involved in early diagenesis (O2, Mn2+, Fe2+, H2S/HS−, and I−) as well as some Fe species (FeS and Fe3+) and sulfur species (Sx2− and S2O$\rm{ _3^{2 - } )}$. Here we demonstrate how in situ data obtained in complex environments can be used to study specific iron and sulfur reactions and processes at (sub)millimeter to centimeter resolution and over short time scales. Examples include the oxidation of Fe2+ by O2 produced by cyanobacterial mats in Yellowstone National Park hot springs and the formation of S2O$\rm{ _3^{2 - } }$ in diffuse flow waters from the hydrothermal vents at Lau Basin. In one example, profiles of redox species in cyanobacterial mats from Yellowstone National Park hot springs show that in the light dissolved Fe2+ is completely removed from the source waters as cyanobacterial mats produce O2 and oxidize the Fe2+. Performing kinetic experiments in the dark and light at the depth of maximum O2 production indicates that the decay of Fe2+ follows a zero order rate law consistent with photosynthesis as the source of O2. These dynamic environments show how kinetic data can be obtained in situ and be used to understand the interactions between biology and chemistry. We know of no other analytical technique that can provide this information in both clear and turbid waters on the time scales (seconds) observed.
Amperometric Enzyme‐Based Biosensor for Direct Detection of Formaldehyde in the Gas Phase: Dependence on Electrolyte Composition
Authors: Achmann Sabine , Hämmerle Martin , Moos Ralf 
Published: December 2007

AbstractAn enzymatic sensor detecting the analyte formaldehyde directly from the gas phase is under investigation. In contrast to existing systems, it enables the quantification of the analyte without prior sampling or accumulation and thus can be used as an online system to monitor the formaldehyde concentration in ambient air. The amperometric sensor depends on the enzymatic conversion of the analyte using formaldehyde dehydrogenase from P. putida [EC. 1.2.1.46] as the recognition element. It shows a linear response curve up to 15 ppm, with a detection limit of 0.03 pm (S/N=3). In order to optimize the sensor performance the electrolyte composition within the sensor was varied with respect to pH value, buffer concentration and the addition of Ca2+ and Mg2+ ions. To elucidate the influence of the mediator and the enzyme on the sensor performance the stability and activity of the electrochemical mediator and the enzyme alone was examined separately in these different electrolytes.
On‐line concentration of proteins by SDS‐CGE with LIF detection
Authors: Yu Cheng‐Ju , Chang Hui‐Chiu , Tseng Wei‐Lung 
Published: December 2007

AbstractWe present a simple approach for on‐line concentration of SDS‐protein complexes by using poly(vinyl alcohol) (PVA) solution in CGE. In comparison to the coated capillary, the presence of EOF in CGE omitted the need to fill the capillaries with polymer solutions prior to the analysis. More importantly, we found that highly reproducible separation of eight proteins by 3.5% PVA was achieved between runs and without the regeneration of high bulk EOF; the RSD of migration times was less than 0.7%. To further improve the concentration sensitivity, neutral PVA was introduced into the capillary with the help of EOF to act as sieving matrix. The occurrence of stacking at the boundary between the PVA and the sample zone is mainly due to the retardation of proteins by PVA. As a result, the LODs at an S/N of 3 for SDS–protein complexes are of the order of sub‐nM to several nM. For example, the LOD for BSA is 0.78 nM, which is a 91‐fold sensitivity enhancement over the normal injection. In addition, our stacking method has been applied to the analyses of proteins in Escherichia coli cells. The peak for β‐galactosidase (E. coli) was observed after 0.1 μM β‐galactosidase was spiked into the E. coli samples.