bluuebunny/crossref_metadata_2025_split huggingface dataset:
Self‐Assembled Heavy Lanthanide Orthovanadate Architecture with Controlled Dimensionality and Morphology
Authors: Qian Liwu , Zhu Jun , Chen Zhu , Gui Yicai , Gong Qiang , Yuan Yanping , Zai Jiantao , Qian Xuefeng 
Published: December 2008

AbstractNearly monodisperse YVO4 architectures with persimmon‐like, cube‐like and nanoparticle shapes have been synthesised on a large scale by means of a complexing‐agent‐assisted solution route. The shape and size of these as‐prepared architectures can be tuned effectively by controlling the reaction conditions, such as reaction time, the molar ratio of complexing agent/Y3+ and different complexing agents. As a typical morphology, the growth process of monodisperse nanopersimmons has been examined. To extend this method, other LnVO4 (Ln=Ce, Gd, Dy, Er) complexes with well‐defined shape and dimensionality can also be achieved by adjusting different rare earth precursors. Further studies reveal that the morphology of the as‐synthesised lanthanide orthovanadate is determined mainly by the interaction between rare earth ion and the complexing agent. Ultraviolet (UV) absorption and photoluminescence spectra show that the optical properties of YVO4 nanopersimmons are relevant to their size and shape. This work sheds some light on the design of well‐defined complex nanostructures, and explores the potential applications of the as‐synthesised architectures.
Enantioselective Hydrogenation and Transfer Hydrogenation of Bulky Ketones Catalysed by a Ruthenium Complex of a Chiral Tridentate Ligand
Authors: Díaz‐Valenzuela M. Belén , Phillips Scott D. , France Marcia B. , Gunn Mary E. , Clarke Matthew L. 
Published: December 2008

AbstractA study on the enantioselective hydrogenation of tertiary alkyl ketones catalysed by a novel class of tridentate–Ru complex is reported. In contrast to the extensively studied [RuCl2(diphos)(di‐primary amine)] complexes, this new class of hydrogenation catalyst smoothly reduces these less reactive bulky ketones with up to 94 % ee. The same catalyst system can also selectively reduce other potentially problematic substrates such as bulky heterocyclic ketones. Unusually for a pressure hydrogenation catalyst, similar enantioselectivity can be obtained under transfer hydrogenation conditions. The transfer hydrogenations are somewhat slower than the pressure hydrogenations, but this drawback is readily overcome, since we have discovered that a microwave accelerated transfer hydrogenation of the above ketones occurs within 20 min at about 90 °C with similar selectivity to that obtained in the pressure hydrogenation system.
In vitro and in vivo Staining Characteristics of Small, Fluorescent, Aβ42‐Binding D‐Enantiomeric Peptides in Transgenic AD Mouse Models
Authors: van Groen Thomas , Kadish Inga , Wiesehan Katja , Funke Susanne A. , Willbold Dieter 
Published: December 2008

AbstractPlaque visualisation: We identified three different D‐enantiomeric peptides that bind to Alzheimer's amyloid β (Aβ1‐42). As there is currently no definitive pre‐mortem diagnosis for Alzheimer's disease, we investigated the peptides' suitability as molecular probes for in vivo imaging in transgenic mouse models.magnified imageOne of the characteristic pathological hallmarks of Alzheimer's disease (AD) are neuritic plaques that consist of amyloid peptide (Aβ). To improve diagnosis and treatment evaluation, neuroimaging tools that make use of Aβ‐binding ligands to visualise amyloid plaques are being developed. We investigate the in vitro and in vivo characteristics of a series of three D‐enantiomeric peptides (D1–D3) that were developed to specifically bind amyloid β1‐42 (Aβ42) in the brains of transgenic AD‐model mice. We stained brain sections of the mice, injected and infused the mice with these small D‐peptides, and examined their staining of Aβ42 in the brain. The experiments demonstrate that the D‐peptides label all plaques that contain Aβ42 in the brain. In contrast, diffuse amyloid β deposits (which do not contain Aβ42) are not stained by any of the D‐peptides. The in vivo and in vitro studies demonstrate that the D‐peptides label all Aβ42 in the brain, and none of the D‐peptides causes inflammation or is taken up by astrocytes or microglia. Furthermore, long‐term infusion of the peptides does not cause inflammation. Together, this demonstrates that these D‐peptides might be suitable for use as molecular probes to measure Aβ plaque load in the living brain for early diagnosis of Alzheimer's disease, or to monitor Aβ42 plaque load during disease progression or during treatment.
NG‐Acylated Aminothiazolylpropylguanidines as Potent and Selective Histamine H2Receptor Agonists
Authors: Kraus Anja , Ghorai Prasanta , Birnkammer Tobias , Schnell David , Elz Sigurd , Seifert Roland , Dove Stefan , Bernhardt Günther , Buschauer Armin 
Published: December 2008

AbstractBioisosteric replacementof the guanidino group in arpromidine‐like histamine H2receptor (H2R) agonists by an acylguanidine moiety is useful for obtaining potent H2R agonists with improved oral bioavailability and blood–brain barrier penetration. We show that bioisosteric replacement of the imidazole ring in NG‐acylated imidazolylpropylguanidines by a 2‐aminothiazol‐5‐yl group resulted in potent H2R agonists with much greater selectivity for the human H2R over H3and H4receptors.magnified imageThe bioisosteric replacement of the guanidino group in arpromidine‐like histamine H2receptor (H2R) agonists by an acylguanidine moiety is a useful approach to obtain potent H2R agonists with improved oral bioavailability and blood–brain barrier penetration. Unfortunately, the selectivity of such NG‐acylated imidazolylpropylguanidines for the H2R is poor, in particular versus histamine H3(H3R) and H4receptors (H4R). This drawback appears to depend on the “privileged” imidazolylpropylguanidine structure. The 2‐amino‐4‐methylthiazol‐5‐yl moiety is a bioisostere of the imidazole ring in the moderately potent H2R‐selective histamine analogue amthamine. This approach was successfully applied to acylguanidine‐type H2R agonists. The aminothiazoles are nearly equipotent to the corresponding imidazoles as H2R agonists. Compared with histamine, the potency is increased up to 40‐fold on the guinea pig right atrium, and up to 125‐ and 280‐fold in GTPase assays with human and guinea pig H2R–GsαSfusion proteins expressed in Sf9 insect cells, respectively. Docking studies on H2R models support the hypothesis that 2‐aminothiazolyl and imidazolyl derivatives interact with H2Rs as bioisosteres. In contrast to the imidazoles, the aminothiazoles are devoid of agonistic or relevant antagonistic effects on H1, H3, and H4receptors. Moreover, unlike amthamine, the 4‐methyl group does not significantly contribute to the H2R agonism of NG‐acylated 2‐amino‐4‐methylthiazol‐5‐ylpropylguanidines.
Toward Docking‐Based Virtual Screening for Discovering Antitubulin Agents by Targeting Taxane and Colchicine Binding Sites
Authors: Soulère Laurent 
Published: December 2008

AbstractDocking‐based virtual screening: Flexible docking, scoring, and virtual screening of ligand databases are on the way to fulfilling the promise. Docking‐based virtual screening that targets taxane and colchicine binding sites will certainly provide new antitubulin agents.magnified imageTubulin proteins play a major role in cell division, and were first identified as attractive targets for cancer therapy over 40 years ago. Recent studies aiming to gain structural insight into the binding mode of antitubulin agents to taxane or colchicine binding sites using NMR and/or molecular‐mechanics‐assisted conformation analysis and docking simulations have been reported. These studies, which represent the main focus of this article, create prospects for the development of docking‐based virtual screening techniques to aid in the discovery of new antitubulin agents.
Photophysics of New Water‐Soluble Terrylenediimide Derivatives and Applications in Biology
Authors: Jung Christophe , Ruthardt Nadia , Lewis Robert , Michaelis Jens , Sodeik Beate , Nolde Fabian , Peneva Kalina , Müllen Klaus , Bräuchle Christoph 
Published: December 2008

AbstractThe photophysical properties of three new water‐soluble terrylenediimide (WS‐TDI) derivatives are investigated and their utilization in biological experiments is demonstrated. Each of these dyes can be excited in the far red region of the visible spectrum, making them good candidates for in‐vivo studies. Single‐molecule techniques characterize their photophysics that is, the number of emitted photons, blinking characteristics and survival times until photobleaching takes place. All three dyes exhibit bright fluorescence, as well as an extremely high resistance against photodegradation compared to other well‐known fluorophores. Due to their different characteristics the three new WS‐TDI derivatives are suitable for specialized biological applications. WS‐TDI dodecyl forms non‐fluorescent aggregates in water which can be disrupted in a hydrophobic environment leading to a monomeric fluorescent form. Due to its high lipophilicity WS‐TDI dodecyl anchors efficiently in lipid bilayers with its alkyl chain and hence can be ideally used to image membranes and membrane‐containing compartments in living cells. In contrast, the positively charged WS‐TDI pyridoxy is a new type of chromophore in the WS‐TDI family. It is fully solubilized in water forming fluorescent monomers and is successfully used to label the envelope of herpes simplex viruses. Finally, it is shown that a WS‐TDI derivative functionalized with N‐hydroxysuccinimide ester moiety (WS‐TDI/NHS ester) provides a versatile reactive dye molecule for the specific labelling of amino groups in biomolecules such as DNA.
How Does a Membrane Protein Achieve a Vectorial Proton Transfer Via Water Molecules?
Authors: Wolf Steffen , Freier Erik , Gerwert Klaus 
Published: December 2008

AbstractWe present a detailed mechanism for the proton transfer from a protein‐bound protonated water cluster to the bulk water directed by protein side chains in the membrane protein bacteriorhodopsin. We use a combined approach of time‐resolved Fourier transform infrared spectroscopy, molecular dynamics simulations, and X‐ray structure analysis to elucidate the functional role of a hydrogen bond between Ser193 and Glu204. These two residues seal the internal protonated water cluster from the bulk water and the protein surface. During the photocycle of bacteriorhodopsin, a transient protonation of Glu204 leads to a breaking of this hydrogen bond. This breaking opens the gate to the extracellular bulk water, leading to a subsequent proton release from the protonated water cluster. We show in detail how the protein achieves vectorial proton transfer via protonated water clusters in contrast to random proton transfer in liquid water.
Synthesis, Crystal Structures, and Thermal Properties of New [ZnX2(2,5‐dimethylpyrazine)] (X = Cl, Br, I) Coordination Compounds
Authors: Wriedt Mario , Jeß Inke , Näther Christian 
Published: December 2008

AbstractEight new halidozinc(II) coordination compounds with 2,5‐dimethylpyrazine as a ligand were prepared. The reaction of ZnX2 (X = Cl, Br, I) and 2,5‐dimethylpyrazine in methanol results in the formation of catena‐(μ2‐2,5‐dimethylpyrazine‐N,N′)dichloridozinc(II) (1), catena‐(μ2‐2,5‐dimethylpyrazine‐N,N′)dibromidozinc(II) (3I and 3II), catena‐(μ2‐2,5‐dimethylpyrazine‐N,N′)diiodidozinc(II) (6), and diiodidobis(2,5‐dimethylpyrazine‐N)zinc(II) (7). In addition, in a solvent‐free reaction of ZnX2 (X = Cl, Br) and 2,5‐dimethylpyrazine,the ligand‐rich compounds bis(dichlorido)bis(2,5‐dimethylpyrazine‐N)(μ2‐2,5‐dimethylpyrazine‐N,N′)dizinc(II) (2), bis(dibromido)bis(2,5‐dimethylpyrazine‐N)(μ2‐2,5‐dimethylpyrazine‐N,N′)dizinc(II) (4), and dibromidobis(2,5‐dimethylpyrazine‐N)zinc(II) 2,5‐dimethylpyrazine solvate (5) were obtained. In the crystal structures of all compounds the zinc atoms are each coordinated by two halide atoms and two 2,5‐dimethylpyrazine ligands within a distorted tetrahedron. The zinc atoms in the ligand‐deficient 1:1 (1:1 = molar ratio of metal salt to ligand) compounds 1 and 6 and in the two polymorphic modifications 3I and 3II are linked by the N‐donor ligands into chains. In contrast, the crystal structure of the 2:3 compounds 2 and 4 are built up of oligomeric discrete [(ZnX2)2(2,3‐dimethylpyrazine)3] units in which each ZnX2 (X = Cl, Br) unit is coordinated by two halide atoms and one bridging and one terminal 2,5‐dimethylpyrazine ligand. The structures of the ligand‐rich 1:2 diiodido compound 7 and the 1:3 dibromido compound 5 consist of discrete monomeric tetrahedral building blocks. In the thermal decomposition reactions of the ligand‐rich compounds 2, 5, and 7, different mass steps are observed. In the first step, the ligand‐deficient 1:1 compounds 1 and 6 are formed in quantitative yields from 2 and 7, respectively, and 5 yields a mixture of 3I and 3II, and the second mass step leads to the formation of new ligand‐deficient 2:1 compounds. On further heating of the compounds, the remaining ligands are discharged. This results in the formation of the zinc(II) halides, which vaporize on further heating. Solvent‐mediated conversion experiments in methanol show that, irrespective of the ratio of zinc(II) halide and ligand, only the 1:1 compounds 1 and 3I are formed and therefore represent the thermodynamically most stable compounds at room temperature. For ZnI2 the 1:2 compound 7 is obtained at ratios of zinc(II) iodide to ligand larger than 1:3, whereas at lower ratios the 1:1 compound 6 is always obtained. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Mercury speciation by CE: An update
Authors: Kubánˇ Petr , Pelcová Pavlína , Margetínová Jana , Kubánˇ Vlastimil 
Published: December 2008

AbstractThis review provides an update on mercury speciation by CE. It includes a brief discussion on physicochemical properties, toxicity and transformation pathways of mercury species (i.e. methyl‐, ethyl‐, phenyl‐ and inorganic mercury) and outlines recent trends in Hg speciation by CE. CE is presented as a complementary technique to chromatographic separation techniques, especially in cases when speed, high efficiency and low sample volumes are required. The development of suitable sample preconcentration/isolation (sample stacking, ion exchange, liquid–liquid–liquid extraction, dual‐cloud point extraction) to achieve low LODs for analysis of trace concentrations of mercury species in real samples is emphasized. Hyphenation of CE to element specific detectors (i.e. electrothermal atomic absorption spectrometry, atomic fluorescence spectrometry, inductively coupled plasma‐optical emission spectrometry, inductively coupled plasma‐mass spectrometry) is discussed as well as a potential of CE in interaction studies that may provide useful information on interaction of various Hg species with selected bio‐macromolecules.
Recent developments of molecularly imprinted polymer in CEC
Authors: Huang Yan‐Ping , Liu Zhao‐Sheng , Zheng Chao , Gao Ru‐Yu 
Published: December 2008

AbstractThis review focuses on developments in the field of molecularly imprinted polymer (MIP) for CEC since August 2006. New technique of CEC‐based MIP, e.g. covalent approach through the formation of Schiff base, miniemulsion polymerization, non‐hydrolytic sol–gel methodology, MIP‐derivatized silica monolithic column, are discussed from the view of MIP preparation. Some thoughts on potential future directions are also expressed in this review.
Temperature dependence of time domain reflectometry–measured soil dielectric permittivity
Authors: Skierucha Wojciech 
Published: December 2008

AbstractThe purpose of this study is to determine the temperature influence on the soil bulk dielectric permittivity, ϵb, calculated from the measurement of the electromagnetic‐wave velocity of propagation along the parallel waveguide in a TDR probe, i.e., a probe working in time domain reflectometry technique. The experimental evidence shows that the existing models do not completely describe the temperature effect. However, it has been confirmed that the observed temperature effect is the result of two competing phenomena: ϵb increases with temperature following the release of bound water from soil solid particles, and ϵb decreases with temperature increase following the temperature effect of free water molecules. It has been found that there is a soil type–characteristic moisture value, θeq, named the equilibrium water content, at which both competing phenomena compensate each other. The equilibrium water content, θeq, is correlated with the soil specific surface area. Based on knowledge of θeq, a temperature‐correction formula is presented that adjusts the TDR soil‐moisture measurements at various temperatures to the corresponding value at 25°C. This decreases the absolute measurement error of soil moisture, θTDR, by the factor of 2 as compared to the uncorrected values.
Simultaneous determination of three anticon‐vulsants using hydrophilic interaction LC‐MS
Authors: Oertel Reinhard , Arenz Norman , Pietsch Jörg , Kirch Wilhelm 
Published: December 2008

AbstractA specific and automated method was developed to quantify the anticonvulsants gabapentin, pregabalin and vigabatrin simultaneously in human serum. Samples were prepared with a protein precipitation. The hydrophilic interaction chromatography (HILIC) with a mobile phase gradient was used to divide off ions of the matrix and for separation of the analytes. Four different HILIC‐columns and two different column temperatures were tested. The Tosoh‐Amid column gave the best results: single small peaks. The anticonvulsants were detected in the multiple reaction monitoring mode (MRM) with ESI‐MS‐MS. Using a volume of 100 μL biological sample the lowest point of the standard curve, i.e. the lower LOQs were 312 ng/mL. The described HILIC‐MS‐MS method is suitable for therapeutic drug monitoring and for clinical and pharmcokinetical investigations of the anticonvulsives.
Identification and quantification of the volatile constituents in Cnidium monnieri using supercritical fluid extraction followed by GC‐MS
Authors: Chen Qinhua , Li Peng , Yuan Fangjun , Cheng Fanjun , He Jing , Liu Jia , Zhang Zhuo 
Published: December 2008

AbstractThe volatile components of Cnidium monnieri were obtained by supercritical fluid extraction (SFE) and analyzed by GC‐MS (identification and determination of metabolites). The compounds were identified according to their retention times and mass spectra. The effects of different parameters, such as extraction pressure, temperature, dynamic extraction time, flow rate of CO2, on the SFE of C. monnieri extracts were investigated. A total of 14 compounds of SFE extracts were identified. Osthole (69.52%), bornyl acetate (10.03%), α‐pinene (4.71%), and imperatorin (2.42%) were the major compounds identified in C. monnieri SFE extracts. The quantitation of osthole and imperatorin were then accomplished. The linear calibration ranges were all 5–1000 μg/mL for osthole and imperatorin by GC‐MS analysis. The recovery of osthole and imperatorin were in the range 96.5–101.8%. The LODs for osthole and imperatorin were 1.0 and 0.6 μg/mL, respectively.
Intuitionistic notions of boundedness in ℕ
Authors: Richman Fred 
Published: December 2008

AbstractWe consider notions of boundedness of subsets of the natural numbers ℕ that occur when doing mathematics in the context of intuitionistic logic. We obtain a new characterization of the notion of a pseudobounded subset and we formulate the closely related notion of a detachably finite subset. We establish metric equivalents for a subset of ℕ to be detachably finite and to satisfy the ascending chain condition. Following Ishihara, we spell out the relationship between detachable finiteness and sequential continuity. Most of the results do not require countable choice. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tall cardinals
Authors: Hamkins Joel D. 
Published: December 2008

AbstractA cardinal κ is tall if for every ordinal θ there is an embedding j: V → M with critical point κ such that j (κ) > θ and Mκ ⊆ M. Every strong cardinal is tall and every strongly compact cardinal is tall, but measurable cardinals are not necessarily tall. It is relatively consistent, however, that the least measurable cardinal is tall. Nevertheless, the existence of a tall cardinal is equiconsistent with the existence of a strong cardinal. Any tall cardinal κ can be made indestructible by a variety of forcing notions, including forcing that pumps up the value of 2κ as high as desired. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Arsenic K‐edge X‐ray absorption spectroscopy of arsenic in seafood
Authors: George Graham N. , Prince Roger C. , Singh Satya P. , Pickering Ingrid J. 
Published: December 2008

AbstractIt is well known that seafood contains high levels of arsenic. For marine animals arsenic is predominantly present as arsenobetaine and related compounds which are not metabolized and are thought to present no toxic hazard to humans. With edible seaweeds, arsenic is present in different forms, of which arsenosugars are the best known. These species may be metabolized by mammals, and the high arsenic contents of these materials represent a significant environmental source for human exposure to arsenicals in some populations. In this work, we explore the utility of As K‐edge X‐ray absorption near‐edge spectroscopy as an in situ probe of the chemical forms of arsenic in seaweeds. We find that three different chemical types of arsenic are present, consistent with arsenate, an arsenosugar or tetra‐alkyl‐arsonium species, and a trivalent arsenic species.
A Discussion of Noise in Dynamic Light Scattering for Particle Sizing
Authors: Yang Hui , Zheng Gang , Li Meng‐chao 
Published: December 2008

AbstractIn order to acquire high quality measurement data from DLS (Dynamic Light Scattering) experiments, serious attention has to be paid to minimizing the noise involved. In this paper, the noise in DLS for particle sizing is addressed for four parts of the measurement system. The first is the noise caused from the low quality of sample preparation and the scattering medium containing too high or too low concentration of analyte. The second is from the view of optics, i.e., the laser must have sufficient power, be stable under all expected conditions, and usually be restricted to a single transverse mode, in case it causes distortion in measurement data. In addition, if the energy of the incident light is too high, strong absorption occurs, which will induce thermal blooming. The optical components must be carefully chosen and designed to minimize noise from the unit itself. The detection area should be calculated to reach the best signal‐to‐noise ratio and an entrance lens with magnification that is too high and that causes distortion in the ACF (Auto Correlation Function) should be avoided. Some new components such as fiber optics and graded‐index may also introduce new noise. The third factor is the photodetector, which must have adequate speed and sensitivity and possess suitably low internal correlations and noise. In addition, the quantum noise from the detector should be subtracted. The fourth factor is that the correlator should be chosen carefully. In some cases, equipment with a higher speed and more channels should be chosen to minimize the statistical noise.
Prediction of electronic, structural and elastic properties of the hardest oxide: TiO2
Authors: Caravaca M. A. , Casali R. A. , Miño J. C. 
Published: December 2008

AbstractThis work combines the theory of elasticity with first principles quantum mechanic calculations to predict the electronic, structural and elastic properties: elastic constants, bulk moduli of the TiO2 (Titania) in the Pnma phase. Band‐structure shows a direct gap in Γ which increases its value under hydrostatic pressure. It has two regimes: in the range 0–50 GPa the band‐gap has a negative second pressure derivative and changes its sign in the range 50–100 GPa. The band gap becomes indirect at pressures above 150 GPa. This phase improves its mechanical stability and insulator properties under extreme conditions of hydrostatic pressures. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)