bluuebunny/crossref_metadata_2025_split huggingface dataset:
Creating and Modulating Microdomains in Pore‐Spanning Membranes
Authors: Orth Alexander , Johannes Ludger , Römer Winfried , Steinem Claudia 
Published: December 2011

AbstractThe architecture of the plasma membrane is not only determined by the lipid and protein composition, but is also influenced by its attachment to the underlying cytoskeleton. Herein, we show that microscopic phase separation of “raft‐like” lipid mixtures in pore‐spanning bilayers is strongly determined by the underlying highly ordered porous substrate. In detail, lipid membranes composed of DOPC/sphingomyelin/cholesterol/Gb3 were prepared on ordered pore arrays in silicon with pore diameters of 0.8, 1.2 and 2 μm, respectively, by spreading and fusion of giant unilamellar vesicles. The upper part of the silicon substrate was first coated with gold and then functionalized with a thiol‐bearing cholesterol derivative rendering the surface hydrophobic, which is prerequisite for membrane formation. Confocal laser scanning fluorescence microscopy was used to investigate the phase behavior of the obtained pore‐spanning membranes. Coexisting liquid‐ordered‐ (lo) and liquid‐disordered (ld) domains were visualized for DOPC/sphingomyelin/cholesterol/Gb3 (40:35:20:5) membranes. The size of the lo‐phase domains was strongly affected by the underlying pore size of the silicon substrate and could be controlled by temperature, and the cholesterol content in the membrane, which was modulated by the addition of methyl‐β‐cyclodextrin. Binding of Shiga toxin B‐pentamers to the Gb3‐doped membranes increased the lo‐phase considerably and even induced lo‐phase domains in non‐phase separated bilayers composed of DOPC/sphingomyelin/cholesterol/Gb3 (65:10:20:5).
Carbonyl‐Functionalized Quaterthiophenes: A Study of the Vibrational Raman and Electronic Absorption/Emission Properties Guided by Theoretical Calculations
Authors: Aragó Juan , Ponce Ortiz Rocío , Nieto‐Ortega Belén , Hernández Víctor , Casado Juan , Facchetti Antonio , Marks Tobin J. , Viruela Pedro M. , Ortí Enrique , López Navarrete Juan T. 
Published: December 2011

AbstractThis work investigates the evolution of the molecular, vibrational, and optical properties within a family of carbonyl‐functionalized quaterthiophenes: 5,5′′′‐diheptanoyl‐2,2′:5′,2′′:5′′,2′′′‐quaterthiophene (1), 5,5′′′‐diperfluorohexylcarbonyl‐2,2′:5′,2′′:5′′,2′′′‐quaterthiophene (2), and 2,7‐[bis(5‐perfluorohexylcarbonylthien‐2‐yl)]‐4H‐cyclopenta[2,1‐b:3,4‐b′]‐dithiophene‐4‐one (3). The analysis is performed by Raman and UV/Vis absorption/excitation/fluorescence spectroscopy in combination with density functional calculations. Theoretical calculations show that substitution with carbonyl groups and perfluorohexyl chains induces progressive quinoidization of the π‐conjugated backbone in comparison to the carbonyl‐free compound 5,5′′′‐dimethyl‐2,2′:5′,2′′:5′′,2′′′‐quaterthiophene (DM‐4T) used as reference. Raman spectra are dominated by a strong Raman line which mainly corresponds to a combination of CC/CC stretching vibrations spreading over the whole thiophene core. This band undergoes a remarkable downshift as a consequence of the structural changes induced by the electron‐withdrawing groups on the π‐conjugated backbone. The band splitting on incorporation of a central carbonyl bridge evidences the formation of two structural domains in the molecule. The excitation and fluorescence spectra recorded at low temperature show well‐resolved vibronic structures associated with the most intense collective CC/CC stretching mode. Optical absorption and fluorescence bands exhibit remarkable bathochromic dispersion on carbonyl functionalization, indicative of extension of π conjugation. TDDFT calculations enable a detailed description of the trends observed in the absorption spectra. Resonance Raman spectra reflect the structural changes predicted for the S0→S1 electronic transition and evidence the cross‐conjugated character that the central carbonyl group confers on 3.
Low temperature photoluminescence studies on semiorganic tris thiourea copper (I) chloride single crystal
Authors: Ariponnammal S. , Chandrasekaran S. , Sanjeeviraja C. 
Published: December 2011

AbstractSemiorganic tris thiourea copper (I) chloride (TTCC) single crystals have been synthesized from copper (II) chloride via slow evaporation technique. The stoichiometry of the grown anhydrous complex crystal has been confirmed by elemental CHNS (C, H, N and S) and atomic absorption spectrophotometric (AAS) analysis. The crystal structure with space group has been confirmed by single crystal and powder X‐ray diffraction (XRD) studies. The FTIR study assigned the presence of functional groups and confirmed the co‐ordination of metal ions with thiourea. It also confirmed the transition from Cu2+ to Cu+ when thiourea combined with Copper (II) chloride. The optical transparency of the crystal has been studied by UV‐Vis spectrum and deduced the energy gap. The room temperature Photoluminescence (PL) spectrum reported maximum emission line at 410.92 nm and Stokes shift has been determined as 75 nm or 16.5 eV. Low temperature luminescence study from 300 K to 77 K exhibited three blue emission peaks and one green emission peak. The green emission band has been assigned to recombination of an electron in a shallow trap and Cu2+. Blue emission has been attributed to S2‐ vacancies. The interesting hysteresis loop has been exhibited by the variation of energy gap with low temperature. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nitrogen‐Doped Carbon Nanotubes as a Highly Active Metal‐Free Catalyst for Selective Oxidation
Authors: Chizari Kambiz , Deneuve Adrien , Ersen Ovidiu , Florea Ileana , Liu Yu , Edouard David , Janowska Izabela , Begin Dominique , Pham‐Huu Cuong 
Published: December 2011

AbstractCatalytic reactions are generally carried out on supported metals or oxides, which act as an active phase and require impregnation and thermal treatment steps. During tests, the metal or oxide nanoparticles could be further sintered, which would induces deactivation. Direct incorporation of the active phase into the matrix of a support could be an elegant alternative to prevent catalyst deactivation. Here, we report that nitrogen‐doped carbon nanotubes (N‐CNTs) can be efficiently employed as a metal‐free catalyst for oxidative reactions that allow the selective transformation of the harmful, gaseous H2S into solid sulfur. The catalyst exhibits a high stability during the test at high space velocity. The macroscopic shaping of the catalyst on the silicon carbide foam also increases its catalytic activity by improving the contact between the reactants and the catalyst. Such macroscopic shaping allows the avoidance of problems linked with transport and handling of nanoscopic materials and also reduces the pressure drop across the catalyst bed to a large extent.
High‐throughput screening for various classes of doping agents using a new ‘dilute‐and‐shoot’ liquid chromatography‐tandem mass spectrometry multi‐target approach
Authors: Guddat S. , Solymos E. , Orlovius A. , Thomas A. , Sigmund G. , Geyer H. , Thevis M. , Schänzer W. 
Published: December 2011

A new multi‐target approach based on liquid chromatography – electrospray ionization tandem mass spectrometry (LC‐(ESI)‐MS/MS) is presented to screen for various classes of prohibited substances using direct injection of urine specimens. With a highly sensitive new generation hybrid mass spectrometer classic groups of drugs – for example, diuretics, beta2‐agonists – stimulants and narcotics are detectable at concentration levels far below the required limits.Additionally, more challenging and various new target compounds could be implemented. Model compounds of stimulant conjugates were studied to investigate a possible screening without complex sample preparation. As a main achievement, the integration of the plasma volume expanders dextran and hydroxyethyl starch (HES), commonly analyzed in time‐consuming, stand‐alone procedures, is accomplished. To screen for relatively new prohibited compounds, a common metabolite of the selective androgen receptor modulator (SARMs) andarine, a metabolite of growth hormone releasing peptide (GHRP‐2), and 5‐amino‐4‐imidazolecarboxyamide ribonucleoside (AICAR) are analyzed. Following a completely new approach, conjugates of di(2‐ethylhexyl) phthalate (DEHP) metabolites are monitored to detect abnormally high levels of plasticizers indicating for illicit blood transfusion.The assay was fully validated for qualitative purposes considering the parameters specificity, intra‐ (3.2–16.6%) and inter‐day precision (0.4–19.9%) at low, medium and high concentration, robustness, limit of detection (1–70 ng/ml, dextran: 30 µg/ml, HES: 10 µg/ml) and ion suppression/enhancement effects.The analyses of post‐administration and routine doping control samples demonstrates the applicability of the method for sports drug testing. This straightforward and reliable approach accomplishes the combination of different screening procedures resulting in a high‐throughput method that increases the efficiency of the labs daily work. Copyright © 2011 John Wiley & Sons, Ltd.
Structural and functional response of methane‐consuming microbial communities to different flooding regimes in riparian soils
Authors: Bodelier Paul L.E. , Bär‐Gilissen Marie‐Jose , Meima‐Franke Marion , Hordijk Kees 
Published: December 2011

AbstractClimate change will lead to more extreme precipitation and associated increase of flooding events of soils. This can turn these soils from a sink into a source of atmospheric methane. The latter will depend on the balance of microbial methane production and oxidation. In the present study, the structural and functional response of methane oxidizing microbial communities was investigated in a riparian flooding gradient. Four sites differing in flooding frequency were sampled and soil‐physico‐chemistry as well as methane oxidizing activities, numbers and community composition were assessed. Next to this, the active community members were determined by stable isotope probing of lipids. Methane consumption as well as population size distinctly increased with flooding frequency. All methane consumption parameters (activity, numbers, lipids) correlated with soil moisture, organic matter content, and conductivity. Methane oxidizing bacteria were present and activated quickly even in seldom flooded soils. However, the active species comprised only a few representatives belonging to the genera Methylobacter, Methylosarcina, and Methylocystis, the latter being active only in permanently or regularly flooded soils.This study demonstrates that soils exposed to irregular flooding harbor a very responsive methane oxidizing community that has the potential to mitigate methane produced in these soils. The number of active species is limited and dominated by one methane oxidizing lineage. Knowledge on the characteristics of these microbes is necessary to assess the effects of flooding of soils and subsequent methane cycling therein.
Impact of historical founder effects and a recent bottleneck on MHC variability in Commander Arctic foxes (Vulpes lagopus)
Authors: Ploshnitsa Anna I. , Goltsman Mikhail E. , Macdonald David W. , Kennedy Lorna J. , Sommer Simone 
Published: December 2011

AbstractPopulations of Arctic foxes (Vulpes lagopus) have been isolated on two of the Commander Islands (Bering and Mednyi) from the circumpolar distributed mainland population since the Pleistocene. In 1970–1980, an epizootic outbreak of mange caused a severe population decline on Mednyi Island. Genes of the major histocompatibility complex (MHC) play a primary role in infectious disease resistance. The main objectives of our study were to compare contemporary variation of MHC class II in mainland and island Arctic foxes, and to document the effects of the isolation and the recent bottleneck on MHC polymorphism by analyzing samples from historical and contemporary Arctic foxes. In 184 individuals, we found 25 unique MHC class II DRB and DQB alleles, and identified evidence of balancing selection maintaining allelic lineages over time at both loci. Twenty different MHC alleles were observed in mainland foxes and eight in Bering Island foxes. The historical Mednyi population contained five alleles and all contemporary individuals were monomorphic at both DRB and DQB. Our data indicate that despite positive and diversifying selection leading to elevated rates of amino acid replacement in functionally important antigen‐binding sites, below a certain population size, balancing selection may not be strong enough to maintain genetic diversity in functionally important genes. This may have important fitness consequences and might explain the high pathogen susceptibility in some island populations. This is the first study that compares MHC diversity before and after a bottleneck in a wild canid population using DNA from museum samples.
Locus‐specific view of flax domestication history
Authors: Fu Yong‐Bi , Diederichsen Axel , Allaby Robin G. 
Published: December 2011

AbstractCrop domestication has been inferred genetically from neutral markers and increasingly from specific domestication‐associated loci. However, some crops are utilized for multiple purposes that may or may not be reflected in a single domestication‐associated locus. One such example is cultivated flax (Linum usitatissimum L.), the earliest oil and fiber crop, for which domestication history remains poorly understood. Oil composition of cultivated flax and pale flax (L. bienne Mill.) indicates that the sad2 locus is a candidate domestication locus associated with increased unsaturated fatty acid production in cultivated flax. A phylogenetic analysis of the sad2 locus in 43 pale and 70 cultivated flax accessions established a complex domestication history for flax that has not been observed previously. The analysis supports an early, independent domestication of a primitive flax lineage, in which the loss of seed dispersal through capsular indehiscence was not established, but increased oil content was likely occurred. A subsequent flax domestication process occurred that probably involved multiple domestications and includes lineages that contain oil, fiber, and winter varieties. In agreement with previous studies, oil rather than fiber varieties occupy basal phylogenetic positions. The data support multiple paths of flax domestication for oil‐associated traits before selection of the other domestication‐associated traits of seed dispersal loss and fiber production. The sad2 locus is less revealing about the origin of winter tolerance. In this case, a single domestication‐associated locus is informative about the history of domesticated forms with the associated trait while partially informative on forms less associated with the trait.
Dinuclear and Mononuclear Chromium Acetylide Complexes
Authors: Egler‐Lucas Carolina , Blacque Olivier , Venkatesan Koushik , López‐Hernández Alberto , Berke Heinz 
Published: December 2011

AbstractReaction of trans‐Cl2Cr(dmpe)2 (1) [dmpe = 1,2‐bis(dimethylphosphanyl)ethane] with 0.5 equiv. of Me3Sn–C≡C–C≡C–SnMe3 or Me3Sn–C≡C–C6H4–C≡C–SnMe3 afforded the dinuclear complexes trans‐[Cl(dmpe)2Cr≡C–C≡C–C≡Cr(dmpe)2Cl] (2), trans‐[Cl(dmpe)2Cr–C≡C–C≡C–Cr(dmpe)2Cl][SnMe3Cl2]2 (2[SnMe3Cl2]2), and trans‐[Cl(dmpe)2Cr–C≡C–C6H4–C≡C–Cr(dmpe)2Cl][SnMe3Cl2]2 (3[SnMe3Cl2]2), which could be transformed to the 2[PF6]2 and 3[BPh4]2 salts. Substitutions of the chloride groups in 2 were carried out to achieve the corresponding iodo (4) and (trimethylsilyl)alkynyl (5) complexes. Utilizing similar reactions and treatment with only 1 equiv. of the corresponding alkynyl ligand [Me3Sn–C≡C–R (R = –SnMe3, –C6H5), Me3Sn–C≡C–C≡C–R (R = –SiMe3, –SnMe3), and Me3Sn–C≡C–C6H4–C≡C–SnMe3] allowed us to prepare a series of mononuclear monoacetylide complexes: trans‐[Cl(dmpe)2Cr–C≡C–R] [R = –SnMe3(6),–C6H5(7)], trans‐[Cl(dmpe)2Cr–C≡C–C≡C–R] [R = –SiMe3(8),–SnMe3(9)], and trans‐[Cl(dmpe)2Cr–C≡C–C6H4–C≡C–SnMe3] (10), respectively. The complexes 2, 2[SnMe3Cl2]2, 2[PF6]2, 3[SnMe3Cl2]2, 3[BPh4]2, and 6–10 displayed paramagnetic behavior. Electrochemical studies performed on the dinuclear complexes (2), (2[SnMe3Cl2]2), (3[SnMe3Cl2]2), and (5) showed one two‐electron redox wave revealing a class‐I type behavior based on the Robin–Day classification, which is untypical for dinuclear complexes bridged by a butadiyne ligand. The complexes were characterized by NMR, ESI–MS, cyclic voltammetry, EPR spectroscopy, magnetic measurements, and exemplary single‐crystal X‐ray diffraction studies for 2, 2[SnMe3Cl2]2, 8, 9, and 10.
Hydrogen‐Bond‐Assisted Helical Folding of Propeller‐Shaped Molecules: Effects of Extended π‐Conjugation on Chiral Selection, Conformational Stability, and Exciton Coupling
Authors: Opsitnick Elizabeth A. , Jiang Xuan , Hollenbeck Andrew N. , Lee Dongwhan 
Published: December 2011

AbstractCooperative interaction between multiple chiral centers dictates the absolute handedness of structural folding. We have designed and prepared a series of chiral C3‐symmetric tris(N‐salicylidenamine) derivatives that adopt three‐blade propeller‐like conformations. Synthetic access to an expanded family of such constructs was aided by enzymatic resolution and C–C cross‐coupling reactions of aryl‐substituted chiral propargylic alcohol derivatives. These key structural components were integrated into molecular propellers of predetermined helical screw sense. Through comparative studies on a homologous set of molecules, we found that installation of phenylene‐ethynylene‐derived π‐conjugation profoundly affected the stabilities of the helically folded structures, as evidenced by UV/Vis and circular dichroism (CD) studies. Increasing the number of hydrogen bonds through additional substitution also enhanced the populations of the folded conformations in solution. In addition to introducing steric bias to control structural folding, linearly π‐conjugated groups function as spatially well‐defined chromophores that give rise to characteristic exciton‐coupled circular dichroism. Absolute configurations of chiral centers could thus be further confirmed by comparing the torsional relationships between pairs of chromophores on adjacent subunits, which are fully consistent with the computationally predicted structural models.
Electrochemical Aptasensor Based on a Macrocyclic Ligand Bearing Neutral Red
Authors: Evtugyn Gennady , Kostyleva Veronika , Sitdikov Rusal , Porfireva Anna , Savelieva Maria , Stoikov Ivan , Antipin Igor , Hianik Tibor 
Published: December 2011

AbstractAn amperometric aptasensor has been developed by immobilization of DNA aptamer with Neutral Red (NR) on polycarboxylated thiacalix[4]arene onto the electropolymerized NR layer at a glassy carbon electrode. The NR reduction current recorded after 10 min incubation decayed with increased thrombin concentration due to limitation of the electron exchange in the surface layer. The aptasensor makes it possible to determine 0.1–50 nM of thrombin (limit of detection 0.05 nM). The aptasensor can be used for the direct determination of thrombin in blood serum and does not exert any alteration of the response in the presence of 100 fold excess of serum proteins.
Ion‐Selective Optodes in a Sampling Capillary for Tear Fluid Analysis
Authors: Lindner Ernő , Bordelon Dwight , Kim Mariya D. , Dergunov Sergey A. , Pinkhassik Eugene , Chaum Edward 
Published: December 2011

AbstractPlasticized PVC membrane‐based potassium or sodium ion‐selective optodes were incorporated into sampling capillaries in combination with sol‐gel‐based hydrogen ion‐selective optodes for the sampling and analysis of minute tear fluid samples. The performance characteristic of the K+/pH and Na+/pH sensor arrays were optimized for an adequate dynamic response range, sensitivity, stability, and response time. The precision and accuracy of the combined sampling/measurement system was evaluated both in stopped flow and continuous flow modes using aqueous standard solutions. By using a two point calibration protocol, with pH standards bracketing the sample, the pH of 20 µL pooled human tear samples could be determined with a precision less than ±0.03 pH units. Errors in the pH measurements have a significant influence on the attainable precision and accuracy of the ion‐exchange‐based K+ and Na+ optodes. Nevertheless, the results of the quantitative assessment of the K+ and Na+ concentrations in “check” standards and pooled human tear fluid samples were within ±5 % of the nominal values or of the results of the determinations with atomic absorption spectrophotometry. Cationic surfactants in artificial tear drops were found to interfere with the K+ and Na+ optode responses. No interference was detected in the presence of anionic and nonionic surfactants.
2‐D t‐ITP/CZE determination of clinical urinary proteins using a microfluidic‐chip capillary electrophoresis device
Authors: Wu Ruige , Yeung William S. B. , Fung Ying‐Sing 
Published: December 2011

AbstractTo replace the time‐consuming sample pretreatment procedure, a microfluidic chip‐CE device incorporating on‐chip sample desalting/preconcentration with transient isotachophoresis (ITP)/capillary zone electrophoresis (CZE) was fabricated to perform sequential on‐chip sample pretreatment and CE determination of four urinary proteins in clinical samples. On‐chip sample desalting, clean‐up and analyte preconcentration enable removing interfering sample matrix prior to transferring analytes to separation capillary for transient ITP/CZE determination. Four important urinary proteins transferrin, β2‐microglobulin, human serum albumin (HSA) and immunoglobulin G (IgG), investigated were shown to achieve quantitation limits sufficiently high to meet medical requirements, sensitivity enhancement up to 40‐fold and detection limits down to 0.3, 0.05, 0.6, 0.5 mg/L, respectively. Compared to the stacking effect, the use of a large sample size was found to be the major factor for sensitivity enhancement. The method reliability is established by close to 100% recoveries and statistical agreement of results from the method developed with currently used clinical radio‐immunoassay method for all four proteins investigated. Moreover, an assay time of less than 10 min is needed in the method developed as compared to 7 h for the radio‐immunoassay method.
Polyelectrolytes in multivalent salt solutions
Authors: Wu Kun‐Mao , Wei Yu‐Fu , Hsiao Pai‐Yi 
Published: December 2011

AbstractWe study conformational and electrophoretic properties of polyelectrolytes (PEs) in tetravalent salt solutions under the action of electric fields by means of molecular dynamics simulations. Chain conformations are found to have a sensitive dependence on the salt concentrationCs. AsCsis increased, the chains first shrink to a globular structure and subsequently re‐expand above a critical concentrationCs*. An external electric field can further alter the chain conformation. If the field strengthEis larger than a critical valueE*, the chains are elongated.E*is shown to be a function ofCsby using two estimatorsEI*andEII*through the study of the polarization energy and the onset point of chain unfolding, respectively. The electrophoretic mobility of the chains depends strongly onCs, and the magnitude increases significantly, accompanying the chain unfolding, whenE>EII*. We study the condensed ion distributions modified by electric fields and discuss the connection of the modification with the change of chain morphology and mobility. Finally,E*is studied by varying the chain lengthN. The inflection point is used as a third estimatorEIII*.EIII*scales asN−0.63(4)andN−0.76(2)atCs=0.0 andCs*, respectively.EII*follows a similar scaling law toEIII*but a crossover appears atCs=Cs*whenNis small. TheEI*estimator fails to predict the critical field, which is due to oversimplifying the critical polarization energy to the thermal energy. Our results provide valuable information to understand the electrokinetics of PE solutions at the molecular level and could be helpful in micro/nanofluidic applications.