bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbohydrate Chain of Ganglioside GM1 as a Ligand: Identification of the Binding Strategies of Three 15 mer Peptides and Their Divergence from the Binding Modes of Growth‐Regulatory Galectin‐1 and Cholera Toxin
Authors: Siebert Hans‐Christian , Born Karin , André Sabine , Frank Martin , Kaltner Herbert , von der Lieth Claus‐Wilhelm , Heck Albert J. R. , Jiménez‐Barbero Jesús , Kopitz Jürgen , Gabius Hans‐Joachim 
Published: November 2005

AbstractThe branched pentasaccharide chain of ganglioside GM1 is a prominent cell surface ligand, for example, for cholera toxin or tumor growth‐regulatory homodimeric galectins. This activity profile via protein recognition prompted us to examine the binding properties of peptides with this specificity. Our study provides insights into the mechanism of molecular interaction of this thus far unexplored size limit of the protein part. We used three pentadecapeptides in a combined approach of mass spectrometry, NMR spectroscopy and molecular modelling to analyze the ligand binding in solution. Availability of charged and hydrophobic functionalities affected the intramolecular flexibility of the peptides differently. Backfolding led to restrictions in two cases; the flexibility was not reduced significantly by association of the ligand in its energetically privileged conformations. Major contributions to the interaction energy arise from the sialic acid moiety contacting Arg/Lys residues and the N‐terminal charge. Considerable involvement of stacking between the monovalent ligand and aromatic rings could not be detected. This carbohydrate binding strategy is similar to how an adenoviral fiber knob targets sialylated glycans. Rational manipulation for an affinity enhancement can now be directed to reduce the flexibility, exploit the potential for stacking and acquire the cross‐linking capacity of the natural lectins by peptide attachment to a suitable scaffold.
Hydrogen Bonding and Dynamic Behaviour in Crystals and Polymorphs of Dicarboxylic–Diamine Adducts: A Comparison between NMR Parameters and X‐ray Diffraction Studies
Authors: Gobetto Roberto , Nervi Carlo , Chierotti Michele R. , Braga Dario , Maini Lucia , Grepioni Fabrizia , Harris Robin K. , Hodgkinson Paul 
Published: November 2005

AbstractFumaric, malonic, maleic, and hydromuconic (HOOCCH2(CH)2CH2COOH) acids were used to prepare a series of hydrogen‐bonded adducts or salts, depending on whether acid–base proton transfer takes place, with the dibase [N(μCH2CH2)3N] in various stoichiometric ratios. The resulting compounds have been investigated by using the 1H MAS, 15N, and 13C cross polarisation magic‐angle spinning (CPMAS) methods and discussed in relation to X‐ray diffraction studies to ascertain the nature of the O‐H⋅⋅⋅O, N⋅⋅⋅H‐O, and N+‐H⋅⋅⋅O− hydrogen bonds between the various species. In addition, two polymorphic forms of the malonic compound and a hydrate in the maleic case were examined. We also present the correlations between the chemical shifts of the hydrogen‐bonded protons and those from the proton transfer reaction (acid‐to‐base) with the heavy atom distances. The dynamic behaviour in the solid‐state of the [N(μCH2CH2)3N] adducts with fumaric 2:1, maleic 1:1 hydrate, and hydromuconic acids, and a malonate 2:1 polymorph adduct have been investigated by using variable‐temperature 1H spin–lattice relaxation times. A substantial agreement between the activation energies obtained from fitting the T1 data and the results of potential energy barrier calculations demonstrates that the facile reorientation of the [N(μCH2CH2)3N] molecule occurs in several of the adducts.
Zinc Hydrazides and Alkoxyhydrazides: Organometallic Compounds with Novel Zn4N8, Zn4N6O and Zn4N4O2 Cage Structures
Authors: Jana Surajit , Fröhlich Roland , Mitzel Norbert W. 
Published: November 2005

AbstractTetrameric [{RZn(NHNMe2)}4] (R = Me, Et), the first organometallic zinc hydrazides to be described, have been prepared by alkane elimination from dialkylzinc solutions and N,N‐dimethylhydrazine. They were characterised by 1H and 13C NMR and IR spectroscopy, mass spectrometry, elemental analysis and X‐ray crystallography. The compounds form asymmetric aggregates containing the novel Zn4N8 core; tetrahedra of Zn atoms bear the alkyl groups at Zn, with the triangular faces bridged by NHNMe2 substituents. The NH groups are connected to two Zn atoms, and the NMe2 groups to one. Hydrolysis of the compounds with water gives [(RZn)4(OH)(NHNMe2)3] as products, which also were characterised as described above. Higher yields of these hydroxo clusters were achieved in one‐pot syntheses by reaction of dialkylzinc solutions with mixtures of N,N‐dimethylhydrazine and water. They contain Zn4N6O cages, in which one hydroxide in the tetrameric hydrazides described above replaces one NHNMe2 group. Similar products can be prepared with alkoxy instead of hydroxy groups, in analogous one‐pot syntheses with alcohols. Alcoholysis of [EtZn(NHNMe2)]4 with methanol or ethanol gave zinc trishydrazide monoalkoxides, [(EtZn)4(OR)(NHNMe2)3] (R = Me, Et), which have constitutions analogous to the monohydroxides. The organozinc bishydrazide bisalkoxides [(MeZn)4(NHNMe2)2(OEt)2] and [(EtZn)4(NHNMe2)2(OEt)2] were obtained in one‐pot reactions from dialkylzinc solutions with mixtures of the hydrazine and alcohol, and their crystal structures, confirmed by spectroscopic methods in solution, show an unsymmetrical aggregation with the novel Zn4N4O2 cage structure.
Total Synthesis of Phorboxazole B
Authors: Li De‐Run , Zhang Dong‐Hui , Sun Cai‐Yun , Zhang Ji‐Wen , Yang Li , Chen Jian , Liu Bo , Su Ce , Zhou Wei‐Shan , Lin Guo‐Qiang 
Published: November 2005

AbstractAn efficient and highly convergent total synthesis of the potent antitumor agent phorboxazole B has been achieved. The synthetic strategy of this synthesis features: 1) a highly efficient substrate‐controlled hydrogenation to construct the functionalized cis‐tetrahydropyrane unit; 2) iterative crotyl addition to synthesize the segment that contains alternating hydroxyl and methyl substituents; 3) Hg(OAc)2/I2‐induced cyclization to establish the cis‐tetrahydropyrane moiety; 4) 1,3‐asymmetric induction in the Mukaiyama aldol reaction to afford the stereogenic centers at C9 and C3; and 5) the exploration of the Still–Gennari olefination reaction to complete the macrolide ring of phorboxazoloe B.
Nitrogen Fixation under Mild Ambient Conditions: Part I—The Initial Dissociation/Association Step at Molybdenum Triamidoamine Complexes
Authors: Le Guennic Boris , Kirchner Barbara , Reiher Markus 
Published: November 2005

AbstractIn several recent studies Schrock and collaborators demonstrated for the first time how molecular dinitrogen can be catalytically transformed under mild and ambient conditions to ammonia by a molybdenum triamidoamine complex. In this work, we investigate the geometrical and electronic structures involved in this process of dinitrogen activation with quantum chemical methods. Density functional theory (DFT) has been employed to calculate the coordination energies of ammonia and dinitrogen relevant for the dissociation/association step in which ammonia is substituted by dinitrogen. In the DFT calculations the triamidoamine chelate ligand has been modeled by a systematic hierarchy of increasingly complex substituents at the amide nitrogen atoms. The most complex ligand considered is an experimentally known ligand with an HMT=3,5‐(2,4,6‐Me3C6H2)2C6H3 substituent. Several assumptions by Schrock and collaborators on key reaction steps are confirmed by our calculations. Additional information is provided on many species not yet observed experimentally. Particular attention is paid to the role of the charge of the complexes. The investigation demonstrates that dinitrogen coordination is enhanced for the negatively charged metal fragment, that is, coordination is more favorable for the anionic metal fragment than for the neutral species. Coordination of N2 is least favorable for the cationic metal fragment. Furthermore, ammonia abstraction from the cationic complex is energetically unfavorable, while NH3 abstraction is less difficult from the neutral and easily feasible from the anionic low‐spin complex.
An Electrochemical Study of the Interactions Between Trace Metals and Humic Substances in Freshwaters by Anodic Stripping Voltammetry with a Thin Mercury Film Rotating Disk Electrode
Authors: Murimboh Catherine A. , Deng Jianfu , Murimboh John , Guthrie Jeffrey W. , Chakrabarti Chuni L. , Lean David R. S. 
Published: November 2005

AbstractAn improved theoretical approach to Anodic Stripping Voltammetry with a Thin Mercury Film Rotating Disk Electrode for elucidating the nature of the interactions of Pb(II), Cd(II) and Zn(II) with humic substances in model solutions of Laurentian fulvic acid, and of Pb(II), Cd(II), Zn(II) and Cu(II) in freshwaters, is presented. Conditional stability constants of Pb(II), Cd(II) and Zn(II) complexes decreased with the ionic potential (z2/r) and increased with softness of the metal ion, indicating strong affinity of soft, polarizable donor ligands on humic substances for softer metal ions, resulting in an appreciable covalent character in electrostatic bonding between the metals and humic substances.
Development and Characterization of Nickel‐NTA‐Polyaniline Modified Electrodes
Authors: Lori Joseph A. , Morrin Aoife , Killard Anthony J. , Smyth Malcolm R. 
Published: November 2005

AbstractThe engineered addition of hexa‐histidine sequences to biomolecules such as antibody fragments has been found to be an excellent means of purifying these materials. This tagging methodology has also been extended to its use as a tool for immobilization and orientation of antibodies on transducer surfaces. Polyvinyl sulfonate‐doped polyanilne (PANI/PVS) can be used as a mediator in amperometric biosensors. This short communication looks at the effect of nickel chelate materials and nickel chelation on this conducting polymer and evaluates it as a potential surface for the immobilization of his‐tagged biomolecules. N‐nitrilotriacetic acid (NTA) was doped into the electropolymerized PANI/PVS at a screen‐printed carbon paste electrode. The resulting NTA‐PANI/PVS film was shown to have comparable electrochemical properties of polymer without the chelating agent. When Ni2+ was applied to the electrode, the incorporated NTA was found to efficiently chelate the metal ions at the electrode surface.
Electrocatalytic Reduction and Determination of Dissolved Oxygen at a Preanodized Screen‐Printed Carbon Electrode Modified with Palladium Nanoparticles
Authors: Yang Chih‐Chio , Kumar Annamalai Senthil , Zen Jyh‐Myng 
Published: November 2005

AbstractEfficient and stable electrocatalytic activity for the reduction of O2 at activated screen‐printed carbon electrodes modified with palladium nanoparticles (SPE*‐Pd) was demonstrated in this study. X‐ray photoelectron spectroscopy confirmed the formation of >CO functional group on electrode surface during the preanodization procedure at 2.0 V (vs. Ag/AgCl). The existence of chloride moieties was also identified possibly from the organic binder of carbon ink used in SPE fabrication. Both >CO and chloride functional groups were essential for the excellent stability of the SPE*‐Pd. Electrochemical impedance spectroscopy verified the enhanced kinetic rate of oxygen reduction reaction at the as‐prepared Pd nanoparticles. The SPE*‐Pd showed ca. 250 mV positive shift in peak potential together with twice increase in peak current compared to those observed at a SPE‐Pt. The calibration plot was linear up to 8 ppm of DO with sensitivity and regression coefficient of 4.49 μA/ppm and 0.9936, respectively. The variation coefficient of ipc for 7 DO determinations with O2‐saturated pH 7.4 PBS was 2.1%. Real sample assays for ground and tap waters gave consistent values to those measured by a commercial dissolved oxygen meter.
Methanol Tolerant Oxygen Reduction Catalysts Derived from Electrochemically Pre‐treated Bi2Pt2–yIryO7 Pyrochlores
Authors: Beck N. K. , Steiger B. , Scherer G. G. , Wokaun A. 
Published: November 2005

AbstractThe electrocatalytic activity for oxygen reduction on Bi2Pt2–yIryO7 (y = 0, 0.5, 1, 1.3, 1.4, 1.5, 2) electrodes was examined in 0.5 M H2SO4 in the presence and absence of 0.5 M methanol, using the rotating ring‐disk electrode technique. These pyrochlore electrodes exhibited oxygen reduction activity with an onset potential at ca. 0.2 V vs. Hg/Hg2SO4 only after pre‐treatment of potential cycling between –0.6 and 0.6 V vs. Hg/Hg2SO4. This “activation” of the pyrochlores is initiated by a reduction process that produces Bi0 and Pt0 at potentials located near the negative limit of the potential cycling range. Depending on the amount of pyrochlore used to fabricate the electrodes and the amount of charge passed during the reductive “activation”, a thick layer of a Pt containing material that differs from the pyrochlore structure may be produced. A pre‐treatment of potential cycling between –0.3 and 0.8 V vs. Hg/Hg2SO4 did not “activate” the pyrochlores. The oxygen reduction activity and the methanol oxidation activity of the electrochemically treated pyrochlores increased in the order: Bi2Pt0.5Ir1.5O7 < Bi2Pt0.6Ir1.4O7 < Bi2Pt0.7Ir1.3O7 < Bi2PtIrO7 < Bi2Pt1.5Ir0.5O7 < Bi2Pt2O7. Electrochemically treated Bi2Ir2O7 exhibited no catalytic activity.
Alternative Catalysts and Carbon Support Material for PEMFC
Authors: Wikander K. , Ekström H. , Palmqvist A. E. C. , Lundblad A. , Holmberg K. , Lindbergh G. 
Published: November 2005

AbstractIn order to investigate the possibility of increasing the reactivity for oxygen reduction reaction (ORR) of the cathode in a PEMFC a series of Pt/C catalysts was prepared using water‐in‐oil microemulsions for synthesizing Pt nanoparticles. The Pt nanoparticles were deposited on porous carbon support (Vulcan XC‐72 or a mesoporous carbon) and the catalysts were processed into MEAs. The MEA samples were evaluated and compared with a commercial sample and with Pt/C catalyst samples prepared using a conventional direct impregnation method. The mesoporous carbon support investigated as a potential alternative to Vulcan XC‐72 has a very high specific surface area and a narrow pore size distribution. The materials were characterized with XRD, TEM, SEM‐EDX, N2 sorption and steady state polarization. It was found that it is possible to increase the ORR reactivity using the microemulsion route for formation of Pt nanoparticles. It was concluded that the MEA processing conditions for the mesoporous carbon support have to be modified to reach improved ORR reactivity, likely due to the large differences in specific surface area, porosity and conductivity compared to the Vulcan carbon.
Protonic Electroceramics for Fuel Cells
Authors: Boehm E. , McEvoy A. J. 
Published: November 2005

AbstractWhereas the conventional solid oxide fuel cell uses an oxygen‐ion conducting electroceramic, materials also exist which, at least over a restricted temperature range, perform as hydrogen ion, or proton, conductors. In principle, solid oxide fuel cells based on these materials are possible. With increasing temperature some degree of oxygen ion mobility is also observed, so that these materials are then mixed ionic conductors. The electrochemical characteristics observed may be influenced strongly by the choice and structure of the contacting electrode material. The open‐circuit voltage for example may be significantly less than that indicated by thermodynamics. In addition the external faradaic efficiency of ionic devices based on mixed conductivity electroceramics may also be reduced. The effects relate to the selectivity of the interface for charge exchange by the diverse carriers. Some results on perovskite cathodic materials contacting cerate protonic conductors are presented.
Electrochemical Impedance and X‐Ray Absorption Spectroscopy (EXAFS) as In‐Situ Methods to Study the PEMFC Anode
Authors: Mazurek M. , Benker N. , Roth C. , Buhrmester T. , Fuess H. 
Published: November 2005

AbstractThe effect of alloy formation on the performance of carbonsupported Pt and Ru fuel cell catalysts has been investigated by electrochemical impedance spectroscopy (EIS), X‐ray absorption spectroscopy (EXAFS) and fuel cell tests. The CO tolerance of the respective anode electrocatalysts has been tested in both reformate and methanol operation. This paper describes results for mixtures of carbon‐supported Pt and carbon‐supported Ru catalysts. The particle sizes of the active metals have been modified by heat‐treatment in nitrogen. It has been observed that the size of Pt and Ru particles has a significant influence on the electrochemical performance, the activity improving for smaller Ru particles. The performance of certain Pt‐Ru mixtures in a single cell fuel cell is comparable with an alloy catalyst.
Arterial spin labeling in small animals: Methods and applications to experimental cerebral ischemia
Authors: Thomas David L. 
Published: November 2005

AbstractASL enables noninvasive, quantitative monitoring of cerebral perfusion to be performed repeatedly over a period of hours. Thus, ASL is an attractive method for basic science studies of the time evolution and pathophysiology of diseases using animal models. In particular, ASL is valuable for basic science studies of evolving tissue status and viability in stroke using animal models of acute ischemia. This study describes both pulsed (PASL) and continuous ASL (CASL) studies of quantitative cerebral perfusion in rodent models of cerebral ischemia. Some technical factors pertinent to these studies are discussed, including a method for measuring arterial blood T1 and double‐echo PASL for measuring cerebral blood flow (CBF) and volume (CBV). Investigations of the CBF response to forebrain ischemia and reperfusion, and of regional variations in CBF and arterial transit time (ATT) are also discussed. J. Magn. Reson. Imaging 2005. © 2005 Wiley‐Liss, Inc.
Genetic, clinical, and imaging characterization of one patient with late‐onset, slowly progressive, pantothenate kinase‐associated neurodegeneration
Authors: Antonini Angelo , Goldwurm Stefano , Benti Riccardo , Prokisch Holger , Ebhardt Monika , Cilia Roberto , Zini Michela , Righini Andrea , Cossu Giovanni , Pezzoli Gianni 
Published: November 2005

AbstractWe report on a patient with late‐onset, pantothenate kinase‐associated neurodegeneration (PKAN) who revealed two new heterozygous mutations at gene testing and showed asymmetric moderately reduced striatal dopamine transporter binding with single photon emission computed tomography, possibly due to prolonged neuroleptic treatment. These findings expand the genetic and imaging spectrum of this rare disorder. © 2005 Movement Disorder Society
Clinical and genetic study of a Brazilian family with spastic paraplegia (SPG6 locus)
Authors: Munhoz Renato P. , Kawarai Toshitaka , Teive Helio A. , Raskin Salmo , Sato Christine , Liang Yan , St. George‐Hyslop Peter H. , Rogaeva Ekaterina 
Published: November 2005

AbstractWe describe a Brazilian family in which inheritance of a G106R mutation in the SPG6 gene (also know as NIPA1) resulted in an autosomal dominant form of hereditary spastic paraplegia (ADHSP). Clinical investigations indicated that this family has a pure form of spastic paraplegia. All patients presented with gait difficulty in their twenties, progressing to frank spastic paraplegia during the next decade. Our report further supports evidence that mutations in SPG6 cause ADHSP. © 2005 Movement Disorder Society
A method for modal reanalysis of topological modifications of structures
Authors: Yang Zhi Jun , Chen Su Huan , Wu Xiao Ming 
Published: November 2005

AbstractA method for structural modal reanalysis for three cases of topological modifications, the number of degrees of freedom (DOFs) is unchanged, decreased, and increased, is presented. In this method, the newly added DOFs are linked to the original DOFs of the modified structure by means of the dynamic reduction so as to obtain the condensed equation. The methods for forming the stiffness and mass increments, ΔK and ΔM, resulting from the three cases of topological modifications of structures are discussed. The extended Kirsch method is used to improve the accuracy of the starting solutions of the initial structure. And then, the eigenvectors of newly added DOFs resulting from topological modification can be recovered. At last, the Rayleigh–Ritz analysis is used to evaluate the eigenvalues and eigenvectors for the modified structure. Three numerical examples are given to illustrate the applications of the present approach. The results show that the proposed method is effective for structural modal reanalysis of three cases of the topological modifications and it is easy to implement on a computer. By comparing with previous method, it can be seen that the present method can give good approximate eigenvalues and eigenvectors, even if the topological modifications are very large. Copyright © 2005 John Wiley & Sons, Ltd.
Isothermal crystallization and spherulite nucleation in blends of polypropylene with metallocene‐prepared polyethylene
Authors: Razavi‐Nouri Mohammad , Hay James N 
Published: November 2005

AbstractThe isothermal crystallization behavior and morphology of a polypropylene (PP)‐based copolymer, a metallocene‐prepared linear low‐density polyethylene (M‐LLDPE) and their three 10/90, 30/70 and 50/50 M‐LLDPE/PP blends have been investigated. The PP and M‐LLDPE contained 5 ethylene and 3.3 mol% hexene‐1 as a comonomer, respectively. Isothermal crystallization studies revealed a different temperature‐dependence on crystallization for M‐LLDPE, PP and their blends and the crystallization half‐life for the M‐LLDPE was higher than either PP or the blends at a certain temperature. The PP‐rich blends also showed a quite similar crystallization rate to that of PP. Investigations on the variation of spherulite growth rate of PP in the blends at different temperatures revealed no significant change and was quite independent of the amount of M‐LLDPE being employed. The morphology studies revealed that the nucleation densities of the PP spherulites decreased by introducing M‐LLDPE into PP and the M‐LLDPE remained as discrete droplets dispersed throughout the PP spherulites. The results obtained were consistent with no miscibility between the two components. Copyright © 2005 Society of Chemical Industry
Characterization of a laser‐nitrided titanium alloy by electron backscattered diffraction and electron probe microanalysis
Authors: Gordin D. M. , Gloriant T. , Bohn M. , Guillou A. , Thibon I. , Ansel D. 
Published: November 2005

AbstractAfter a laser gas nitriding treatment of the Ti‐7.5Al (atom %) titanium‐based alloy, we used a combination of electron backscattered diffraction (EBSD) in scanning electron microscope and electron probe microanalysis (EPMA) techniques in order to efficiently characterize the different phases in the resolidified layer. Representative measurements of chemical composition and reliable determination of crystal structure were possible for each phase of the complex microstructure. The reaction zone is formed by a mixture of isostructural TiN phases with dendritic and/or ‘coarse’ needles morphology, fixed into a α′‐Ti matrix (martensite) with a thin needle aspect. The nitrogen solubility was found to remain very low in the α′‐Ti matrix (up to 2–3 atom %), while in the TiN phase, an aluminum solubility as high as 4 atom % was measured, reducing drastically the nitrogen content into a Ti79N17Al4 chemical composition. Copyright © 2005 John Wiley & Sons, Ltd.