bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Case of anti Carbolithiation of Alkynes Resulting from Intramolecular Lithium Coordination
Authors: Fressigné Catherine , Girard Anne‐Lise , Durandetti Muriel , Maddaluno Jacques 
Published: April 2008

AbstractThe mechanism of the intramolecular carbolithiation of lithiated propargylic ether 2 has been investigated both experimentally and theoretically. The results show that the action of one equivalent of n‐butyllithium on 1 is sufficient to trigger halogen–lithium exchange and the subsequent heterocyclization step. Interestingly, the reaction stops at the stage of dihydrobenzofuran 6; no spontaneous elimination of lithium ethylate was observed. The fact that the E configuration of this adduct was exclusively produced suggests that the reaction proceeds by following an unprecedented anti addition on the alkyne. According to DFT calculations, this unexpected outcome is related to the intramolecular coordination of the lithium by one oxygen atom of the terminal acetal appendage: the O–Li interaction, which persists all along the ring‐closure process, drives the cation to the E site of the final olefin. The calculations also show that in the absence of this coordination (as in conformers B and C of acetal 2), the Z olefin that results from a classical syn addition of the aryllithium should be obtained. The experiments were repeated with allene 1 d. In this case, one equivalent of n‐butyllithium suffices to trigger not only the exchange and the cyclization, but also the final elimination of lithium ethoxide. The DFT results indicate that the intramolecular addition of the original aryllithium on the central carbon atom of the allene 2 b yields the expected benzofuran skeleton 3 b, which bears a lithiated lateral chain at the 3‐position. Both cyclizations go through low‐lying transition states, as is expected for rapid reactions at low temperature.
Cowpea Mosaic Virus Capsid: A Promising Carrier for the Development of Carbohydrate Based Antitumor Vaccines
Authors: Miermont Adeline , Barnhill Hannah , Strable Erica , Lu Xiaowei , Wall Katherine A. , Wang Qian , Finn M. G. , Huang Xuefei 
Published: April 2008

AbstractImmunotherapy targeting tumor cell surface carbohydrates is a promising approach for cancer treatment. However, the low immunogenecity of carbohydrates presents a formidable challenge. We describe here the enhancement of carbohydrate immunogenicity by an ordered display on the surface of the cowpea mosaic virus (CPMV) capsid. The Tn glycan, which is overexpressed on numerous cancer cell surfaces, was selected as the model antigen for our study. Previously it has been shown that it is difficult to induce a strong T cell‐dependent immune response against the monomeric form of Tn presented in several ways on different carriers. In this study, we first synthesized Tn antigens derivatized with either a maleimide or a bromoacetamide moiety that was conjugated selectively to a cysteine mutant of CPMV. The glycoconjugate was then injected into mice and pre‐ and post‐immune antibody levels in the mice sera were measured by enzyme‐linked immunosorbant assays. High total antibody titers and, more importantly, high IgG titers specific for Tn were obtained in the post‐immune day 35 serum, suggesting the induction of T cell‐dependent antibody isotype switching by the glycoconjugate. The antibodies generated were able to recognize Tn antigens presented in their native conformations on the surfaces of both MCF‐7 breast cancer cells and the multidrug resistant breast cancer cell line NCI‐ADR RES. These results suggest that the CPMV capsid can greatly enhance the immunogenicity of weak antigens such as Tn and this can provide a promising tool for the development of carbohydrate based anti‐cancer vaccines.
Chiral Bisphosphazides as Dual Basic Enantioselective Catalysts
Authors: Naka Hiroshi , Kanase Nobuhiko , Ueno Masahiro , Kondo Yoshinori 
Published: April 2008

AbstractChiral bisphosphazides complexed with lithium salts efficiently catalyze the direct enantioselective 1,4‐addition of dialkyl malonates to acyclic enones. Spectroscopic studies on the stoichiometry of the bisphosphazide and lithium salt have indicated the formation of a 1:1 species as the active enantioselective catalyst. It is suggested that the catalyst generates a complex of the protonated phosphazide and the chiral nucleophile as the key intermediate. The phosphazide moiety appears to be a promising dual basic functionality for stereo‐ and chemoselective catalytic transformations.
Selective Formation of 2‐Imidazolines and 2‐Substituted Oxazoles by Using a Three‐Component Reaction
Authors: Elders Niels , Ruijter Eelco , de Kanter Frans J. J. , Groen Marinus B. , Orru Romano V. A. 
Published: April 2008

AbstractSelective formation of 2H‐2‐imidazolines and 2‐substituted oxazoles by using a multicomponent reaction of amines, either aldehydes or ketones, and α‐acidic isocyano amides or esters is described. By selecting the appropriate solvent, AgI or CuI catalyst, or by employing a weak Brønsted acid, the product formation can be fully controlled and directed quantitatively to the desired heterocyclic scaffold. The described experimental procedures not only significantly increase the scope of compatible inputs for this complexity‐generating three‐component reaction, but also allow for considerable chemical diversity: At least four diversity points in two distinct scaffolds can be exploited in this way.
Ein Gleichnis für den Chemieunterricht
Authors: Richter Harald , Schmidkunz Heinz , Kreher Richard P. 
Published: April 2008

AbstractSteht im Chemieunterricht der Sekundarstufe 2 das Thema Reaktionskinetik an, dann sollten auch Konkurrenzreaktionen in die Unterrichtsgestaltung einbezogen werden. Zum Einstieg in dieses Thema empfiehlt es sich, an einen gängigen (meist bereits in der Sekundarstufe 1 eingeführten) Sprachgebrauch zu erinnern: „Es gibt ungesättigte Kohlenwasserstoffe, die durch vollständige Addition von Wasserstoff oder Brom gesättigt werden.”︁ Bei einer verständlichen Planung der Lehrkräfte können die animistischen Hintergründe dieser Redensart Schüler und Schülerinnen motivieren, die Reaktivitäten von zwei verschiedenen Alkenen bei einer Konkurrenzreaktion mit Spannung zu betrachten.
Das Projekt Forscher Ferien
Authors: Demuth Reinhard , Efler‐Mikat Daniela , Kleinert Katrin 
Published: April 2008

AbstractMit dem Forscher Ferien‐Projekt ist der Versuch unternommen worden, eine Kompensation von Lerndefiziten durch außerschulische Lernangebote vorzunehmen. Dieser Beitrag stellt das Projekt vor und gibt einen ersten Erfahrungsbericht über die „Forscher Ferien”︁.
Two Cases with Similar Pseudoaneurysms but Different Outcomes
Authors: Bildirici Ulaş , Agacdiken Aysen , Ural Ertan , Kahraman Goksel , Komsuoglu Baki 
Published: April 2008

AbstractThe pseudoaneurysm is a rare cardiac pathology, in which the left ventricular free wall ruptures and the pericardium surrounds the rupture in combination with thrombus and inflammation and thus prevents the development of a hemopericardium. Left ventricular pseudoaneurysm may remain silent unless it gives rise to cardiac tamponade, collapse, and finally sudden death. In this case report, we present two cases with left ventricular pseudoaneurysms in the same area. One of them had a stable outcome and the other had a fatal outcome. Copyright © 2008 Wiley Periodicals, Inc.
Theory of diffraction from eukaryotic flagellar axonemes
Authors: Iwamoto Hiroyuki 
Published: April 2008

AbstractExisting theories for diffraction from cylindrically symmetrical and helical objects are applied to the axonemes of eukaryotic flagella and cilia, motile organelles responsible for locomotion of cells, transportation of food and mucus, etc. Each axoneme has a scaffold of microtubules arranged in the “9 + 2” scheme. Motor proteins dynein and other proteins are associated with the scaffold with apparent axial periodicities, and their exact arrangement would be best explored by X‐ray diffraction. Here, various symmetries are assumed (helical and nonhelical) in the arrangement of these proteins, and the reflections that will emerge are predicted, hereby providing a practical means to analyze diffraction patterns currently being recorded in the latest synchrotron radiation facilities. Cell Motil. Cytoskeleton 2008. © 2008 Wiley‐Liss, Inc.
Molecular and developmental biology of the hemangioblast
Authors: Xiong Jing‐Wei 
Published: April 2008

AbstractThe hemangioblast hypothesis was proposed a century ago. The existence of hemangioblasts is now demonstrated in mouse and human embryonic stem cell (ESC) ‐derived embryoid bodies (EBs), in the mouse and zebrafish gastrula, and in adults. The hemangioblast is believed to derive from mesodermal cells, and is enriched in the Bry+Flk1+ and Flk1+Scl+ cell populations in EBs and in the posterior primitive streak of the mouse gastrula and in the ventral mesoderm of the zebrafish gastrula. However, recent studies suggest that the hemangioblast does not give rise to all endothelial and hematopoietic lineages in mouse and zebrafish embryos. Although several signaling pathways are known to involve the generation of hemangioblasts, it remains largely unknown how the hemangioblast is formed and what are the master genes controlling hemangioblast development. This review will summarize our current knowledge, challenges, and future directions on molecular and developmental aspects of the hemangioblast. Developmental Dynamics 237:1218–1231, 2008. © 2008 Wiley‐Liss, Inc.
Synthesis of Enantiopure Ruthenium Tricarbonyl Complexes of a Bicyclic Cyclopentadienone Derivative
Authors: Kim Min‐soo , Lee Jun Won , Lee Jae Eun , Kang Jahyo 
Published: April 2008

Abstract(–)‐Menthone was converted stereoselectively into 3‐menthylpropargyl alcohol 8 in several steps and subsequently converted into enantiopure cyclopentadienone ruthenium carbonyl complexes. In the malonate cases, ruthenacycle 15 was also formed during the cyclization reaction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Transition‐Metal‐Free Synthesis of Perdeuterated Imidazolium Ionic Liquids by Alkylation and H/D Exchange
Authors: Giernoth Ralf , Bankmann Dennis 
Published: April 2008

AbstractEconomic, transition‐metal‐free syntheses of partially or completely deuterated imidazolium ionic liquids (ILs) were developed. Double alkylation starting from imidazole afforded side‐chain deuterated imidazolium ionic liquids, which subsequently were fully deuterated by H/D‐exchange on the cation ring. Isotopic exchange was studied for a range of ionic liquids, solvents and bases. Here, the presence of small amounts of basic impurities was found to significantly affect the exchange behaviour.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
The Tetracyanoquinodimethane Motif in Overcrowded Bistricyclic Aromatic Enes: Avoiding Thermochromism
Authors: Pogodin Sergey , Suissa Michal Rachel , Levy Amalia , Cohen Shmuel , Agranat Israel 
Published: April 2008

AbstractThe overcrowded bistricyclic aromatic enes (BAEs) [10‐[10‐(dicyanomethylene)‐9(10H)‐anthracenylidene]‐9(10H)‐anthracenylidene]propanedinitrile (7) and [10‐[10‐oxo‐9(10H)‐anthracenylidene]‐9(10H)‐anthracenylidene)]propanedinitrile(8) were synthesized by a condensation of bianthrone (2) with malononitrile in the presence of TiCl4 and pyridine. The crystal and molecular structure of 7 were determined. It crystallizes in two polymorphic forms, belonging to the space groups P21/c and P21/n. DFT calculations of 7 and 8 show that the overcrowding due to introducing dicyanomethylene substituents to 10 and 10′ positions is more pronounced in the twisted conformations, decreasing their stabilities. The enthalpy differences between the anti‐folded and the lowest lying twisted conformations in BAEs 7 and 8 are 61.3 and 42.3 kJ/mol, respectively. In accordance with theory, BAEs 7 and 8 do not exhibit thermochromic behavior. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Application of capillary zone electrophoresis for separation of water‐soluble gold monolayer‐protected clusters
Authors: Lo Chung Keung , Paau Man Chin , Xiao Dan , Choi Martin M. F. 
Published: April 2008

AbstractAn effective capillary electrophoretic technique for separating samples of negatively charged, polydisperse, water‐soluble gold monolayer‐protected cluster (Au MPC) protected by monolayers of N‐acetyl‐L‐cysteine has been developed. The separation mechanisms of the Au MPC in CZE suggest that the larger core sizes Au MPC emerge first from the capillary. The electrophoretic separation depends on pH, buffer concentration, and organic modifiers. The addition of aliphatic alcohols to the run buffer can improve the separation of Au MPC by reducing the EOF and changing the selectivity between the Au MPCs. The enhancement of resolution is attributed to the more significant difference in the charge‐to‐size ratio between the Au MPCs. The run buffer containing 20 v/v % ethanol provides the best separation for water‐soluble Au MPC. Our proposed CE method provides a powerful tool to evaluate and separate the water‐soluble Au MPC products.
Capillary electrophoresis chemiluminescent detection system equipped with a two‐step postcolumn flow interface for detection of some enkephalin‐related peptides labeled with acridinium ester
Authors: Guo Longhua , Qiu Bin , Jiang Yingyan , You Zuyao , Lin Jin‐Ming , Chen Guonan 
Published: April 2008

AbstractDespite its low equipment cost and simple design, as one of the sensitive detectors for CE, the chemiluminescence (CL) detector was less developed compared to the detectors of MS and LIF. The main reasons were the limitation of CL reagents, the repeatability problems and the relatively low sensitivity compared to LIF. In this paper, a highly sensitive CE‐CL detection system was developed for detection of some enkephalin‐related peptides labeled with acridinium ester. A new detection interface was designed for CE with CL detection of acridinium ester and its labeled analytes. The interface included two sections: one was used to acidify the capillary outflow so that the corresponding acridinium pseudo‐base form can be changed into acridinium ester form by adding excess acid to the system; the other was designed to provide a suitable solution to produce the CL from acridinium ester. The effect factors, such as pH, the concentration of reaction reagents and the flow rates of the reagents, were investigated. The results showed that acridinium ester had similar CL properties in this interface when pH values of CE BGE were changed from 2.0 to 10.8. The interface was used to detect acridinium ester and three acridinium ester‐labeled enkephalin‐related peptides, the corresponding LODs were found to be in the attomole range. This CL detection system proved to be of high sensitivity, good repeatability, and relatively low cost.
Consortium analysis of 7 candidate SNPs for ovarian cancer
Authors: Ramus Susan J. , Vierkant Robert A. , Johnatty Sharon E. , Pike Malcolm C. , Van Den Berg David J. , Wu Anna H. , Pearce Celeste Leigh , Menon Usha , Gentry‐Maharaj Aleksandra , Gayther Simon A. , DiCioccio Richard A. , McGuire Valerie , Whittemore Alice S. , Song Honglin , Easton Douglas F. , Pharoah Paul D.P. , Garcia‐Closas Montserrat , Chanock Stephen , Lissowska Jolanta , Brinton Louise , Terry Kathryn L. , Cramer Daniel W. , Tworoger Shelley S. , Hankinson Susan E. , Berchuck Andrew , Moorman Patricia G. , Schildkraut Joellen M. , Cunningham Julie M. , Liebow Mark , Kjaer Susanne Krüger , Hogdall Estrid , Hogdall Claus , Blaakaer Jan , Ness Roberta B. , Moysich Kirsten B. , Edwards Robert P. , Carney Michael E. , Lurie Galina , Goodman Marc T. , Wang‐Gohrke Shan , Kropp Silke , Chang‐Claude Jenny , Webb Penelope M. , Chen Xiaoqing , Beesley Jonathan , Chenevix‐Trench Georgia , Goode Ellen L. 
Published: April 2008

AbstractThe Ovarian Cancer Association Consortium selected 7 candidate single nucleotide polymorphisms (SNPs), for which there is evidence from previous studies of an association with variation in ovarian cancer or breast cancer risks. The SNPs selected for analysis were F31I (rs2273535) in AURKA, N372H (rs144848) in BRCA2, rs2854344 in intron 17 of RB1, rs2811712 5′ flanking CDKN2A, rs523349 in the 3′ UTR of SRD5A2, D302H (rs1045485) in CASP8 and L10P (rs1982073) in TGFB1. Fourteen studies genotyped 4,624 invasive epithelial ovarian cancer cases and 8,113 controls of white non‐Hispanic origin. A marginally significant association was found for RB1 when all studies were included [ordinal odds ratio (OR) 0.88 (95% confidence interval (CI) 0.79–1.00) p = 0.041 and dominant OR 0.87 (95% CI 0.76–0.98) p = 0.025]; when the studies that originally suggested an association were excluded, the result was suggestive although no longer statistically significant (ordinal OR 0.92, 95% CI 0.79–1.06). This SNP has also been shown to have an association with decreased risk in breast cancer. There was a suggestion of an association for AURKA, when one study that caused significant study heterogeneity was excluded [ordinal OR 1.10 (95% CI 1.01–1.20) p = 0.027; dominant OR 1.12 (95% CI 1.01–1.24) p = 0.03]. The other 5 SNPs in BRCA2, CDKN2A, SRD5A2, CASP8 and TGFB1 showed no association with ovarian cancer risk; given the large sample size, these results can also be considered to be informative. These null results for SNPs identified from relatively large initial studies shows the importance of replicating associations by a consortium approach. © 2008 Wiley‐Liss, Inc.
In vitro bioactivity of melt‐derived glass 46S6 doped with magnesium
Authors: Dietrich Elodie , Oudadesse Hassane , Lucas‐Girot Anita , Mami Mohamed 
Published: April 2008

AbstractMelt‐derived glasses in the system SiO2‐CaO‐Na2O‐P2O5 were synthesized pure or doped with magnesium from 0.4 to 1.2 wt %, for applications as biomaterials in bony surgery. This chemical element has been chosen because of its high physiological interest. Its introduction for different contents in melt derived glasses has never been studied. The bioactivity of glasses was assessed by immersion of the samples in the simulated body fluid solution. Changes in glass surface morphology and composition after immersion were evaluated by several physico‐chemical techniques. The aim of this work was to characterize the formation of the apatite‐like layer at the glass surface, after in vitro assays and to evaluate the kinetic reaction between the glass and the surrounding synthetic fluids. Results indicate that magnesium influences the formation and the evolution of the newly formed layers: (1) it promotes the dissolution of the silica network, (2) it increases the thickness of the silica gel layer formed conventionally prior to the apatite‐like layer, and (3) it slows down the crystallization of the apatite layer. However, the intensity of these effects depends on the content of magnesium introduced in the glass matrix. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Improvement of metal and tissue adhesion on surface‐modified parylene C
Authors: Wahjudi Paulin N. , Oh Jin H. , Salman Salam O. , Seabold Jason A. , Rodger Damien C. , Tai Yu‐Chong , Thompson Mark E. 
Published: April 2008

AbstractA general method for chemical surface functionalization of parylene C [PC, (para‐CH2‐C6H3Cl‐CH2‐)n] films is reported. Friedel‐Crafts acylation is used to activate the surface of the PC film, and the resulting carbonyl groups are then used to form a range of different organic functional groups to the surface of the parylene film, including alcohol, imine, thiol, phthalimide, amine, and maleimide. The presence of these functional groups on the parylene surface was confirmed by Fourier transform infrared spectroscopy. Static water drop contact angle measurements were also used to demonstrate the changes in hydrophilicity of the PC film surface, consistent with each of the surface modifications. Enhanced metal (gold) adhesion was achieved by anchoring a thiol group onto the acylated surface of PC film. Acylation of parylene with 2‐chloropropionyl chloride gave a surface bound chloropropionyl group. Grafting of poly‐N‐isopropylacrylamide (pNIPAM) onto the chloropropionyl substituted PC film via atom transfer radical polymerization (ATRP) was carried out. The grafted pNIPAM on the parylene surface leads to temperature‐dependent cellular tissue adhesion on the PC film. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
A new generation of high flex life polyurethane urea for polymer heart valve—Studies on in vivo biocompatibility and biodurability
Authors: Thomas Vinoy , Jayabalan Muthu 
Published: April 2008

AbstractDevelopment of new generation high flex life polyurethane urea (HFL18‐PU) with appropriate elastic modulus, biocompatibility, blood compatibility, resistant to calcification, and biodurability for the long‐term use as cardiac device is still a challenge. This study reports the development of a fully aliphatic, ether‐free physically cross‐linked and low elastic modulus (6.841 ± 0.27 MPa) polyurethane urea having in vivo biostability, in vivo biocompatibility and high flex‐life (721 ± 30 million cycles) that can satisfy the requirements for the fabrication of tri‐leaflet heart valve. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Biological response to micron‐ and nanometer‐sized particles known as potential wear products from artificial hip joints: Part I: Selection and characterization of model particles
Authors: Gemeinert M. , Dörfel I. , Griepentrog M. , Gross U. , Klaffke D. , Knabe C. , Kranz I. , Österle W. 
Published: April 2008

AbstractThe aim of this work was to select and characterize model particles, which correspond to real wear products from artificial hip joints, and to investigate the dispersing behavior of these powders. Commercially available nano and microparticles of corundum, graphite, and chromium oxide were selected or alternatively self‐produced by milling. These powders were characterized regarding density, specific surface area, crystalline phases, particle size distributions and shape. Volume‐based particle size distributions Q3(d) were measured after dispersing in water, water with dispersant, Ringers solution, and cell culture solution (Dulbecco's Modified Eagle's Medium (DMEM)) by laser diffraction and ultrasonic spectroscopy. Nanopowders formed agglomerates in the micrometer range in cell culture solutions. The micropowders showed only a marginal agglomeration. The median diameters of the dispersed nanopowders were even bigger than those of micropowders. Calculations of the number‐based size distribution Q0(d) showed that in spite of the agglomeration the predominant number of the nano and microparticles is in the sub micrometer range, with only one exception, the micrographite powder. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009