bluuebunny/crossref_metadata_2025_split huggingface dataset:
Desymmetrization of N‐Sulfonated Aziridines by Alkyllithium Reagents in the Presence of Chiral Ligands
Authors: Müller Paul , Riegert David , Bernardinelli Gérald 
Published: February 2004

AbstractThe stereochemical course of the rearrangement of the N‐sulfonylaziridines 5, 15, and 25 in the presence of s‐BuLi/(−)‐sparteine to the bicyclic sulfonamides 4, 16, and 17, respectively, has been investigated chemically and by X‐ray structure analysis. The absolute configurations of the products were, in all cases, opposite to those of the alcohols formed upon rearrangement of the corresponding epoxides. Similarily, the allylic sulfonamide 10, resulting from rearrangement of 7‐[(4‐methylphenyl)sulfonyl]‐7‐azabicyclo[4.1.0]heptane (7) under the same reaction conditions, had the (R)‐configuration, while cyclohexen‐3‐ol, obtained upon rearrangement of cyclohexene oxide, is known to be (S)‐configured. Deuterium labelling showed that the rearrangement of 7 proceeds via enantioselective α‐elimination to a carbene, which undergoes a 1,2‐H shift.
Triplet‐Sensitized Photodeprotection of Oligonucleotides in Solution and on Microarray Chips
Authors: Wöll Dominik , Walbert Stefan , Stengele Klaus‐Peter , Albert Tom J. , Richmond Todd , Norton Jason , Singer Michael , Green Roland D. , Pfleiderer Wolfgang , Steiner Ulrich E. 
Published: February 2004

AbstractConditions and kinetics of triplet sensitization as a method for increasing the light sensitivity of photolabile protecting groups used for the photolithographic synthesis of oligonucleotide microarrays were quantitatively studied with the photolabile 2‐(2‐nitrophenyl)propyl protecting group in homogeneous solutions and on glass substrates by using laser flash photolysis, continuous illumination with HPLC analysis, fluorescence dye labelling, and hybridization. In terms of efficiency and avoidance of chemical side reactions, 9H‐thioxanthen‐9‐one was the most‐suitable sensitizer. Both in solution and on a glass substrate, the photostationary kinetics were quantitatively modelled and the relevant kinetic parameters determined. While the sensitization kinetics was diffusion‐controlled both in solution and on the chip, the photostationary kinetics was essentially of zero order only on the chip because here the triplet‐quenching effect of the released photoproduct 2‐(2‐nitrophenyl)propene was suppressed as a consequence of the inhomogeneous reaction that took place in a narrow diffusion zone above the surface from where the photoproducts could quickly escape. The kinetic simulation allowed quantitative estimate of the density of reactive groups on the surface. It was further demonstrated that, with 9H‐thioxanthen‐9‐one as a sensitizer, high‐density oligonucleotide microarrays of high quality can be produced with one‐third of the normal exposure time.
New Triterpene Saponins from Acanthophyllum pachystegium
Authors: Haddad Mohamed , Miyamoto Tomofumi , Ramezani Mohammad , Lacaille‐Dubois Marie‐Aleth 
Published: February 2004

AbstractFour new triterpenoid saponins, pachystegiosides A (1), B (2), C (3), and D (4), were isolated from the roots of Acanthophyllum pachystegium K. H. Their structures were elucidated by means of a combination of homo‐ and heteronuclear 2D‐NMR techniques (COSY, TOCSY, NOESY, HSQC, and HMBC) and by FAB‐MS. The new compounds were characterized as 3‐O‐{O‐β‐D‐galactopyranosyl‐(1→2)‐O‐[β‐D‐xylopyranosyl‐(1→3)]‐β‐D‐glucuronopyranosyl}quillaic acid 28‐{O‐β‐D‐xylopyranosyl‐(1→3)‐O‐β‐D‐xylopyranosyl‐(1→4)‐O‐α‐L‐rhamnopyranosyl‐(1→2)‐O‐[3,4‐di‐O‐acetyl‐β‐D‐quinovopyranosyl‐(1→4)]‐β‐D‐fucopyranosyl}ester (1), 3‐O‐{O‐β‐D‐galactopyranosyl‐(1→2)‐O‐[β‐D‐xylopyranosyl‐(1→3)]‐β‐D‐glucuronopyranosyl}quillaic acid 28‐{O‐β‐D‐xylopyranosyl‐(1→3)‐O‐β‐D‐xylopyranosyl‐(1→4)‐O‐α‐L‐rhamnopyranosyl‐(1→2)‐O‐[4‐O‐acetyl‐β‐D‐quinovopyranosyl‐(1→4)]‐β‐D‐fucopyranosyl} ester (2), 3‐O‐{O‐β‐D‐galactopyranosyl‐(1→2)‐O‐[β‐D‐xylopyranosyl‐(1→3)]‐β‐D‐glucuronopyranosyl}quillaic acid 28‐{O‐β‐D‐xylopyranosyl‐(1→4)‐O‐α‐L‐rhamnopyranosyl‐(1→2)‐O‐[4‐O‐acetyl‐β‐D‐quinovopyranosyl‐(1→4)]‐β‐D‐fucopyranosyl} ester (3), and gypsogenic acid 28‐[O‐β‐D‐glucopyranosyl‐(1→2)‐O‐β‐D‐glucopyranosyl‐(1→6)‐O‐β‐D‐glucopyranosyl‐(1→3)‐β‐D‐galactopyranosyl] ester (4).
Structure‐based discovery of a new affinity ligand to pancreatic α‐amylase
Authors: Westerfors Maria , Tedebark Ulf , Andersson Hans O , Öhrman Sara , Choudhury Devapriya , Ersoy Oguz , Shinohara Yasuro , Axén Andreas , Carredano Enrique , Baumann Herbert 
Published: January 2004

AbstractA ligand useful for affinity capture of porcine pancreatic α‐amylase was found by virtual screening of the commercially available compound data base MDL® Available Chemicals Directory. Hits from the virtual screening were investigated for binding by nuclear magnetic resonance (NMR) and surface plasmon resonance. Selected compounds were tested for inhibition of the enzyme using a NMR‐based assay. One of the binders found was covalently coupled to a chromatographic resin and a column, packed with this resin, could retain α‐amylase, which subsequently was eluted by introduction of the known inhibitor acarbose to the elution buffer. Copyright © 2003 John Wiley & Sons, Ltd.
Molecular imprinting of nitrophenol and hydroxybenzoic acid isomers: effect of molecular structure and acidity on imprinting
Authors: Huang Xiaodong , Kong Liang , Li Xin , Zheng Chaojun , Zou Hanfa 
Published: January 2004

AbstractThree nitrophenol isomer‐imprinted polymers were prepared under the same conditions using 4‐vinylpyridine as a functional monomer. Different recognition capacities for template molecules were observed for the three polymers. Another imprinting system with stronger acidity than nitrophenol isomers, 2‐hydroxybenzoic acid (salicylic acid) and 4‐hydroxybenzoic acid, was imprinted using 4‐vinylpyridine or acrylamide as functional monomer respectively. Both 4‐hydroxybenzoic acid‐imprinted polymers using the two monomers showed recognition ability for the template molecule. However, when acrylamide was chosen as functional monomer, the salicylic acid‐imprinted polymer showed very weak recognition for the template molecule, whereas strong recognition ability of the resultant polymer for salicylic acid was observed with 4‐vinylpyridine as functional monomer. It seems that the structure and acidity of template molecules is responsible for the difference in recognition, by influencing the formation and strength of interaction between template molecule and functional monomer during the imprinting process. An understanding of the mechanism of molecular imprinting and molecular recognition of MIPs will help to predict the selectivity of MIPs on the basis of template molecule properties. Copyright © 2003 John Wiley & Sons, Ltd.
A survey of the year 2002 literature on applications of isothermal titration calorimetry
Authors: Cliff Matthew J. , Ladbury John E. 
Published: January 2004

AbstractIsothermal titration calorimetry (ITC) is becoming widely accepted as a key instrument in any laboratory in which quantification of biomolecular interactions is a requisite. The method has matured with respect to general acceptance and application development over recent years. The number of publications on ITC has grown exponentially over the last 10 years, reflecting the general utility of the method. Here all the published works of the year 2002 in this area have been surveyed. We review the broad range of systems to which ITC is being directed and classify these into general areas highlighting key publications of interest. This provides an overview of what can be achieved using this method and what developments are likely to occur in the near future. Copyright © 2003 John Wiley & Sons, Ltd.
A survey of the year 2002 commercial optical biosensor literature
Authors: Rich Rebecca L. , Myszka David G. 
Published: January 2004

AbstractWe have compiled 819 articles published in the year 2002 that involved commercial optical biosensor technology. The literature demonstrates that the technology's application continues to increase as biosensors are contributing to diverse scientific fields and are used to examine interactions ranging in size from small molecules to whole cells. Also, the variety of available commercial biosensor platforms is increasing and the expertise of users is improving. In this review, we use the literature to focus on the basic types of biosensor experiments, including kinetics, equilibrium analysis, solution competition, active concentration determination and screening. In addition, using examples of particularly well‐performed analyses, we illustrate the high information content available in the primary response data and emphasize the impact of including figures in publications to support the results of biosensor analyses. Copyright © 2003 John Wiley & Sons, Ltd.
Biosynthesis of tannase and gallic acid from tannin rich substrates by Rhizopus oryzae and Aspergillus foetidus
Authors: Mukherjee Gargi , Banerjee Rintu 
Published: February 2004

AbstractModified solid‐state fermentation (MSSF) of tannin‐rich substrates for production of tannase and gallic acid was carried out using two fungal cultures, Rhizopus oryzae (RO IIT RB‐13, NRRL 21498) and Aspergillus foetidus (GMRB013 MTCC 3557). The tannin rich substrates included powdered fruits of Terminalia chebula and Caesalpinia digyna pod cover powder. The different environmental parameters for the maximum production of tannase and gallic acid were optimized through media engineering. The highest yield of tannase and gallic acid was obtained after 60 h in case of Rhizopus oryzae and after 72 h by Aspergillus foetidus with 3 ml of induced inoculum. The optimum initial pH of the fermentation was found to be 4.5 in case of Rhizopus oryzae and 5.0 for Aspergillus foetidus. MSSF was carried out at the optimum conditions of 30 °C and 80% relative humidity. Collectively, the data reveal the potential of the modified solid‐state fermentation process for the production of tannase and gallic acid from tannin‐rich substrates with R. oryzae and A. foetidus.
Influence of retrogression and reaging on microstructure, mechanical properties and susceptibility to stress corrosion cracking of an Al‐Zn‐Mg alloy
Authors: Zieliński A. , Chrzanowski J. , Warmuzek M. , Gazda A. , Jezierska E 
Published: February 2004

AbstractThe aim of the present work was to determine the influence of the retrogression and reaging (RRA) heat treatment on the correlation between microstructure, mechanical properties and susceptibility to stress corrosion cracking (SCC) of the AlZn5Mg1 alloy in dry air and sea water. The alloy received in the T6 temper was subjected to 9 different heat treatments, including retrogression at temperature 453–513 K for 600–3600 s, and reaging at temperature 363 K or 403 K for 16 h, 24 h or 48 h. The susceptibility to SCC was investigated by slow strain rate tensile tests at 10−6 s−1 strain rate; change in time to failure, fracture energy and reduction in area were taken into account. Generally, the heat treatment improving mechanical properties increased susceptibility to SCC. The observed effects were discussed in terms of change in microstructure, especially size and distribution of phase precipitates. The role of change in dislocation network was the most likely of no importance.
Weak forms of elimination of imaginaries
Authors: Casanovas Enrique , Farré Rafel 
Published: February 2004

AbstractWe study the degree of elimination of imaginaries needed for the three main applications: to have canonical bases for types over models, to define strong types as types over algebraically closed sets and to have a Galois correspondence between definably closed sets B such that A ⊆ B ⊆ acl(A) and closed subgroups of the Galois group Aut(acl(A)/A). We also characterize when the topology of the Galois group is the quotient topology. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Static and free vibration analyses of rectangular plates by the new version of the differential quadrature element method
Authors: Wang Yongliang , Wang Xinwei , Zhou Yong 
Published: February 2004

AbstractA new version of the differential quadrature method is presented in this paper to overcome the difficulty existing in the ordinary differential quadrature method for applying multi‐boundary conditions in two‐dimensional problems. Since the weighting coefficients of the first derivative are the same as for the ordinary differential quadrature method even with the introduction of multi‐degree‐of‐freedom at the boundary points, the method is easier to extend to two‐ or three‐dimensional problems. A new version of the differential quadrature plate element has been established for demonstration. The essential difference from the existing old version of the differential quadrature plate element is the way the weighting coefficients are determined. The methodology is worked out in detail and some numerical examples are given to show the efficiency of the present method. Copyright © 2004 John Wiley & Sons, Ltd.
Radical copolymerization of 2‐trifluoromethylacrylic monomers. II. Kinetics, monomer reactivities, and penultimate effect in their copolymerization with norbornenes and vinyl ethers
Authors: Ito Hiroshi , Okazaki Masaki , Miller Dolores C. 
Published: February 2004

AbstractRadical copolymerizations of electron‐deficient 2‐trifluoromethylacrylic (TFMA) monomers, such as 2‐trifluoromethylacrylic acid and t‐butyl 2‐trifluoromethylacrylate (TBTFMA), with electron‐rich norbornene derivatives and vinyl ethers with 2,2′‐azobisisobutyronitrile as the initiator were investigated in detail through the analysis of the kinetics in situ with 1H NMR and through the determination of the monomer reactivity ratios. The norbornene derivatives used in this study included bicyclo[2.2.1]hept‐2‐ene (norbornene) and 5‐(2‐trifluoromethyl‐1,1,1‐trifluoro‐2‐hydroxylpropyl)‐2‐norbornene. The vinyl ether monomers were ethyl vinyl ether, t‐butyl vinyl ether, and 3,4‐dihydro‐2‐H‐pyran. Vinylene carbonate was found to copolymerize with TBTFMA. Although none of the monomers underwent radical homopolymerization under normal conditions, they copolymerized readily, producing a copolymer containing 60–70 mol % TFMA. The copolymerization of the TFMA monomer with norbornenes and vinyl ethers deviated from the terminal model and could be described by the penultimate model. The copolymers of TFMA reported in this article were evaluated as chemical amplification resist polymers for the emerging field of 157‐nm lithography. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1478–1505, 2004
Preparation of fully cross‐linked CNBR/PP‐g‐GMA and CNBR/PP/PP‐g‐GMA thermoplastic elastomers and their morphology, structure and properties
Authors: Xu Xiaodong , Qiao Jinliang , Yin Jinghua , Gao Ying , Zhang Xiaohong , Ding Yongtao , Liu Yiqun , Xin Zhirong , Gao Jianming , Huang Fan , Song Zhihai 
Published: February 2004

AbstractBinary CNBR/PP‐g‐GMA and ternary CNBR/PP/PP‐g‐GMA thermoplastic elastomers were prepared by reactive blending carboxy nitrile rubber (CNBR) powder with nanometer dimension and polypropylene functionalized with glycidyl methacrylate (PP‐g‐GMA). Morphology observation by using an atomic force microscope (AFM) and TEM revealed that the size of CNBR dispersed phase in CNBR/PP‐g‐GMA binary blends was much smaller than that of the corresponding CNBR/PP binary blends. Thermal behavior of CNBR/PP‐g‐GMA and CNBR/PP blends was studied by DSC. Comparing with the plain PP‐g‐GMA, Tc of PP‐g‐GMA in CNBR/PP‐g‐GMA blends increased about 10 °C. Both thermodynamic and kinetic effects would influence the crystallization behavior of PP‐g‐GMA in CNBR/PP‐g‐GMA blends. At a fixed content of CNBR, the apparent viscosity of the blending system increased with increasing the content of PP‐g‐GMA. FTIR spectrum verified that the improvement of miscibility of CNBR and PP‐g‐GMA was originated from the reaction between carboxy end groups of CNBR and epoxy groups of GMA grafted onto PP molecular chains. Comparing with CNBR/PP blends, the tensile strength, stress at 100% strain, and elongation at break of CNBR/PP‐g‐GMA blends were greatly improved. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1042–1052, 2004
Miscible blends containing a liquid crystalline polymer via optimized hydrogen bonding: Correlation to theory
Authors: Viswanathan Sriram , Dadmun M. D. 
Published: February 2004

AbstractBlending a liquid crystalline polymer (LCP) with an amorphous polymer to create a molecular composite offers a method to use the desirable properties of an LCP at a more modest cost. However, very few such blends are miscible. Our earlier findings (Viswanathan, S.; Dadmun, M. D. Macromol Rapid Commun 2001, 22, 779–782; Macromolecules 2001, 35, 5049–5060; Macromolecules 2003, 36, 3196–3205) demonstrate that it is possible to create a true molecular composite by inducing miscibility in a blend containing an LCP and an amorphous polymer by slightly modifying the structure of the polymer constituents to promote hydrogen bonding between the two polymers. This result is interpreted to indicate that separation of the hydroxyl groups along the amorphous polymer chain enhances the accessibility of the OH to intermolecularly hydrogen bond to CO groups and increases the miscibility of the blends. In this report, the phase diagrams for these blends are correlated to the theoretical phase diagrams that are determined using Coleman and Painter's association model, indicating excellent agreement between theory and experiment. This correlation also provides quantification of the functional group accessibility (via K) as a function of copolymer composition, which agrees very well with the previous phase behavior results and interpretation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1010–1022, 2004
Thermodynamics of adsorption of uranyl ions onto amidoximated poly(acrylonitrile)/poly(N‐vinyl 2‐pyrrolidone) interpenetrating polymer networks
Authors: Pekel Nursel , Şahiner Nurettin , Güven Olgun 
Published: February 2004

AbstractThe interaction of uranyl ions (UO) with interpenetrating polymer networks (IPNs) based on amidoximated poly(acrylonitrile)/poly(N‐vinyl 2‐pyrrolidone) was examined. The adsorption capacity of IPN hydrogels as well as the adsorption kinetics and the effect of temperature on UO ion adsorption were investigated. Thermodynamic quantities and kinetic parameters were calculated with adsorption isotherm data. The initial adsorption‐rate values for each temperature were calculated, and the corresponding rate constants decreased with increasing temperature. The adsorption enthalpy, entropy, and free energy of the UO ion with amidoximated IPN hydrogels were calculated from basic thermodynamic relations. It was assessed that adsorption occurred by strong electrostatic interactions with an adsorption enthalpy of −31.5 kJ/mol. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 986–993, 2004
Preparation of block copolymer vesicles in solution
Authors: Lim Soo Patrick , Eisenberg Adi 
Published: February 2004

AbstractBlock copolymer vesicles can be prepared in solution from a variety of different amphiphilic systems. Polystyrene‐block‐poly(acrylic acid), polystyrene‐block‐poly(ethylene oxide), and many other block copolymer systems can produce vesicles of a wide range of sizes; those in the range of 100–1000 nm have been explored extensively. Different factors, such as the absolute and relative block lengths, the presence of additives (ions, homopolymers, and surfactants), the water content in the solvent mixture, the nature and composition of the solvent, the temperature, and the polydispersity of the hydrophilic block, provide control over the types of vesicles produced. Their high stability, resistance to many external stimuli, and ability to package both hydrophilic and hydrophobic compounds make them excellent candidates for use in the medical, pharmaceutical, and environmental fields. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 923–938, 2004
Desorption behavior of a surfactant in a linear low‐density polyethylene blend at elevated temperatures
Authors: Lee Kangseok , Shim Sang Eun , Lee Byung H. , Hong Seong Uk , Choe Soonja 
Published: February 2004

AbstractThe desorption behavior of a surfactant in a linear low‐density polyethylene (LLDPE) blend at elevated temperatures of 50, 70, and 80 °C was studied with Fourier transform infrared spectroscopy. The composition of the LLDPE blend was 70:30 LLDPE/low‐density polyethylene. Three different specimens (II, III, and IV) were prepared with various compositions of a small molecular penetrant, sorbitan palmitate (SPAN‐40), and a migration controller, poly(ethylene acrylic acid) (EAA), in the LLDPE blend. The calculated diffusion coefficient (D) of SPAN‐40 in specimens II, III, and IV, between 50 and 80 °C, varied from 1.74 × 10−11 to 6.79 × 10−11 cm2/s, from 1.10 × 10−11 to 5.75 × 10−11 cm2/s, and from 0.58 × 10−11 to 4.75 × 10−11 cm2/s, respectively. In addition, the calculated activation energies (ED) of specimens II, III, and IV, from the plotting of ln D versus 1/T between 50 and 80 °C, were 42.9, 52.7, and 65.6 kJ/mol, respectively. These values were different from those obtained between 25 and 50 °C and were believed to have been influenced by the interference of Tinuvin (a UV stabilizer) at elevated temperatures higher than 50 °C. Although the desorption rate of SPAN‐40 increased with the temperature and decreased with the EAA content, the observed spectral behavior did not depend on the temperature and time. For all specimens stored over 50 °C, the peak at 1739 cm−1 decreased in a few days and subsequently increased with a peak shift toward 1730 cm−1. This arose from the carbonyl stretching vibration of Tinuvin, possibly because of oxidation or degradation at elevated temperatures. In addition, the incorporation of EAA into the LLDPE blend suppressed the desorption rate of SPAN‐40 and retarded the appearance of the 1730 cm−1 peak. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1114–1126, 2004
Simple universal permeation apparatus
Authors: Al‐Ati Tareq , Garza Jorge , Hotchkiss Joseph H. 
Published: February 2004

AbstractA number of methods and commercial apparatuses for measuring the permeability of polymeric films and sheet materials have been successfully developed. Generally, the equipment is complex, expensive and specific to certain permeants, but all operate on similar basic principles. Because of our interest in a wide range of permeants, including fixed gases and organic vapours, we have built an inexpensive apparatus that can measure permeation to gas, moisture and organic vapours. We also require outputs that can provide not only permeability data but also proved solubility and diffusion coefficients. The apparatus is built around a commercially available thermal conductivity detector. Copyright © 2003 John Wiley & Sons, Ltd.