bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and characterization of poly(imide‐urethane) based on novel chain‐extender containing both imide and sulphone functions
Authors: Qin XiuMin , Yang XiaoHui , Wang XinLing , Wang MingJun 
Published: August 2005

AbstractSeveral new glycols containing both imide and sulfone groups, sulfonyl bisimide glycol (SBIG), were prepared from primary aromatic diamine, trimellitic anhydride and excess low molecular glycols. Then these SBIGs were used as chain extender to prepare a series of thermoplastic poly(imide‐urethane) (PIU), which introduced imide rings into the backbones. Compared to conventional linear polyurethane (PU), these PIUs exhibited better thermal stabilities because of the presence of the sulfone and built‐in imide groups. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4469–4477, 2005
Synthesis, structure, and characterization of nematic liquid‐crystalline thermosets based on bisacrylates
Authors: Hu Jian‐She , Zhang Bao‐Yan , Yao Dan‐Shu , Xiao Wen‐Qiang , Dong Yan‐Li 
Published: August 2005

AbstractFour bisacrylate mesogenic monomers and the corresponding liquid‐crystalline thermosets were synthesized. The chemical structures of the intermediate compounds and monomers obtained were confirmed by elemental analyses, Fourier transform infrared, and 1H NMR and 13C NMR spectra. The mesomorphic properties and thermal stability were investigated with differential scanning calorimetry, thermogravimetric analysis, polarized optical microscopy, and X‐ray diffraction measurements. The influence of the curing temperatures and time on the phase behavior and thermal stability of the thermosets was discussed. All the monomers and thermosets exhibited a nematic schlieren texture. However, the monomers only showed the melting transition, and the thermosets displayed the glass transition. The experimental results demonstrated that the monomer structures strongly affected the phase behavior and the curing reaction rate, and the glass‐transition temperatures and thermal stability of the thermosets increased with the curing temperature and time. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4478–4485, 2005
Polymerization of substituted acetylenes by various rhodium catalysts: Comparison of catalyst activity and effect of additives
Authors: Nakazato Atsushi , Saeed Irfan , Katsumata Toru , Shiotsuki Masashi , Masuda Toshio , Zednik Jiri , Vohlidal Jiri 
Published: August 2005

AbstractThis research deals with comparison of the activity of various Rh catalysts in the polymerization of monosubstituted acetylenes and the effect of various amines used in conjunction with [Rh(nbd)Cl]2 in the polymerization of phenylacetylene. A zwitterionic Rh complex, Rh+(nbd)[(η6‐C6H5)B−(C6H5)3] (3), was able to polymerize phenylacetylene (5a), t‐butylacetylene (5b), N‐propargylhexanamide (5c) and n‐hexyl propiolate (5d), and displayed higher activity than the other catalysts examined, that is [Rh(nbd)Cl]2 (1), [Rh(cod)(O‐o‐cresol)]2 (2), and Rh‐vinyl complex (4). Monomers 5a and 5c polymerized virtually quantitatively or in fair yields with all these catalysts, while monomer 5b was polymerizable only with catalyts 3 and 4. Monomer 5d did not polymerize in high yields with these Rh complexes. The catalytic activity tended to decrease in the order of 3 > 4 > 2 > 1. Although polymerization of 5a did not proceed at all in toluene with [Rh(nbd)Cl]2 alone, it smoothly polymerized in the presence of various amines as cocatalysts. The polymerization rate as well as the molecular weight of polymer depended on the basicity and steric bulkiness of amines. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4530–4536, 2005
Assessment of acute and chronic pain symptoms in children with cystic fibrosis
Authors: Koh Jeffrey L. , Harrison Dale , Palermo Tonya M. , Turner Helen , McGraw Terrence 
Published: August 2005

AbstractPain is important to assess and treat in children with cystic fibrosis (CF), because pain symptoms may limit children's ability to participate in their CF‐related care and may reduce their overall well‐being and quality of life. The aims of this study were to: 1) assess acute and chronic pain symptoms as reported by children with CF, and 2) examine the relationship between pain symptoms and disease severity as measured by percentage of forced expired volume in 1 sec (FEV1%). Forty‐six children completed a self‐report questionnaire assessing characteristics of chronic disease‐related pain (frequency, intensity, duration, associated emotional upset, and location of pain). Children also rated their pain intensity associated with common CF‐related procedures. The primary locations of pain reported were the abdominal/pelvic region, chest, and head/neck. Forty‐six percent of the sample described pain occurring at least once per week. Most children reported their pain intensity as mild and of short duration. However, a small subgroup of children reported longer‐lasting and moderately intense pain. Children with chest pain were found to be particularly at risk for experiencing more functional limitations and a significantly lower FEV1% compared to children without chest pain. The majority of children reported that nonpharmacological therapies (e.g., medication, rest, or distracting activities) provided some pain relief. Disease‐related pain is common for children and adolescents with CF, suggesting that pain assessment should be a routine part of their clinical care. Further research is clearly needed to better understand the sources of pain and how best to provide relief. Pediatr Pulmonol. © 2005 Wiley‐Liss, Inc.
Structure and stability of a model three‐helix‐bundle protein on tailored surfaces
Authors: Knotts Thomas A. , Rathore Nitin , de Pablo Juan J. 
Published: August 2005

AbstractThe interaction of protein molecules with surfaces is important in numerous applications. Theoretical work on protein adsorption has been limited. In particular, it is difficult to obtain quantitative predictions about the structure and stability of proteins on surfaces. In this study, density‐of‐states‐based simulations were performed on a Gō‐like model of a three‐helix‐bundle fragment from protein A (PDB ID: 1bdd). Both mechanical and thermal stability were investigated on neutral and attractive surfaces and compared to that in the absence of a surface. It was found that attaching the peptide to any type of surface decreases its melting temperature by as much as 9 K, depending upon orientation. Calorimetric cooperativity, as measured by van't Hoff to calorimetric enthalpy ratios, similarly decreased. It was also found that the mechanical strength of the peptide attached to surfaces is degraded to varying extents, depending upon the surface type and protein orientation. A comparison of mechanical and thermal stability showed that the two are not synonymous, but occur through different pathways, and that system configurations that are more thermally stable are not always so mechanically. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Temperature‐dependent structural and functional features of a hyperthermostable enzyme using elastic neutron scattering
Authors: Koutsopoulos Sotirios , van der Oost John , Norde Willem 
Published: August 2005

AbstractThe dynamic behavior of an endoglucanase from the hyperthermophilic microorganism Pyrococcus furiosus was investigated using elastic neutron scattering. The temperature dependence of the atomic motions was correlated with conformational and functional characteristics of the enzyme. The onset of biological function at temperatures higher than approximately 25°C (the hyperthermostable enzyme is essentially inactive at room temperature) was associated with a dynamical transition in the anharmonic motions domain. This transition from the nonactive to the enzymatically active conformation involved structurally similar conformational substates in the energy landscape. From the mean‐square displacement of the protein atoms, the molecular flexibility and the effective force constants were calculated at different temperature zones. The results showed that the activity increases at higher temperatures where the intramolecular bonds are weakened and the overall rigidity of the protein is decreased. Further temperature increase resulted in significantly increased atomic fluctuations featuring heat denaturation of the protein. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Proton transfer in a Thr200His mutant of human carbonic anhydrase II
Authors: Bhatt Deepa , Tu Chingkuang , Fisher S. Zoë , Hernandez Prada Jose A. , McKenna Robert , Silverman David N. 
Published: August 2005

AbstractHuman carbonic anhydrase II (HCA II) has a histidine at position 64 (His64) that donates a proton to the zinc‐bound hydroxide in catalysis of the dehydration of bicarbonate. To examine the effect of the histidine location on proton shuttling, His64 was replaced with Ala and Thr200 replaced with histidine (H64A‐T200H HCAII), effectively relocating the proton shuttle residue ∼ 2 Å closer to the zinc‐bound hydroxide compared to wild type HCA II. The crystal structure of H64A‐T200H HCA II at 1.8 Å resolution shows the side chain of His200 directly hydrogen‐bonded with the zinc‐bound solvent. Different proton transfer processes were observed at pH 6 and at pH 8 during the catalytic hydration‐dehydration cycle, measured by mass spectrometry as the depletion of 18O from C18O2 by H64A‐T200H HCA II. The process at pH 6.0 is attributed to proton transfer between the side chain of His200 and the zinc‐bound hydroxide, in analogy with proton transfer involving His64 in wild‐type HCA II. At pH 8.0 it is attributed to proton transfer between bicarbonate and the zinc‐bound hydroxide, as supported by the dependence of the rate of proton transfer on bicarbonate concentration and on solvent hydrogen isotope effects. This study establishes that a histidine directly hydrogen‐bonded to the zinc‐bound hydroxide, can adopt the correct distance geometry to support proton transfer. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Impedance spectroscopy on organic bulk‐heterojunction solar cells
Authors: Glatthaar M. , Mingirulli N. , Zimmermann B. , Ziegler T. , Kern R. , Niggemann M. , Hinsch A. , Gombert A. 
Published: August 2005

AbstractWe measured the electrical impedance spectra of organic bulk‐heterojunction solar cells based on an absorber blend of poly(3‐hexylthiophene) and [6,6]‐phenyl C61‐butyric acid methyl ester. Comparing the spectra of the non‐treated device and after two consecutive treatments with applied forward bias voltage at 110 °C, we observed a region in the semiconductor with a low conductivity, which was expanding after the treatments. We concluded that this region is a depletion region at the aluminium contact. This was confirmed by the bias dependence of the impedance spectra. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Leveraging the Advantages Offered by Microfluidics to Enhance the Drug Discovery Process
Authors: Wong Hawkes Stephanie Y. F. , Chapela Maria J. V. , Montembault Mickael 
Published: August 2005

AbstractWhy is GlaxoSmithKline (GSK) interested in Microsystems Technology (MST) and how can MST be utilised in organic synthesis and biological screening for lead optimisation? The highly competitive world of the drug market forces pharmaceutical companies to undertake expensive searches for safe and effective leads. Although industrialisation and high‐throughput implementation of traditionally scaled technology has served to increase the individual productivity of the medicinal chemist in the pharmaceutical industry, this is still insufficient to identify the best lead. Microfluidics and MST are regarded as two of the more promising new disruptive techniques for carrying out ultra‐high‐throughput chemical synthesis. The utilisation of microchannels in organic synthesis has a wide range of advantages, for example, lower reaction times than for macroscale synthesis , the use of minute amounts of reagents and solvents, reduction of costs and avoidance of storage. The ultimate aim is to create a microreactor environment capable of performing in a fast serial mode, where the synthesis, purification and screening of small quantities of thousands of compounds a day are handled with ease, thereby reducing the cycle time per synthesis‐assay run. The tiny amounts of compounds produced in the microchannels are compatible with modern miniaturised screening techniques that require less than a nano‐mole of test compound. Close integration of the chemistry generator with the assay also eliminates storage and supply‐chain issues. Larger amounts of compounds can be obtained by numbering up (paralleling) the microreactors.
Electrochemical Combinatorial Organic Syntheses Using Microflow Systems
Authors: Suga Seiji , Okajima Masayuki , Fujiwara Kazuyuki , Yoshida Jun‐ichi 
Published: August 2005

AbstractThe “cation flow” method, in which highly reactive carbocations are generated in the absence of nucleophiles by low temperature electrolysis and are allowed to react with carbon nucleophiles in the microflow system to achieve direct electrooxidative CC bond formation, has been developed. As an extension of the cation flow method, an electrochemical paired microflow system that involves concurrent anodic generation of carbocations and cathodic generation of carbon nucleophiles followed by their reactions to achieve straightforward CC bond formation has also been developed.
Continuous‐Flow Chemical Processing in Three‐Dimensional Microchannel Network for On‐Chip Integration of Multiple Reactions in a Combinatorial Mode
Authors: Kikutani Yoshikuni , Ueno Masaharu , Hisamoto Hideaki , Tokeshi Manabu , Kitamori Takehiko 
Published: August 2005

AbstractChemical syntheses using microchemical chips have been intensively investigated in recent years, but they have still not fully reached the stage of practical use. Combinatorial synthesis has been expected to be one of their useful applications. Benefits of using microchips, such as reduction in quantity of reagents and wastes, are thought to be suited for combinatorial syntheses, where numerous variations of products have to be synthesized each in small amounts. There are two modes of combinatorial syntheses using microchemical chips. One is sequential synthesis, in which reactant solutions are introduced sequentially in various combinations to a reaction microchannel. The other is parallel synthesis, where the number of reaction channels is the same as the number of final products, and starting materials are distributed to all the reaction channels in different combinations. Sequential synthesis has been considered as the more favorable way, because, especially when libraries of starting materials are large, numerous microchannels and complicated pipings for distribution of reagents to the channels are required for the parallel mode. Therefore, research on parallel microcombinatorial syntheses has been done only rarely, whereas there have been many reports of sequential microcombinatorial syntheses. Against this trend, our research group has taken an alternative path and tried to integrate both parallel reaction microchannels onto a glass microchip and channels for distributing reactant solutions to each reaction channel in a combinatorial mode. Microchips fabricated by laminating multiple layers of glass substrates have been used to construct three‐dimensional microchannel networks necessary for mixing reagent flows in different combinations. We utilized low Reynolds number multi‐phase laminar flow and developed micro‐unit operations (MUOs). By combining MUOs in the multi‐phase continuous laminar flows, microchemical systems were constructed. We called this micro‐integration methodology “continuous‐flow chemical processing (CFCP)”, and by using it, a sequence of various operations in chemical syntheses could be integrated on a microchemical chip. Not just simple mixing of two reagents, which was most commonly done in microreactors, but also multi‐step processes including other chemical operations, such as extraction and separation, could be carried out via CFCP. In the first part of this short review article, we explain CFCP with an example. Then, a microchemical chip with a three‐dimensional microchannel network for a parallel reaction system is introduced. Finally, we present a case in which CFCP was realized in a three‐dimensional microchannel network.
The Application of Microreactors in Combinatorial Chemistry
Authors: Watts Paul 
Published: August 2005

AbstractThe miniaturisation of chemical reactors offers many fundamental and practical advantages of relevance to the pharmaceutical and fine chemicals industries, which are constantly searching for controllable, information‐rich, high‐throughput and environmentally friendly methods of producing products with a high degree of chemical selectivity. This review explores how miniaturisation may revolutionise chemical synthesis, highlighting in particular the commercial and environmental benefits of this new technology in combinatorial synthesis.
Synthesis of a Library of Ciprofloxacin Analogues By Means of Sequential Organic Synthesis in Microreactors
Authors: Schwalbe Thomas , Kadzimirsz Daniel , Jas Gerhard 
Published: August 2005

AbstractThe realm of combinatorial chemistry is strongly based on the concept of parallel chemistry and its ease of automation. Although this batch‐type approach in general may be considered a success story, some limitations remain rarely addressable by conventional approaches. Particularly, scaling‐up problems such as the re‐synthesis of multigram amounts of active compounds as well as the synthesis of building blocks and scaffolds in large amounts may prove to be problematic. Our expertise in continuous chemistry prompted us to develop a microreaction system for sequential organic synthesis that should overcome these limitations. In the present contribution we describe this system as well as its application to the first library approach towards fluoro‐quinolone antibiotics such as Ciprofloxacin solely using microreaction technology. A known one‐pot batch procedure for the synthesis of this compound class was split in its individual reaction steps, which were successfully adapted to a continuous conduct. After some optimisation studies the overall sequence was suitable for chemical diversification. Particularly it was shown, that the first step of the synthesis – the acylation reaction of a β‐dimethylamino acrylate with trifluoro‐benzoic acid chloride – was accessible to synthesis of high quantities without any difficulties to yield a primary building block suitable for subsequent library synthesis. In a first diversification step, the Michael addition of a set of primary amines was followed by nucleophilic ring closure providing the difluoro‐quinolone system, which was subjected to a second diversification step by means of a nucleophilic aromatic substitution reaction. Thus, a number of Ciprofloxacin analogues could be synthesised in good overall yield and purity. Isolated yields ranged from 71 to 85% in the first diversification step and from 59 to 99% in the second step.
A Novel Method for High‐Throughput Reduction of Compounds through Automated Sequential Injection into a Continuous‐Flow Microfluidic Reactor
Authors: Jones Richard , Gödörházy Lajos , Szalay Dániel , Gerencsér János , Dormán György , Ürge László , Darvas Ferenc 
Published: August 2005

AbstractA high‐throughput system for heterogeneous hydrogenation through the integration of a microfluidic reactor into an automated injector‐fraction collector robot is described. The reduction of a small nitro compound library is used to demonstrate the high‐throughput capability of the system and the results are compared to those of a batch reactor.
Determination of agrochemical compounds in soya plants by imaging matrix‐assisted laser desorption/ionisation mass spectrometry
Authors: Mullen Alexander K. , Clench Malcolm R. , Crosland Susan , Sharples Kate R. 
Published: August 2005

AbstractDetection and imaging of the herbicide mesotrione (2‐(4‐mesyl‐2‐nitrobenzoyl)cyclohexane‐1,3‐dione) and the fungicide azoxystrobin (methyl (E)‐2‐{2‐[6‐(2‐cyanophenoxy)pyrimidin‐4‐yloxy]phenyl}‐3‐methoxyacrylate), on the surface of the soya leaf, and the detection and imaging of azoxystrobin inside the stem of the soya plant, have been achieved using matrix‐assisted laser desorption/ionisation quadrupole time‐of‐flight mass spectrometry. In leaf analysis experiments, the two pesticides were deposited onto the surface of individual soya leaves on growing plants. The soya leaves were removed and prepared for direct and indirect (following blotting onto matrix‐coated cellulose membranes) imaging analysis at different periods after initial pesticide application. In stem analysis experiments, azoxystrobin was added to the nutrient solution of a soya plant growing in a hydroponics system. The plant was left for 48 h, and then horizontal and vertical stem sections were prepared for direct imaging analysis. The images obtained demonstrate the applicability of MALDI imaging to the detection and imaging of small organic compounds in plant tissue and further extend the analytical repertoire of the versatile MALDI technique. Copyright © 2005 John Wiley & Sons, Ltd.
Enhancement of matrix‐assisted laser desorption/ionization photodissociation tandem time‐of‐flight mass spectra; spectral reduction and cleanup of isotopomeric contamination
Authors: Moon Jeong Hee , Yoon So Hee , Kim Myung Soo 
Published: August 2005

AbstractWeak signal intensity and poor precursor ion selection are the major difficulties in tandem time‐of‐flight (TOF) mass spectrometry of ions generated by matrix‐assisted laser desorption/ionization (MALDI). Even though the latter can be overcome in photodissociation (PD) tandem TOF mass spectrometry via ion pulse‐PD laser pulse synchronization, clean monoisotopic selection of precursor ions of highm/zcan often be difficult for various reasons. A considerable enhancement of post‐source decay (PSD) and PD tandem mass spectra has been achieved in this work via single‐ion detection and post‐acquisition reduction of the spectra. Also, an algorithm has been developed to clean up isotopomeric contamination when the resolution for precursor ion selection is less than adequate. A high‐quality tandem TOF mass spectrum which results from PD of virtually monoisotopic precursor ions has been obtained. Copyright © 2005 John Wiley & Sons, Ltd.
Characterization of adducts formed between human serum albumin and the butadiene metabolite epoxybutanediol
Authors: Lindh Christian H. , Kristiansson Monica H. , Berg‐Andersson Ulrika A. , Cohen Arieh S. 
Published: August 2005

Abstract1,3‐Butadiene (BD) has been classified as a potential human carcinogen. It occurs in the environment as well as in industrial settings. In humans, BD is readily metabolized to reactive epoxides (e.g. 1,2‐epoxy‐3,4‐butanediol). In this study, conjugates between human serum albumin (HSA) and EBD were synthesized (molar ratios of 1:600, 1:1 and 1:0.1; HSA/EBD) under physiological conditions. The 1:600 conjugate and a blank HSA sample were digested with trypsin to obtain specific peptides that were fractionated by preparative liquid chromatography (LC). The fractions were analyzed using nanoelectrospray quadrupole time‐of‐flight mass spectrometry (nanoES‐QqTOFMS). Adducted HSA tryptic peptides were identified and the adducted amino acid residues were identified by sequence analysis based on tandem mass spectrometry (MS/MS). A total of 26 2,3,4‐trihydroxybutyl (THB) adducts were identified on 23 tryptic peptides in the HSA/EBD conjugate. The adducted amino acids were the N‐terminal aspartic acid residue, six glutamic acid residues, five histidine residues and 14 lysine residues. Results from the nanoES‐QqTOFMS experiments were used to set up a more sensitive liquid chromatographic/mass spectrometric (LC/MS) analysis using selected reaction monitoring. Eight of the adducted peptides could be detected in tryptic digests of the 1:0.1 HSA/EBD conjugate. Copyright © 2005 John Wiley & Sons, Ltd.