bluuebunny/crossref_metadata_2025_split huggingface dataset:
ABA‐type liquid crystalline triblock copolymers via nitroxide‐mediated radical polymerization: Design, synthesis, and morphologies
Authors: Gao Long‐Cheng , Pan Qi‐Wei , Wang Chao , Yi Yi , Chen Xiao‐Fang , Fan Xing‐He , Zhou Qi‐Feng 
Published: November 2007

AbstractWe have designed and synthesized rod–coil–rod triblock copolymers of controlled molecular weight by two‐step nitroxide‐mediated radical polymerization, where the rod part consists of “mesogen‐jacketed liquid crystalline polymer” (MJLCP). The MJLCP segment examined in our studies is poly{2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene} (MPCS) while the coil part is polyisoprene (PI). Characterization of the triblock copolymers by GPC, 1H and 13C NMR spectroscopies, TGA, DSC confirmed that the triblock copolymers were comprised of microphase‐separated low Tg amorphous PI and high Tg PMPCS blocks. Analysis of POM and 1D, 2D‐WAXD demonstrated that the triblock copolymers formed nematic liquid crystal phase. Morphological studies using TEM indicated the sample formed lamellar structure. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5949–5956, 2007
Pressure relaxation of polystyrene and its comparison to the shear response
Authors: Meng Yan , Simon Sindee L. 
Published: November 2007

AbstractIsothermal pressure relaxation as a function of temperature in two pressure ranges has been measured for polystyrene using a self‐built pressurizable dilatometer. A master curve for pressure relaxation in each pressure regime is obtained based on the time–temperature superposition principle, and time–pressure superposition of the two master curves is found to be applicable when the master curves are referenced to their pressure‐dependent Tg. The pressure relaxation master curves, the shift factors, and retardation spectra obtained from these curves are compared with those obtained from shear creep compliance measurements for the same material. The shift factors for the bulk and shear responses have the same temperature dependence, and the retardation spectra overlap at short times. Our results suggest that the bulk and shear response have similar molecular origin, but that long‐time chain mechanisms available to shear are lost in the bulk response. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3375–3385, 2007
Colloid Probe AFM and XPS Study of Time‐Dependent Aging of Amine Plasma Polymer Coatings in Aqueous Media
Authors: Tarasova Anna , Hamilton‐Brown Paul , Gengenbach Thomas , Griesser Hans J. , Meagher Laurence 
Published: November 2007

AbstractEffects of surface oxidation on the properties of amine plasma polymer (pp) films in aqueous media have not been widely studied, despite their use to control bio‐interfacial properties. Changes in the surface composition of allylamine and heptylamine pp films, on water exposure, were followed by XPS. The surface potential was monitored via AFM measurements and comparison to DLVO theory. Analysis of XPS data implied high initial oxidation rates (rapid quenching of surface radicals). Oxidation of the pp films followed evolution of carbon‐based rather than nitrogen‐based species. Analysis of AFM force data showed changes in the sign of the surface potential with aging from positive to negative. Implications, for example for surface immobilization of molecules in aqueous environments, are also discussed.magnified image
Allylamine Plasma Polymer Coatings of Interior Surfaces in Small Trench Structures
Authors: Besch Wilfried , Foest Rüdiger , Schröder Karsten , Ohl Andreas 
Published: November 2007

AbstractThe modification of interior surfaces in small trench structures was studied for plasma polymerization processes. Pulsed AAm microwave plasmas were applied to deposit thin films at varied applied microwave powers. Specially designed test specimens served as substrates to investigate trenches with AR from 2 to 10. Thin films coated on external and interior surfaces were analyzed with FT‐IR spectroscopy and XPS measurements. Dense films with similar morphology are observed in all locations. Chemical composition does neither depend on AR nor on depth. In conclusion, this type of AAm plasma polymer deposition is useful for conformal coating of deep trenches with high AR.magnified image
Proteomic analysis of protein expression changes in a model of gliomagenesis
Authors: McBee Joshua K. , Yu Li‐Rong , Kinoshita Yoshito , Uo Takuma , Beyer Richard P. , Veenstra Timothy D. , Morrison Richard S. 
Published: November 2007

AbstractLoss of p53 function is a common event in a variety of human cancers including tumors of glial origin. Using an in vitro mouse model of malignant astrocyte transformation, three cleavable isotope coded affinity tag (cICAT) experiments were performed comparing cultured wild‐type astrocytes and two p53−/− astrocyte cultures before and after malignant transformation. We identified and quantitated an average of 1366 proteins per experiment and demonstrated that the protein quantitation ratios in each individual cICAT experiment correlated well to ratios determined in the other two studies. These data were further supported by microarray analysis which also correlated to changes in protein expression. The results showed significant changes in protein expression in association with malignant transformation. Proteins overexpressed in malignant astrocytes were typically involved in ribosome biogenesis/protein synthesis and DNA replication, while underexpressed proteins were generally associated with the regulation of cell cycle checkpoint control, tumor suppression, and apoptosis. Among the significantly up‐regulated proteins and transcripts in malignant mouse astrocytes were members of the minichromosome maintenance (MCM) family. Western blot analysis verified increased expression of MCM proteins in malignant human astrocytoma cell lines, which had not previously been described. These results demonstrate the usefulness of the cICAT approach for comparing differences in protein expression profiles between normal and malignant cells.
Proteomics of brain synapses and molecular dissection of synaptic subdomains
Authors: Li Ka Wan , Smit August B. 
Published: November 2007

AbstractSynapses form the nuts and bolts of the brain. Synaptic transmission involves an intricate network of synaptic proteins that forms the molecular machinery underlying transmitter release, activation of transmitter receptors, and signal transduction cascades. It is generally believed that neuronal activity‐dependent change of synaptic efficacy is at the basis of learning and memory and is encoded by sequential molecular events at the synapse. In the past 2–3 years, a number of proteomics studies have been performed on synaptic subdomains, including synaptic vesicles, postsynaptic density, synaptic lipid raft, synapse protein complexes, as well as on synaptic protein PTMs, notably phosphorylation. The activity‐dependent dynamics of protein constituents of the synapse are starting to be examined by quantitative proteomics. It is anticipated that these analyses will yield novel insights into the organization of the synapse, and will generate testable hypotheses of synapse function and regulation both in health and disease.
The confirmation of the denatured structure of pyrrolidone carboxyl peptidase under nondenaturing conditions: Difference in helix propensity of two synthetic peptides with single amino acid substitution
Authors: Umezaki Taro , Iimura Satoshi , Noda Yasuo , Segawa Shin‐ichi , Yutani Katsuhide 
Published: November 2007

AbstractIn the denatured state (D1 state) of cystein‐free pyrrolidone carboxyl peptidase (PCP‐0SH) from Pyrococcus furiosus, a hyperthermophile under nondenaturing conditions, a fairly stable α‐helix (α6‐helix) has been determined from H/D exchange‐NMR experiments. On the other hand, the α6‐helix region of the proline‐mutant at position 199 (A199P) was unstructured in the D1 state unlike that of the wild‐type PCP‐0SH, although the folded conformations of both proteins were almost identical to each other. This finding has been deduced from the information regarding the remaining amide hydrogens in the HSQC spectra after H/D exchanges in the D1 state. To confirm this inference, we examined the helical propensities of two synthetic peptides from their NMR structural analysis in the presence of trifluoroethanol (TFE). One is an 18‐residue peptide called the wild‐type H6‐peptide corresponding to the α6‐helix (from Ser188 to Glu205) of the wild‐type PCP‐0SH, and the other is the mutant H6‐peptide corresponding to the α6‐helix region of A199P. The NOE‐contact information obtained from the 2D‐1H‐NOESY spectra measured for both peptides in the presence of 30% TFE clearly demonstrated that the wild‐type H6‐peptide had a high helical propensity, but the mutant H6‐peptide was almost totally unstructured. The TFE‐induced helical propensities for these peptide fragments confirmed the conclusions deduced from the H/D exchange data measured in the D1 states of two proteins. Proteins 2008. © 2007 Wiley‐Liss, Inc.
Role of the IXI/V motif in oligomer assembly and function of StHsp14.0, a small heat shock protein from the acidothermophilic archaeon, Sulfolobus tokodaii strain 7
Authors: Saji Hitoshi , Iizuka Ryo , Yoshida Takao , Abe Tetsuya , Kidokoro Shun‐ichi , Ishii Noriyuki , Yohda Masafumi 
Published: November 2007

AbstractSmall heat shock proteins (sHsps) are one of the most ubiquitous molecular chaperones. They are grouped together based on a conserved domain, the α‐crystallin domain. Generally, sHsps exist as oligomers of 9–40 subunits, and the oligomers undergo reversible temperature‐dependent dissociation into smaller species as dimers, which interact with denaturing substrate proteins. Previous studies have shown that the C‐terminal region, especially the consensus IXI/V motif, is responsible for oligomer assembly. In this study, we examined deletions or mutations in the C‐terminal region on the oligomer assembly and function of StHsp14.0, an sHsp from an acidothermophilic archaeon, Sulfolobus tokodaii strain 7. Mutated StHsp14.0 with C‐terminal deletion or replacement of IIe residues in the IXI/V motif to Ala, Ser, or Phe residues could not form large oligomers and lost chaperone activity. StHsp14.0WKW, whose Ile residues in the IXI/V motif are changed to Trp, existed as an oligomer like that of the wild type. However, it dissociates to small oligomers and exhibits chaperone activity at relatively lowered temperature. Replacement of two Ile residues in the motif to relatively small residues, Ala or Ser, also resulted in the change of β‐sheet rich secondary structure and decrease of hydrophobicity. Interestingly, StHsp14.0 mutant with amino acid replacements to Phe kept almost the same secondary structure and relatively high hydrophobicity despite that it could not form an oligomeric structure. The results show that hydrophobicity and size of the amino acids in the IXI/V motif in the C‐terminal region are responsible not only for assembly of the oligomer but also for the maintenance of β‐sheet rich secondary structure and hydrophobicity, which are important for the function of sHsp. Proteins 2008. © 2007 Wiley‐Liss, Inc.
Understanding the structural and functional differences between mouse thyrotropin‐releasing hormone receptors 1 and 2
Authors: Deflorian Francesca , Engel Stanislav , Colson Anny‐Odile , Raaka Bruce M. , Gershengorn Marvin C. , Costanzi Stefano 
Published: November 2007

AbstractMultiple computational methods have been employed in a comparative study of thyrotropin‐releasing hormone receptors 1 and 2 (TRH‐R1 and TRH‐R2) to explore the structural bases for the different functional properties of these G protein‐coupled receptors. Three‐dimensional models of both murine TRH receptors have been built and optimized by means of homology modeling based on the crystal structure of bovine rhodopsin, molecular dynamics simulations, and energy minimizations in a membrane‐aqueous environment. The comparison between the two models showed a correlation between the higher flexibility and higher basal activity of TRH‐R2 versus the lesser flexibility and lower basal activity of TRH‐R1 and supported the involvement of the highly conserved W6.48 in the signaling process. A correlation between the level of basal activity and conformational changes of TM5 was detected also. Comparison between models of the wild type receptors and their W6.48A mutants, which have reversed basal activities compared with their respective wild types, further supported these correlations. A flexible molecular docking procedure revealed that TRH establishes a direct interaction with W6.48 in TRH‐R2 but not in TRH‐R1. We designed and performed new mutagenesis experiments that strongly supported these observations. Proteins 2008; 71:783–794. Published 2007 Wiley‐Liss, Inc.
Evolution of the β‐propeller fold
Authors: Chaudhuri Indronil , Söding Johannes , Lupas Andrei N. 
Published: November 2007

Abstractβ‐Propellers are toroidal folds, in which repeated, four‐stranded β‐meanders are arranged in a circular and slightly tilted fashion, like the blades of a propeller. They are found in all domains of life, with a strong preponderance among eukaryotes. Propellers show considerable sequence diversity and are classified into six separate structural groups by the SCOP and CATH databases. Despite this diversity, they often show similarities across groups, not only in structure but also in sequence, raising the possibility of a common origin. In agreement with this hypothesis, most propellers group together in a cluster map of all‐β folds generated by sequence similarity, because of numerous pairwise matches, many of which are individually nonsignificant. In total, 45 of 60 propellers in the SCOP25 database, covering four SCOP folds, are clustered in this group and analysis with sensitive sequence comparison methods shows that they are similar at a level indicative of homology. Two mechanisms appear to contribute to the evolution of β‐propellers: amplification from single blades and subsequent functional differentiation. The observation of propellers with nearly identical blades in genomic sequences show that these mechanisms are still operating today. Proteins 2008. © 2007 Wiley‐Liss, Inc.
Strategies for the cost‐effective use of oral antidiabetic drugs
Authors: Burrill Peter , Krentz Andrew 
Published: November 2007

AbstractThe UK prevalence of diabetes continues to increase, alongside the development of new drug classes and management guidelines. As a result, prescriptions for and spending on antidiabetic drugs continue to grow. In this article the authors discuss how to maximise treatment results and minimise spending by optimising each step in the diabetes management pathway. Copyright © 2007 Wiley Interface Ltd
A framework for capturing and analyzing the failures due to system/component interactions
Authors: Nepal Bimal P. , Yadav Om P. , Monplaisir Leslie , Murat Alper 
Published: November 2007

AbstractTo keep up with the speed of globalization and growing customer demands for more technology‐oriented products, modern systems are becoming increasingly more complex. This complexity gives rise to unpredictable failure patterns. While there are a number of well‐established failure analysis (physics‐of‐failure) models for individual components, these models do not hold good for complex systems as their failure behaviors may be totally different. Failure analysis
of individual components does consider the environmental interactions but is unable to capture the system interaction effects on failure behavior. These models are based on the assumption of independent failure mechanisms. Dependency relationships and interactions of components in a complex system might give rise to some new types of failures that are not considered during the individual failure analysis of that component. This paper presents a general framework for failure modes and effects analysis (FMEA) to capture and analyze component interaction failures. The advantage of the proposed methodology is that it identifies and analyzes the system failure modes due to the interaction between the components. An example is presented to demonstrate the application of the proposed framework for a specific product architecture (PA) that captures interaction failures between different modules. However, the proposed framework is generic and can also be used in other types of PA. Copyright © 2007 John Wiley & Sons, Ltd.
Analysis of perfluoroalkyl anion fragmentation pathways for perfluoroalkyl carboxylates and sulfonates during liquid chromatography/tandem mass spectrometry: evidence for fluorine migration prior to secondary and tertiary fragmentation
Authors: Arsenault Gilles , McAlees Alan , McCrindle Robert , Riddell Nicole 
Published: November 2007

AbstractIt is known that under liquid chromatography/electrospray tandem mass spectrometry (LC/ES‐MS/MS) conditions, the perfluorocarboxylate anion [RFCO2]− first loses CO2 to give a perfluoroalkyl anion R, [(MH)CO2]−, which can subsequently fragment to give inter alia lower mass carbanions. It has been suggested in a previous study that such secondary fragmentation involves cleavage of CnF2n segments. Our study of the LC/ES‐MS/MS of a series of 13C‐labeled perfluoroalkyl carboxylic acids (PFCAs) indicates that fragmentation of the R anion does not involve simple 'unzipping' of a primary perfluoroalkyl anion of the type F3C(CF2)xCF. For example, we have discovered that the secondary transition for the mass‐labeled PFOA, perfluoro‐1,2,3,4‐13C4‐octanoic acid (MPFOA), gives two signals of equal intensity at m/z 169 and 172. We propose a mechanism of fragmentation that involves rapid fluorine shifts, after the initial decarboxylation, which generate a series of new anions prior to secondary and tertiary fragmentation. Copyright © 2007 John Wiley & Sons, Ltd.
Differential ionisation of natural antioxidant polyenes in electrospray and nanospray mass spectrometry
Authors: Guaratini Thais , Gates Paul J. , Pinto Ernani , Colepicolo Pio , Lopes Norberto P. 
Published: November 2007

AbstractCarotenoids are natural products with high economic relevance for the pharmaceutical industries and are a common subject for biochemical research. Reported here is a comparative study of the ionisation of carotenoids by electrospray mass spectrometry (ESI‐MS) and nanospray mass spectrometry (nanoESI‐MS). The results demonstrate that, along with solvent choice, the influence of the different ionisation processes of ESI and nanoESI are fundamental in determining how ionisation is achieved and which ions (molecular ion or protonated molecule) are observed in MS. The increased understanding afforded by this study will help in the development of unequivocal microanalytical methods for carotenoids and related antioxidant polyenes. Copyright © 2007 John Wiley & Sons, Ltd.
Metal–ligand solution equilibria studied by electrospray ionization mass spectrometry: correlation between ion intensity and acid–base equilibria in solution
Authors: Di Marco Valerio B. , Bombi G. Giorgio , Ranaldo Martina , Traldi Pietro 
Published: November 2007

AbstractElectrospray ionization mass spectrometry (ESI‐MS) is increasingly used in the study of metal–ligand equilibria in aqueous solutions. However, the correlation between conditions in solution and mass spectra in the gas phase is far from being completely established. In the present work the equation i = kC0f was used to correlate relative ion intensity (i) in an ESI mass spectrum, the stoichiometric concentration (C0) in solution of the complex which produced this ion, and the fraction (f) of complex having the same protonation state as that of the ion detected in the spectrum. This equation takes into account that metal–ligand complexes have acid–base properties, and that these properties affect the efficiency by which the ions are brought from the solution to the gas phase. The equation was experimentally checked by electrospraying solutions containing aluminium(III) and any of the four ligands 3,4‐dihydroxybenzoic acid, 3‐hydroxy‐2‐(1H)pyridinone, citric acid, and ethylenediaminetetramethylenephosphonic acid at different pH values. ESI‐MS experimental i values and C0f values calculated from literature data were plotted versus the solution pH. Values are correlated in the majority of cases, thus confirming the validity of the approach proposed. Correlation is lost, as expected, for low f or C0 values, and when extensive gas‐phase reactions occur. The equation i = kC0f can be used to estimate quantitative data for unknown metal–ligand solutions analyzed by ESI‐MS. Copyright © 2007 John Wiley & Sons, Ltd.
Quantification of rat brain neurotransmitters and metabolites using liquid chromatography/electrospray tandem mass spectrometry and comparison with liquid chromatography/electrochemical detection
Authors: Tareke Eden , Bowyer John F. , Doerge Daniel R. 
Published: November 2007

AbstractAnalytical methodology based on solid‐phase extraction, polar reversed‐phase liquid chromatography, and electrospray tandem mass spectrometry (LC/MS/MS) with isotope dilution was developed and validated for quantifying the neurotransmitters, dopamine and serotonin, and their major metabolites in brain tissue. Limits of detection (0.1–20 pg/mg tissue) were sufficient for analysis of multiple neurotransmitters in rat brain regions, including parietal cortex, hypothalamus, pituitary, substantia nigra, and striatum. Method performance was compared with contemporaneous measurements using a well‐established procedure based on ion‐pairing reversed‐phase liquid chromatography and amperometric detection. The principal advantages of the LC/MS/MS method include a more robust sample purification procedure, an optimized chromatographic separation, and the qualitative and quantitative assurance that comes from coeluting isotopically labeled internal standards; however, sensitivity did not consistently improve upon that provided by amperometric detection. This methodology may be particularly useful for applications in which simultaneous determinations are required for drugs and their affected neurotransmitters in specific brain regions. Published in 2007 by John Wiley & Sons, Ltd.
Development of a rapid and validated method for investigating the metabolism of scoparone in rat using ultra‐performance liquid chromatography/electrospray ionization quadruple time‐of‐flight mass spectrometry
Authors: Wang Xijun , Lv Haitao , Sun Hui , Liu Lian , Sun Wenjun , Cao Hongxin 
Published: November 2007

AbstractScoparone (6,7‐dimethoxycoumarin) is known to have a wide range of pharmacological properties. In this study, a rapid and validated ultra‐performance liquid chromatography/electrospray ionization quadruple time‐of‐flight mass spectrometry (UPLC/ESI‐QTof‐MS) method was developed to investigate the metabolism of scoparone in rat for the first time. The new method reduced the sample handling and analytical time by three‐ to six‐fold, and the detection limit by five‐ to 1000‐fold, compared to published methods. Far more metabolites were detected and identified compared to published data, which were preliminarily identified as scopoletin, isoscopoletin, isofraxidin, and fraxidin, respectively, when subjected to tandem mass spectrometry analyses. It is found that the metabolic trajectory of scoparone in rat focused on phase I metabolism which is obviously different from published results, and revealed a wide range of pharmacological properties of scoparone partly attributed to the bioactivities of its metabolites. Copyright © 2007 John Wiley & Sons, Ltd.