bluuebunny/crossref_metadata_2025_split huggingface dataset:
Water sorption into poly[(2‐hydroxyethyl methacrylate)‐co‐(1‐vinyl‐2‐pyrrolidone)]at 310 K
Authors: Malak Mark , Hill David JT , Whittaker Andrew K 
Published: October 2003

AbstractPoly(2‐hydroxyethyl methacrylate) and copolymers of 2‐hydroxyethyl methacrylate (HEMA) and 1‐vinyl‐2‐pyrrolidone (VP) in the form of cylindrical samples (≈8 mm × 20 mm) have been prepared and the sorption of water into these cylinders has been studied by the mass‐uptake methods and by magnetic‐resonance imaging. The equilibrium water contents for the cylinders were found to vary systematically with the copolymer composition. Diffusion of water into the cylinders was found to follow Fickian behaviour for cylinders with high HEMA contents, with the diffusion coefficients obtained from mass‐uptake studies dependent on the copolymer composition, varying from 1.7 × 10−11 m2 s−1 for poly(HEMA) to 2.0 × 10−11 m2 s−1 for poly(HEMA‐co‐VP) with a composition of 1:1. However, NMR‐imaging studies showed that, while the profiles of the water diffusion fronts for cylinders with high HEMA contents were Fickian, that for the 1:1 copolymer was not and indicated that the mechanism was Case III. The polymers which were rich in VP were characterized by a water‐sorption process which follows Case‐III behaviour. Copyright © 2003 Society of Chemical Industry
Calorimetric and rheological characterization of a high‐performance epoxy curable at low temperatures
Authors: Rocks J , Halter M , George G , Vohwinkel F 
Published: October 2003

AbstractCuring and gelation ofN,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM, Araldite®MY721) in the presence of an anhydride hardener mixture were studied by calorimetric and dynamic rheological measurements. The cure kinetics of the homogeneous and low‐temperature‐curable epoxy system were evaluated from 40 to 140 °C, and the apparent activation energies of the curing reaction were calculated from different thermokinetic models. By comparison of different calorimetric and rheological methods, it was found that the results from the isothermal calorimetric measurements are in good agreement with the results obtained from isothermal rheological experiments, while the kinetic parameter calculations based on dynamic calorimetric measurements are not reliable results. These differences mainly arise from the fact that dynamic measurements have many underlying assumptions and do not consider the equilibrium condition. Copyright © 2003 Society of Chemical Industry
Curing kinetics and thermomechanical behaviour of co‐anhydride cured aminoglycidyl epoxy resins
Authors: Rocks Jens , George Graeme A , Vohwinkel Friedrich 
Published: October 2003

AbstractThe curing behaviour and thermomechanical properties of a technical grade ofN,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM, Araldite®MY721), cured in the presence of an anhydride hardener mixture consisting of maleic anhydride (MA) and pyromellitic acid dianhydride (PMDA) was studied by calorimetric and dynamic mechanical analysis. The cure kinetics and the influence of varying stoichiometric anhydride‐to‐epoxy ratios were evaluated and the apparent activation energy was calculated according to Barrett's method. High extents of conversion from DSC studies of the MY721‐resin were reached after room temperature cure, without an added catalyst, for 24 h, followed by a post‐curing step of 1 h at 90 °C. The ultimate glass transition temperatures for the molar anhydride/epoxy ratio,r= 0.8, were close to the decomposition temperature, and indications were obtained that the network structure consists of two independent sub‐networks. It is suggested that two separate mechanisms contribute to the curing reaction at room temperature. First, the tertiary amine structure, intrinsic to aminoglycidyl resins, may act as an internal catalyst for the anhydride ring opening, and secondly, the unsaturated bond of MA participates in the curing reaction by nucleophilic attack, such as from tertiary amines or carboxylate or alkoxide anions. From a study of a range of different aminoglycidyl resins, this low‐temperature curing behaviour is found to be a general phenomenon. Copyright © 2003 Society of Chemical Industry
Yield behaviour of a melt‐compounded polyethylene–intercalated montmorillonite nanocomposite
Authors: Truss Rowan W , Lee Ang Chiean 
Published: October 2003

AbstractThe yield behaviour of a series of melt‐mixed polyethylene–modified montmorillonite nanocomposites has been studied as a function of temperature and strain rate and compared to the behaviour of the base polymer. The processing conditions used gave an intercalated structure as assessed by X‐ray diffraction. Although there was a modest improvement in stiffness with clay content, the yield behaviour was insensitive to the addition of the clay. Both the base polymer and the nanocomposites showed double yield points. These were analysed as activated rate processes, with the activation energies consistent with the low strain yield point being associated with the α2 molecular relaxation and the higher strain yield point with ‘c’ axis slip. Copyright © 2003 Society of Chemical Industry
Initiation in the free radical (co)polymerization of dialkyl fumarates and dicyclohexyl fumarate/tert‐butyl vinyl ether investigated by a nitroxide trapping technique
Authors: Hirano Emari , Zetterlund Per B , Takaoka Toshiaki , Yamada Bunichiro , Buckley Robbie , Jenkins Ian D , Busfield W Ken 
Published: October 2003

AbstractInitiation in the free radical polymerization of dicyclohexyl fumarate (DCHF), isopropyl phenyl fumarate (iPPF) and isopropyl benzyl fumarate (iPBF), and the copolymerization of DCHF with tert‐butyl vinyl ether (E), initiated by di‐tert‐butyl peroxalate, has been investigated at 60 °C. The rate coefficient for addition of the tert‐butoxy radical to the fumarates is of the order 105 M−1 s−1 with differences between the different fumarates being at most a factor of about two. A significant amount of monomer addition to the primary propagating radical in the case of DCHF occurred despite competition with trapping, indicating that the first propagation step is orders of magnitude faster than the propagation step for macroradicals.In the copolymerization system DCHF/E, second‐generation carbon‐centered radicals containing two fumarate units were formed, whereas the corresponding species in the homopolymerization of E was not observed. This is consistent with the fact that E does not undergo homopolymerization. Copyright © 2003 Society of Chemical Industry
Reaction behavior of sterically hindered α‐(substituted methyl)acrylic esters with tert‐butoxy radicals studied by a nitroxide trapping technique
Authors: Sato Eriko , Zetterlund Per B , Yamada Bunichiro , Busfield W Ken , Jenkins Ian D 
Published: October 2003

AbstractThe nitroxide free radical trapping technique in connection with HPLC and electrospray ionization mass spectrometry has been employed to study reactions of tert‐butoxy radicals with methyl α‐(2‐methyl‐2‐carbomethoxypropyl)acrylate (methyl methacrylate dimer (MMAD)) and methyl α‐(2,2,2‐tris(carbomethoxy)ethyl)acrylate (M(TM)EA). It has been shown that the adduct radical derived from MMAD undergoes β‐fragmentation and expels the 2‐carbomethoxy‐2‐propyl radical. No fragmentation was detected in the case of M(TM)EA. Rate coefficients of trapping and β‐fragmentation of the tert‐butoxy radical in the literature have enabled estimations of absolute rate coefficients for additions of the tert‐butoxy radical and the methyl radical to monomer, hydrogen abstraction from monomer by the tert‐butoxy radical, and β‐fragmentation of the adduct radical (MMAD only). The reactions of tert‐butoxy radicals with M(TM)EA are slower than with MMAD due to the steric hindrance of the α‐substituent. Copyright © 2003 Society of Chemical Industry
A kinetic study of the thermally initiated free radical reactions of styrene with octanedithiol as a model for the reactions of multifunctional thiols with divinylbenzene
Authors: Ang Julie B , Hill David JT , Pomery Peter J , Toh Huan 
Published: October 2003

AbstractThe kinetics of chain reactions of octanedithiol with styrene, thermally initiated with TX29B50 (a 50:50 wt% solution of TX29 diperoxy initiator in a phthalate plasticizer), have been studied over a range of initiator concentrations, a range of mixture formulations and a range of temperatures. This system has been investigated as a model system for the reactions of polyfunctional thiols with divinyl benzene. The reactions have been shown to follow first‐order kinetics for both the thiol and the ene species and to be characterized by a dependence on the initiator concentration to the power of one half. The kinetic rate parameters have been shown to adhere to Arrhenius behaviour. A kinetic model for the chain reactions for this system has been proposed. Copyright © 2003 Society of Chemical Industry
Simultaneous FT‐NIR and ESR analyses to yield propagation rate coefficients for polymerization of methyl methacrylate based monomers
Authors: Le Tri T , Hill David JT 
Published: October 2003

AbstractA hyphenated instrumental approach has been used to obtain reliable values for the propagation rate coefficients as a function of conversion for polymerizations of methyl methacrylate (MMA) and a mixture of MMA and ethyleneglycol dimethacrylate (EGDMA) with a 1:1 concentration of double bonds, from near the onset of the Trommsdorf region into the glass region. ESR spectroscopy was used to measure the radical concentration while FT‐NIR fibre‐optic spectroscopy was employed to measure instantaneously the double‐bond concentration within the temperature‐controlled cavity of the ESR instrument during polymerization. The advantage of this approach to the measurement of the rate coefficient is that it is equally applicable to branching and linear polymerizations. For the polymerization of methyl methacrylate, the values of the rate coefficient at the lowest conversions at which reliable values could be obtained were in agreement with recently reported values obtained by the PLP‐SEC method. For the lowest conversions, the values obtained were 403 l mol−1 s−1 at 306 K for MMA and 520 l mol−1 s−1 at 310 K for a 1:1 mixture of MMA and EGDMA. Copyright © 2003 Society of Chemical Industry
A study of the radiation degradation of styrene/alkane and α‐methylstyrene/alkane copolymers
Authors: Cardona Francisco , Hill David JT , Pomery Peter J , Whittaker Andrew K 
Published: October 2003

AbstractThe effects of copolymer composition and microstructure on the radiation chemistry of styrene/alkane and α‐methylstyrene/alkane copolymers have been studied. The primary radical species formed on radiolysis of the copolymers at 77 K, and identified by ESR spectroscopy, are the same as those formed during radiolysis of the homopolymers. The yields of radicals for the copolymer are as predicted assuming that the cross‐section is proportional to the electron density of each component; however, there is some evidence of radical migration to aromatic groups at 77 K. Changes in molecular structure on irradiation were detected by using 13C NMR spectroscopy. Evidence of the consumption of terminal double bonds, and chain scission in α‐methylstyrene/alkane copolymers was found. Measurements of viscosity supported the mechanism of cross‐linking predominating in styrene/alkane copolymers, while in α‐methylstyrene/alkane copolymers chain scission was the major result of irradiation. Copyright © 2003 Society of Chemical Industry
Characterisation of grafted supports used for solid‐phase synthesis
Authors: Blakey Idriss , Day Gary , Girjes Ebtihal , Hunter David S , Rasoul Firas 
Published: October 2003

AbstractA series of ‘pellicular’ type supports were fabricated by direct gamma‐radiation‐mediated graft polymerisation of styrene onto polypropylene, followed by aminomethylation. Raman spectroscopy was used for measuring the level of penetration of polystyrene graft into polypropylene, and other structural features such as density of graft and depth of functionalisation. The kinetics of the coupling of fluorenylmethylcarbamate (Fmoc)‐labelled amino acids, to the aminomethylated polystyrene grafts have been measured by UV absorption followed cleavage of the Fmoc chromophore. The Raman spectroscopy results showed that for this series of experiments the calculated rate coefficient for coupling of Fmoc‐labelled amino acids was primarily dependent on graft thickness, but was also influenced by the proportion of polystyrene graft to polypropylene. In general, it was also shown that with increasing loading capacity of support the calculated rate coefficient for amino‐acid coupling decreased correspondingly. In addition, a support that had both a high rate coefficient and a high loading capacity was prepared from polypropylene base material with a co‐continuous porous structure (high surface area). Copyright © 2003 Society of Chemical Industry
Aberrant profiles of native and oxidized glycoproteins in Alzheimer plasma
Authors: Yu Han‐Ling , Chertkow Howard M. , Bergman Howard , Schipper Hyman M. 
Published: October 2003

AbstractA proteomic approach was employed to elucidate possible differential expression of native and oxidized glycoproteins using pooled plasma samples derived from ten patients with sporadic Alzheimer's disease (AD) and pooled plasma samples from nine normal elderly control (NEC) subjects. The plasma samples were fractionated by sequential affinity chromatography on heparin‐agarose (HepA) and concanavalin A‐agarose (ConA) columns followed by separation on one‐dimensional and two‐dimensional polyacrylamide gels. Carbonylation (oxidation) of proteins was monitored by in‐strip derivatization with 2,4‐dinitrophenylhydrazine (DNP) and anti‐DNP immunoblotting. Nine spots representing glycoproteins which showed enrichment or high specific oxidation indices in AD HepA‐ConA 2‐D gels relative to NEC samples were analyzed by matrix‐assisted laser desorption‐time of flight‐mass spectrometry and identified with high probability (p < 0.001) as isoforms of human transferrin (Tf), hemopexin (Hpx) and α‐1‐antitrypsin (α‐1‐AT). These glycoproteins were concentrated, respectively, 5‐, 6.5‐ and 107‐fold in HepA‐ConA eluates derived from AD plasma relative to the NEC samples. Specific oxidation indices of the identified Tf and Hpx isoforms in AD plasma were respectively, 7.4 and 2.8 relative to NEC. Our findings provide further evidence for systemic derangements in heme/iron/redox homeostasis and activation of the acute phase response in sporadic AD. Moreover, the data implicate isoforms of Tf, Hpx and α‐1‐AT as potential biological markers of this condition.
Proteomics of the dissimilatory iron‐reducing bacterium Shewanella oneidensis MR‐1, using a matrix‐assisted laser desorption/ionization‐tandem‐time of flight mass spectrometer
Authors: Vanrobaeys Frank , Devreese Bart , Lecocq Elke , Rychlewski Leszek , De Smet Lina , Van Beeumen Jozef 
Published: October 2003

AbstractShewanella oneidensis MR‐1 is a gram‐negative facultative aerobic bacterium living at oxic‐anoxic interfaces in nature. The plasticity of terminal electron‐acceptors used under anaerobic conditions is huge, but the adaptation to these different environmental conditions remains unclear. In this work, we used a proteomic approach to study the protein content when the organism is grown under anaerobic respiration conditions on insoluble ferric oxide. By analysis of two‐dimensional gel patterns of soluble protein extracts, we discovered 20 differentially displayed proteins. The protein spots were further analyzed by mass spectrometry for which we used, in addition to nano‐high‐performance liquid chromatography coupled to an electrospray ionization‐quadrupole‐time of flight instrument, a recently introduced matrix‐assisted laser desorption/ionization (MALDI) tandem‐time of flight mass spectrometer. The instrument allows the acquisition of high quality spectra, in both the mass spectrometry and tandem mass spectrometry mode, and is therefore able to identify protein spots unambiguously. Advantageous to electrospray ionization is a minimised sample handling, inherent to MALDI ionization, and the presence of high energy fragmentation ions, generating sequence information that also can differentiate isobaric amino acids. With this strategy, we could point out a regulatory protein that is up‐regulated under iron(III) respiration. This protein, the aerobic respiration control protein (ArcA), has been reported as being a regulator during anaerobiosis in other species. To our knowledge, this is the first report of the possible involvement of ArcA from S. oneidensis MR‐1 in the reduction of ferric oxide.
Proteome analysis of the rat cornea during angiogenesis
Authors: Thompson Larry J. , Wang Feng , Proia Alan D. , Peters Kevin G. , Jarrold Brad , Greis Kenneth D. 
Published: October 2003

AbstractAngiogenesis is the formation of new blood vessels from the pre‐existing vasculature. However, the study of this complex process is often hampered by the lack of a suitable cell‐based model and the tools to study the biochemical events that lead to new blood vessel growth. The most widely accepted model for angiogenesis is the in vivo rat corneal model. In this model, the cornea, which is normally an avascular tissue, is stimulated to undergo angiogenesis in response to silver nitrate cauterization or to the implantation of an exogenous angiogenic agent. The physical changes associated with the new vessel growth can be readily monitored visually, but the regulated biochemical events that result in the growth and remodeling of the new vessels are much more challenging to decipher. In this report, a proteomics approach is evaluated for its utility in deciphering the biochemical events during a time course of angiogenic stimulation. At various time points post‐silver nitrate cautery, corneas were harvested, solubilized, and analyzed by two‐dimensional gel electrophoresis. Protein expression profiles at the various stages of angiogenesis were compared to those of control corneas. One hundred and eleven differentially‐expressed proteins were identified by either matrix‐assisted laser desorption/ionization‐time of flight mass spectrometry or liquid chromatography‐coupled electrospray ionization tandem mass spectrometry. Many of the proteins up‐regulated during the angiogenesis process were identified as blood‐related proteins, thus validating the development of functional blood vessels in the normally avascular tissue of the cornea. Furthermore, detection of differentially‐regulated proteins in cauterized versus control tissue clearly validated the utility of a proteomics approach to study this model of angiogenesis. However, in order to get at the key regulatory proteins in the angiogenesis process, it is clear that additional scale‐up and enrichment approaches will be required.
Approaches for the quantification of protein concentration ratios
Authors: Moritz Bernd , Meyer Helmut E. 
Published: October 2003

AbstractThe function of a protein is modulated by its abundance and its degree of specific post‐translational modifications such as phosphorylation, glycosylation or truncation. Consequently, changes of protein concentration and the extent of their post‐translational modifications has a great influence on the activity of intracellular substrate degradation processes, on the activity of intracellular biosynthetic pathways, on the cell cycle or on the function of a single cell in a whole organism. Defects in this area lead to diseases like cancer or neurodegeneration. Therefore, it is a challenge to quantify changes within the proteome in the diseased state or between developmental stages and to use the results obtained for the maximization of product yields in biotechnology or for the development of new drug targets to fight against diseases. In order to determine the intracellular concentration of a protein it is necessary to spike the cell sample with the same protein in a pure form. If the concentration changes of many proteins have to be determined, it takes a long time to obtain all these proteins in a pure form. Therefore, most approaches in this field are restricted to the determination of protein abundance ratios between two states such as diseased or healthy tissues. In this case the proteins in the sample of state A function as an internal standard for the proteins in the sample of state B and vice versa. The most common techniques in this field are the comparison of two‐dimensional gel spot intensities after staining or the integration of mass spectrometric peak intensities after stable isotope labelling with 13C, 15N, 18O or deuterium. The results, advantages and drawbacks of these approaches are discussed. Stable isotope labelling in combination with mass spectrometry is more accurate than the comparison of spot intensities and has the potential for the investigation of highly complex tissue samples.
Signal pathway profiling of ovarian cancer from human tissue specimens using reverse‐phase protein microarrays
Authors: Wulfkuhle Julia D. , Aquino Joy A. , Calvert Valerie S. , Fishman David A. , Coukos George , Liotta Lance A. , Petricoin Emanuel F. 
Published: October 2003

AbstractDefects in cell signaling pathways play a central role in cancer cell growth, survival, invasion and metastasis. An important goal of proteomics is to characterize and develop “circuit maps” of these signaling pathways in normal and diseased cells. We have used reverse‐phase protein array technology coupled with laser capture microdissection and phospho‐specific antibodies to examine the activation status of several key molecular “gates” involved in cell survival and proliferation signaling in human ovarian tumor tissue. The levels of activated extracellular‐regulated kinase (ERK1/2) varied considerably in tumors of the same histotype, but no significant differences between histotypes were observed. Advanced stage tumors had slightly higher levels of phosphorylated ERK1/2 compared to early stage tumors. The activation status of Akt and glycogen synthase kinase 3β, key proteins and indicators of the state of the phosphatidylinositol 3‐kinase/Akt pro‐survival pathway also showed more variation within each histotype than between the histoypes studied. Our results demonstrate the utility of reverse phase protein microarrays for the multiplexed analysis of signal transduction from discreet cell populations of cells procured directly from human ovarian tumor specimens and suggest that patterns in signal pathway activation in ovarian tumors may be patient‐specific rather than type or stage specific.
Identification of chromatin‐related protein interactions using protein microarrays
Authors: Coleman Matthew A. , Miller Kristi A. , Beernink Peter T. , Yoshikawa Daniel M. , Albala Joanna S. 
Published: October 2003

AbstractDynamic structural changes in chromatin are mediated by protein interactions that modulate multiple cellular processes including replication, transcription, recombination and DNA repair. Complexes that recognize chromatin are defined by several distinct groups of proteins that either directly modify histones or interact with histone‐DNA complexes. A protein microarray format was used to analyze the interaction of various DNA repair proteins with chromatin components. We applied proteins, antibodies and DNA to functionalized glass slides and interrogated the slides with our proteins of interest to identify novel protein‐protein interactions for proteins involved in DNA double‐strand break repair. Here we demonstrate that the DNA repair protein RAD51B, and not its cognate partner RAD51C, interacts with histones and not nucleosomes. Nucleosome‐specific interactions were demonstrated with the recently identified SWI/SNF protein, SMARCAL1. Unique RAD51B‐histone interactions were corroborated using Far Western analysis. This is the first demonstration of an interaction between RAD51B and histone proteins that may be important for the successful repair of DNA double‐strand breaks.