bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydroxyl‐ and amine‐terminated hyperbranched polyurethanes using AB2‐type azide monomers: Synthesis, characterization, fluorescence, and charge‐transfer complexation studies
Authors: Sivakumar Chickiyan , Nasar A. Sultan 
Published: May 2009

AbstractNovel AB2‐type azide monomers such as 3,5‐bis(4‐methylolphenoxy)carbonyl azide (monomer 1), 3,5‐bis(methylol)phenyl carbonyl azide (monomer 2), 4‐(methylol phenoxy) isopthaloyl azide (monomer 3), and 5‐(methylol) isopthaloyl azide (monomer 4) were synthesized. Melt and solution polymerization of these monomers yielded hydroxyl‐ and amine‐terminated hyperbranched polyurethanes with and without flexible ether groups. The structures of theses polymers were established using FT‐IR and NMR spectroscopy. The molecular weights (Mw) of the polymers were found to vary from 3.2 × 103 to 5.5 × 104 g/mol depending on the experimental conditions used. The thermal properties of the polymers were evaluated using TGA and DSC: the polymer obtained from monomer (1) exhibited lowest Tg and highest thermal stability and the polymer obtained from monomer (2) registered the highest Tg and lowest thermal stability. All the polymers displayed fluorescence maxima in the 425–525 nm range with relatively narrow peak widths indicating that they had pure and intense fluorescence. Also, the polymers formed charge transfer (CT) complexes with electron acceptor molecules such as 7,7,8,8‐tetracyano‐quino‐dimethane (TCNQ) and 1,1,2,2‐tetracyanoethane (TCNE) as evidenced by UV‐visible spectra. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3337–3351, 2009
Design, synthesis, and characterization of a partially chlorinated acrylic copolymer for low‐loss and thermally stable graded index plastic optical fibers
Authors: Koike Kotaro , Mikeš František , Okamoto Yoshiyuki , Koike Yasuhiro 
Published: May 2009

AbstractAs a novel material of low loss and high thermal stability, a graded index plastic optical fiber (GI POF) comprised of a copolymer of methyl α‐chloro acrylate (MCA) and 2,2,2‐trichloroethyl methacrylate (TCEMA) was prepared and the thermal, mechanical, and optical characteristics were investigated. Although each homopolymer had low loss and desirable high thermal stability, they had crucial disadvantages for the fiber fabrication process. To draw a MCA polymer (PMCA) fiber, it has to be heated above 270 °C. However, the polymer started to decompose at a lower temperature and produced numerous bubbles. In contrast, TCEMA polymer (PTCEMA) is too brittle to roll up during heat drawing. In this study, we succeeded to improve the strong viscoelasticity and the low decomposition temperature of PMCA and the brittleness of PTCEMA by copolymerizing MCA and TCEMA. In addition, the glass transition temperatures (Tg) of the copolymers were in the range of 133–147 °C and the transmittances of the copolymers were much higher than that of PMMA which has been commonly used as a base material of POF. A suitable GI POF was obtained using the MCA and TCEMA copolymer. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3352–3361, 2009
Photophysical and electrochemical characterization of new poly(arylene vinylene) copolymers containing quinoline or bisquinoline segments
Authors: Mikroyannidis John A. , Fakis Mihalis , Spiliopoulos Ioakim K. 
Published: May 2009

AbstractFour new fluorescent conjugated vinylene‐copolymers incorporating quinoline or bisquinoline segments along the backbone were synthesized by Heck coupling. Three of them were fluorenevinylene‐copolymers and contained quinoline (PQFV, PQFVT) or bisquinoline segments (PBQFV). One of them (PBQPV) was phenylenevinylene‐copolymer and contained bisquinoline segments. All the copolymers were soluble in common organic solvents and had relatively low glass transition temperature (Tg = 50–56 °C for fluorenevinylenes and Tg < 25 °C for phenylenevinylene). In THF solutions, the quinoline‐containing copolymers showed absorption maxima at 411–420 nm while the bisquinoline‐containing ones exhibited maxima at 357–361 nm. The emission maxima of solutions were 465–490 nm. The copolymers showed high quantum yields up to 64%. The films exhibited absorption and emission maxima in the range of 371–437 nm and 480–521 nm, respectively. All copolymers revealed reversible reduction with electron affinity of 2.66–3.53 eV and irreversible oxidation scans with ionization potential of 5.39–5.53 eV. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3370–3379, 2009
Determination of block size in poly(ethylene oxide)‐b‐polystyrene block copolymers by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Girod Marion , Mazarin Michaël , Phan Trang N. T. , Gigmes Didier , Charles Laurence 
Published: May 2009

AbstractCharacterization of block size in poly(ethylene oxide)‐b‐poly(styrene) (PEO‐b‐PS) block copolymers could be achieved by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) after scission of the macromolecules into their constituent blocks. The performed hydrolytic cleavage was demonstrated to specifically occur on the targeted ester function in the junction group, yielding two homopolymers consisting of the constitutive initial blocks. This approach allows the use of well‐established MALDI protocols for a complete copolymer characterization while circumventing difficulties inherent to amphiphilic macromolecule ionization. Although the labile end‐group in PS homopolymer was modified by the MALDI process, PS block size could be determined from MS data since polymer chains were shown to remain intact during ionization. This methodology has been validated for a PEO‐b‐PS sample series, with two PEO of number average molecular weight (Mn) of 2000 and 5000 g mol−1andMn(PS) ranging from 4000 to 21,000 g mol−1. Weight average molecular weight (Mw), and thus polydispersity index, could also be reached for each segment and were consistent with values obtained by size exclusion chromatography. This approach is particularly valuable in the case of amphiphilic copolymers for whichMnvalues as determined by liquid state nuclear magnetic resonance might be affected by micelle formation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3380–3390, 2009
One‐pot double click reactions for the preparation of H‐shaped ABCDE‐type quintopolymer
Authors: Gungor Eda , Hizal Gurkan , Tunca Umit 
Published: May 2009

AbstractWe employed for the first time double click reactions: Cu(I) catalyzed azide‐alkyne 1,3‐dipolar cycloaddition and Diels–Alder (4 + 2) reactions for the preparation of H‐shaped polymer possessing pentablocks with different chemical nature (H‐shaped quintopolymer) using one‐pot technique. H‐shaped quintopolymer consists of poly(ethylene glycol) (PEG)‐poly(methylmethacrylate) (PMMA) and poly(ε‐caprolactone) (PCL)‐polystyrene (PS) blocks as side chains and poly (tert‐butylacrylate) (PtBA) as a main chain. For the preparation of H‐shaped quintopolymer, PEG‐b‐PMMA and PCL‐b‐PS copolymers with maleimide and alkyne functional groups at their centers, respectively, were synthesized and simply reacted in one‐pot with PtBA with α‐anthracene‐ω‐azide end functionalities in N,N‐dimethylformamide (DMF) using CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) as catalyst at 120 °C for 48 h. The precursors and the target H‐shaped quintopolymer were characterized comprehensively by 1H NMR, UV, FTIR, GPC, and triple detection GPC. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3409–3418, 2009
Electrical and self‐heating properties of UHMWPE‐EMMA‐NiCF composite films
Authors: Isaji Setsuko , Bin Yuezhen , Matsuo Masaru 
Published: May 2009

AbstractConductive polymer composites (CPC) containing nickel‐coated carbon fiber (NiCF) as filler were prepared using ultra‐high molecular weight polyethylene (UHMWPE) or its mixture with ethylene‐methyl methacrylate (EMMA) as matrix by gelation/crystallization from dilute solution. The electrical conductivity, its temperature dependence, and self‐heating properties of the CPC films were investigated as a function of NiCF content and composition of matrix in details. This article reported the first successful result for getting a good positive temperature coefficient (PTC) effect with 9–10 orders of magnitude of PTC intensity for UHMWPE filled with NiCF fillers where the pure UHMWPE was used as matrix. At the same time, it was found that the drastic increase of resistivity occurred in temperature range of 120–200 °C, especially in the range of 180–200 °C, for the specimens with matrix ratio of UHMWPE and EMMA (UHMWPE/EMMA) of 1/0 and 1/1 (NiCF = 10 vol %). The SEM observation revealed to the difference between the surfaces of NiCF heated at 180 and 200 °C. Researches on the self‐heating properties of the composites indicated a very high heat transfer for this kind of CPCs. For the 1/1 composite film with 10 vol % NiCF, surface temperature (Ts) reached 125 °C within 40 s under direct electric field where the supplied voltage was only 2 V corresponding to the supplied power as 0.9 W. When the supplied voltage was enough high to make Ts beyond the melting point of UHMWPE component, the Ts and its stability of CPC films were greatly influenced by the PTC effect. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1253–1266, 2009
Characterization of multicomponent polymer trilayers with resonant soft X‐ray reflectivity
Authors: Ade H. , Wang C. , Garcia A. , Yan H. , Sohn K. E. , Hexemer A. , Bazan G. C. , Nguyen T.‐Q. , Kramer E. J. 
Published: May 2009

AbstractResonant soft X‐ray reflectivity (RSoXR) has been used to quantify the layer thicknesses and the interfacial widths of a single, complex thin film with three polymeric layers supported on an inorganic substrate. By adjusting the photon energy, the sensitivity to particular interfaces within the trilayer can be selectively enhanced. The results significantly improve and broaden the capabilities of RSoXR, which has previously only been demonstrated and used for bilayers on silicon substrates. The capability of RSoXR to characterize polymer trilayers was not readily predictable from prior bilayer results, as the RSoXR characterization of bilayers benefits from a strong X‐ray reflection from the substrate that serves as a reference beam with which the reflections from the other interfaces interfere with. The impact of having the capability to investigate trilayers is exemplified by discussing the utility of RSoXR to characterize organic electronic light emitting multilayers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1291–1299, 2009
Nonisothermal crystallization behavior of poly(m‐xylene adipamide)/montmorillonite nanocomposites
Authors: Magniez K. , Fox B. L. , Looney M. G. 
Published: May 2009

AbstractThis article reports the nonisothermal crystallization behavior of MXD6 and its clay nanocomposite system (MXD6/MMT) using differential scanning calorimetry (DSC). The DSC experimental data were analyzed by theoretical modeling of the crystallization kinetics using the Avrami, Ozawa, Jeziorny, and the combined Avrami–Ozawa semiempirical models. It has been determined that these models adequately described the crystallization behavior of the MXD6 nanocomposite at cooling rates below 20 °C/min, but there was a deviation from linear dependence at higher cooling rates. This was attributed to changes of both the free energy and the cooling crystallization function K(T) over the entire crystallization process, as well as possible relaxation effects leading to structural rearrangements. In addition, the activation energy determined using the differential isoconversional method of Friedman was also found to vary, indicating changes in both the free energy and crystallization mechanism. Despite the lack of a reliable theoretical model, the heterogeneous nucleating activity of the MMT nanoparticles was demonstrated and quantified using Dobreva's method (ϕ = 0.71), and the crystallization rate for the nanocomposite system was found to be greater than pure MXD6 by up to 79% at 40 °C/min. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1300–1312, 2009
Plasma‐Assisted Atomic Layer Deposition of Al2O3 at Room Temperature
Authors: Kääriäinen Tommi O. , Cameron David C. 
Published: May 2009

AbstractA new design of plasma source has been used for the plasma‐assisted atomic layer deposition (PA‐ALD) of Al2O3 films at room temperature. In this PA‐ALD reactor the plasma is generated by capacitive coupling directly in the deposition chamber adjacent to the substrate but can be separated from it by a grid to reduce the ion bombardment while maintaining the flow of radicals directly to the substrate surface. During the ALD cycle a mixture of nitrogen and argon was introduced into the reactor to act as a purge gas between precursor pulses and to facilitate the generation of a plasma during the plasma cycle. Sequential exposures of TMA and excited O2 precursors were used to deposit Al2O3 films on Si(100) substrates. A plasma discharge was activated during the oxygen gas pulse to form radicals in the reactor space. The experiments showed that the growth rate of the film increased with increasing plasma power and with increasing O2 pulse length before saturating at higher power and longer O2 pulse length. The growth rate saturated at the level of 1.78 Å·cycle−1. EDS analysis showed that the films were oxygen rich and had carbon as an impurity. This can be explained by the presence of bonds between hydrocarbons from the unreacted TMA precursor and excess oxygen in the film. ATR‐FTIR spectroscopy measurements indicated a change in growth mechanism when the distance between the location of the radical generation and the substrate was varied. A similar effect was observed with the use of different plasma power levels.
Quality of life issues following surgery for vulval cancer: a case report
Authors: Mcclurg Doreen , Hagen Suzanne 
Published: May 2009

AbstractBackground and Purpose. Surgical intervention for vulvar cancer and vulvar intraepithelial neoplasia causes mutilation of the genital area and can impose significant bladder, bowel and sexual dysfunction. This case report outlines how conservative interventions such as pelvic floor muscle training (PFMT) may reduce the long‐term morbidities of such dysfunction. Method. The patient underwent 16 weeks of PFMT in conjunction with advice on fluid intake and bladder training. Results. An increase in pelvic floor muscle strength and endurance were recorded. Improved bladder control as demonstrated by a reduction in frequency of voiding (from 15 to 7 per 24 hours), and number of pads used (from 6 to 3 per 24 hours) was evident. The impact of urinary incontinence on everyday life was much less at the end of the treatment period as measured by the Incontinence Impact Questionnaire with a change in score from 21 (maximum impact) to 10. Conclusions. These positive results indicate that further research is needed to investigate the effect of PFMT on bladder function following such surgery. Copyright © 2009 John Wiley & Sons, Ltd.
Insights into the anthrax lethal factor–substrate interaction and selectivity using docking and molecular dynamics simulations
Authors: Dalkas Georgios A. , Papakyriakou Athanasios , Vlamis‐Gardikas Alexios , Spyroulias Georgios A. 
Published: May 2009

AbstractThe anthrax toxin of the bacterium Bacillus anthracis consists of three distinct proteins, one of which is the anthrax lethal factor (LF). LF is a gluzincin Zn‐dependent, highly specific metalloprotease with a molecular mass of ∼90 kDa that cleaves most isoforms of the family of mitogen‐activated protein kinase kinases (MEKs/MKKs) close to their amino termini, resulting in the inhibition of one or more signaling pathways. Previous studies on the crystal structures of uncomplexed LF and LF complexed with the substrate MEK2 or a MKK‐based synthetic peptide provided structure‐activity correlations and the basis for the rational design of efficient inhibitors. However, in the crystallographic structures, the substrate peptide was not properly oriented in the active site because of the absence of the catalytic zinc atom. In the current study, docking and molecular dynamics calculations were employed to examine the LF‐MEK/MKK interaction along the catalytic channel up to a distance of 20 Å from the zinc atom. This residue‐specific view of the enzyme‐substrate interaction provides valuable information about: (i) the substrate selectivity of LF and its inactivation of MEKs/MKKs (an issue highly important not only to anthrax infection but also to the pathogenesis of cancer), and (ii) the discovery of new, previously unexploited, hot‐spots of the LF catalytic channel that are important in the enzyme/substrate binding and interaction.
Variants of human thymidylate synthase with loop 181–197 stabilized in the inactive conformation
Authors: Lovelace Leslie L. , Johnson Saphronia R. , Gibson Lydia M. , Bell Brittnaie J. , Berger Sondra H. , Lebioda Lukasz 
Published: May 2009

AbstractLoop 181–197 of human thymidylate synthase (hTS) populates two major conformations, essentially corresponding to the loop flipped by 180°. In one of the conformations, the catalytic Cys195 residue lies distant from the active site making the enzyme inactive. Ligands stabilizing this inactive conformation may function as allosteric inhibitors. To facilitate the search for such inhibitors, we have expressed and characterized several mutants designed to shift the equilibrium toward the inactive conformer. In most cases, the catalytic efficiency of the mutants was only somewhat impaired with values ofkcat/Kmreduced by factors in a 2–12 range. One of the mutants, M190K, is however unique in having the value ofkcat/Kmsmaller by a factor of ∼7500 than the wild type. The crystal structure of this mutant is similar to that of thewthTS with loop 181–197 in the inactive conformation. However, the direct vicinity of the mutation, residues 188–194 of this loop, assumes a different conformation with the positions of Cαshifted up to 7.2 Å. This affects region 116–128, which became ordered in M190K while it is disordered inwt. The conformation of 116–128 is however different than that observed in hTS in the active conformation. The side chain of Lys190 does not form contacts and is in solvent region. The very low activity of M190K as compared to another mutant with a charged residue in this position, M190E, suggests that the protein is trapped in an inactive state that does not equilibrate easily with the active conformer.
Effect of protein structure on deamidation rate in the Fc fragment of an IgG1 monoclonal antibody
Authors: Sinha Sandipan , Zhang Lei , Duan Shaofeng , Williams Todd D. , Vlasak Josef , Ionescu Roxana , Topp Elizabeth M. 
Published: May 2009

AbstractThe effects of secondary structure on asparagine (N) deamidation in a 22 amino acid sequence (369‐GFYPSDIAVEWESNGQPENNYK‐390) of the crystallizable (Fc) fragment of a human monoclonal antibody (Fc IgG1) were investigated using high‐resolution ultra performance liquid chromatography with tandem mass spectrometry (UPLC/MS). Samples containing either the intact Fc IgG (∼50 kD) (“intact protein”), or corresponding synthetic peptides (“peptide”) were stored in Tris buffer at 37°C and pH 7.5 for up to forty days, then subjected to UPLC/MS analysis with high energy MS1 fragmentation. The peptide deamidated only at N382 to form the isoaspartate (isoD382) and aspartate (D382) products in the ratio of ∼4:1, with a half‐life of ∼3.4 days. The succinimide intermediate (Su382) was also detected; deamidation was not observed for the other two sites (N387 and N388) in peptide samples. The intact protein showed a 30‐fold slower overall deamidation half‐life of ∼108 days to produce the isoD382 and D387 products, together with minor amounts of D382. Surprisingly, the D382 and isoD387 products were not detected in intact protein samples and, as in the peptide samples, deamidation was not detected at N388. The results indicate that higher order structure influences both the rate of N‐deamidation and the product distribution.
Detection of early unfolding events in a dimeric protein by amide proton exchange and native electrospray mass spectrometry
Authors: Mobley James A. , Poliakov Anton 
Published: May 2009

AbstractOligomeric proteins generally undergo unfolding through a dissociation/denaturation mechanism wherein the subunits first dissociate and then unfold. This mechanism can be detected by the fact that the proteins exhibit a concentration dependence of the denaturation curve. However, the concentration dependence does not answer the question of whether there are thermally induced conformational changes that facilitate subunit dissociation. To fully probe these mechanisms it is desirable to have an analytical approach that is capable of measuring both subunit dissociation and protein denaturation in a highly sensitive manner. In this article, we demonstrate that the combined use of native mass spectrometry to detect subunit mixing, and amide hydrogen/deuterium exchange to detect transient unfolding events can provide a very unique insight into the pre‐melting transitions in a protein oligomer. Both methods keep an isotopic record of each transformation event, without the dependence on equilibrium of the unfolding reaction. Here, we use a combined form of H/D exchange/mass spectrometry and isotopic labeling/native electrospray mass spectrometry to study the pre‐unfolding events of Bacillus subtilis NAD+ synthetase, a symmetrical dimer protein, which plays a vital role in the lifecycle of the bacteria. In the experimental outcome provided, we were able to clearly illustrate that at elevated temperatures, the NAD synthetase dimer undergoes reversible dissociation without monomer unfolding, while at temperatures where monomer unfolding is observed to take place, the rate of dimer dissociation still yet exceeds the rate of unfolding. Information provided by combining these two mass spectrometric methods was found to be very robust, and allowed us to establish an NAD synthetase unfolding model, where primary dissociation occurs prior to the complete unfolding of the NAD+ synthetase.
Prognostic value of modeled PSA clearance on biochemical relapse free survival after radical prostatectomy
Authors: You Benoit , Girard Pascal , Paparel Philippe , Freyer Gilles , Ruffion Alain , Charrié Anne , Hénin Emilie , Tod Michel , Perrin Paul 
Published: May 2009

AbstractPURPOSESUsing population kinetic approach, we modeled PSA decline equations in patients with prostate cancer after radical prostatectomy (RP). We looked for relationships between early PSA decrease profile, characterized by PSA clearance (CLPSA) or half‐life (HLPSA), and the 2‐year biochemical relapse free survival (bRFS).PATIENTS AND METHODSWe performed a retrospective study on 55 patients treated with RP and with at least 2 PSA measurements in the post‐operative month. A population kinetic model was investigated with NONMEM®. The prognostic factors regarding bRFS were assessed using univariate and multivariate analyses.RESULTSThe best model describing the PSA post‐operative decrease was bi‐compartmental and fit patient data well. Median CLPSA was 0.034 (terciles were 0.023 and 0.048). The significant prognostic factors associated with a better bRFS with univariate analysis were lower CLPSA terciles (2‐year bRFS = 100% vs. 85.1% vs. 66.7% if CLPSA < 0.023, 0.023 ≤ CLPSA < 0.048 or CLPSA ≥ 0.0480, P = 0.006) as well as initial PSA < 7 ng/ml, pT2 stage (vs. pT3), pN0 (vs. pN1) and low main Gleason score (3/5 vs. 4/5). Among these factors, CLPSA was the only independent prognostic factor with multivariate analysis regarding bRFS (HR = 0.92, 95%CI = [0.86–0.98], P = 0.0088).CONCLUSIONCLPSA determined with 4 PSA concentrations in the first month following the RP may predict the biochemical relapse risk of prostate cancer patients, thus enabling early identification of high‐risk patients requiring adjuvant treatment. A prospective validation of these results is required. Prostate 69:1325–1333, 2009. © 2009 Wiley‐Liss, Inc.