bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyfluorenes containing tetraphenylthiophene segments: Synthesis, photophysics, and electroluminescence
Authors: Mikroyannidis John A. 
Published: May 2006

Abstract2,5‐Bis(4‐bromophenyl)‐3,4‐diphenylthiophene was synthesized from benzyl chloride and sulfur and through the subsequent bromination of the intermediate 2,3,4,5‐tetraphenylthiophene. It was condensed with 2,7‐dibromo‐9,9‐dihexylfluorene via a nickel‐mediated Yamamoto coupling reaction to afford a new series of statistical copolymers with various compositions. In addition, poly(9,9‐dihexylfluorene) (PF) was synthesized under the same conditions for comparison. All the polymers were soluble in common organic solvents such as tetrahydrofuran (THF), chloroform, and dichloromethane. Their glass‐transition temperatures increased with an increase in the tetraphenylthiophene (TPT) content in the polymers, and they were 63–149 °C. The solutions of the polymers in THF emitted intense blue light with a photoluminescence maximum at 418–440 nm and quantum yields of 0.32–0.62. Thin films of the polymers with TPT fractions lower than 20 mol % emitted blue‐green light with two well‐resolved peaks at 445 and 520 nm and an optical band gap of about 2.85 eV. A thin film of the polymer with aTPT fraction of 50 mol % emitted pure blue light with a maximum at 419 nm and an optical band gap of 3.28 eV. An enhancement of the light‐emitting‐diode brightness by a factor of ∼8 with respect to that of PF was achieved in apolymer containing 5 mol % TPT. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4015–4026, 2006
New chiral [N,N,N]‐ligand containing titanium/zirconium precatalysts for 1‐hexene polymerization
Authors: Sudhakar Padmanabhan , Sundararajan Govindarajan 
Published: May 2006

AbstractThe ring‐opening reaction of (S)‐N‐tosyl‐2‐phenylaziridine by benzylamine in ethanol at 80 °C resulted in the formation of the (S,S)‐bis(N‐tosyl‐2‐amino‐2‐phenylethyl)benzylamine ligand in a 60% yield. The corresponding titanium complex, 1‐TiCl2, was prepared by the reaction of the dilithiated parent ligand with TiCl4. This precatalyst, in combination with methylaluminoxane, was capable of polymerizing 1‐hexene with good activities, resulting in the formation of good yields of low‐dispersity, high‐molecular‐weight polymers at low temperatures but higher yields of lower molecular weight polymers at higher temperatures. 1H and 13C NMR spectra of the polymers suggested high isotacticity and predominant chain termination via β‐hydride elimination. The enantiomerically pure catalysts, (R,R)‐1‐TiCl2 and (S,S)‐1‐TiCl2, showed nearly identical polymerization results at various polymerization temperatures. However, when the catalyst was prepared from a racemic ligand, the obtained polymers had lower molecular weights with a bimodal distribution. This observation suggested diastereomeric aggregation of the racemic catalyst, which was well supported by the NMR studies, and a modified Arrhenius plot (the natural logarithm of the number‐average molecular weight vs the reciprocal of the temperature) also showed sigmoidal behavior, indicating the existence of two or more active species. Analogous zirconium precatalysts showed similar results in the polymerization of 1‐hexene. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4006–4014, 2006
Living radical emulsion polymerization using the nanoprecipitation technique: An extension to atom transfer radical polymerization
Authors: Chan‐Seng Delphine , Georges Michael K. 
Published: May 2006

AbstractLiving radical polymerizations of styrene were performed under emulsion atom transfer radical polymerization conditions with latexes prepared by a nanoprecipitation technique recently developed for the stable free‐radical polymerization process. Latexes were prepared by the precipitation of a solution of low‐molecular‐weight polystyrene in acetone into a solution of a surfactant in water. The resulting particles were swollen with styrene and then heated. The effects of various surfactants and hydrophobic ligands, the reaction temperature, and the ligand/copper(I) bromide ratio were studied. The best results were obtained with the nonionic surfactant Brij 98 in combination with the hydrophobic ligand N,N‐bis(2‐pyridylmethyl)octadecylamine and a ligand/copper(I) bromide ratio of 1.5 at a reaction temperature of 85–90 °C. Under these conditions, latexes with good colloidal stability with average particle diameters of 200 nm were obtained. The molecular weight distributions of the polystyrenes were narrow, although the experimental molecular weights were slightly larger than the theoretical ones because not all the macroinitiator appeared to reinitiate. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4027–4038, 2006
Synthesis and properties of polyimides bearing acid groups on long pendant aliphatic chains
Authors: Yasuda Tomohiro , Li Yi , Miyatake Kenji , Hirai Michiko , Nanasawa Masato , Watanabe Masahiro 
Published: May 2006

AbstractA series of novel polyimide electrolytes having long pendant sulfo‐ or phosphoalkoxy groups were synthesized for fuel‐cell applications. Sulfodecyloxy‐, phosphodecyloxy‐, and sulfophenoxydodecyloxy‐substituted benzidine monomers were synthesized from dihydroxybenzidine. These monomers were copolymerized with naphthalene tetracarboxylic dianhydride and fluorenylidene dianiline to give the corresponding polyimides. A flexible, ductile, and self‐standing membrane was obtained via casting from the polyimide solution. Because the acid groups were on long pendant side chains and away from the main chains, the polyimide membrane showed improved oxidative and hydrolytic stability in comparison with the polyimides with sulfonic acid groups on the main chains or on the short side chains. High thermal stability (no glass‐transition temperature and a decomposition temperature > 200 °C) was also obtained. The polyimide membrane displayed high proton conductivity of 10−1 S cm−1 at 120 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3995–4005, 2006
Synthesis and characterization of new aromatic polyamides bearing crown ethers or their dipodal counterparts in the pendant structure. II. Benzo‐15‐crown‐5 and ortho‐bis[2‐(2‐ethoxyethoxy)ethoxy]benzene
Authors: Calderón Verónica , García Félix , De la Peña José L. , Maya Eva M. , Lozano Ángel E. , de la Campa José G. , de Abajo Javier , García José Miguel 
Published: May 2006

AbstractThis article describes the synthesis and characterization of two diacid monomers, each containing a benzo‐15‐crown‐5 subunit or its dipodal counterpart. Both novel monomers were reacted with technical aromatic diamines with Yamazaki's direct polyamidation method to render modified polyisophthalamides with high molecular weights containing side moieties of cyclic and acyclic ethylene oxide sequences. All the polymers were soluble in aprotic polar solvents and showed high glass‐transition temperatures in the range of 190–345 °C. The polymers with side crown ethers showed much higher glass‐transition temperatures than those with acyclic linear side ethylene oxide arms. The chemical composition, particularly with respect to the diamine and the open or closed character of the pendent ethylene oxide sequence, also affected other general properties such as the mechanical resistance, mechanical modulus, or water absorption. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4063–4075, 2006
Synthesis of laterally attached side‐chain liquid‐crystalline polynorbornenes with high mesogen density by ring‐opening metathesis polymerization
Authors: Pugh Coleen , Zhu Pukun , Kim Guehyun , Zheng Joe X. , Rubal Michael J. , Cheng Stephen Z. D. 
Published: May 2006

Abstract(±)‐exo,endo‐5,6‐Bis{[[11′‐[2″,5″‐bis[2‐(3′‐fluoro‐4′‐n‐alkoxyphenyl)ethynyl]phenyl]undecyl]oxy]carbonyl}bicyclo[2.2.1]hept‐2‐ene (n = 1–12) monomers were polymerized by ring‐opening metathesis polymerization in tetrahydrofuran at room temperature with Mo(CHCMe2Ph)(N‐2,6‐iPr2Ph)(OtBu)2 as the initiator to produce polymers with number‐average degrees of polymerization of 8–37 and relatively narrow polydispersities (polydispersity index = 1.08–1.31). The thermotropic behavior of these materials was independent of the molecular weight and therefore representative of that of a polymer at approximately 15 repeat units. The polymers exhibited an enantiotropic nematic mesophase when n was 2 or greater. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4076–4087, 2006
Effects of fluid shear stress on mRNA expression of carbonic anhydrase II in polarized rat osteoclasts
Authors: Zhang Qinghong , Liang Xing , Zhu Baoming , Dong Qiang , Xu Ling , Xia Lu , Hu Jian , Fu Jun , Liu Mengtao 
Published: May 2006

AbstractThe present study was designed to determine the effects of fluid shear stress on the mRNA expression of carbonic anhydrase II (CAII) in polarized rat osteoclasts. Cellular morphology of the polarized osteoclasts generated by a mechanical anatomical technique was examined by tartrate‐resistant acid phosphatase (TRAP) staining and the osteoclastic resorption of dentine slices. The polarized osteoclasts were then stress‐loaded by using a flow shear stress device newly developed by the osteoclast research group (patent number 200420034438; China), at 9 dyne/cm2 for various time periods [0 (control group), 15, 30, 60, and 120 min], or at various stress levels [0 (control), 0.9, 2.9, 8.7, and 26.3 dyne/cm2] for 30 min. The mRNA expression of CAII was quantified using real‐time fluorescent quantitative PCR (RT‐PCR) and the data were analyzed with SPSS 12.0 software. The polarized osteoclasts were larger than regular monocytes (about 30 μm diameter) with irregular configuration, and the majority of polarized osteoclasts appeared to be spherical and had approximately 2–20 nuclei. The TRAP positive polarized osteoclasts showed asymmetrical red staining in the cytoplasm, and had many filaments and vacuoles. These cells formed resorptive pits in dentine slices. The levels of CAII mRNA expression were shown to be time‐dependent, with the E+5 copy numbers being 7.88 ± 0.09, 11.14 ± 0.12, 15.83 ± 0.18, 1.94 ± 0.02, and 1.37 ± 0.01 in cells treated at 9 dyne/cm2 for 0, 15, 30, 60 and 120 min, respectively (P < 0.05). The levels of CAII mRNA expression (E+5 copy numbers) in cells treated with the stress levels of 0, 0.9, 2.9, 8.7 and 26.3 dyne/cm2 were 7.97 ± 0.201, 11.26 ± 0.688, 15.94 ± 0.201, 31.88 ± 1.496, and 45.08 ± 2.639, respectively (P < 0.05). These results indicate that there is a relationship between the fluid shear stress and the mRNA expression of CAII in polarized rat osteoclasts.
Clinical trials update from the American College of Cardiology: Darbepoetin alfa, ASTEROID, UNIVERSE, paediatric carvedilol, UNLOAD and ICELAND
Authors: Cleland John G.F. , Coletta Alison P. , Nikitin Nikolay P. , Clark Andrew L. 
Published: May 2006

AbstractThis article provides information and a commentary on trials relevant to the pathophysiology, prevention and treatment of heart failure, presented at the American College of Cardiology 55th Annual Scientific Session held in March 2006. All reports should be considered as preliminary data, as analyses may change in the final publication.Darbepoetin alfa increased haemoglobin levels in heart failure patients and improved some aspects of quality of life compared to placebo. In the ASTEROID study rosuvastatin significantly reduced LDL‐cholesterol levels and induced regression of atherosclerosis in patients with CAD. Rosuvastatin also produced a significant reduction in LDL‐cholesterol levels in heart failure patients in the UNIVERSE study, but had no effect on left ventricular remodelling compared to placebo. The paediatric carvedilol study failed to show a benefit of carvedilol in children with heart failure. Ultrafiltration produced a greater weight and fluid loss than intravenous diuretics in heart failure patients with volume overload in the UNLOAD study but did not exert a greater improvement in breathlessness; however, ultrafiltration did reduce readmission rates. The ICELAND MI study showed that CMR imaging was more sensitive than ECG or clinical criteria for detecting myocardial infarction.
Growth of Mytilus galloprovincialis after the Prestige oil spill
Authors: Peteiro Laura G. , Babarro José M.F. , Labarta Uxío , Fernández-Reiriz María José 
Published: May 2006

AbstractGrowth of mussel Mytilus galloprovincialis using raft culture was investigated for the first cultured generation following the Prestige oil spill off northwestern Spain. Seed from three natural populations along the Galician coastline, Pindo, Miranda, and Redes, was transplanted to a raft culture system in Ría de Ares-Betanzos. The physiological and biochemical status of mussels at the onset of culture and the degree of oil exposure three months after the spill (February 2003) have been described already, but here growth patterns of three populations sampled monthly from seeding to thinning-out (March/August 2003) and from thinning-out to harvest (August 2003/February 2004) were assessed. Mussels from Pindo (the area most affected by the oil spill) showed significantly less growth by weight than the other populations, resulting in a lower yield at harvest. The percentage of mussels classified as “large” in the Pindo population at harvest was also significantly less than that of the other two mussel populations.
Heavy Metal Stress and Sulfate Uptake in Maize Roots
Authors: Nocito Fabio F. , Lancilli Clarissa , Crema Barbara , Fourcroy Pierre , Davidian Jean-Claude , Sacchi Gian Attilio 
Published: May 2006

Abstract
ZmST1;1, a putative high-affinity sulfate transporter gene expressed in maize (Zea mays) roots, was functionally characterized and its expression patterns were analyzed in roots of plants exposed to different heavy metals (Cd, Zn, and Cu) interfering with thiol metabolism. The ZmST1;1 cDNA was expressed in the yeast (Saccharomyces cerevisiae) sulfate transporter mutant CP154-7A. Kinetic analysis of sulfate uptake isotherm, determined on complemented yeast cells, revealed that ZmST1;1 has a high affinity for sulfate (Km value of 14.6 ± 0.4 μm). Cd, Zn, and Cu exposure increased both ZmST1;1 expression and root sulfate uptake capacity. The metal-induced sulfate uptakes were accompanied by deep alterations in both thiol metabolism and levels of compounds such as reduced glutathione (GSH), probably involved as signals in sulfate uptake modulation. Cd and Zn exposure strongly increased the level of nonprotein thiols of the roots, indicating the induction of additional sinks for reduced sulfur, but differently affected root GSH contents that decreased or increased following Cd or Zn stress, respectively. Moreover, during Cd stress a clear relation between the ZmST1;1 mRNA abundance increment and the entity of the GSH decrement was impossible to evince. Conversely, Cu stress did not affect nonprotein thiol levels, but resulted in a deep contraction of GSH pools. Our data suggest that during heavy metal stress sulfate uptake by roots may be controlled by both GSH-dependent or -independent signaling pathways. Finally, some evidence suggesting that root sulfate availability in Cd-stressed plants may limit GSH biosynthesis and thus Cd tolerance are discussed.
Necrosis- and Ethylene-Inducing Peptide from Fusarium oxysporum Induces a Complex Cascade of Transcripts Associated with Signal Transduction and Cell Death in Arabidopsis
Authors: Bae Hanhong , Kim Moon S. , Sicher Richard C. , Bae Hyeun-Jong , Bailey Bryan A. 
Published: May 2006

Abstract
Treatment of Arabidopsis (Arabidopsis thaliana) with a necrosis- and ethylene-inducing peptide (Nep1) from Fusarium oxysporum inhibited both root and cotyledon growth and triggered cell death, thereby generating necrotic spots. Nep1-like proteins are produced by divergent microbes, many of which are plant pathogens. Nep1 in the plant was localized to the cell wall and cytosol based on immunolocalization results. The ratio of chlorophyll a fluorescence (F685 nm/F730 nm) significantly decreased after 75-min treatment with Nep1 in comparison to the control. This suggested that a short-term compensation of photosynthesis occurred in response to localized damage to cells. The concentrations of most water-soluble metabolites analyzed were reduced in Arabidopsis seedlings after 6 h of Nep1 treatment, indicating that the integrity of cellular membranes had failed. Microarray results showed that short-term treatment with Nep1 altered expression of numerous genes encoding proteins putatively localized to organelles, especially the chloroplast and mitochondria. Short-term treatment with Nep1 induced multiple classes of genes involved in reactive oxygen species production, signal transduction, ethylene biosynthesis, membrane modification, apoptosis, and stress. Quantitative PCR was used to confirm the induction of genes localized in the chloroplast, mitochondria, and plasma membrane, and genes responsive to calcium/calmodulin complexes, ethylene, jasmonate, ethylene biosynthesis, WRKY, and cell death. The majority of Nep1-induced genes has been associated with general stress responses but has not been critically linked to resistance to plant disease. These results are consistent with Nep1 facilitating cell death as a component of diseases caused by necrotrophic plant pathogens.
Determination of Structural Requirements and Probable Regulatory Effectors for Membrane Association of Maize Sucrose Synthase 1
Authors: Hardin Shane C. , Duncan Kateri A. , Huber Steven C. 
Published: May 2006

Abstract
Sucrose (Suc) synthase (SUS) cleaves Suc to form UDP glucose and fructose, and exists in soluble and membrane-associated forms, with the latter proposed to channel UDP glucose to the cellulose-synthase complex on the plasma membrane of plant cells during synthesis of cellulose. However, the structural features responsible for membrane localization and the mechanisms regulating its dual intracellular localization are unknown. The maize (Zea mays) SUS1 isoform is likely to have the intrinsic ability to interact directly with membranes because we show: (1) partial membrane localization when expressed in Escherichia coli, and (2) binding to carbonate-stripped plant microsomes in vitro. We have undertaken mutational analyses (truncations and alanine substitutions) and in vitro microsome-binding assays with the SUS1 protein to define intrinsic membrane-binding regions and potential regulatory factors that could be provided by cellular microenvironment. The results suggest that two regions of SUS1 contribute to membrane affinity: (1) the amino-terminal noncatalytic domain, and (2) a region with sequence similarity to the C-terminal pleckstrin homology domain of human pleckstrin. Alanine substitutions within the pleckstrin homology-like domain of SUS1 reduced membrane association in E. coli and with plant microsomes in vitro without reducing enzymatic activity. Microsomal association of wild-type SUS1 displayed cooperativity with SUS1 protein concentration and was stimulated by both lowering the pH and adding Suc. These studies offer insight into the molecular level regulation of SUS1 localization and its participation in carbon partitioning in plants. Moreover, transgenics with active SUS mutants altered in membrane affinity may be of technological utility.
Redox Regulation of a Novel Plastid-Targeted β-Amylase of Arabidopsis
Authors: Sparla Francesca , Costa Alex , Lo Schiavo Fiorella , Pupillo Paolo , Trost Paolo 
Published: May 2006

Abstract
Nine genes of Arabidopsis (Arabidopsis thaliana) encode for β-amylase isozymes. Six members of the family are predicted to be extrachloroplastic isozymes and three contain predicted plastid transit peptides. Among the latter, chloroplast-targeted β-amylase (At4g17090) and thioredoxin-regulated β-amylase (TR-BAMY; At3g23920; this work) are experimentally demonstrated to be targeted to plastids. Recombinant TR-BAMY was catalytically active only when expressed as a mature protein, i.e. with no transit peptide. Mature TR-BAMY was a monomer of 60 kD, hydrolyzing soluble starch with optimal activity between pH 6.0 and 8.0. The activity of recombinant TR-BAMY was strictly dependent on redox potential with an Em,7.0 of −302 ± 14 mV. Thioredoxins f1, m1, and y1 of Arabidopsis were all able to mediate the reductive activation of oxidized TR-BAMY. Site-specific mutants showed that TR-BAMY oxidative inhibition depended on the formation of a disulfide bridge between Cys-32 and Cys-470. Consistent with TR-BAMY redox dependency, total β-amylase activity in Arabidopsis chloroplasts was partially redox regulated and required reducing conditions for full activation. In Arabidopsis, TR-BAMY transcripts were detected in leaves, roots, flowers, pollen, and seeds. TR-BAMY may be the only β-amylase of nonphotosynthetic plastids suggesting a redox regulation of starch metabolism in these organelles. In leaves, where chloroplast-targeted β-amylase is involved in physiological degradation of starch in the dark, TR-BAMY is proposed to participate to a redox-regulated pathway of starch degradation under specific stress conditions.
NUCLEAR FUSION DEFECTIVE1 Encodes the Arabidopsis RPL21M Protein and Is Required for Karyogamy during Female Gametophyte Development and Fertilization
Authors: Portereiko Michael F. , Sandaklie-Nikolova Linda , Lloyd Alan , Dever Chad A. , Otsuga Denichiro , Drews Gary N. 
Published: May 2006

Abstract
Karyogamy, or nuclear fusion, is essential for sexual reproduction. In angiosperms, karyogamy occurs three times: twice during double fertilization of the egg cell and the central cell and once during female gametophyte development when the two polar nuclei fuse to form the diploid central cell nucleus. The molecular mechanisms controlling karyogamy are poorly understood. We have identified nine female gametophyte mutants in Arabidopsis (Arabidopsis thaliana), nuclear fusion defective1 (nfd1) to nfd9, that are defective in fusion of the polar nuclei. In the nfd1 to nfd6 mutants, failure of fusion of the polar nuclei is the only defect detected during megagametogenesis. nfd1 is also affected in karyogamy during double fertilization. Using transmission electron microscopy, we showed that nfd1 nuclei fail to undergo fusion of the outer nuclear membranes. nfd1 contains a T-DNA insertion in RPL21M that is predicted to encode the mitochondrial 50S ribosomal subunit L21, and a wild-type copy of this gene rescues the mutant phenotype. Consistent with the predicted function of this gene, an NFD1-green fluorescent protein fusion protein localizes to mitochondria and the NFD1/RPL21M gene is expressed throughout the plant. The nfd3, nfd4, nfd5, and nfd6 mutants also contain T-DNA insertions in genes predicted to encode proteins that localize to mitochondria, suggesting a role for this organelle in nuclear fusion.