bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of montmorillonite treatment and montmorillonite dispersion state on the crystallization behavior of poly(ethylene terephthalate)/montmorillonite nanocomposites
Authors: Yin Ming , Li Chuncheng , Guan Guohu , Zhang Dong , Xiao Yaonan 
Published: July 2009

AbstractTiO2/SiO2 sol was intercalated into montmorillonite (MMT), which was pretreated with polyvinylpyrrolidone (PVP). A series of poly(ethylene terephthalate) (PET)/MMT hybrids were prepared using the obtained MMT as polycondensation catalysts. X‐ray diffraction (XRD) results proved that MMT dispersion states could be controlled by the amount of TiO2/SiO2 sol that was incorporated into MMT, ranging from agglomeration to exfoliation. The crystallization behavior of PET/MMT composites synthesized in this study was characterized by differential scanning calorimeter (DSC), polarized optical microscope (POM) and scanning electron microscopy (SEM) to clarify the effects of clay treatment and its dispersion state on the crystallization behavior of the PET substrate. The results indicated that MMT treated with less PVP would retain relatively higher nucleation efficiency while when MMT containing more PVP, the nucleation effect of MMT became weaker. If MMT formed big grains within PET substrate, the disturbance of the growing crystals was negligible; but the exfoliation of MMT layers would greatly magnify the spatial constraint which would slow down the crystallization process of PET matrix. For certain exfoliated PET/MMT composites, the crystallization rate was even lower than that of pure PET though clay content was low. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Influence of doping anions on the ion exchange behavior of polypyrrole
Authors: Li Sheng , Qiu Yubing , Guo Xingpeng 
Published: July 2009

AbstractThe ion exchange behavior of polypyrrole (PPy) doped with a variety of dopants (A), namely chloride, nitrate, para‐toluene sulfonate (pTS−), and dodecyl sulfonate (DS−), was investigated by means of cyclic voltammetry (CV) in NaCl, NapTS, and AlCl3 aqueous solutions. The results show that PPy/pTS and PPy/DS films had the best anion and cation exchange ability, respectively. However, the ion exchange ability evaluated by CV charge cannot describe the exact amount of exchanged ions. For that reason, a new ion exchange experiment was designed to evaluate the amount of ions removed from NaCl aqueous solution to AlCl3 or NapTS aqueous solution. In addition, the ion exchange ratio is defined as the ratio of the charge associated with ion ejection to the synthesis charge, and can be conveniently converted to operating exchange capability (OEC). The ion exchange ratio and OEC can be used to characterize and evaluate the ion exchange ability of PPy/A films in different conditions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
The effect of coupling agent on the microwave properties of the melt‐spun iron/earth nanocomposites
Authors: Guozhi Xie , Ping Wang , Liukui Yuan , Baoshan Zhang , Pinghua Lin , Huaixian Lu 
Published: July 2009

AbstractThe effects of silane coupling agent doping on the microstructure and microwave properties of melt‐spun Nd‐Fe‐Co alloys were investigated. All as‐milled powders, with or without silane coupling agent treatment, were characterized as flake‐like shape. However, it is found that with the addition of 0.25 mL coupling agent, the as‐milled Nd‐Fe‐Co powders can deagglomerate and become more uniform dispersion with smaller thickness. In contrast, the excessive addition of coupling agent led to somewhat higher thickness of the flakes and much more amount of coupling agent on the surface of powder. The electromagnetic properties show that the Reflection loss will arrive −27.1 dB at 4.2 GHz, for the addition of 0.25 mL coupling agent powders. The probably reasons for this are discussed on the basis of the morphology of the powders, uniform dispersion and the physical coating between the polymer and coupling agent. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis of membranes of poly(vinyl ether)s and their gas permeability
Authors: Sakaguchi Toshikazu , Koide Yohei , Hashimoto Tamotsu 
Published: July 2009

AbstractCationic polymerizations of various vinyl ethers with cyclic substituents were performed with BF3OEt2. The polymers had relatively high molecular weight (Mn: 18,900–132,000), although the polymerization of phenyl vinyl ether did not proceed. According to differential scanning calorimetry, the obtained poly(vinyl ether)s showed higher glass transition temperatures than room temperature. These poly(vinyl ether)s gave free‐standing membranes both by a solution‐casting method and by a hot‐press method. In the membranes prepared by solution‐casting, the oxygen permeability coefficients of these membranes were in the range of 0.81–6.01 barrers, and poly(2‐adamanthyl vinyl ether) showed the highest gas permeability among them. Gas permeability of the membranes prepared by hot‐press was lower than that of the membranes prepared by solution‐casting. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Platinum Films with Controlled 3‐Dimensional Nanoscopic Morphologies and Their Effects on Surface Enhanced Raman Scattering
Authors: Lee Hyun‐Ju , Lee U‐Hwang , Park Jin‐Young , Yoo Sang‐Hoon , Park Sungho , Kwon Young‐Uk 
Published: July 2009

AbstractThe synthesis of Pt thin films with a controlled nanoscopic architecture that can support surface enhanced Raman scattering (SERS) is reported. The syntheses are achieved by replicating the pores of a type of mesoporous silica thin film whose pore structure could be described as a regular array of vertical channels of ∼9 nm in diameter and their interconnections, forming a 3‐dimensional pore network. Electrochemical deposition into the pores followed by the removal of the templates produced Pt films composed of arrays of vertically standing Pt nanorods with narrow gaps between them. The 3‐dimensional nanostructure increases the surface area and enables the Pt film to absorb visible light. SERS studies of rhodamine 6G and benzenethiol on such Pt films as substrates reveals that the control of the nanostructure is critical for the SERS effect.
Characterization of electrochemical activity of a strain ISO2‐3 phylogenetically related to Aeromonas sp. isolated from a glucose‐fed microbial fuel cell
Authors: Chung Kyungmi , Okabe Satoshi 
Published: July 2009

AbstractThe microbial communities associated with electrodes in closed and open circuit microbial fuel cells (MFCs) fed with glucose were analyzed by 16S rRNA approach and compared. The comparison revealed that bacteria affiliated with the Aeromonas sp. within the Gammaproteobacteria constituted the major population in the closed circuit MFC (harvesting electricity) and considered to play important roles in current generation. We, therefore, attempted to isolate the dominant bacteria from the anode biofilm, successfully isolated a Fe (III)‐reducing bacterium phylogenetically related to Aeromonas sp. and designated as strain ISO2‐3. The isolated strain ISO2‐3 could grow and concomitantly produce current (max. 0.24 A/m2) via oxidation of glucose or hydrogen with an electrode serving as the sole electron acceptor. The strain could ferment glucose, but generate less electrical current. Cyclic voltammetry supported the strain ISO2‐3 was electrically active and likely to transfer electrons to the electrode though membrane‐associated compounds (most likely c‐type cytochrome). This mechanism requires intimate contact with the anode surface. Scanning electron microscopy revealed that the strain ISO2‐3 developed multiplayer biofilms on the anode surface and also produced anchor‐like filamentous appendages (most likely pili) that may promote long‐range electron transport across the thick biofilm. Biotechnol. Bioeng. 2009; 104: 901–910. © 2009 Wiley Periodicals, Inc.
Expression of merA, trxA, amoA, and hao in continuously cultured Nitrosomonas europaea cells exposed to cadmium sulfate additions
Authors: Radniecki Tyler S. , Semprini Lewis , Dolan Mark E. 
Published: July 2009

AbstractThe effects of CdSO4 additions on the gene expressions of a mercury reductase, merA, an oxidative stress protein, trxA, the ammonia‐monooxygenase enzyme (AMO), amoA, and the hydroxylamine oxidoreductase enzyme (HAO), hao, were examined in continuously cultured N. europaea cells. The reactor was fed 50 mM NH4+ and was operated for 78 days with a 6.9 days hydraulic retention time. Over this period, six successive batch additions of CdSO4 were made with increasing maximum concentrations ranging from 1 to 60 µM Cd2+. The expression of merA was highly correlated with the level of Cd2+ within the reactor (Rs = 0.90) with significant up‐regulation measured at non‐inhibitory Cd2+ concentrations. Cd2+ appears to target AMO specifically at lower concentrations and caused oxidative stress at higher concentrations, as indicated by the SOURs (specific oxygen uptake rates) and the up‐regulation of trxA. Since Cd2+ inhibition is irreversible and amoA was up‐regulated in response to Cd2+ inhibition, it is hypothesized that de novo synthesis of the AMO enzyme occurred and was responsible for the observed recovery in activity. Continuously cultured N. europaea cells were more resistant to Cd2+ inhibition than previously examined batch cultured cells due to the presence of Mg2+ and Ca2+ in the growth media, suggesting that Cd2+ enters the cell through Mg2+ and Ca2+ import channels. The up‐regulation of merA during exposure to non‐inhibitory Cd2+ levels indicates that merA is an excellent early warning signal for Cd2+ inhibition. Biotechnol. Bioeng. 2009; 104: 1004–1011. © 2009 Wiley Periodicals, Inc.
Construction of Hansenula polymorpha strains with improved thermotolerance
Authors: Ishchuk Olena P. , Voronovsky Andriy Y. , Abbas Charles A. , Sibirny Andriy A. 
Published: July 2009

AbstractThe methylotrophic yeast Hansenula polymorpha has the potential to be used in the process of simultaneous saccharification and fermentation (SSF) of xylan derived xylose at elevated temperatures. To improve parameters of high‐temperature resistance and high‐temperature fermentation of H. polymorpha, strains carrying deletion of acid trehalase gene (ATH1) and overexpressing genes coding for heat‐shock proteins Hsp16p and Hsp104p were constructed. Results indicate that the corresponding recombinant strains have up to 12‐fold increased tolerance to heat‐shock treatment. The deletion of ATH1 gene and constitutive expression of HSP16 and HSP104 resulted in up to 5.8‐fold improvement of ethanol production from xylose at 50°C. Although the maximum ethanol concentration achieved from xylose was 0.9 g L−1, our model H. polymorpha strains with elevated thermotolerance can be further modified by metabolic engineering to construct improved high‐temperature ethanol producers from this pentose. Biotechnol. Bioeng. 2009; 104: 911–919. © 2009 Wiley Periodicals, Inc.
Bacterial artificial chromosome library for genome‐wide analysis of Chinese hamster ovary cells
Authors: Omasa Takeshi , Cao Yihua , Park Joon Young , Takagi Yasuhiro , Kimura Shuichi , Yano Hidenori , Honda Kohsuke , Asakawa Shuichi , Shimizu Nobuyoshi , Ohtake Hisao 
Published: July 2009

AbstractChinese hamster ovary (CHO) cell lines are widely used for scientific research and biotechnology. A CHO genomic bacterial artificial chromosome (BAC) library was constructed from a mouse dihydrofolate reductase (DHFR) gene‐amplified CHO DR1000L‐4N cell line for genome‐wide analysis of CHO cell lines. The CHO BAC library consisted of 122,281 clones and was expected to cover the entire CHO genome five times. A CHO chromosomal map was constructed by fluorescence in situ hybridization (FISH) imaging using BAC clones as hybridization probes (BAC‐FISH). Thirteen BAC‐FISH marker clones were necessary to identify all the 20 individual chromosomes in a DHFR‐deficient CHO DG44 cell line because of the aneuploidy of the cell line. To determine the genomic structure of the exogenous Dhfr amplicon, a 165‐kb DNA region containing exogenous Dhfr was cloned from the BAC library using high‐density replica (HDR) filters and Southern blot analysis. The nucleotide sequence analysis revealed a novel genomic structure in which the vector sequence containing Dhfr was sandwiched by long inverted sequences of the CHO genome. Biotechnol. Bioeng. 2009; 104: 986–994. © 2009 Wiley Periodicals, Inc.
Simultaneous saccharification and co‐fermentation of paper sludge to ethanol by Saccharomyces cerevisiae RWB222—Part I: Kinetic modeling and parameters
Authors: Zhang Jiayi , Shao Xiongjun , Townsend Oliver V. , Lynd Lee R. 
Published: July 2009

AbstractA kinetic model was developed to predict batch simultaneous saccharification and co‐fermentation (SSCF) of paper sludge by the xylose‐utilizing yeast Saccharomyces cerevisiae RWB222 and the commercial cellulase preparation Spezyme CP. The model accounts for cellulose and xylan enzymatic hydrolysis and competitive uptake of glucose and xylose. Experimental results show that glucan and xylan enzymatic hydrolysis are highly correlated, and that the low concentrations of xylose encountered during SSCF do not have a significant inhibitory effect on enzymatic hydrolysis. Ethanol is found to not only inhibit the specific growth rate, but also to accelerate cell death. Glucose and xylose uptake rates were found to be competitively inhibitory, but this did not have a large impact during SSCF because the sugar concentrations are low. The model was used to evaluate which constants had the greatest impact on ethanol titer for a fixed substrate loading, enzyme loading, and fermentation time. The cellulose adsorption capacity and cellulose hydrolysis rate constants were found to have the greatest impact among enzymatic hydrolysis related constants, and ethanol yield and maximum ethanol tolerance had the greatest impact among fermentation related constants. Biotechnol. Bioeng. 2009; 104: 920–931. © 2009 Wiley Periodicals, Inc.
Biosynthesis of 2‐Hydroxy and iso‐Even Fatty Acids is Connected to Sphingolipid Formation in Myxobacteria
Authors: Ring Michael W. , Schwär Gertrud , Bode Helge B. 
Published: July 2009

Abstract2‐Hydroxy fatty acids can be found in several different organisms, including bacteria. In this study, we have studied the biosynthesis of 2‐hydroxy fatty acids in the myxobacteria Myxococcus xanthus and Stigmatella aurantiaca, resulting in the identification of a family of stereospecific fatty acid α‐hydroxylases. Although the stereospecificities of the hydroxylases differ between these two species, they share a common function in supporting fatty acid α‐oxidation; that is, the oxidative shortening of fatty acids. Whereas in S. aurantiaca this process takes place during normal vegetative growth, in M. xanthus it takes place only under developmental conditions. We were also able to identify serine palmitoyltransferase encoding genes involved in sphingolipid biosynthesis as well as sphingolipids themselves in both types of myxobacteria, and were able to show that the α‐hydroxylation reaction is in fact dependent on the presence of fatty acids bound to sphingolipids.
STD‐NMR Studies Suggest that Two Acceptor Substrates for GlfT2, a Bifunctional Galactofuranosyltransferase Required for the Biosynthesis of Mycobacterium tuberculosis Arabinogalactan, Compete for the Same Binding Site
Authors: Szczepina Monica G. , Zheng Ruixiang Blake , Completo Gladys C. , Lowary Todd L. , Pinto B. Mario 
Published: July 2009

AbstractThe mycobacterial cell wall is a complex architecture, which has, as its major structural component, a lipidated polysaccharide covalently bound to peptidoglycan. This structure, termed the mycolyl–arabinogalactan–peptidoglycan complex, possesses a core galactan moiety composed of approximately 30 galactofuranosyl (Galf) resides attached via alternating β‐(1→6) and β‐(1→5) linkages. Recent studies have shown that the entire galactan is synthesized by the action of only two bifunctional galactofuranosyltransferases, GlfT1 and GlfT2. We report here saturation‐transfer difference (STD) NMR spectroscopy studies with GlfT2 using two trisaccharide acceptor substrates, β‐D‐Galf‐(1→6)‐β‐D‐Galf‐(1→5)‐β‐D‐Galf‐O(CH2)7CH3 (2) and β‐D‐Galf‐(1→5)‐β‐D‐Galf‐(1→6)‐β‐D‐Galf‐O(CH2)7CH3 (3), as well as the donor substrate for the enzyme, UDP‐Galf. Competition STD‐NMR titration experiments and saturation transfer double difference (STDD) experiments with 2 and 3 were undertaken to explore the bifunctionality of this enzyme, in particular to answer whether one or two active sites are responsible for the formation of both β‐(1→5)‐ and β‐(1→6)‐Galf linkages. It was demonstrated that 2 and 3 bind competitively at the same site; this suggests that GlfT2 has one active site pocket capable of catalyzing both β‐(1→5) and β‐(1→6) galactofuranosyl transfer reactions. The addition of UDP‐Galf to GlfT2 in the presence of either 2 or 3 generated a tetrasaccharide product; this indicates that the enzyme was catalytically active under the conditions at which the STD‐NMR experiments were carried out.
Influence of the Nucleophile on the Candida antarctica Lipase B‐Catalysed Resolution of a Chiral Acyl Donor
Authors: García‐Urdiales Eduardo , Ríos‐Lombardía Nicolás , Mangas‐Sánchez Juan , Gotor‐Fernández Vicente , Gotor Vicente 
Published: July 2009

AbstractThe resolution of methyl (±)‐3‐hydroxypentanoate catalysed by Candida antarctica lipase B has been performed by using ammonia and benzyl amine as nucleophiles. In all cases, the lipase reacts faster with the R enantiomer of the ester, but when benzyl amine is used, the enantiomeric ratio is approximately three times as high as that measured for ammonia. The analysis of the molecular dynamics simulations carried out over the corresponding deacylation transition state analogues indicated specular binding modes between enantiomers that vary greatly upon the nucleophile used. For the case of ammonia, an intramolecular hydrogen bond between the β‐hydroxyl group and the protons of the nucleophile is established. However, the presence of the substituent in benzyl amine disrupts this interaction. Instead, the acyl chain binds to a more restrictive area of the protein where the higher number of contacts established with the side chains of Thr40, Gln157 and Ile189 have been identified as the reason for the higher enantioselectivity observed in the aminolysis reaction.
Mechanisms in the Reaction of Palladium(II)–π‐Allyl Complexes with Aryl Halides: Evidence for NHC Exchange Between Two Palladium Complexes
Authors: Normand Adrien T. , Nechaev Mikhail S. , Cavell Kingsley J. 
Published: July 2009

AbstractA detailed experimental and DFT study (PBE level) of the reaction of [Pd(η3‐C3H5)(tmiy)(PR3)]BF4 (tmiy=tetramethylimidazolin‐2‐ylidene, PR3=phosphane), precursors to monoligated Pd0 species, with aryl electrophiles yielding 2‐arylimidazolium salt is reported. Experiments establish that an autocatalytic ligand transfer mechanism is preferred over PdIV and σ‐bond metathesis pathways, and that transmetalation is the rate‐determining step. Calculations indicate that the key step involves the concerted exchange of NHC and iodo ligands between two different PdII complexes. This is corroborated by experimental results showing the slower reaction of complexes containing the bulkier dipdmiy (dipdmiy = diisopropyldimethylimidazolin‐2‐ylidene).
A Cascade FRET‐Mediated Ratiometric Sensor for Cu2+Ions Based on Dual Fluorescent Ligand‐Coated Polymer Nanoparticles
Authors: Frigoli Michel , Ouadahi Karima , Larpent Chantal 
Published: July 2009

AbstractCore‐shell type dual fluorescent nanoparticles (NPs) in the 16 nm diameter range with a selective ligand (cyclam) attached to the surface and two fluorophores—9,10‐diphenyl‐anthracene (donor, D) and pyrromethene PM 567 (acceptor, A)—embedded within the polymer core were synthesized and their fluorescent and copper‐sensing properties were studied and compared to single D‐doped and A‐doped NPs. The acceptor (A) and donor (D) dyes were chosen to allow two sequential Förster resonance energy transfer (FRET) processes from D to A and from the encapsulated dyes to copper complexes that form at the surface and act as quenchers. NPs with different D/A loads were readily obtained by two consecutive entrapments of the dyes. Dual NPs present tunable fluorescence emission that is dependent on the doping ratio. FRET from D to A results in sensitized emission from A upon excitation of D, with FRET efficiencies reaching 80 % at high acceptor loads. A 9‐fold amplification of the signal of A is observed at high D‐to‐A ratios. Single‐ and dual‐dye‐doped NPs were used to detect the presence of cupric ions in water by using the quenching of fluorescence as a transduction signal. In accordance with the spectral overlaps and the values of the critical distance (R0) of D– and A–copper complex pairs, the acceptor is much more sensitive than the donor. In dual fluorescent NPs, the sensitized emission of A is efficiently attenuated whereas the remaining emission of D is much less affected, allowing the detection of copper in a ratiometric manner upon excitation at a single (D) wavelength. Dual‐dye‐doped NPs with the highest acceptor loads (23 A‐per‐NP) were found to be the most sensitive for the detection of copper over a wide range of concentrations (20 nM to 8.5 μM). Owing to its great convenience and modularity, the cascade FRET strategy based on dual fluorescent NPs holds great promise for the design of various sensing nanodevices.
Oxyma: An Efficient Additive for Peptide Synthesis to Replace the Benzotriazole‐Based HOBt and HOAt with a Lower Risk of Explosion[1]
Authors: Subirós‐Funosas Ramon , Prohens Rafel , Barbas Rafael , El‐Faham Ayman , Albericio Fernando 
Published: July 2009

AbstractOxyma [ethyl 2‐cyano‐2‐(hydroxyimino)acetate] has been tested as an additive for use in the carbodiimide approach for formation of peptide bonds. Its performance in relation to those of HOBt and HOAt, which have recently been reported to exhibit explosive properties, is reported. Oxyma displayed a remarkable capacity to inhibit racemization, together with impressive coupling efficiency in both automated and manual synthesis, superior to those of HOBt and at least comparable to those of HOAt, and surpassing the latter coupling agent in the more demanding peptide models. Stability assays showed that there was no risk of capping the resin under standard coupling conditions. Finally, calorimetry assays (DSC and ARC) showed decomposition profiles for benzotriazole‐based additives that were consistent with their reported explosivities and suggested a lower risk of explosion in the case of Oxyma.
Stereospecific Synthesis of β3‐Amino Acid Derivatives from Propargylic Alcohols: Efficient Solution‐Phase Synthesis of Oligopeptides without Coupling Agents
Authors: Temperini Andrea , Terlizzi Raffaella , Testaferri Lorenzo , Tiecco Marcello 
Published: July 2009

AbstractA stereospecific synthesis of β3‐amino acids has been accomplished starting from readily available and enantioenriched propargylic alcohols. This conversion can be effected in only three steps by selenium‐mediated organic transformations of the carbon–carbon triple bond. This method is especially attractive because the reactive Se‐phenyl selenocarboxylate intermediates can be trapped with the amine functionality of an amino acid derivative. Through this strategy a chain elongation at the N‐terminus has been effected. The N‐deprotection and repetition of the homologation with other Se‐phenyl selenocarboxylate intermediates produced β‐ and mixed α/β‐oligopeptides without the use of coupling agents.