bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fabrication and characterization of double‐network agarose/polyacrylamide nanofibers by electrospinning
Authors: Cho Min Kyoung , Singu Bal Sydulu , Na Yang Ho , Yoon Kuk Ro 
Published: September 2015

ABSTRACTThis study focused on the preparation of electrospun cross‐linked double‐network (DN) of agarose/polyacrylamide (PAAm) nanofibers. The agarose formed the first‐network that was physical‐linked by the agar helix bundles. After UV‐irradiation, the chemically crosslinked PAAm was formed as the second network. The resulting cross‐linked DN agarose/PAAm nanofibers were characterized by scanning electron microscopy (SEM), contact angle, attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FT‐IR), thermogravimetric analysis (TGA), and tensile test. SEM analysis shows the agarose/PAAM nanofibers present with the thickness of 187 nm. Agarose/PAAm nanofibers were showing FT‐IR spectral peaks at ∼1660, 1590, and 1070 cm−1 indicating the presence of both agarose and polyacrylamide in the crosslinked DN Agarose/PAAm nanofiber sheet, it suggests the strong interaction and good compatibility between the two components. Agarose/PAAm nanofiber sheet was showing thermal stability close to the pure polyacrylamide. From the tensile test study, agarose/PAAm strength improved by 66.66% compared to the pure agarose. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42914.
Reduction in cadmium‐induced toxicity by c‐Jun modulation in mouse embryo limb bud cells
Authors: Kapron Carolyn M. , Cheng Le 
Published: September 2015

BackgroundWhile it is known that cadmium‐exposed embryonic cells have increased activation of c‐Jun N‐terminal kinase (JNK), the role of this stress signaling pathway in the embryotoxic response is not clear. Thus, the effects of modification of the transcription factor c‐Jun, one of the downstream targets of JNK, on cadmium‐induced embryotoxicity were investigated in primary cultures of mouse embryo limb bud cells.MethodsCultures of limb bud cells harvested on day 11 of gestation were pretreated with antisense oligonucleotides (ASO) to c‐Jun to reduce its expression, and then incubated with cadmium in the form of cadmium chloride. Toxicity was measured through assessments of cell proliferation and differentiation, while the effectiveness of the ASO in reducing c‐Jun was assessed through Western blotting using phosphorylation‐specific antibodies.ResultsWhen cells were treated with ASO c‐Jun, the total amounts of c‐Jun and also cadmium‐induced c‐Jun activation were diminished. Cadmium‐induced cytotoxicity, indicated by reduced cell numbers and differentiation, was found to decrease when cells were exposed to the antisense oligonucleotides to c‐Jun. In addition, limb cell numbers and differentiation were also enhanced by exposure to ASO in the absence of cadmium.ConclusionThe JNK pathway, and particularly the downstream effector c‐Jun, appears to play an important role in regulating cell survival and differentiation in mouse embryo limb bud cells both in the presence and absence of the toxic metal cadmium. Birth Defects Research (Part A) 103:1039–1045, 2015. © 2015 Wiley Periodicals, Inc.
Persistent astrocyte activation in the fragile X mouse cerebellum
Authors: Pacey Laura K. K. , Guan Sihui , Tharmalingam Sujeenthar , Thomsen Christian , Hampson David R. 
Published: September 2015

AbstractBackgroundFragile X Syndrome, the most common single gene cause of autism, results from loss of the RNA‐binding protein FMRP. Although FMRP is highly expressed in neurons, it has also recently been identified in glia. It has been postulated that in the absence of FMRP, abnormal function of non‐neuronal cells may contribute to the pathogenesis of the disorder. We previously demonstrated reduced numbers of oligodendrocyte precursor cells and delayed myelination in the cerebellum of fragile X (Fmr1) knockout mice.MethodsWe used quantitative western blotting and immunocytochemistry to examine the status of astrocytes and microglia in the cerebellum of Fmr1 mice during development and in adulthood.ResultsWe report increased expression of the astrocyte marker GFAP in the cerebellum of Fmr1 mice starting in the second postnatal week and persisting in to adulthood. At 2 weeks postnatal, expression of Tumor Necrosis Factor Receptor 2 (TNFR2) and Leukemia Inhibitory Factor (LIF) were elevated in the Fmr1 KO cerebellum. In adults, expression of TNFR2 and the glial marker S100β were also elevated in Fmr1 knockouts, but LIF expression was not different from wild‐type mice. We found no evidence of microglial activation or neuroinflammation at any age examined.ConclusionsThese findings demonstrate an atypical pattern of astrogliosis in the absence of microglial activation in Fmr1 knockout mouse cerebellum. Enhanced TNFR2 and LIF expression in young mice suggests that changes in the expression of astrocytic proteins may be an attempt to compensate for delayed myelination in the developing cerebellum of Fmr1 mice.
Identification and Characterization of the Streptazone E Biosynthetic Gene Cluster in Streptomyces sp. MSC090213JE08
Authors: Ohno Shoto , Katsuyama Yohei , Tajima Yuka , Izumikawa Miho , Takagi Motoki , Fujie Manabu , Satoh Noriyuki , Shin‐ya Kazuo , Ohnishi Yasuo 
Published: September 2015

AbstractStreptazone derivatives isolated from Streptomyces species are piperidine alkaloids with a cyclopenta[b]pyridine scaffold. Previous studies indicated that these compounds are polyketides, but the biosynthetic enzymes responsible for their synthesis are unknown. Here, we have identified the streptazone E biosynthetic gene cluster in Streptomyces sp. MSC090213JE08, which encodes a modular type I PKS and tailoring enzymes that include an aminotransferase, three oxidoreductases, and two putative cyclases. The functions of the six tailoring enzymes were analyzed by gene disruption, and two putative biosynthetic intermediates that accumulated in particular mutants were structurally elucidated. On the basis of these results, we propose a pathway for the biosynthesis of streptazone E in which the two putative cyclases of the nuclear transport factor 2–like superfamily are responsible for C−C bond formation coupled with epoxide ring opening to give the five‐membered ring of streptazone E.
In Vitro Reconstitution of Formylglycine‐Generating Enzymes Requires Copper(I)
Authors: Knop Matthias , Engi Pascal , Lemnaru Roxana , Seebeck Florian P. 
Published: September 2015

AbstractFormylglycine‐generating enzymes (FGEs) catalyze O2‐dependent conversion of specific cysteine residues of arylsulfatases and alkaline phosphatases into formylglycine. The ability also to introduce unique aldehyde functions into recombinant proteins makes FGEs a powerful tool for protein engineering. One limitation of this technology is poor in vitro activity of reconstituted FGEs. Although FGEs have been characterized as cofactor‐free enzymes we report that the addition of one equivalent of CuI increases catalytic efficiency more than 20‐fold and enables the identification of stereoselective C−H bond cleavage at the substrate as the rate‐limiting step. These findings remove previous limitations of FGE‐based protein engineering and also pose new questions about the catalytic mechanism of this O2‐utilizing enzyme.
Electrostatic Grafting of a Palladium N‐Heterocyclic Carbene Catalyst on a Periodic Mesoporous Organosilica and its Application in the Suzuki–Miyaura Reaction
Authors: Rajabi Fatemeh , Schaffner Dirk , Follmann Sascha , Wilhelm Christian , Ernst Stefan , Thiel Werner R. 
Published: September 2015

AbstractA periodic mesoporous organosilica material functionalized with a Pd N‐heterocyclic carbene complex was synthesized by applying an electrostatic grafting method. The resulting hybrid material was characterized by solid‐state 29Si and 13C cross‐polarization magic‐angle spinning NMR spectroscopy, XRD, thermogravimetric analysis, and BET measurements. The hybrid was applied as a catalyst for the Suzuki–Miyaura cross‐coupling between aryl chlorides and phenylboronic acid under heterogeneous and aerobic conditions. The supported catalyst exhibited excellent activity and stability and it could be reused at least six times without any loss of activity. Atomic absorption spectroscopy detected no Pd contamination in the products, and leaching tests verified that the reaction was truly heterogeneous.
Iridicycle‐Catalysed Imine Reduction: An Experimental and Computational Study of the Mechanism
Authors: Chen Hsin‐Yi Tiffany , Wang Chao , Wu Xiaofeng , Jiang Xue , Catlow C. Richard A. , Xiao Jianliang 
Published: September 2015

AbstractThe mechanism of imine reduction by formic acid with a single‐site iridicycle catalyst has been investigated by density functional theory (DFT), NMR spectroscopy, and kinetic measurements. The NMR and kinetic studies suggest that the transfer hydrogenation is turnover‐limited by the hydride formation step. The calculations reveal that, amongst a number of possibilities, hydride formation from the iridicycle and formate probably proceeds by an ion‐pair mechanism, whereas the hydride transfer to the imino bond occurs in an outer‐sphere manner. In the gas phase, in the most favourable pathway, the activation energies in the hydride formation and transfer steps are 26–28 and 7–8 kcal mol−1, respectively. Introducing one explicit methanol molecule into the modelling alters the energy barrier significantly, reducing the energies to around 18 and 2 kcal mol−1 for the two steps, respectively. The DFT investigation further shows that methanol participates in the transition state of the turnover‐limiting hydride formation step by hydrogen‐bonding to the formate anion and thereby stabilising the ion pair.
Chelate‐Thiolate‐Coordinate Ligands Modulating the Configuration and Electrochemical Property of Dinitrosyliron Complexes (DNICs)
Authors: Yeh Shih‐Wey , Lin Chih‐Wei , Liu Bai‐Heng , Tsou Chih‐Chin , Tsai Ming‐Li , Liaw Wen‐Feng 
Published: September 2015

AbstractAs opposed to the reversible redox reaction ({Fe(NO)2}10 reduced‐form DNIC [(NO)2Fe(S(CH2)3S)]2− (1)⇌{Fe(NO)2}9 oxidized‐form [(NO)2Fe(S(CH2)3S)]−), the chemical oxidation of the {Fe(NO)2}10 DNIC [(NO)2Fe(S(CH2)2S)]2− (2) generates the dinuclear {Fe(NO)2}9–{Fe(NO)2}9 complex [(NO)2Fe(μ‐SC2H4S)2Fe(NO)2]2− (3) bridged by two terminal [SC2H4S]2− ligands. On the basis of the Fe K‐edge pre‐edge energy and S K‐edge XAS, the oxidation of complex 1 yielding [(NO)2Fe(S(CH2)3S)]− is predominantly a metal‐based oxidation. The smaller S1‐Fe1‐S2 bond angle of 94.1(1)° observed in complex 1 (S1‐Fe1‐S2 88.6(1)° in complex 2), compared to the bigger bond angle of 100.9(1)° in the {Fe(NO)2}9 DNIC [(NO)2Fe(S(CH2)3S)]−, may be ascribed to the electron‐rich {Fe(NO)2}10 DNIC preferring a restricted bite angle to alleviate the electronic donation of the chelating thiolate to the electron‐rich {Fe(NO)2}10 core. The extended transition state and natural orbitals for chemical valence (ETS‐NOCV) analysis on the edt‐/pdt‐chelated {Fe(NO)2}9 and {Fe(NO)2}10 DNICs demonstrates how two key bonding interactions, that is, a FeS covalent σ bond and thiolate to the Fe d charge donation, between the chelating thiolate ligand and the {Fe(NO)2}9/10 core could be modulated by the backbone lengths of the chelating thiolate ligands to tune the electrochemical redox potential (E1/2=−1.64 V for complex 1 and E1/2=−1.33 V for complex 2) and to dictate structural rearrangement/chemical transformations (S‐Fe‐S bite angle and monomeric vs. dimeric DNICs).
Catalytic Transfer Hydrogenation with a Methandiide‐Based Carbene Complex: An Experimental and Computational Study
Authors: Weismann Julia , Gessner Viktoria H. 
Published: September 2015

AbstractThe transfer hydrogenation (TH) reaction of ketones with catalytic systems based on a methandiide‐derived ruthenium carbene complex was investigated and optimised. The complex itself makes use of the noninnocent behaviour of the carbene ligand (MCR2→MHC(H)R2), but showed only moderate activity, thus requiring long reaction times to achieve sufficient conversion. DFT studies on the reaction mechanism revealed high reaction barriers for both the dehydrogenation of iPrOH and the hydrogen transfer. A considerable improvement of the catalytic activity could be achieved by employing triphenylphosphine as additive. Mechanistic studies on the role of PPh3 in the catalytic cycle revealed the formation of a cyclometalated complex upon phosphine coordination. This ruthenacycle was revealed to be the active species under the reaction conditions. The use of the isolated complex resulted in high catalytic activities in the TH of aromatic as well as aliphatic ketones. The complex was also found to be active under base‐free conditions, suggesting that the cyclometalation is crucial for the enhanced activity.
Functionality, Effectiveness, and Mechanistic Evaluation of a Multicatalyst‐Promoted Reaction Sequence by Electrospray Ionization Mass Spectrometry
Authors: Alachraf M. Wasim , Wende Raffael C. , Schuler Sören M. M. , Schreiner Peter R. , Schrader Wolfgang 
Published: September 2015

AbstractA multicatalytic three‐step reaction consisting of epoxidation, hydrolysis, and enantioselective monoacylation of cyclohexene was studied by using mass spectrometry (MS). The reaction sequence was carried out in a one‐pot reaction using a multicatalyst. All reaction steps were thoroughly analyzed by electrospray ionization (ESI) MS (and MS/MS), as well as high‐resolution MS for structure elucidation. These studies allow us to shed light on the individual mode of action of each catalytic moiety. Thus, we find that under the epoxidation conditions, the catalytically active N‐methyl imidazole for the terminal acylation step is partially deactivated through oxidation. This observation helps to explain the lower efficiency of the catalyst in the last step compared to the monoacylation performed separately. All reactive intermediates and products of the reaction sequence, as well as of the side‐reactions, were monitored, and we present a working mechanism of the reaction.
Hetero‐Selective DNA‐Like Duplex Stabilized by Donor–Acceptor Interactions
Authors: Doi Tetsuya , Sakakibara Takumi , Kashida Hiromu , Araki Yasuyuki , Wada Takehiko , Asanuma Hiroyuki 
Published: September 2015

AbstractWe report on the characterization of a novel hetero‐selective DNA‐like duplex of pyrene and anthraquinone pseudo base pairs. The pyrene/anthraquinone pairs showed excellent selectivity in hetero‐recognition and even trimers were found to form a hetero‐duplex. Pyrene and anthraquinone moieties were tethered on acyclic D‐threoninol linkers and linked to adjacent residues by using standard phosphoramidite chemistry. When pyrene and anthraquinone were incorporated at pairing positions in complementary strands of natural DNA oligonucleotides, the duplex was stabilized significantly. Moreover, a pyrene hexamer and an anthraquinone hexamer formed a stable artificial hetero‐duplex without the assistance of natural base pairs. The pyrene/anthraquinone pair was so stable that even trimers formed a hetero‐duplex under conditions in which natural DNA strands of three residues do not.
Lewis Acid Coupled Electron Transfer of Metal–Oxygen Intermediates
Authors: Fukuzumi Shunichi , Ohkubo Kei , Lee Yong‐Min , Nam Wonwoo 
Published: September 2015

AbstractRedox‐inactive metal ions and Brønsted acids that function as Lewis acids play pivotal roles in modulating the redox reactivity of metal–oxygen intermediates, such as metal–oxo and metal–peroxo complexes. The mechanisms of the oxidative CH bond cleavage of toluene derivatives, sulfoxidation of thioanisole derivatives, and epoxidation of styrene derivatives by mononuclear nonheme iron(IV)–oxo complexes in the presence of triflic acid (HOTf) and Sc(OTf)3 have been unified as rate‐determining electron transfer coupled with binding of Lewis acids (HOTf and Sc(OTf)3) by iron(III)–oxo complexes. All logarithms of the observed second‐order rate constants of Lewis acid‐promoted oxidative CH bond cleavage, sulfoxidation, and epoxidation reactions of iron(IV)–oxo complexes exhibit remarkably unified correlations with the driving forces of proton‐coupled electron transfer (PCET) and metal ion‐coupled electron transfer (MCET) in light of the Marcus theory of electron transfer when the differences in the formation constants of precursor complexes were taken into account. The binding of HOTf and Sc(OTf)3 to the metal–oxo moiety has been confirmed for MnIV–oxo complexes. The enhancement of the electron‐transfer reactivity of metal–oxo complexes by binding of Lewis acids increases with increasing the Lewis acidity of redox‐inactive metal ions. Metal ions can also bind to mononuclear nonheme iron(III)–peroxo complexes, resulting in acceleration of the electron‐transfer reduction but deceleration of the electron‐transfer oxidation. Such a control on the reactivity of metal–oxygen intermediates by binding of Lewis acids provides valuable insight into the role of Ca2+ in the oxidation of water to dioxygen by the oxygen‐evolving complex in photosystem II.
Three‐Dimensional Nitrogen‐Doped Reduced Graphene Oxide–Carbon Nanotubes Architecture Supporting Ultrafine Palladium Nanoparticles for Highly Efficient Methanol Electrooxidation
Authors: Song Hejie , Yang Liming , Tang Yanhong , Yan Dafeng , Liu Chengbin , Luo Shenglian 
Published: September 2015

AbstractA three‐dimensional (3D) nitrogen‐doped reduced graphene oxide (rGO)–carbon nanotubes (CNTs) architecture supporting ultrafine Pd nanoparticles is prepared and used as a highly efficient electrocatalyst. Graphene oxide (GO) is first used as a surfactant to disperse pristine CNTs for electrochemical preparation of 3D rGO@CNTs, and subsequently one‐step electrodeposition of the stable colloidal GO–CNTs solution containing Na2PdCl4 affords rGO@CNTs‐supported Pd nanoparticles. Further thermal treatment of the Pd/rGO@CNTs hybrid with ammonia achieves not only in situ nitrogen‐doping of the rGO@CNTs support but also extraordinary size decrease of the Pd nanoparticles to below 2.0 nm. The resulting catalyst is characterized by scanning and transmission electron microscopy, X‐ray diffraction, Raman spectroscopy, and X‐ray photoelectron spectroscopy. Catalyst performance for the methanol oxidation reaction is tested through cyclic voltammetry and chronoamperometry techniques, which shows exceedingly high mass activity and superior durability.
Sustainable Synthesis of Chiral Tetrahydrofurans through the Selective Dehydration of Pentoses
Authors: Foster Robert W. , Tame Christopher J. , Bučar Dejan‐Krešimir , Hailes Helen C. , Sheppard Tom D. 
Published: September 2015

AbstractL‐Arabinose is an abundant resource available as a waste product of the sugar beet industry. Through use of a hydrazone‐based strategy, L‐arabinose was selectively dehydrated to form a chiral tetrahydrofuran on a multi‐gram scale without the need for protecting groups. This approach was extended to other biomass‐derived reducing sugars and the mechanism of the key cyclization investigated. This methodology was applied to the synthesis of a range of functionalized chiral tetrahydrofurans, as well as a formal synthesis of 3R‐3‐hydroxymuscarine.
Increased Microbial Butanol Tolerance by Exogenous Membrane Insertion Molecules
Authors: Hinks Jamie , Wang Yaofeng , Matysik Artur , Kraut Rachel , Kjelleberg Staffan , Mu Yuguang , Bazan Guillermo C. , Wuertz Stefan , Seviour Thomas 
Published: September 2015

AbstractButanol is an ideal biofuel, although poor titers lead to high recovery costs by distillation. Fluidization of microbial membranes by butanol is one of the major factors limiting titers in butanol‐producing bioprocesses. Starting with the hypothesis that certain membrane insertion molecules would stabilize the lipid bilayer in the presence of butanol, we applied a combination of in vivo and in vitro techniques within an in silico framework to describe a new approach to achieve solvent tolerance in bacteria. Single‐molecule tracking of a model supported bilayer showed that COE1‐5C, a five‐ringed oligo‐polyphenylenevinylene conjugated oligoelectrolyte (COE), reduced the diffusion rate of phospholipids in a microbially derived lipid bilayer to a greater extent than three‐ringed and four‐ringed COEs. Furthermore, COE1‐5C treatment increased the specific growth rate of E. coli K12 relative to a control at inhibitory butanol concentrations. Consequently, to confer butanol tolerance to microbes by exogenous means is complementary to genetic modification of strains in industrial bioprocesses, extends the physiological range of microbes to match favorable bioprocess conditions, and is amenable with complex and undefined microbial consortia for biobutanol production. Molecular dynamics simulations indicated that the π‐conjugated aromatic backbone of COE1‐5C likely acts as a hydrophobic tether for glycerophospholipid acyl chains by enhancing bilayer integrity in the presence of high butanol concentrations, which thereby counters membrane fluidization. COE1‐5C‐mitigated E. coli K12 membrane depolarization by butanol is consistent with the hypothesis that improved growth rates in the presence of butanol are a consequence of improved bilayer stability.
Deterministic K‐means secure coverage clustering with periodic authentication for wireless sensor networks
Authors: Bala Krishna M. , Doja M. N. 
Published: September 2015

SummaryInnovative and emerging developments in sensor networks are proven to be the backbone for real‐time applications such as satellite communications, military and border area surveillance systems, health care systems, traffic monitoring systems, seismic and underwater monitoring systems, and agriculture and habitat environment systems. Coverage and clustering techniques enable the sensor network to operate in group‐based and region‐based communication and thus save the node energy. Energy‐efficient protocols save the node energy and increase the network life cycle in a resource‐constrained sensor network. Cluster head (CH) node manages and controls the operations such as network topology, coverage area, and routing paths (multi‐paths and fault‐tolerant paths) of the network. In this paper, we present deterministic K‐means secure coverage clustering (K‐SCC) with periodic authentication. The proposed protocol uses coverage clustering technique with periodic authentication between the CH node and sensor nodes to establish the secure channel in the network. Maximum cover of K nodes is maintained in the secure coverage cluster to achieve authenticated communication between the sensor nodes in the network. The proposed K‐SCC protocol is compared with the existing protocols such as deterministic‐SCC and random‐SCC protocols. Simulation results indicate that the proposed K‐SCC protocol achieves an average of 84% coverage ratio (cluster/sensor node ratio) as compared with 62% coverage ratio in the existing SCC protocols. Simulations also indicate that the proposed K‐SCC protocol consumes 20% less energy as compared with the existing SCC protocol. Copyright © 2015 John Wiley & Sons, Ltd.