bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multistep Oxidase–Lyase Reactions: Synthesis of Optically Active 2‐Hydroxyketones by Using Biobased Aliphatic Alcohols
Authors: Pérez‐Sánchez María , Müller Christoph R. , Domínguez de María Pablo 
Published: May 2013

AbstractEnzymatic multistep reactions are presently an important research field, from which integrated and efficient synthetic protocols can be created, accompanied by a diminished waste formation (avoiding downstream units operations). This article explores the benzaldehyde lyase (BAL) catalyzed crossed carboligation of benzaldehyde with different aliphatic aldehydes to afford optically active α‐hydroxyketones. To this end, different biobased aliphatic alcohols were in situ oxidized to aldehydes by oxidase from Hansenula sp. and subsequently carboligated with benzaldehyde by BAL in the same reactor system. For short nonbranched aliphatic alcohols, moderate to high conversions in carboligations (15–99 %) with excellent enantioselectivities (98–99 %, R), were achieved. Both enzymes also exhibited activities at high concentrations of benzaldehyde (up to 200 mM) and with butanol as cosolvent, albeit at the cost of lower conversions, presumably owing to kinetic reasons. After needed optimization of the biocatalyst (e.g., through genetic evolution, whole‐cell setup) and the process setup (e.g., stepwise addition of substrates, reaction time), the herein reported concept might provide promising entries in the field of asymmetric synthesis, delivering useful building blocks starting from biobased materials, and in an integrative manner.
Kinetic Studies on sec‐Alcohol Racemization with Dicarbonylchloro(pentabenzylcyclopentadienyl)‐ and Dicarbonylchloro(pentaphenylcyclopentadienyl)ruthenium Catalysts
Authors: Mavrynsky Denys , Murzin Dmitry Yu. , Leino Reko 
Published: May 2013

AbstractPentasubstituted cyclopentadienyl complexes of ruthenium R5CpRu(CO)2Cl (R=Ph, benzyl) form, upon activation with tBuOK, highly active catalysts for racemization of chiral sec‐alcohols. In combination with suitable resolving enzymes, such catalyst systems can efficiently be utilized for dynamic kinetic resolution reactions providing chiral alcohols, after hydrolysis of the corresponding acetates, in high yields and high enantiomeric purities. Here, three such ruthenium complexes were first characterized by NMR spectroscopy and cyclic voltammetry analysis (CVA) for elucidating their electronic characteristics in detail. Then, accurate kinetic studies were performed providing for the first time the calculated racemization rate constants for such catalyst systems. Furthermore, the dependence of the racemization rate on the electronic structure of the catalyst was investigated from the Hammett constants, substitution patterns of the substrate, and by isotopic labeling studies. The results obtained support the earlier suggested racemization reaction mechanism and indicated that the electron‐rich catalyst Bn5CpRu(CO)2Cl (Bn=benzyl) racemizes electron‐rich substrates more efficiently and in most cases faster than its pentaphenyl substituted analogue, formerly often considered as the leading catalyst candidate for dynamic kinetic resolution applications. The electron‐deficient catalyst Ph5CpRu(CO)2Cl, in turn, is more efficient for electron‐poor substrates.
Multistimuli‐Responsive Supramolecular Organogels Formed by Low‐Molecular‐Weight Peptides Bearing Side‐Chain Azobenzene Moieties
Authors: Fatás Paola , Bachl Jürgen , Oehm Stefan , Jiménez Ana I. , Cativiela Carlos , Díaz Díaz David 
Published: May 2013

AbstractThis work demonstrates that the incorporation of azobenzene residues into the side chain of low‐molecular‐weight peptides can modulate their self‐assembly process in organic solvents leading to the formation of stimuli responsive physical organogels. The major driving forces for the gelation process are hydrogen bonding and π–π interactions, which can be triggered either by thermal or ultrasound external stimuli, affording materials having virtually the same properties. In addition, a predictive model for gelation of polar protic solvent was developed by using Kamlet–Taft solvent parameters and experimental data. The obtained viscoelastic materials exhibited interconnected multistimuli responsive behaviors including thermal‐, photo‐, chemo‐ and mechanical responses. All of them displayed thermoreversability with gel‐to‐sol transition temperatures established between 33–80 °C and gelation times from minutes to several hours. Structure–property relationship studies of a designed peptide library have demonstrated that the presence and position of the azobenzene residue can be operated as a versatile regulator to reduce the critical gelation concentration and enhance both the thermal stability and mechanical strength of the gels, as demonstrated by comparative dynamic rheology. The presence of N‐Boc protecting group in the peptides showed also a remarkable effect on the formation and properties of the gels. Despite numerous examples of peptide‐based gelators known in the literature, this is the first time in which low‐molecular‐weight peptides bearing side chain azobenzene units are used for the synthesis of “intelligent” supramolecular organogels. Compared with other approaches, this strategy is advantageous in terms of structural flexibility since it is compatible with a free, unprotected amino terminus and allows placement of the chromophore at any position of the peptide sequence.
Ion‐Pair‐Based Assemblies Comprising Pyrrole–Pyrazole Hybrids
Authors: Maeda Hiromitsu , Chigusa Kengo , Sakurai Tsuneaki , Ohta Kazuchika , Uemura Shinobu , Seki Shu 
Published: May 2013

AbstractModified 3,5‐dipyrrolylpyrazole (DPP) derivatives in their protonated form produce planar [2+2]‐type complexes with trifluoroacetate (TFA) ions. These complexes serve as constituent components of ion‐pair‐based assemblies. An essential strategy for the construction of dimension‐controlled organized structures based on these [2+2]‐type complexes is the introduction of aryl rings bearing long alkyl chains, which enables the formation of 2D patterns at interfaces, supramolecular gels, and mesophases.
Salimabromide: Unexpected Chemistry from the Obligate Marine Myxobacterium Enhygromyxa salina
Authors: Felder Stephan , Dreisigacker Sandra , Kehraus Stefan , Neu Edith , Bierbaum Gabriele , Wright Patrick R. , Menche Dirk , Schäberle Till F. , König Gabriele M. 
Published: May 2013

AbstractMarine myxobacteria (Enhygromyxa, Plesiocystis, Pseudoenhygromyxa, Haliangium) are phylogenetically distant from their terrestrial counterparts. Salimabromide is the first natural product from the Plesiocystis/Enhygromyxa clade of obligatory marine myxobacteria. Salimabromide has a new tetracyclic carbon skeleton, comprising a brominated benzene ring, a furano lactone residue, and a cyclohexane ring, bridged by a seven‐membered cyclic moiety. The absolute configuration was deduced from experimental and calculated CD data. Salimabromide revealed antibiotic activity towards Arthrobacter cristallopoietes.
All‐pass dispersion synthesis using microwave C‐sections
Authors: Gupta Shulabh , Sounas Dimitrios , Zhang Qingfeng , Caloz Christophe 
Published: May 2013

ABSTRACTA closed‐form iterative procedure for synthesizing quasi‐arbitrary phase responses with cascaded microwave C‐section all‐pass phasers is presented. The synthesis consists in mapping the transmission poles of the cascaded C‐section structure onto the transmission poles of the specified transfer function, where the latter poles are computed using a closed‐form polynomial generation method. The real and complex transmission poles of the specified transfer function are realized using C‐sections of different lengths and different couplings coefficients. The proposved synthesis is validated by both full‐wave analysis and measured multilayer prototypes. Copyright © 2013 John Wiley & Sons, Ltd.
Expression of EphA8‐Fc in transgenic mouse embryos induces apoptosis of neural epithelial cells during brain development
Authors: Kim Yujin , Park Eunjeong , Noh Hyuna , Park Soochul 
Published: May 2013

ABSTRACTEphAs and ephrin‐As are expressed in multiple regions of the developing brain and have been implicated in regulating brain size. Here, we report the identification of a novel mechanism in which reverse signaling through ephrin‐As controls neural epithelial cell number in the developing brain. Ectopic expression of EphA8‐Fc in transgenic embryos induced apoptosis of neural epithelial cells, which was accompanied by a dramatic decrease in brain size. The number of ephrin‐A5‐expressing cells was significantly reduced in the brain region where EphA8‐Fc was ectopically expressed. Furthermore,in vitroculture of the dissociated neuroepithelial cells revealed that EphA8‐Fc enhanced apoptotic cell death of the ephrinA5‐expressing cells in a caspase‐dependent manner. Thus, our results suggest that reverse signaling through ephrin‐As is biochemically linked with caspase‐dependent proapoptotic signaling during early brain development. © 2013 Wiley Periodicals, Inc. Develop Neurobiol 73: 702–712, 2013
Delimiting shades of gray: phylogeography of theNorthernFulmar,Fulmarus glacialis
Authors: Kerr Kevin C. R. , Dove Carla J. 
Published: May 2013

AbstractTheNorthernFulmar (Fulmarus glacialis) is a common tube‐nosed seabird with a disjunctHolarctic range. Taxonomic divisions within theNorthernFulmar have historically been muddled by geographical variation notably including highly polymorphic plumage. Recent molecular analyses (i.e.,DNAbarcoding) have suggested that genetic divergence betweenAtlantic andPacific populations could be on par with those typically observed between species. We employ a multigene phylogenetic analysis to better explore the level of genetic divergence between these populations and to test an old hypothesis on the origin of the modern distribution of color morphs across their range. Additionally, we test whether mutations in the melanocortin‐1 receptor gene (MC1R) are associated with dark plumage in theNorthernFulmar. We confirmed that mitochondrial lineages in theAtlantic andPacific populations are highly divergent, but nuclear markers revealed incomplete lineage sorting. Genetic divergence between these populations is consistent with that observed between many species ofProcellariiformes and we recommend elevating these two forms to separate species. We also find thatMC1Rvariation is not associated with color morph but rather is better explained by geographical divergence.
Analysis of the Hysteretic Behaviour of 3D Spin Crossover Compounds by Using an Ising‐Like Model
Authors: Chiruta Daniel , Linares Jorge , Garcia Yann , Dahoo Pierre Richard , Dimian Mihai 
Published: May 2013

AbstractIn this contribution, we use a recently developed Monte Carlo technique to investigate the impact of ferro‐, antiferromagnetic interactions for different thermodynamic parameters in a three‐dimensional Ising‐like model. We present the role of temperature and pressure on the first‐order phase‐transition between a low‐spin and a high‐spin state and identify different response curves. The analysis of one‐ and two‐step spin‐crossover behaviour has been performed by using a self‐consistent approach, because it is known that for a system with both short‐ and long‐range interactions, the Hamiltonian does not have an exact solution. However, by constructing the distributions of the states with Monte Carlo entropic sampling and by taking into account the temperature degeneracy dependence between low‐spin and high‐spin states, we could solve the Hamiltonian. We provide herein a systematic comparison to our previous experimental works and as part of our continuous interest in spin crossover nanosystems, we present a size effect study.
Quantification of the Nucleophilic Reactivities of Ethyl Arylacetate Anions
Authors: Corral‐Bautista Francisco , Mayr Herbert 
Published: May 2013

AbstractThe kinetics of the reactions of substituted ethyl arylacetates with quinone methides and structurally related diethyl benzylidenemalonates have been studied in DMSO. The second‐order rate constants (lg k2) correlated linearly with the electrophilicities E according to the linear free‐energy relationship lg k2 = sN(N + E), allowing us to determine the nucleophilicity parameters N and sN for these anions. The nucleophilic reactivities of the carbanions vary from N = 27.5 for the parent compound to N = 20.0 for the 4‐nitro‐substituted derivative.
A reductionist mechanistic model for bioconcentration of neutral and weakly polar organic compounds in fish
Authors: Kuo Dave T.F. , Di Toro Dominic M. 
Published: May 2013

Abstract

The bioconcentration factor (BCF) of neutral and weakly polar organic chemicals in fish is modeled using independently calibrated models of chemical partitioning (freely dissolved fraction of chemical in the aqueous phase [φsys] and wet-weight fish–water partition coefficient [KFW]), respiratory exchange (respiratory update rate constant [k1], and respiratory elimination rate constant [k2 = k1/KFW]), and biotransformation (whole-body biotransformation rate constant [kM]) as BCF = φsysKFW/(1 + kM/k2). Existing k1 models tend to overestimate for chemicals with log KOW &lt; 3.5, which constituted 30% to 50% of the examined chemicals. A revised k1 model covering a wider log KOW range (0–8.5) is presented k1 = (5.46 × 10−6 MW + 0.261/KOW)−1, where MW is the molecular weight. The biotransformation rate constant kM is modeled using biota internal partitioning and Abraham parameters as reactivity descriptors. The reductionist model was tested using 3 different BCF data sets (US Environmental Protection Agency's Estimation Programs Interface [EPI], n = 548; Hertfordshire, n = 210; Arnot–Gobas, n = 1855) and compared with the following 3 state-of-the-art models: 1) the EPI Suite BCFBAF module, 2) the European Commision's Computer Assisted Evaluation of industrial chemical Substances According to Regulations (CAESAR), and 3) the EPI/Arnot mechanistic kinetic model. The reductionist model performed comparably with the alternative models (root mean square errors [RMSEs] = 0.72–0.77), with only 5 fitting parameters and no training against experimental BCFs. Respiratory elimination and biotransformation dominate the total depuration (i.e., [k2 + kM]/kT ≥ 0.8) for approximately 98% of the data entries, thus validating the reductionist approximation. Mechanistic models provide greater insights into bioaccumulation and are more sensitive to biological variation. All three BCF data sets and relevant properties and checkpoint values necessary for reproducing predictions of the reductionist model have been documented. The present study shows that a streamlined mechanistic model of BCF is possible for assessment purposes. Environ Toxicol Chem 2013;32:2089–2099. © 2013 SETAC
Invasive dreissenid mussels and round gobies: A benthic pathway for the trophic transfer of microcystin
Authors: Poste Amanda E. , Ozersky Ted 
Published: May 2013

Abstract

In the present preliminary study, the authors identify 2 pathways through which invasive dreissenid mussels can transfer microcystin to higher trophic levels: either directly, through consumption by benthivorous fish such as the round goby; or indirectly, through their biodeposits, which are an important food source for benthic invertebrates. The results suggest that dreissenid mussels represent a potentially important benthic pathway for the food web transfer of microcystin. Environ Toxicol Chem 2013;32:2159–2164. © 2013 SETAC
Enzymatic biomarkers as tools to assess environmental quality: A case study of exposure of the honeybee Apis mellifera to insecticides
Authors: Carvalho Stephan M. , Belzunces Luc P. , Carvalho Geraldo A. , Brunet Jean-Luc , Badiou-Beneteau Alexandra 
Published: May 2013

Abstract

The present study was intended to evaluate the responses of enzymes in the honeybee Apis mellifera after exposure to deltamethrin, fipronil, and spinosad and their use as biomarkers. After determination of the median lethal doses (LD50), honeybees were exposed at doses of 5.07 ng/bee and 2.53 ng/bee for deltamethrin, 0.58 ng/bee and 0.29 ng/bee for fipronil, and 4.71 ng/bee and 2.36 ng/bee for spinosad (equivalent to 1/10th [LD50/10] and 1/20th [LD50/20] of the LD50, respectively). The responses of acetylcholinesterase (AChE), carboxylesterases (CaEs-1–3), glutathione-S-transferase (GST), catalase (CAT), and alkaline phosphatase (ALP) were assessed. The results showed that deltamethrin, fipronil, and spinosad modulated these biomarkers differentially. For the enzyme involved in the defense against oxidative stress, fipronil and spinosad induced CAT activity. For the remaining enzymes, 3 response profiles were identified. First, exposure to deltamethrin induced slight effects and modulated only CaE-1 and CaE-2, with opposite effects. Second, spinosad exhibited an induction profile for most of the biomarkers, except AChE. Third, fipronil did not modulate AChE, CaE-2, or GST, increased CAT and CaE-1, and decreased ALP. Thus, this set of honeybee biomarkers appears to be a promising tool to evaluate environmental and honeybee health, and it could generate fingerprints to characterize exposures to pesticides. Environ Toxicol Chem 2013;32:2117–2124. © 2013 SETAC
TYPIFYING IRRIGATED AREAS TO SUPPORT POLICY DESIGN AND IMPLEMENTATION: THE CASE OF THE GUADALQUIVIR RIVER BASIN
Authors: Gómez‐Limón J. A. , Arriaza M. , Villanueva A. J. 
Published: May 2013

ABSTRACTIrrigated agriculture in the Guadalquivir River Basin (GRB, southern Spain) has changed dramatically over the last decade, both in terms of the type of crops grown and also irrigation technology (water use efficiency). The main cause for this has been the irruption of modern olive groves, characterized by lower water demand (around 1500 m3 ha‐1) and the use of drip irrigation systems. In addition to the increase in olive plantations, accounting for approximately half of the 850 000 ha irrigated in the GRB, there has also been an intense process of modernization and intensification of irrigated agriculture, as shown by the latest Inventory of Irrigated Areas of Andalusia (2008). All these changes make it necessary to redefine irrigated areas, not only on the basis of their crop mix, but also taking into account a full array of key variables, such as irrigated area managerial features (water allotments, water pricing, etc.) and farm structural features (irrigation systems, etc.). This study classifies the irrigation areas in the GRB into five homogeneous clusters by means of factor and cluster analysis. This full typology of irrigated areas could provide useful information for policymakers to improve the design and the implementation of agricultural and water planning policies. Copyright © 2013 John Wiley & Sons, Ltd.
TRADITIONAL IRRIGATION AND WATER MANAGEMENT PRACTICES IN HIGHLAND ETHIOPIA: CASE STUDY IN DANGILA WOREDA
Authors: Belay Mehretie , Bewket Woldeamlak 
Published: May 2013

ABSTRACTThis paper examines traditional irrigation practices and their contribution to rural livelihoods in Dangila woreda (district) in the north‐western highlands of Ethiopia. Data were collected from November 2010 to May 2011 through a questionnaire survey of 126 irrigators and field observation of irrigation practices. The results show that over 90% of the irrigators used furrow systems. Around 54% of them reported that irrigation had contributed 11–20% to their household incomes in the past 12 years (1999/2000–2010/2011). The majority of the farmers agreed that the use of irrigation has increased in area coverage, crop outputs and contribution to household incomes over the past two decades. Water was distributed on rotation turns headed by water committees that were headed by individuals locally referred to as Yewha Abat (water fathers). Over 60% of the respondents indicated that they faced water and irrigable land shortages where the latter significantly influence households' irrigation income (significant at p < 0.0005). Although traditional irrigation has been known in the study area for many years, the attention offered to it from state agencies has not been encouraging. The study recommends appropriate institutional support to be provided to smallholder irrigators to improve the overall performance of traditional irrigation schemes. Copyright © 2013 John Wiley & Sons, Ltd.
Synthesis and Characterization of Chitosan Tripolyphosphate Nanoparticles and its Encapsulation Efficiency Containing Russell's Viper Snake Venom
Authors: Venkatesan C. , Vimal S. , Hameed A. S. Sahul 
Published: May 2013

ABSTRACTChitosan Tripolyphosphate (CS/TPP) nanoparticle is a biodegradable and nontoxic polysaccharide, used as a carrier for drug delivery. The morphology and particle‐size measurements of the nanoparticles were studied by field emission scanning electron microscopy and Fourier Transform Infrared Spectroscopy (FTIR). This study aims to evaluate the impact of Russell's viper venom encapsulation on various factors and loading capacity, in addition to explore the physicochemical structure of nanoparticles. FTIR confirmed that tripolyphosphoric groups of TPP linked with ammonium groups of CS in the nanoparticles. Our results showed that CS can react with TPP to form stable cationic nanoparticles. The results also showed that encapsulation efficiency of venom at different concentrations of 20, 40, 60, 500, and 1000 µg/mL were achieved for CS/TPP nanoparticles at different concentrations of 1.5, 2, and 3 mg/mL. The cytotoxicity of CS/TPP nanoparticles was evaluated by MTT (‐3 (4, 5‐Dimethylthiazol‐2‐yl)‐2, 5‐diphenyltetrazolium bromide, a tetrazole) assay. © 2013 Wiley Periodicals, Inc. J BiochemMol Toxicol 27:406‐411, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/jbt.21502
High‐energy X‐ray tomography analysis of a metal packing biofilm reactor for the production of lipopeptides byBacillus subtilis
Authors: Zune Quentin , Soyeurt Delphine , Toye Dominique , Ongena Marc , Thonart Philippe , Delvigne Frank 
Published: May 2013

AbstractBACKGROUNDWhereas multi‐species biofilm reactors are commonly used for the treatment of liquid and solid wastes, new strategies are progressing for the development of single species biofilm for the production of high‐value metabolites. Technically, this new concept relies on the design of bioreactors able to promote biofilm formation and on the identification of the key physico‐chemical parameters involved in biofilm formation.RESULTSAn experimental setting comprising a liquid continuously recirculated on a metal structured packing has been used to promoteBacillus subtilisGA1biofilm formation. The colonization of the packing has been visualized non‐invasively by X‐ray tomography. This analysis revealed an uneven, conical, distribution of the biofilm inside the packing. Compared with a submerged culture carried out in a stirred tank reactor, significant modification of the lipopeptide profile has been observed in the biofilm reactor with the disappearance of fengycin and iturin fractions and an increase of the surfactin fraction. In addition, considering the biofilm reactor design, no foam formation has been observed during the culture.CONCLUSIONSThe configuration of this biofilm reactor set‐up allows for a higher surfactin production by comparison with a submerged culture while avoiding foam formation. Additionally, scale‐up could easily be performed by increasing the number of packing elements. © 2013 Society of Chemical Industry