bluuebunny/crossref_metadata_2025_split huggingface dataset:
Increasing AIP Macrocycle Size Reveals Key Features of agr Activation in Staphylococcus aureus
Authors: Johnson Jeffrey G. , Wang Boyuan , Debelouchina Galia T. , Novick Richard P. , Muir Tom W. 
Published: March 2015

AbstractThe agr locus in the commensal human pathogen, Staphylococcus aureus, is a two‐promoter regulon with allelic variability that produces a quorum‐sensing circuit involved in regulating virulence within the bacterium. Secretion of unique autoinducing peptides (AIPs) and detection of their concentrations by AgrC, a transmembrane receptor histidine kinase, coordinates local bacterial population density with global changes in gene expression. The finding that staphylococcal virulence can be inhibited through antagonism of this quorum‐sensing pathway has fueled tremendous interest in understanding the structure–activity relationships underlying the AIP–AgrC interaction. The defining structural feature of the AIP is a 16‐membered, thiolactone‐containing macrocycle. Surprisingly, the importance of ring size on agr activation or inhibition has not been explored. In this study, we address this deficiency through the synthesis and functional analysis of AIP analogues featuring enlarged and reduced macrocycles. Notably, this study is the first to interrogate AIP function by using both established cell‐based reporter gene assays and newly developed in vitro AgrC‐I binding and autophosphorylation activity assays. Based on our data, we present a model for robust agr activation involving a cooperative, three‐points‐of‐contact interaction between the AIP macrocycle and AgrC.
The bigger they are, the harder they fall: A topical review on sedimented solutes for solid‐state NMR
Authors: Ravera Enrico 
Published: March 2015

ABSTRACTSample preparation for solid‐state NMR of soluble proteins is all but a trivial accomplishment and often represents the factor that determines the success of the experiments, despite the dramatic methodological and technological improvements in the field of SSNMR. Several different sample preparation have been proposed and applied over the years, with varied results. Among those methods we have proposed the use of sedimentation for obtaining samples with high sensitivity and resolution. This review aims at covering the applications of NMR to sedimented solutes from its first description to the latest developments with implications in the field of DNP. © 2015 Wiley Periodicals, Inc. Concepts Magn Reson Part A 43A: 209–227, 2015.
Thymol Bromination – A Comparison between Enzymatic and Chemical Catalysis
Authors: Sabuzi Federica , Churakova Ekaterina , Galloni Pierluca , Wever Ron , Hollmann Frank , Floris Barbara , Conte Valeria 
Published: March 2015

AbstractThe catalytic activity of the vanadium‐dependent bromoperoxidase isolated from the brown alga Ascophyllum nodosum is compared with the activity of a cheap, commercially available V‐catalyst precursor in the bromination of thymol. Organic solvents have been avoided to make the system appealing from a sustainable chemistry point of view. It is noteworthy that, notwithstanding the low solubility of the substrate, the thymol bromination reactions were performed in water, with a safe brominating source, under mild conditions, and with relatively inexpensive reagents. In this regard, the greenness of the systems was evaluated by the estimation of the E‐factor value; the result is that the chemical reaction has a lower environmental impact than the enzymatic process, with an E‐factor in the range of eco‐friendly processes.
Interception of Nazarov Reactions of Allenyl Vinyl Ketones with Dienes: (3+2)‐ versus (4+3)‐Cycloaddition and Subsequent Rearrangement
Authors: Morgan Timothy D. R. , LeFort François M. , Li Zhe , Marx Vanessa M. , Boyd Russell J. , Burnell D. Jean 
Published: March 2015

AbstractCapture of the cyclic oxyallyl cation intermediates from the BF3‐mediated Nazarov reactions of three allenyl vinyl ketones with various dienes was accomplished by (3+2)‐ and (4+3)‐cycloaddition. The relative amounts of these types of products were dependent on the substitution on the diene, and this could be linked to steric hindrance. Treatment of the (3+2)‐cycloaddition products with BF3·Et2O led mainly to decomposition but also to ring‐opened molecules and ring‐enlarged structures. The computed Gibbs energies of the (3+2)‐cycloaddition products, the products of the acid treatment and of some transition states leading to rearranged products were compared.
Synthesis and Characterization of Co3O4/Multiwalled Carbon Nanotubes Nanocomposite for Amperometric Sensing of Hydrazine
Authors: Zhang Jie , Liu Haijing , Dou Meiling , Wang Feng , Liu Jingjun , Li Zhilin , Ji Jing 
Published: March 2015

AbstractCo3O4 nanoparticles (NPs) were synthesized and decorated on the multi‐walled carbon nanotubes (MWCNTs) through a simple hydrothermal procedure. The deposited Co3O4 NPs on the sidewalls of MWCNTs were found to be cubic crystal structure and homogenously dispersed with a narrow particle size distribution centered at around 6 nm. The Co3O4/MWCNTs nanocomposite was then utilized for the electrochemical detection of hydrazine, and exhibited a high sensitivity of 34.5 µA mM−1, a low detection limit of 0.8 µM (S/N=3), a wide linear range of 20 µM to 1.1 mM along with a short response time of less than 5 s.
One‐Pot Methods for the Protection and Assembly of Sugars
Authors: Zulueta Medel Manuel L. , Janreddy Donala , Hung Shang‐Cheng 
Published: March 2015

AbstractIn recent years, there has been rapid expansion of glycan synthesis, fueled by the recognition that the structural complexity of sugars translates to a myriad of biological functions. Such chemical syntheses involve many challenges, mostly due to the regio‐ and stereochemical aspects of glycosidic bond formation. One‐pot strategies were developed to assist in attaining faster and more economical access to the glycan constructs. In this front, achievements in protecting group manipulation, glycosylation, and combinations of these have been reported. Protecting group manipulations in one pot take advantage of the reaction compatibility of commonly used transformations, many of which occur in high regioselectivity. Sequential glycosylations, on the other hand, rely on leaving group orthogonalities and reactivity tuning, as well as the preactivation technique. Altogether, these approaches offer attractive means to the much needed glycan structures and, consequently, help usher in advances in glycoscience.
The synthesis of new coke‐resistant support and its application in propane dehydrogenation to propene
Authors: Zhou Shijian , Zhou Yuming , Zhang Yiwei , Sheng Xiaoli , Zhang Zewu 
Published: March 2015

AbstractBACKGROUNDZSM‐5 zeolite has been used as a common support for PtSn‐based catalyst in the propane dehydrogenation reaction. But owing to its high acidy, coke accommodation and stability of the catalyst are not satisfactory. Here, in order to improve the performance, the new hierarchical‐porous ZSM‐5 (abbreviated henceforth as ZQ) has been synthesized.RESULTSBy the introduction of hierarchical‐pores in ZQ, the pore structure was changed, the acid content was decreased, and the surface properties were promoted. These modifications to zeolite greatly improved the capacity of catalysts to accommodate coke. Moreover, the coke deposit on PtSnNa/ZQ migrated from active metal to the support. As expected, by using the catalyst PtSnNa/ZQ, the catalytic performance of propane dehydrogenation to propene and the stability of the catalyst were significantly promoted.CONCLUSIONSThe new hierarchical‐porous ZSM‐5 support (ZQ) exhibits enhanced capacity to accommodate coke, and PtSnNa/ZQ enabled better propane conversion and improved catalyst stability. © 2015 Society of Chemical Industry
The larval head structures of Podagricomela shirahatai (Chûjô) (Chrysomelidae, Galerucinae, Alticini) and morphological effects of leaf mining
Authors: Hua Yi , Beutel Rolf G. , Ge Si‐Qin , Yang Xing‐Ke 
Published: March 2015

ABSTRACTCover illustration. The larvae of the leaf beetle species Podagricomela shirahatai are specialized leaf‐miners. In this issue of the Journal of Morphology, Hua et al. (pp. 446–457 10.1002/jmor.20352) present a detailed morphological analysis of the head structures of P. shirahatai and discuss the morphological adaptations to leaf mining in these larvae.
Incorporating Virtual Reactions into a Logic‐based Ligand‐based Virtual Screening Method to Discover New Leads
Authors: Reynolds Christopher R. , Muggleton Stephen H. , Sternberg Michael J. E. 
Published: March 2015

AbstractThe use of virtual screening has become increasingly central to the drug development pipeline, with ligand‐based virtual screening used to screen databases of compounds to predict their bioactivity against a target. These databases can only represent a small fraction of chemical space, and this paper describes a method of exploring synthetic space by applying virtual reactions to promising compounds within a database, and generating focussed libraries of predicted derivatives. A ligand‐based virtual screening tool Investigational Novel Drug Discovery by Example (INDDEx) is used as the basis for a system of virtual reactions. The use of virtual reactions is estimated to open up a potential space of 1.21×1012 potential molecules. A de novo design algorithm known as Partial Logical‐Rule Reactant Selection (PLoRRS) is introduced and incorporated into the INDDEx methodology. PLoRRS uses logical rules from the INDDEx model to select reactants for the de novo generation of potentially active products. The PLoRRS method is found to increase significantly the likelihood of retrieving molecules similar to known actives with a p‐value of 0.016. Case studies demonstrate that the virtual reactions produce molecules highly similar to known actives, including known blockbuster drugs.
The mammalian blastema: regeneration at our fingertips
Authors: Simkin Jennifer , Sammarco Mimi C. , Dawson Lindsay A. , Schanes Paula P. , Yu Ling , Muneoka Ken 
Published: March 2015

AbstractIn the mouse, digit tip regeneration progresses through a series of discrete stages that include inflammation, histolysis, epidermal closure, blastema formation, and redifferentiation. Recent studies reveal how each regenerative stage influences subsequent stages to establish a blastema that directs the successful regeneration of a complex mammalian structure. The focus of this review is on early events of healing and how an amputation wound transitions into a functional blastema. The stepwise formation of a mammalian blastema is proposed to provide a model for how specific targeted treatments can enhance regenerative performance in humans.
Analysis of cracking in steel fibre‐reinforced concrete (SFRC) structures in bending using probabilistic modelling
Authors: Rossi Pierre , Daviau‐Desnoyers Dominic , Tailhan Jean‐Louis 
Published: March 2015

AbstractAn improvement to the probabilistic discrete cracking model for fibre‐reinforced concretes, originally developed by Rossi, is proposed in this paper.This new model features the following:– Crack formation and propagation in the concrete is taken into account by using special interface elements. These elements open once the normal tensile stress at their centre of gravity reaches the tensile strength of the element. The probabilistic aspect of the cracking process is taken into account by the fact that the tensile strength is randomly distributed throughout the mesh elements.– Immediately after the formation of cracks, the fibre bridging effect is considered by a damage model approach. The probabilistic aspect consists of randomly distributing the post‐cracking energy.The improved numerical model is used to analyse the bending behaviour of three SFRC beams made from the same material. The numerical simulations are compared with experimental results in terms of the global behaviour of and cracking processes in the beams.
Defects in epoxy‐coated reinforcement and their impact on the service life of a concrete structure
Authors: Keßler Sylvia , Angst Ueli , Zintel Marc , Gehlen Christoph 
Published: March 2015

AbstractEpoxy‐coated reinforcement (ECR) as a means of protection against chloride‐induced corrosion of steel in concrete is used in only a few countries due to doubts concerning its effectiveness. A common misconception is that possible defects in the coating are particularly weak points as these might favour high local corrosion rates and thus loss of steel cross‐section. This work discusses why a certain number of small defects can be tolerated. It is argued that prolongation of the initiation phase is caused by a higher critical chloride content compared with uncoated steel due to the “size effect”. Additionally, the propagation phase for ECR is likely to be extended due to the severely restricted cathodic area that limits the corrosion rate. This paper presents experimental and numerical tests to verify these assumptions.
Empirical validation of integrated learning performances for hydrologic phenomena: 3rd‐grade students' model‐driven explanation‐construction
Authors: Forbes Cory T. , Zangori Laura , Schwarz Christina V. 
Published: March 2015

AbstractWater is a crucial topic that spans the K‐12 science curriculum, including the elementary grades. Students should engage in the articulation, negotiation, and revision of model‐based explanations about hydrologic phenomena. However, past research has shown that students, particularly early learners, often struggle to understand hydrologic phenomena and that scientific modeling remains underemphasized in elementary science learning environments. More research is, therefore, needed to understand and promote early learners' engagement in domain‐specific modeling practices. To address this need, we are engaged in design‐based research to foster and investigate 3rd‐grade students' model‐based explanations for the water cycle. Here, we report on the development of a set of empirically based learning performances that integrate core discipline‐specific concepts and the practice of scientific modeling. This framework (i) grounds the iterative adaptation and enhancement of a commonly used curricular unit focused on water and (ii) lays the foundation for ongoing development of an associated learning progression that spans K‐12 grades. Second, we report on findings from research investigating 3rd‐grade students' model‐based explanations within the context of the water cycle. Results illustrate epistemic features of mechanism‐based causal claims elementary students generate and highlight both target concepts and modeling practices emphasized in students' model‐based explanations for hydrologic cycling. © 2015 Wiley Periodicals, Inc. J Res Sci Teach 52: 895–921, 2015.
Exploiting the potential energy landscape to sample free energy
Authors: Ballard Andrew J. , Martiniani Stefano , Stevenson Jacob D. , Somani Sandeep , Wales David J. 
Published: March 2015

We review a number of recently developed strategies for enhanced sampling of complex systems based on knowledge of the potential energy landscape. We describe four approaches, replica exchange, Kirkwood sampling, superposition‐enhanced nested sampling, and basin sampling, and show how each of them can exploit information for low‐lying potential energy minima obtained using basin‐hopping global optimization. Characterizing these minima is generally much faster than equilibrium thermodynamic sampling, because large steps in configuration space between local minima can be used without concern for maintaining detailed balance. WIREs Comput Mol Sci 2015, 5:273–289. doi: 10.1002/wcms.1217This article is categorized under:

Structure and Mechanism > Molecular Structures
Structure and Mechanism > Computational Biochemistry and Biophysics
Structure and Mechanism > Computational Materials Science
Nitrogen‐Rich Alkali Metal Salts (Na and K) of [Bis(N,N‐bis(1H‐tetrazol‐5‐yl)amine)‐zinc(II)] Anion: Syntheses, Crystal Structures, and Energetic Properties
Authors: Li Fugang , Zhao Wenyuan , Chen Sitong , Zhang Tonglai , Zhou Zunning , Yang Li 
Published: March 2015

AbstractTwo nitrogen‐rich alkali metal salts based on nitrogen‐rich anion [Zn(bta)2]2–: {[Na2Zn(bta)2(H2O)8]·H2O}n (1) and {[K2Zn(bta)2(H2O)4]}n (2) were synthesized by reactions of alkali hydroxide, N,N‐bis(1H‐tetrazol‐5‐yl)amine (H2bta), and zinc chloride in aqueous solutions. The crystal structures of 1 and 2 were determined by low temperature single‐crystal X‐ray diffraction and fully characterized by elemental analysis and FT‐IR spectroscopy. The structures demonstrate that an infinite 1‐dimensional (1D) chain structure is constructed by Na+ ions and bridging water molecules in compound 1, which is connected by extensive hydrogen bonds forming a complex 3D network, whereas compound 2 features a more complicated 3D metal‐organic framework (MOF). The thermal behaviors of 1 and 2 were investigated by differential scanning calorimetry (DSC) measurements. The DSC results illustrate that both compounds exhibit high thermal stabilities (decomposition temperature > 345 °C). In addition, the heats of formation were calculated on the basis of the experimental constant‐volume energies of combustion measured by using bomb calorimetry. Lastly, the sensitivities towards impact and friction were assessed according to Bundesamt für Materialforschung (BAM) standard methods.
People of Adam: Divine Healing and Racial Cosmopolitanism in the Early Twentieth-Century Transvaal, South Africa
Authors: Cabrita Joel 
Published: March 2015

AbstractThis article analyses the intersection between cosmopolitanism and racist ideologies in the faith healing practices of the Christian Catholic Apostolic Church in Zion. Originally from Illinois, USA, this organization was the period's most influential divine healing group. Black and white members, under the leadership of the charismatic John Alexander Dowie, eschewed medical assistance and proclaimed God's power to heal physical affliction. In affirming the deity's capacity to remake human bodies, church members also insisted that God could refashion biological race into a capacious spiritual ethnicity: a global human race they referred to as the “Adamic” race. Zionist universalist teachings were adopted by dispossessed and newly urbanized Boer ex-farmers in Johannesburg, Transvaal, before spreading to the soldiers of the British regiments recently arrived to fight the Boer states in the war of 1899–1902. Zionism equipped these estranged white “races” with a vocabulary to articulate political reconciliation and a precarious unity. But divine healing was most enthusiastically received among the Transvaal's rural Africans. Amidst the period's hardening segregation, Africans seized upon divine healing's innovative racial teachings, but both Boers and Africans found disappointment amid Zion's cosmopolitan promises. Boers were marginalized within the new racial regimes of the Edwardian empire in South Africa, and white South Africans had always been ambivalent about divine healing's incorporations of black Africans into a unitary race. This early history of Zionism in the Transvaal reveals the constriction of cosmopolitan aspirations amidst fast-narrowing horizons of race, nation, and empire in early twentieth-century South Africa.
ON THE NOTION OF CANONICAL DERIVATIONS FROM OPEN ASSUMPTIONS AND ITS ROLE IN PROOF-THEORETIC SEMANTICS
Authors: FRANCEZ NISSIM 
Published: March 2015

AbstractThe paper proposes an extension of the definition of a canonical proof, central to proof-theoretic semantics, to a definition of a canonical derivation from open assumptions. The impact of the extension on the definition of (reified) proof-theoretic meaning of logical constants is discussed. The extended definition also sheds light on a puzzle regarding the definition of local-completeness of a natural-deduction proof-system, underlying its harmony.
THE RELEVANCE OF PREMISES TO CONCLUSIONS OF CORE PROOFS
Authors: TENNANT NEIL 
Published: March 2015

AbstractThe rules for Core Logic are stated, and various important results about the system are summarized. We describe its relationship to other systems, such as Classical Logic, Intuitionistic Logic, Minimal Logic, and the Anderson–Belnap relevance logicR. A precise, positive explication is offered of what it is for the premises of a proof to connect relevantly with its conclusion. This characterization exploits the notion of positive and negative occurrences of atoms in sentences. It is shown that all Core proofs are relevant in this precisely defined sense. We survey extant results about variable-sharing in rival systems of relevance logic, and find that the variable-sharing conditions established for them are weaker than the one established here for Core Logic (and for its classical extension). Proponents of other systems of relevance logic (such asRand its subsystems) are challenged to formulate a stronger variable-sharing condition, and to prove thatRor any of its subsystems satisfies it, but that Core Logic does not. We give reasons for pessimism about the prospects for meeting this challenge.
Transfer hydrogenation catalysis in cells as a new approach to anticancer drug design
Authors: Soldevila-Barreda Joan J. , Romero-Canelón Isolda , Habtemariam Abraha , Sadler Peter J. 
Published: March 2015

AbstractOrganometallic complexes are effective hydrogenation catalysts for organic reactions. For example, Noyori-type ruthenium complexes catalyse reduction of ketones by transfer of hydride from formate. Here we show that such catalytic reactions can be achieved in cancer cells, offering a new strategy for the design of safe metal-based anticancer drugs. The activity of ruthenium(II) sulfonamido ethyleneamine complexes towards human ovarian cancer cells is enhanced by up to 50 × in the presence of low non-toxic doses of formate. The extent of conversion of coenzyme NAD+ to NADH in cells is dependent on formate concentration. This novel reductive stress mechanism of cell death does not involve apoptosis or perturbation of mitochondrial membrane potentials. In contrast, iridium cyclopentadienyl catalysts cause cancer cell death by oxidative stress. Organometallic complexes therefore have an extraordinary ability to modulate the redox status of cancer cells.
Enterohemorrhagic Escherichia coli senses low biotin status in the large intestine for colonization and infection
Authors: Yang Bin , Feng Lu , Wang Fang , Wang Lei 
Published: March 2015

AbstractEnterohemorrhagic Escherichia coli (EHEC) is an important foodborne pathogen that infects humans by colonizing the large intestine. Here we identify a virulence-regulating pathway in which the biotin protein ligase BirA signals to the global regulator Fur, which in turn activates LEE (locus of enterocyte effacement) genes to promote EHEC adherence in the low-biotin large intestine. LEE genes are repressed in the high-biotin small intestine, thus preventing adherence and ensuring selective colonization of the large intestine. The presence of this pathway in all nine EHEC serotypes tested indicates that it is an important evolutionary strategy for EHEC. The pathway is incomplete in closely related small-intestinal enteropathogenic E. coli due to the lack of the Fur response to BirA. Mice fed with a biotin-rich diet show significantly reduced EHEC adherence, indicating that biotin might be useful to prevent EHEC infection in humans.