bluuebunny/crossref_metadata_2025_split huggingface dataset:
Water input and water release from the subducting Nazca Plate along southern Central Chile (33°S–46°S)
Authors: Völker David , Stipp Michael 
Published: May 2015

AbstractThe age of the subducting Nazca Plate off Chile increases northward from 0 Ma at the Chile Triple Junction (46°S) to 37 Ma at the latitude of Valparaíso (32°S). Age‐related variations in the thermal state of the subducting plate impact on (a) the water influx to the subduction zone, as well as on (b) the volumes of water that are released under the continental fore arc or, alternatively, carried beyond the arc. Southern Central Chile is an ideal setting to study this effect, because other factors for the subduction zone water budget appear constant. We determine the water influx by calculating the crustal water uptake and by modeling the upper mantle serpentinization at the outer rise of the Chile Trench. The water release under fore arc and arc is determined by coupling FEM thermal models of the subducting plate with stability fields of water‐releasing mineral reactions for upper and lower crust and hydrated mantle. Results show that both the influx of water stored in, and the outflux of water released from upper crust, lower crust, and mantle vary drastically over segment boundaries. In particular, the oldest and coldest segments carry roughly twice as much water into the subduction zone as the youngest and hottest segments, but their release flux to the fore arc is only about one fourth of the latter. This high variability over a subduction zone of <1500 km length shows that it is insufficient to consider subduction zones as uniform entities in global estimates of subduction zone fluxes.
A new perspective on environmental controls of marine nitrogen fixation
Authors: Landolfi A. , Koeve W. , Dietze H. , Kähler P. , Oschlies A. 
Published: May 2015

AbstractGrowing slowly, marine N2 fixers are generally expected to be competitive only where nitrogen (N) supply is low relative to that of phosphorus (P) with respect to the cellular N:P ratio (R) of nonfixing phytoplankton. This is at odds with observed high N2 fixation rates in the oligotrophic North Atlantic where the ratio of nutrients supplied to the surface is elevated in N relative to the average R (16:1). In this study, we investigate several mechanisms to solve this puzzle: iron limitation, phosphorus enhancement by preferential remineralization or stoichiometric diversity of phytoplankton, and dissolved organic phosphorus (DOP) utilization. Combining resource competition theory and a global coupled ecosystem‐circulation model, we find that the additional N and energy investments required for exoenzymatic breakdown of DOP give N2 fixers a competitive advantage in oligotrophic P‐starved regions. Accounting for this mechanism expands the ecological niche of N2 fixers also to regions where the nutrient supply is high in N relative to R, yielding, in our model, a pattern consistent with the observed high N2 fixation rates in the oligotrophic North Atlantic.
Impact angle control of interplanetary shock geoeffectiveness: A statistical study
Authors: Oliveira Denny M. , Raeder Joachim 
Published: May 2015

AbstractWe present a survey of interplanetary (IP) shocks using Wind and ACE satellite data from January 1995 to December 2013 to study how IP shock geoeffectiveness is controlled by IP shock impact angles. A shock list covering one and a half solar cycle is compiled. The yearly number of IP shocks is found to correlate well with the monthly sunspot number. We use data from SuperMAG, a large chain with more than 300 geomagnetic stations, to study geoeffectiveness triggered by IP shocks. The SuperMAG SML index, an enhanced version of the familiar AL index, is used in our statistical analysis. The jumps of the SML index triggered by IP shock impacts on the Earth's magnetosphere are investigated in terms of IP shock orientation and speed. We find that, in general, strong (high speed) and almost frontal (small impact angle) shocks are more geoeffective than inclined shocks with low speed. The strongest correlation (correlation coefficient R = 0.78) occurs for fixed IP shock speed and for varied IP shock impact angle. We attribute this result, predicted previously with simulations, to the fact that frontal shocks compress the magnetosphere symmetrically from all sides, which is a favorable condition for the release of magnetic energy stored in the magnetotail, which in turn can produce moderate to strong auroral substorms, which are then observed by ground‐based magnetometers.
Predictive actuator fault‐tolerant control under ellipsoidal bounding
Authors: Witczak Marcin , Buciakowski Mariusz , Aubrun Christophe 
Published: May 2015

SummaryThe paper is devoted to the issue of a robust predictive fault‐tolerant control for linear discrete‐time systems with an application of an ellipsoidal inner bounding of a robust invariant set. The crucial issue is to maintain the state of the system inside the robust invariant feasible set, which is a set of states guaranteeing the stability of the proposed control strategy. The approach begins with fault estimation, and then the fault is compensated along with a robust controller. In a case when robust fault compensation does not provide expected results, which means that the current state does not belong to the robust invariant set, then a suitable predictive control action is performed in order to enhance the ellipsoidal invariant set. This appealing phenomenon makes it possible to enlarge the domain of attraction of the possibly faulty system that makes the proposed approach an efficient solution to the fault‐tolerant control problem. The final part of the paper shows an illustrative example regarding a two‐tank system. Copyright © 2015 John Wiley & Sons, Ltd.
Synthesis of Derivatized Chitooligomers using Transglycosidases Engineered from the Fungal GH20 β‐N‐Acetylhexosaminidase
Authors: Slámová Kristýna , Krejzová Jana , Marhol Petr , Kalachova Lubica , Kulik Natallia , Pelantová Helena , Cvačka Josef , Křen Vladimír 
Published: May 2015

AbstractThe synthesis of oligosaccharides using mutant glycosidases has been dynamically developing due to the need for novel carbohydrate‐based materials. Chitooligomers (β‐1→4‐linked oligomers of N‐acetylglucosamine) are bioactive compounds applicable in many industrial and pharmacological areas; however, their accessibility is still rather low. In this work, GH20 β‐N‐acetylhexosaminidase from the fungus Talaromyces flavus was engineered by site‐directed mutagenesis to obtain three efficiently transglycosylating variants with ca. 200‐times suppressed hydrolytic activity. Thus, we have prepared the first GH20 transglycosidases. In the reactions catalyzed by these mutant β‐N‐acetylhexosaminidases we were able to easily prepare and isolate both natural and modified chitooligomers in sufficient amounts for their complete spectral characterization and possible further application. The presented method for the synthesis of chitooligomers with aglycones suitable for linking to other biological structures is simple and robust enough to be easily scaled up.magnified image
Efficient Synthesis of Chiral Indolines using an Imine Reductase from Paenibacillus lactis
Authors: Li Hao , Luan Zheng‐Jiao , Zheng Gao‐Wei , Xu Jian‐He 
Published: May 2015

AbstractAn enzymatic process for the efficient asymmetric reduction of 3H‐indoles as well as 3H‐indole iodides was developed for the first time. Using a new imine reductase identified from Paenibacillus lactis (PlSIR), various chiral indolines were facilely synthesized in good yields and excellent enantiopurities (up to >99% ee) under mild reaction conditions.magnified image
Engineering a Thermostable Transketolase for Unnatural Conversion of (2S)‐Hydroxyaldehydes
Authors: Abdoul Zabar Juliane , Lorillière Marion , Yi Dong , Saravanan Thangavelu , Devamani Titu , Nauton Lionel , Charmantray Franck , Hélaine Virgil , Fessner Wolf‐Dieter , Hecquet Laurence 
Published: May 2015

AbstractTransketolase (TK) from various origins (including Escherichia coli and yeast) has been described to be fully enantiomer specific for (2R)‐hydroxyaldehyde substrates. A thermostable TK from Geobacillus stearothermophilus (TKgst) was found to display a minor reactivity for (2S)‐hydroxylated aldehydes. To improve this activity by directed protein evolution, we have built a library of TKgst variants by site saturation mutagenesis on two key positions L382 and D470. The best TKgst double mutant L382D/D470S shows up to 4‐ and 5‐fold higher activities towards L‐lactaldehyde and L‐glyceraldehyde as acceptor substrates, respectively. Preparative utility of this mutant was demonstrated by the one‐step synthesis of valuable L‐ribulose and its 5‐deoxy analogue with the L‐erythro (3S,4S) configuration, which were previously inaccessible by using common TK sources.magnified image
Exploiting Enzymatic Dynamic Reductive Kinetic Resolution (DYRKR) in Stereocontrolled Synthesis
Authors: Applegate Gregory A. , Berkowitz David B. 
Published: May 2015

AbstractOver the past two decades, the domains of both frontline synthetic organic chemistry and process chemistry have seen an increase in crosstalk between asymmetric organic/organometallic approaches and enzymatic approaches to stereocontrolled synthesis. This review highlights the particularly auspicious role for dehydrogenase enzymes in this endeavor, with a focus on dynamic reductive kinetic resolutions (DYRKR) to “deracemize” building blocks, often setting two stereocenters in so doing. The scope and limitations of such dehydrogenase‐mediated processes are overviewed, as are future possibilities for the evolution of enzymatic DYRKR.magnified image
Recent Developments in Enzymatic Synthesis of Modified Sialic Acid Derivatives
Authors: Yu Ching‐Ching , Withers Stephen G. 
Published: May 2015

AbstractSialic acid‐containing glycans play important roles in biology, but their synthesis by standard chemical approaches is challenging. Enzymatic assembly is generally a better approach. In the last two decades, a number of bacterial sialyltransferases (STs) and trans‐sialidases have been identified and a number of them found to exhibit broad substrate specificity. In this review, we will focus on the donor and acceptor substrate specificities of these enzymes along with the enzymatic routes employed to prepare sialosides bearing modifications at specific positions on the sialic acid carbon skeleton. Understanding the substrate tolerance of these enzymes will help researchers to choose the best biocatalyst for the assembly of specific sialosides, which can be valuable tools in the study of or inhibition of sialidases and STs and sialic acid‐binding proteins. In addition, the ability to study these processes using synthetic sialylated glycans will lead to a greater understanding of their biology and will lead to new therapeutic targets.magnified image
Hemorrhagic shock due to ruptured left and right gastric artery aneurysm
Authors: Nishimura Takeshi , Sakata Hiroyuki , Yamada Taihei , Osako Takaaki , Kohama Keisuke , Kako Yasukazu , Achiwa Sachiko , Furukawa Yoshitaka , Nakao Atsunori , Kotani Joji 
Published: May 2015

CaseWe report a case of hemorrhagic shock due to a ruptured gastric artery aneurysm successfully treated with transarterial embolization. A 72‐year‐old woman with cholangitis presented with hemoperitoneum following a ruptured aneurysm of the gastric artery.OutcomeEmergent computed tomography and angiography were carried out and the patient was found to have spontaneous bleeding from both branches of the left and right gastric arteries. Transcatheter embolization was carried out at the distal branch of both gastric arteries with a coil. The patient recovered well with no recurrent bleeding.Conclusions Although rare, visceral artery rupture should be considered in the differential diagnosis of unexplained hemorrhagic shock with abrupt onset of hemoperitoneum. Computed tomography and angiography are useful tools for obtaining prompt and accurate localization of the bleeding points.
The Mechanism of Ligand‐Induced Activation or Inhibition of μ‐ and κ‐Opioid Receptors
Authors: Yuan Shuguang , Palczewski Krzysztof , Peng Qian , Kolinski Michal , Vogel Horst , Filipek Slawomir 
Published: May 2015

AbstractG‐protein‐coupled receptors (GPCRs) are important targets for treating severe diseases. However why certain molecules act as activators whereas others, with similar structures, block GPCR activation, is poorly understood since the same molecule can activate one receptor subtype while blocking another closely related receptor. To shed light on these central questions, we used all‐atom, long‐time‐scale molecular dynamics simulations on the κ‐opioid and μ‐opioid receptors (κOR and μOR). We found that water molecules penetrating into the receptor interior mediate the activating versus blocking effects of a particular ligand–receptor interaction. Both the size and the flexibility of the bound ligand regulated water influx into the receptor. The solvent‐accessible inner surface area was found to be a parameter that can help predict the function of the bound ligand.
Mussel‐Inspired Protein Nanoparticles Containing Iron(III)–DOPA Complexes for pH‐Responsive Drug Delivery
Authors: Kim Bum Jin , Cheong Hogyun , Hwang Byeong Hee , Cha Hyung Joon 
Published: May 2015

AbstractA novel bioinspired strategy for protein nanoparticle (NP) synthesis to achieve pH‐responsive drug release exploits the pH‐dependent changes in the coordination stoichiometry of iron(III)–3,4‐dihydroxyphenylalanine (DOPA) complexes, which play a major cross‐linking role in mussel byssal threads. Doxorubicin‐loaded polymeric NPs that are based on FeIII–DOPA complexation were thus synthesized with a DOPA‐modified recombinant mussel adhesive protein through a co‐electrospraying process. The release of doxorubicin was found to be predominantly governed by a change in the structure of the FeIII–DOPA complexes induced by an acidic pH value. It was also demonstrated that the fabricated NPs exhibited effective cytotoxicity towards cancer cells through efficient cellular uptake and cytosolic release. Therefore, it is anticipated that FeIII–DOPA complexation can be successfully utilized as a new design principle for pH‐responsive NPs for diverse controlled drug‐delivery applications.
A Nonaromatic Thiophene‐Fused Heptalene and Its Aromatic Dianion
Authors: Oshima Hiroya , Fukazawa Aiko , Sasamori Takahiro , Yamaguchi Shigehiro 
Published: May 2015

AbstractHeptalene, a nonaromatic, bicyclic 12 π‐electron system with a twisted structure, is of great interest with regard to its potential Hückel aromaticity in the two‐electron oxidized or reduced forms. The synthesis of thiophene‐fused heptalene 5 from the reductive transannular cyclization of bisdehydro[12]annulene 4, and its solid‐state structure, which was confirmed by X‐ray crystallographic analysis, is presented. Chemical reduction of 5 readily generated the corresponding dianion, which was successfully isolated as [(K[2.2.2]cryptand)+]252−. The X‐ray crystallographic analysis of the dianion revealed a shallower saddle structure for the heptalene moiety and a lesser degree of bond alternation relative to 5. 1H NMR spectroscopy exposed the effect of a diamagnetic ring current on dianion 52−, which was corroborated by nucleus‐independent chemical shift (NICS) calculations. These results demonstrate that the heptalene dianion, containing 14 π‐electrons, does indeed exhibit pronounced degrees of Hückel aromaticity.
Cobalt(III)‐katalysierte C‐H‐Aminocarbonylierung von Arenen und Alkenen mit Isocyanaten und Acylaziden
Authors: Li Jie , Ackermann Lutz 
Published: May 2015

AbstractNützliche C‐H‐Aminocarbonylierungen von nichtaktivierten (Hetero)Arenen und Alkenen mit hoher Toleranz für funktionelle Gruppen konnten mit einem Cobalt(III)‐Katalysator realisiert werden. Die C‐H‐Funktionalisierungen zeigten exzellente Chemo‐, Regio‐ und Diastereoselektivitäten und ermöglichten eine stufenökonomische Umsetzung von Isocyanaten oder Acylaziden.
Verursacht Dynamik das komplexe Infrarotspektrum von NO an Kupfer(II)‐Zentren in Zeolithen?
Authors: Göltl Florian , Sautet Philippe , Hermans Ive 
Published: May 2015

AbstractKupfer‐ausgetauschte SSZ‐13‐Zeolithe sind sehr effiziente Materialien für die selektive katalytische Reduktion von NOx mit Ammoniak (deNOx‐SCR). Die Charakterisierung der Verteilung der Kupfer‐Zentren in solchen Materialien ist von größter Bedeutung, um deren Aktivität zu verstehen. In dieser Studie haben wir Infrarotspektren von NO adsorbiert an Kupfer‐Zentren mittels Ab‐initio‐Molekulardynamiksimulationen modelliert. Für die meisten Zentren haben wir komplexe Infrarotspektren mit mehreren Peaks gefunden, die durch thermische Bewegung der Kationen und der Adsorbate verursacht werden. Wir konstruierten ein Spektrum eines spezifischen Katalysators bei endlicher Temperatur, welches exzellent mit Literaturdaten übereinstimmt. Die Resultate ermöglichen eine Zuordnung der aktiven und inaktiven Zentren für die deNOx‐SCR. Unseres Wissens ist dies die erste Arbeit, die über solch komplexe Spektren für einzelne adsorbierte Moleküle an einzelnen aktiven Zentren in heterogenen Katalysatoren berichtet. Wir gehen davon aus, dass ähnliche Effekte auch in einer Vielzahl anderer Systeme mit beweglichen aktiven Zentren zu finden sind.
A Simple, High‐Yield Synthesis of DNA Duplexes Containing a Covalent, Thermally Cleavable Interstrand Cross‐Link at a Defined Location
Authors: Gamboa Varela Jacqueline , Gates Kent S. 
Published: May 2015

AbstractInterstrand DNA–DNA cross‐links are highly toxic to cells because these lesions block the extraction of information from the genetic material. The pathways by which cells repair cross‐links are important, but not well understood. The preparation of chemically well‐defined cross‐linked DNA substrates represents a significant challenge in the study of cross‐link repair. Here a simple method is reported that employs “post‐synthetic” modifications of commercially available 2′‐deoxyoligonucleotides to install a single cross‐link in high yield at a specified location within a DNA duplex. The cross‐linking process exploits the formation of a hydrazone between a non‐natural N4‐amino‐2′‐deoxycytidine nucleobase and the aldehyde residue of an abasic site in duplex DNA. The resulting cross‐link is stable under physiological conditions, but can be readily dissociated and re‐formed through heating–cooling cycles.
Copper‐Catalyzed Intermolecular Asymmetric Propargylic Dearomatization of Indoles
Authors: Shao Wen , Li He , Liu Chuan , Liu Chen‐Jiang , You Shu‐Li 
Published: May 2015

AbstractThe first copper‐catalyzed intermolecular dearomatization of indoles by an asymmetric propargylic substitution reaction was developed. This method provides a highly efficient synthesis of versatile furoindoline and pyrroloindoline derivatives containing a quaternary carbon stereogenic center and a terminal alkyne moiety with up to 86 % yield and 98 % ee.
Ketene as a Reaction Intermediate in the Carbonylation of Dimethyl Ether to Methyl Acetate over Mordenite
Authors: Rasmussen Dominik B. , Christensen Jakob M. , Temel Burcin , Studt Felix , Moses Poul Georg , Rossmeisl Jan , Riisager Anders , Jensen Anker D. 
Published: May 2015

AbstractUnprecedented insight into the carbonylation of dimethyl ether over Mordenite is provided through the identification of ketene (CH2CO) as a reaction intermediate. The formation of ketene is predicted by detailed DFT calculations and verified experimentally by the observation of doubly deuterated acetic acid (CH2DCOOD), when D2O is introduced in the feed during the carbonylation reaction.
Highly Stereoselective Synthesis of Natural‐Product‐Like Hybrids by an Organocatalytic/Multicomponent Reaction Sequence
Authors: Echemendía Radell , de La Torre Alexander F. , Monteiro Julia L. , Pila Michel , Corrêa Arlene G. , Westermann Bernhard , Rivera Daniel G. , Paixão Márcio W. 
Published: May 2015

AbstractIn an endeavor to provide an efficient route to natural product hybrids, described herein is an efficient, highly stereoselective, one‐pot process comprising an organocatalytic conjugate addition of 1,3‐dicarbonyls to α,β‐unsaturated aldehydes followed by an intramolecular isocyanide‐based multicomponent reaction. This approach enables the rapid assembly of complex natural product hybrids including up to four different molecular fragments, such as hydroquinolinone, chromene, piperidine, peptide, lipid, and glycoside moieties. The strategy combines the stereocontrol of organocatalysis with the diversity‐generating character of multicomponent reactions, thus leading to structurally unique peptidomimetics integrating heterocyclic, lipidic, and sugar moieties.
Cobalt(III)‐Catalyzed Aryl and Alkenyl CH Aminocarbonylation with Isocyanates and Acyl Azides
Authors: Li Jie , Ackermann Lutz 
Published: May 2015

AbstractExpedient CH aminocarbonylations of unactivated (hetero)arenes and alkenes were accomplished with a cobalt(III) catalyst that shows high functional group tolerance. The CH functionalization occurred with excellent chemo‐, site‐, and diastereoselectivity and enabled step‐economical reactions with isocyanates or acyl azides.
Can Dynamics Be Responsible for the Complex Multipeak Infrared Spectra of NO Adsorbed to Copper(II) Sites in Zeolites?
Authors: Göltl Florian , Sautet Philippe , Hermans Ive 
Published: May 2015

AbstractCopper‐exchanged SSZ‐13 is a very efficient material in the selective catalytic reduction of NOx using ammonia (deNOx‐SCR) and characterizing the underlying distribution of copper sites in the material is of prime importance to understand its activity. The IR spectrum of NO adsorbed to divalent copper sites are modeled using ab initio molecular dynamics simulations. For most sites, complex multi‐peak spectra induced by the thermal motion of the cation as well as the adsorbate are found. A finite temperature spectrum for a specific catalyst was constructed, which shows excellent agreement with previously reported data. Additionally these findings allow active and inactive species in deNOx‐SCR to be identified. To the best of our knowledge, this is the first time such complex spectra for single molecules adsorbed to single active centers have been reported in heterogeneous catalysis, and we expect similar effects to be important in a large number of systems with mobile active centers.
Titanium Trisulfide Monolayer: Theoretical Prediction of a New Direct‐Gap Semiconductor with High and Anisotropic Carrier Mobility
Authors: Dai Jun , Zeng Xiao Cheng 
Published: May 2015

AbstractA new two‐dimensional (2D) layered material, namely, titanium trisulfide (TiS3) monolayer, is predicted to possess novel electronic properties. Ab initio calculations show that the perfect TiS3 monolayer is a direct‐gap semiconductor with a bandgap of 1.02 eV, close to that of bulk silicon, and with high carrier mobility. More remarkably, the in‐plane electron mobility of the 2D TiS3 is highly anisotropic, amounting to about 10 000 cm2 V−1 s−1 in the b direction, which is higher than that of the MoS2 monolayer, whereas the hole mobility is about two orders of magnitude lower. Furthermore, TiS3 possesses lower cleavage energy than graphite, suggesting easy exfoliation for TiS3. Both dynamical and thermal stability of the TiS3 monolayer is examined by phonon‐spectrum calculation and Born–Oppenheimer molecular dynamics simulation. The desired electronic properties render the TiS3 monolayer a promising 2D atomic‐layer material for applications in future nanoelectronics.