bluuebunny/crossref_metadata_2025_split huggingface dataset:
One‐Dimensional Arsenic Allotropes: Polymerization of Yellow Arsenic Inside Single‐Wall Carbon Nanotubes
Authors: Hart Martin , Chen Ji , Michaelides Angelos , Sella Andrea , Shaffer Milo S. P. , Salzmann Christoph G. 
Published: July 2018

AbstractThe pnictogen nanomaterials, including phosphorene and arsenene, display remarkable electronic and chemical properties. Yet, the structural diversity of these main group elements is still poorly explored. Here we fill single‐wall carbon nanotubes with elemental arsenic from the vapor phase. Using electron microscopy, we find chains of highly reactive As4 molecules as well as two new one‐dimensional allotropes of arsenic: a single‐stranded zig‐zag chain and a double‐stranded zig‐zag ladder. These linear structures are important intermediates between the gas‐phase clusters of arsenic and the extended sheets of arsenene. Raman spectroscopy indicates weak electronic interaction between the arsenic and the nanotubes which implies that the formation of the new allotropes is driven primarily by the geometry of the confinement. The relative stabilities of the new arsenic structures are estimated computationally. Band‐gap calculations predict that the insulating As4 chains become semiconducting, once converted to the zig‐zag ladder, and form a fully metallic allotrope of arsenic as the zig‐zag chain.
Rationally Designed Semisynthetic Natural Product Analogues for Stabilization of 14‐3‐3 Protein–Protein Interactions
Authors: Andrei Sebastian A. , de Vink Pim , Sijbesma Eline , Han Ling , Brunsveld Luc , Kato Nobuo , Ottmann Christian , Higuchi Yusuke 
Published: July 2018

AbstractThe natural product family of fusicoccanes are stabilizers of 14‐3‐3 mediated protein–protein interactions (PPIs), some of which possess antitumor activity. In this study, the first use of molecular dynamics (MD) to rationally design PPI stabilizers with increased potency is presented. Synthesis of a focused library, with subsequent characterization by fluorescence polarization, mutational studies, and X‐ray crystallography confirmed the power of the MD‐based design approach, revealing the potential for an additional hydrogen bond with the 14‐3‐3 protein to lead to significantly increased potency. Additionally, these compounds exert their action in a cellular environment with increased potency. The newly found polar interaction could provide an anchoring point for new small‐molecule PPI stabilizers. These results facilitate the development of fusicoccanes towards drugs or tool compounds, as well as allowing the study of the fundamental principles behind PPI stabilization.
Totalsynthese der Keramamide A und L aus einer gemeinsamen Vorstufe durch späte Indolsynthese und Revision ihrer Konfiguration
Authors: Junk Lukas , Kazmaier Uli 
Published: July 2018

AbstractDie marinen Naturstoffe Keramamid A und L, Vertreter der Klasse der Anabaenopeptin‐artigen Peptide, wurden zum ersten Mal mittels einer konvergenten und flexiblen Route synthetisiert. Der Aufbau der substituierten Tryptophan‐Einheiten erfolgte hierbei ganz am Ende der Synthese am cyclischen Peptid, was die Herstellung beider Naturstoffe aus einer gemeinsamen Vorstufe ermöglichte. Durch die Synthese verschiedener Epimere konnte festgestellt werden, dass die ursprünglich postulierte relative Konfiguration beider Naturstoffe nicht der tatsächlichen entspricht.
Copper‐Catalyzed Tandem Hydrocupration and Diastereo‐ and Enantioselective Borylalkyl Addition to Aldehydes
Authors: Jang Won Jun , Yun Jaesook 
Published: July 2018

AbstractWe report the copper‐catalyzed stereoselective addition of in situ generated chiral boron‐α‐alkyl intermediates to various aldehydes including α,β‐unsaturated aldehydes under mild conditions. This tandem and multicomponent method facilitated the synthesis of enantiomerically enriched 1,2‐hydroxyboronates bearing contiguous stereocenters in good yield with high diastereo‐ and enantioselectivity up to a ratio greater than 98:2. In particular, α,β‐unsaturated aldehydes were successfully used as electrophiles in Cu−H catalysis through 1,2‐addition without significant reduction. The resulting 1,2‐hydroxyboronates were used in various transformations.
Combining Electrodeposition and Optical Microscopy for Probing Size‐Dependent Single‐Nanoparticle Electrochemistry
Authors: Lemineur Jean‐François , Noël Jean‐Marc , Ausserré Dominique , Combellas Catherine , Kanoufi Frédéric 
Published: July 2018

AbstractElectrodeposition of nanoparticles (NPs) is a promising route for the preparation of highly electroactive nanostructured electrodes. By taking advantage of progressive electrodeposition, disordered arrays with a wide size distribution of Ag NPs are produced. Combined with surface‐reaction monitoring by using highly sensitive backside absorbing‐layer optical microscopy (BALM), such arrays offer a platform for screening size‐dependent electrochemistry at the single NP level. In particular, this strategy allows rationalizing the electrodeposition dynamics at the single‐NP level (>10 nm), up to the point of quantifying the presence of metal nanoclusters (<2 nm), and probing easier NP oxidation with size decrease, either through electrochemical or galvanic reactions.
Domino Pd0‐Catalyzed C(sp3)–H Arylation/Electrocyclic Reactions via Benzazetidine Intermediates
Authors: Rocaboy Ronan , Dailler David , Zellweger Florian , Neuburger Markus , Salomé Christophe , Clot Eric , Baudoin Olivier 
Published: July 2018

AbstractThe Pd0‐catalyzed C(sp3)‐H arylation of 2‐bromo‐N‐methylanilides leads to unstable benzazetidine intermediates that rearrange to benzoxazines through 4π electrocyclic ring‐opening and 6π electrocyclization. The introduction of a bulky, non‐activatable amide group on the nitrogen atom was key to favor the challenging reductive elimination step and disfavor undesired reaction pathways.
A Practical and General Amidation Method from Isocyanates Enabled by Flow Technology
Authors: Williams Jason D. , Kerr William J. , Leach Stuart G. , Lindsay David M. 
Published: July 2018

AbstractThe addition of carbon nucleophiles to isocyanates represents a conceptually flexible and efficient approach to the preparation of amides. This general synthetic strategy has, however, been relatively underutilized owing to narrow substrate tolerance and the requirement for less favourable reaction conditions. Herein, we disclose a high‐yielding, mass‐efficient, and scalable method with appreciable functional group tolerance for the formation of amides by reaction of Grignard reagents with isocyanates. Through the application of flow chemistry and the use of substoichiometric amounts of CuBr2, this process has been developed to encompass a broad range of substrates, including reactants found to be incompatible with previously published procedures.
A Multifunctional Dye‐doped Liquid Crystal Polymer Actuator: Light‐Guided Transportation, Turning in Locomotion, and Autonomous Motion
Authors: Ge Feijie , Yang Rong , Tong Xia , Camerel Franck , Zhao Yue 
Published: July 2018

AbstractA strip of a liquid crystal elastomer doped with a near‐infrared dye with one side crosslinked monodomain and the other crosslinked polydomain along the thickness behaves like a multifunctional photoactuator without the need for a support. A flat strip with two ends fixed on substrate surface forms a moving bump under laser scanning, which can be used as light‐fueled conveyor to transport an object. Cutting off and laser scanning the bump with two free ends makes a soft and flexible millimeter‐scale crawler that can not only move straight and climb an inclined surface, but also undergo light‐guided turning to right or left as a result of combined out‐of‐plane and in‐plane actuation. Based on the self‐shadowing mechanism, with one end of the strip fixed on substrate surface, it can execute a variety of autonomous arm‐like movements under constant laser illumination, such as bending–unbending and twisting, depending on the laser incident angles with respect to the strip actuator.
Ion Hydration and Ion Pairing as Probed by THz Spectroscopy
Authors: Schwaab Gerhard , Sebastiani Federico , Havenith Martina 
Published: July 2018

AbstractIon hydration is of pivotal importance for many fundamental processes. Various spectroscopic methods are used to study the retardation of the hydration bond dynamics in the vicinity of anions and cations. Here we introduce THz‐FTIR spectroscopy as a powerful method to answer the open questions. We show through dissection of THz spectra that we can pinpoint characteristic absorption features that can be attributed to the rattling modes of strongly hydrating ions within their hydration cages as well as vibrationally induced charge fluctuations in the case of weakly hydrating ions. Further analysis yields information on anion–cation cooperativity, the size of the dynamic hydration shell, as well as the lifetimes of these collective ion‐hydration water modes and their connecting thermal bath states. Our study provides evidence for a non‐additive behavior, thus questioning the simplified Hofmeister model. THz spectroscopy enables ion pairing to be observed and quantified at a high salt concentration.
Arylfluorosulfate‐Based Electrophiles for Covalent Protein Labeling: A New Addition to the Arsenal
Authors: Martín‐Gago Pablo , Olsen Christian A. 
Published: July 2018

AbstractSelective covalent modification of a targeted protein is a powerful tool in chemical biology and drug discovery, with applications ranging from identification and characterization of proteins and their functions to the development of targeted covalent inhibitors. Most covalent ligands contain an affinity motif and an electrophilic warhead that reacts with a nucleophilic residue of the targeted protein. Because the electrophilic warhead is prone to react and modify off‐target nucleophiles, its reactivity should be balanced carefully to maximize target selectivity. Arylfluorosulfates have recently emerged as latent electrophiles for selective labeling of context‐specific tyrosine and lysine residues in protein pockets. Here, we review the recent but intense introduction of arylfluorosulfates into the arsenal of available warheads for selective covalent modification of proteins. We highlight the untapped potential of this functional group for use in chemical biology and drug discovery.
Carbon Nitride Materials for Water Splitting Photoelectrochemical Cells
Authors: Volokh Michael , Peng Guiming , Barrio Jesús , Shalom Menny 
Published: July 2018

AbstractGraphitic carbon nitride materials (CNs) have emerged as suitable photocatalysts and heterogeneous catalysts for various reactions thanks to their tunable band gap, suitable energy‐band position, high stability under harsh chemical conditions, and low cost. However, the utilization of CN in photoelectrochemical (PEC) and photoelectronic devices is still at an early stage owing to the difficulties in depositing high‐quality and homogenous CN layer on substrates, its wide band gap, poor charge‐separation efficiency, and low electronic conductivity. In this Minireview, we discuss the synthetic pathways for the preparation of various structures of CN on substrates and their underlying photophysical properties and current photoelectrochemical performance. The main challenges for CN incorporation into PEC cell are described, together with possible routes to overcome the standing limitations toward the integration of CN materials in PEC and other photoelectronic devices.
Total Synthesis of Keramamides A and L from a Common Precursor by Late‐Stage Indole Synthesis and Configurational Revision
Authors: Junk Lukas , Kazmaier Uli 
Published: July 2018

AbstractThe marine natural products keramamide A and L, members of the class of anabaenopeptin‐type peptides, were synthesized for the first time by a convergent and flexible route. The installation of the substituted tryptophan moieties was accomplished at the very end of the synthesis on the cyclic peptides, and thus enabled the synthesis of both natural products from one common precursor. The preparation of several epimers clearly indicates that the originally proposed relative configurations of both Keramamides A and L were not correct.
Visible Light Mediated Aryl Migration by Homolytic C−N Cleavage of Aryl Amines
Authors: Alpers Dirk , Cole Kevin P. , Stephenson Corey R. J. 
Published: July 2018

AbstractThe photocatalytic preparation of aminoalkylated heteroarenes from haloalkylamides via a 1,4‐aryl migration from nitrogen to carbon, conceptually analogous to a radical Smiles rearrangement, is reported. This method enables the substitution of amino groups in heteroaromatic compounds with aminoalkyl motifs under mild, iridium(III)‐mediated photoredox conditions. It provides rapid access to thienoazepinone, a pharmacophore present in multiple drug candidates for potential treatment of different conditions, including inflammation and psychotic disorders.
A Continuously Regenerable Chiral Ammonia Borane for Asymmetric Transfer Hydrogenations
Authors: Zhou Qiwen , Meng Wei , Yang Jing , Du Haifeng 
Published: July 2018

AbstractA novel chiral ammonia borane was designed and developed through the dehydrogenation of ammonia borane with a chiral phosphoric acid, which was highly effective for the asymmetric transfer hydrogenation of imines and β‐enamino esters to afford high levels of reactivities and enantioselectivities. Significantly, this chiral ammonia borane can be continuously regenerated during the transfer hydrogenation with the assistance of water and ammonia borane, which made it possible to obtain satisfactory results using only 0.1 mol % of the chiral phosphoric acid. Notably, the role of chiral phosphoric acid is to produce the chiral ammonia borane.
Photocatalytic degradation of norfloxacin and its intermediate degradation products using nitrogen‐doped activated carbon–CuS nanocomposite assisted by visible irradiation
Authors: Nekouei Shahram , Nekouei Farzin 
Published: July 2018

We have synthesized a nitrogen‐doped activated carbon (NAC) derived from oak using KOH and N2 thermal treatment at 400 °C as well as CuS nanoparticles. The NAC was decorated with the synthesized CuS to apply as a photocatalyst for degradation of norfloxacin (NOR). Before its application for photodegradation, the adsorbent/photocatalyst structural properties were investigated using X‐ray diffraction, X‐ray photoelectron spectroscopy, Raman spectroscopy and scanning electron microscopy. The photocatalytic degradation of NOR was successfully done under visible light using NAC–CuS. The results revealed that the investigated fluoroquinolone degraded very efficiently and pseudo‐first‐order kinetics was adopted for the photodegradation process. In addition, isothermal studies showed that the adsorption process in darkness followed the Langmuir model. The degradation characteristics of the NAC–CuS photocatalyst were studied for 120 min and 15 h under visible light for degradation of NOR, exhibiting a good efficiency for NOR removal. During 120 min of degradation, some intermediate degradation products that can be considered as secondary pollutants were produced. Then, to degrade these pollutants the radiation time was increased up to 15 h. The results displayed a perfect degradation of NOR and its secondary pollutants. The effective variables including pH, degradation time and photocatalyst dosage were optimized and studied in a multivariate method using Design Expert 7. Determination of photodegradation products was carried out using liquid chromatography–mass spectrometry. The results are of significance for estimating the environmental fate of NOR in aqueous media.
Enhanced photocatalytic activity of Ag3PO4 via Fullerene C60 modification
Authors: Song Limin , Yang Jinfeng , Chen Qian , Zhang Shujuan 
Published: July 2018

Fullerene‐C60‐modified Ag3PO4 photocatalysts (C60/Ag3PO4) were prepared via facile chemical precipitation. The structures, morphology and photocatalytic properties of C60/Ag3PO4 were characterized by X‐ray diffractometry (XRD), transmission electron microscopy (TEM), photoluminescence (PL) spectrometry, and ultraviolet–visible (UV–vis) absorption spectrometry. C60/Ag3PO4 exhibits considerably higher photocatalytic activity for degradation of Methyl Orange. The degradation conversion reached 93% after 8 min of light irradiation. Besides, the enhancement of photocatalytic activity could be attributed to the active species •OH, which can be ascribed to strong synergistic effect between Fullerene C60 and Ag3PO4.
Development of novel EST‐SSR markers for Phyllanthus emblica (Phyllanthaceae) and cross‐amplification in two related species
Authors: Liu Xiongfang , Ma Hong , Li Taiqiang , Li Zhenghong , Wan Youming , Liu Xiuxian , Fu Liyong 
Published: July 2018

Premise of the StudyA novel set of EST‐SSR markers was developed for Phyllanthus emblica (Phyllanthaceae) to investigate the genetic structure and gene flow, identify novel genes of interest, and develop markers for assisted breeding.Methods and ResultsBased on the transcriptome data of P. emblica, 83 EST‐SSR primer pairs were designed; 52 primer pairs were successfully amplified, with 20 showing polymorphisms in 90 individuals from three populations of P. emblica. The number of alleles per locus varied from 11 to 44. The observed and expected levels of heterozygosity for the 20 loci ranged from 0.240 to 0.868 and 0.754 to 0.933, respectively. Cross‐species amplification was successful for all 20 loci in each of the two related species, P. reticulatus and Leptopus chinensis.ConclusionsThese markers will be valuable for studying the population genetics and for mining genes of P. emblica, and may be useful for studies of related species.
Residency and reproductive status of yellowfin tuna in a proposed large‐scale pelagic marine protected area
Authors: Richardson Andrew J. , Downes Katie J. , Nolan Emma T. , Brickle Paul , Brown Judith , Weber Nicola , Weber Sam B. 
Published: July 2018

Abstract

Since the year 2000, the designation of remote, large‐scale marine protected areas (LSMPAs) has closed over 15 × 106 km2 of ocean to commercial fishing. Yet, while these mega‐reserves have collectively made a major contribution toward meeting global targets for marine conservation, their effectiveness for the protection of highly mobile, pelagic species remains largely unknown.
This study reports on the spatial behavior and reproductive status of yellowfin tuna (Thunnus albacares) inhabiting a proposed LSMPA around Ascension Island (tropical Atlantic), with the aim of evaluating the conservation benefits for this economically important species.
Using a combination of satellite archival tags and conventional mark–recapture it was shown that individual tuna can remain within Ascension Island waters for periods of between 100 and 200 days, with core residency areas (50% “utilization distributions”) generally extending <200 km from shore. The vast majority of activity occurred within 92.6 km (50 nmi) of the island and coincided with a “no‐take zone” established around the island in 2016. However, dispersive movements out of this zone were observed in some satellite‐tagged individuals, possibly marking the beginning of more extensive oceanic migrations.
Gonad staging of 342 individuals sampled over a 32 month period found no evidence of reproductively active (ripe) individuals, strongly suggesting that tuna foraging around Ascension Island migrate elsewhere to breed.
Study results provide further evidence of the importance of oceanic islands as residency areas for pelagic megafauna, helping to justify their inclusion within LSMPAs. In the absence of local recruitment, however, these individuals will remain susceptible to exploitation on spawning grounds located outside of reserves, ultimately limiting their effectiveness and thus calling for further research to identify and protect the areas where species are most vulnerable.
Ground‐penetrating radar and electrical resistivity tomography studies in the biblical Pisidian Antioch city, southwest Anatolia
Authors: Balkaya Çağlayan , Kalyoncuoğlu Ümit Yalçın , Özhanlı Mehmet , Merter Gözde , Çakmak Olcay , Talih Güven İ. 
Published: July 2018

AbstractPisidian Antioch was founded as a military base in the Hellenistic period around 300 bc. A consecutive archaeological structure, extending 55 m long, mainly includes two adjacent abscissas and a wall remain thought to be a watchtower. An integrated geophysical survey including ground‐penetrating radar (GPR) and electrical resistivity tomography (ERT) techniques was conducted to determine the existence of counterparts of this structure in a small‐scale area. GPR scans acquired via zigzag mode using 500 MHz antenna along 45 parallel lines were evaluated by a series of basic data processing steps. Considering the results obtained, two‐dimensional (2D) ERT data collected in a restricted area using Wenner‐alpha array along 41 parallel lines were inverted using 2D and three‐dimensional (3D) tomographic inversion schemes. On the basis of the findings obtained from various GPR and ERT imaging techniques, the existence of one of the abscissa, displaying dimensional parameters being in good accordance with those of ones still standing on the west side of the survey area was clearly revealed. Moreover, some regular anomalies, which can be attributed to the remains of the watchtower in question and various wall ruins, were successfully traced from the GPR depth slices. The existence of an antisymmetric geometry for the consecutive archaeological structure under investigation was also determined in the survey area. Combining all of that information, a possible 3D virtual image of the military headquarters was then created, and this pointed out a small square quadriburgia characteristic of the structure investigated. Thus, we can conclude that the integration of GPR and ERT and imaging techniques used in the evaluation were quite effective to provide useful prior information for the subterranean targets in the non‐excavated parts of the ancient city. An archaeological evaluation by trial trenching is therefore required to confirm the results of the archaeo‐geophysical survey in the investigation area.
Metabolic engineering of Escherichia coli for the enhanced production of l‐tyrosine
Authors: Kim Byoungjin , Binkley Robert , Kim Hyun Uk , Lee Sang Yup 
Published: July 2018

AbstractDespite wide applications of l‐tyrosine in the market, microbial overproduction of l‐tyrosine has been a great challenge due to the complex gene regulations involved in its biosynthetic pathway. To this end, effects of knocking out tyrR on the l‐tyrosine production were further explored during the strain development. Also, blocking cellular uptake of l‐tyrosine by knocking out tyrosine transporters was examined with respect to l‐tyrosine production. Using feedback‐resistant aroG and tyrA genes (aroGfbr and tyrAfbr hereafter) as initial overexpression targets, which encode 3‐deoxy‐7‐phosphoheptulonate synthase and chorismate mutase or prephenate dehydrogenase, respectively, various combinations of genes were subsequently overexpressed in the Escherichia coli wild‐type and tyrR knockout strain, and their effects on the l‐tyrosine production were examined. Co‐overexpression of aroGfbr, aroL and tyrC, a gene from Zymomonas mobilis functionally similar to tyrAfbr, but insensitive to l‐tyrosine, led to the greatest l‐tyrosine production regardless of the strains and plasmid constructs examined in this study. The strain BTY2.13 overexpressing the abovementioned three genes together with the removal of the l‐tyrosine‐specific transporter (tyrP) produced 43.14 g/L of l‐tyrosine by fed‐batch fermentation using the exponential feeding followed by DO‐stat feeding method. This outcome suggested that the tyrR gene knockout was not mandatory for the l‐tyrosine overproduction, but the production performance of strains having tyrR appeared to be highly affected by vector systems and feeding methods. With an optimal vector system and a feeding method, tyrP knockout appeared to be more effective in enhancing the l‐tyrosine than tyrR knockout.