bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vitro Biosynthesis of the Nonproteinogenic Amino Acid Methoxyvinylglycine
Authors: Patteson Jon B. , Dunn Zachary D. , Li Bo 
Published: April 2018

AbstractOxyvinylglycines are a family of nonproteinogenic amino acids featuring an essential vinyl ether conferring mechanism‐based inhibition of pyridoxal phosphate enzymes. The gene clusters for a few oxyvinylglycines are known, yet the biosynthetic origin of the vinyl ether is elusive. The in vitro biosynthesis of methoxyvinylglycine or l‐2‐amino‐4‐methoxy‐trans‐3‐butenoic acid (AMB) is reported. It is shown that AMB is made from glutamate as an alanyl‐AMB dipeptide and the rationale is provided for the N‐term Ala. Using a chemical capture method, the order and timing of the modifications on non‐ribosomal peptide synthetase (NRPS)‐bound substrates was determined, including a cryptic hydroxylation of the Glu β‐carbon. Eliminating this hydroxy group likely generates a key α,β‐dehydroamino acid intermediate that facilitates decarboxylation. This work sheds light on vinyl ether biosynthesis and uncovers new NRPS chemistry.
Versatile Three‐Dimensional Porous Cu@Cu2O Aerogel Networks as Electrocatalysts and Mimicking Peroxidases
Authors: Ling Pinghua , Zhang Qiang , Cao Tingting , Gao Feng 
Published: April 2018

AbstractA facile strategy is presented to form 3D porous Cu@Cu2O aerogel networks by self‐assembling Cu@Cu2O nanoparticles with the diameters of ca. 40 nm for constructing catalytic interfaces. Unexpectedly, the prepared Cu@Cu2O aerogel networks display excellent electrocatalytic activity to glucose oxidation at a low onset potential of ca. 0.25 V. Moreover, the Cu@Cu2O aerogels also can act as mimicking‐enzymes including horseradish peroxidase and NADH peroxidase, and show obvious enzymatic catalytic activities to the oxidation of dopamine (DA), o‐phenyldiamine (OPD), 3,3,5,5‐tetramethylbenzidine (TMB), and dihydronicotinamide adenine dinucleotide (NADH) in the presence of H2O2. These 3D Cu@Cu2O aerogel networks are a new class of porous catalytic materials as mimic peroxidases and electrocatalysts and offer a novel platform to construct catalytic interfaces for promising applications in electrochemical sensors and artificial enzymatic catalytic systems.
Mapping the Excited‐State Potential Energy Surface of a Photomolecular Motor
Authors: Hall Christopher R. , Browne Wesley R. , Feringa Ben L. , Meech Stephen R. 
Published: April 2018

AbstractA detailed understanding of the operation and efficiency of unidirectional photomolecular rotary motors is essential for their effective exploitation in molecular nanomachines. Unidirectional motion relies on light‐driven conversion from a stable (1 a) to a metastable (1 b) conformation, which then relaxes through a thermally driven helix inversion in the ground state. The excited‐state surface has thus far only been experimentally characterised for 1 a. Here we probe the metastable, 1 b, excited state, utilising ultrafast transient absorption and femtosecond stimulated Raman spectroscopy. These reveal that the “dark” excited‐state intermediate between 1 a and 1 b has a different lifetime and structure depending on the initial ground‐state conformation excited. This suggests that the reaction coordinate connecting 1 a to 1 b differs to that for the reverse photochemical process. The result is contrasted with earlier calculations.
Chemiluminescent Probes for Activity‐Based Sensing of Formaldehyde Released from Folate Degradation in Living Mice
Authors: Bruemmer Kevin J. , Green Ori , Su Timothy A. , Shabat Doron , Chang Christopher J. 
Published: April 2018

AbstractFormaldehyde (FA) is a common environmental toxin that is also produced naturally in the body through a wide range of metabolic and epigenetic processes, motivating the development of new technologies to monitor this reactive carbonyl species (RCS) in living systems. Herein, we report a pair of first‐generation chemiluminescent probes for selective formaldehyde detection. Caging phenoxy‐dioxetane scaffolds bearing different electron‐withdrawing groups with a general 2‐aza‐Cope reactive formaldehyde trigger provides chemiluminescent formaldehyde probes 540 and 700 (CFAP540 and CFAP700) for visible and near‐IR detection of FA in living cells and mice, respectively. In particular, CFAP700 is capable of visualizing FA release derived from endogenous folate metabolism, providing a starting point for the use of CFAPs and related chemical tools to probe FA physiology and pathology, as well as for the development of a broader palette of chemiluminescent activity‐based sensing (ABS) probes that can be employed from in vitro biochemical to cell to animal models.
Dynamic Nuclear Polarization NMR Spectroscopy of Polymeric Carbon Nitride Photocatalysts: Insights into Structural Defects and Reactivity
Authors: Li Xiaobo , Sergeyev Ivan V. , Aussenac Fabien , Masters Anthony F. , Maschmeyer Thomas , Hook James M. 
Published: April 2018

AbstractMetal‐free polymeric carbon nitrides (PCNs) are promising photocatalysts for solar hydrogen production, but their structure–photoactivity relationship remains elusive. Two PCNs were characterized by dynamic‐nuclear‐polarization‐enhanced solid‐state NMR spectroscopy, which circumvented the need for specific labeling with either 13C‐ or 15N‐enriched precursors. Rapid 1D and 2D data acquisition was possible, providing insights into the structural contrasts between the PCNs. Compared to PCN_B with lower performance, PCN_P is a more porous and more active photocatalyst that is richer in terminal N−H bonds not associated with interpolymer chains. It is proposed that terminal N−H groups act as efficient carrier traps and reaction sites.
Goldkatalysierte, regiospezifische C‐H‐Anellierung von ortho‐Ethinylbiarylen mit Anthranilen: π‐Extension durch Ringerweiterung auf dem Weg zu N‐haltigen PAKs
Authors: Zeng Zhongyi , Jin Hongming , Sekine Kohei , Rudolph Matthias , Rominger Frank , Hashmi A. Stephen K. 
Published: April 2018

AbstractWir beschreiben einen neuen, kurzen und flexiblen Weg zu verschiedenen N‐haltigen polycyclischen aromatischen Kohlenwasserstoffen (PAK) über eine goldkatalysierte π‐Erweiterungsreaktion von Anthranilen mit o‐Ethinylbiarylen als Reagenzien. Diese Strategie nutzt leicht zugängliche Edukte, ist aufgrund einer hohen Stufen‐ und Atomökonomie einfach und zeigt eine gute Toleranz gegenüber funktionellen Gruppen, ein Hochskalieren ist ebenfalls möglich. Der mechanistische Vorschlag für die Tandemreaktion beinhaltet eine nukleophile Addition/Ringöffnung/regiospezifische C‐H‐Anellierung/Protodesaurierung und abschließend eine Friedel‐Crafts‐artige Cyclisierung. Photophysikalische Studien der Produkte zeigen eine violett‐blaue Fluoreszenz mit einer Quantenausbeute von bis zu 0.45.
Catalytic Dinitrogen Reduction to Ammonia at a Triamidoamine–Titanium Complex
Authors: Doyle Laurence R. , Wooles Ashley J. , Jenkins Lucy C. , Tuna Floriana , McInnes Eric J. L. , Liddle Stephen T. 
Published: April 2018

AbstractCatalytic reduction of N2 to NH3 by a Ti complex has been achieved, thus now adding an early d‐block metal to the small group of mid‐ and late‐d‐block metals (Mo, Fe, Ru, Os, Co) that catalytically produce NH3 by N2 reduction and protonolysis under homogeneous, abiological conditions. Reduction of [TiIV(TrenTMS)X] (X=Cl, 1A; I, 1B; TrenTMS=N(CH2CH2NSiMe3)3) with KC8 affords [TiIII(TrenTMS)] (2). Addition of N2 affords [{(TrenTMS)TiIII}2(μ‐η1:η1‐N2)] (3); further reduction with KC8 gives [{(TrenTMS)TiIV}2(μ‐η1:η1:η2:η2‐N2K2)] (4). Addition of benzo‐15‐crown‐5 ether (B15C5) to 4 affords [{(TrenTMS)TiIV}2(μ‐η1:η1‐N2)][K(B15C5)2]2 (5). Complexes 3–5 treated under N2 with KC8 and [R3PH][I], (the weakest H+ source yet used in N2 reduction) produce up to 18 equiv of NH3 with only trace N2H4. When only acid is present, N2H4 is the dominant product, suggesting successive protonation produces [{(TrenTMS)TiIV}2(μ‐η1:η1‐N2H4)][I]2, and that extruded N2H4 reacts further with [R3PH][I]/KC8 to form NH3.
Cleavable Binary Dyads: Simplifying Data Extraction and Increasing Storage Density in Digital Polymers
Authors: Cavallo Gianni , Poyer Salomé , Amalian Jean‐Arthur , Dufour Florent , Burel Alexandre , Carapito Christine , Charles Laurence , Lutz Jean‐François 
Published: April 2018

AbstractDigital polymers are uniform macromolecules that store monomer‐based binary sequences. Molecularly stored information is usually extracted from the polymer by a tandem mass spectrometry (MS/MS) measurement, in which the coded chains are fragmented to reveal each bit (i.e. basic coded monomer unit) of the sequence. Here, we show that data‐extraction can be greatly simplified by favoring the formation of MS/MS fragments containing two bits instead of one. In order to do so, digital poly(alkoxyamine phosphodiester)s, containing binary dyads in each repeat unit, were prepared by an orthogonal solid‐phase approach involving successive phosphoramidite and radical‐radical coupling steps. Three different sets of monomers were considered to build these polymers. In all cases, four coded building blocks—two hydroxy‐nitroxides and two phosphoramidite monomers—were required to build the dyads. Among the three studied monomer sets, one combination allowed synthesis of uniform sequence‐coded polymers. The resulting polymers led to clear dyad‐containing fragments in MS/MS and could therefore be efficiently decoded. Additionally, an algorithm was created to detect specific dyad fragments, thus enabling automated sequencing.
In Situ Monitoring of RAFT Polymerization by Tetraphenylethylene‐Containing Agents with Aggregation‐Induced Emission Characteristics
Authors: Liu Shunjie , Cheng Yanhua , Zhang Haoke , Qiu Zijie , Kwok Ryan T. K. , Lam Jacky W. Y. , Tang Ben Zhong 
Published: April 2018

AbstractA facile and efficient approach is demonstrated to visualize the polymerization in situ. A group of tetraphenylethylene (TPE)‐containing dithiocarbamates were synthesized and screened as agents for reversible addition fragmentation chain transfer (RAFT) polymerizations. The spatial‐temporal control characteristics of photochemistry enabled the RAFT polymerizations to be ON and OFF on demand under alternating visible light irradiation. The emission of TPE is sensitive to the local viscosity change owing to its aggregation‐induced emission characteristic. Quantitative information could be easily acquired by the naked eye without destroying the reaction system. Furthermore, the versatility of such a technique was well demonstrated by 12 different polymerization systems. The present approach thus demonstrated a powerful platform for understanding the controlled living radical polymerization process.
Gold‐Catalyzed Regiospecific C−H Annulation of o‐Ethynylbiaryls with Anthranils: π‐Extension by Ring‐Expansion En Route to N‐Doped PAHs
Authors: Zeng Zhongyi , Jin Hongming , Sekine Kohei , Rudolph Matthias , Rominger Frank , Hashmi A. Stephen K. 
Published: April 2018

AbstractWe describe a novel, short, and flexible approach to diverse N‐doped polycyclic aromatic hydrocarbons (PAHs) through gold‐catalyzed π‐extension of anthranils with o‐ethynylbiaryls as reagents. This strategy uses easily accessible starting materials, is simple due to high step and atom economy, and shows good functional‐group compatibility as well as scale‐up potential. Mechanistically, the tandem reaction is proposed to involve a nucleophilic addition/ring opening/regiospecific C−H annulation/protodeauration sequence terminated by a Friedel–Crafts‐type cyclization. Photophysical studies of the products indicated violet‐blue fluorescence emission with quantum yields up to 0.45.
Propagation of Enzyme‐Induced Surface Events inside Polymer Nanoassemblies for a Fast and Tunable Response
Authors: Zhuang Jiaming , Seçinti Hatice , Zhao Bo , Thayumanavan S. 
Published: April 2018

AbstractWe report a new molecular design strategy that allows for the propagation of surface enzymatic events inside a supramolecular assembly for accelerated molecular release. The approach addresses a key shortcoming encountered with many of the currently available enzyme‐induced disassembly strategies, which rely on the unimer–aggregate equilibria of amphiphilic assemblies. The enzymatic response of the host to predictably tune the kinetics of guest‐molecule release can be programmed by controlling substrate accessibility through electrostatic complexation with a complementary polymer. Accelerated guest release in response to the enzyme is shown to be accomplished by a cooperative mechanism of enzyme‐triggered supramolecular host disassembly and host reorganization.
Humanistic‐experiential therapies in the treatment of generalised anxiety: A perspective
Authors: Timulak Ladislav 
Published: April 2018

AbstractThis study discusses the current status of evidence‐based psychological therapies for generalised anxiety disorder (GAD). It points to the dominance of cognitive‐behavioural therapies (CBTs) and compares this dominance with the position of humanistic‐experiential therapies (HEPs) in this area. The paper hypothesises several reasons for this situation, including historical developments as well as HEPs’ ambivalence around embracing mainstream mental health classification systems, and corresponding types of research. The paper then highlights some recent developments in HEPs for anxiety disorders (particularly emotion‐focused therapy; EFT); developments that are breaking new conceptual grounds while also generating new outcome research.
Looking for the bare necessities
Authors: Krishnan Sandeep K. , Dean Larry S. 
Published: April 2018

Key Points

The authors suggest that the early durability of the CoreValve implant should not be in question based on the results of this modestly sized, but well‐done postmortem observational study.
Given the ever‐expanding knowledge of valvular degeneration, one thing is clear: more research and study is needed before any routine change in clinical practice, such as change it antithrombotic therapy, can be recommended.
Further autopsy studies of patients who die outside of typical healthcare settings and who have had a longer median implant time would aid greatly in furthering the understanding of the degeneration and natural history of bioprosthetic transcatheter heart valves.
Early stent thrombosis: Nearly gone, but never forgotten
Authors: Seto Arnold H. , Kern Morton J. 
Published: April 2018

Key Points

Early stent thrombosis occurs in ∼1% of patients treated with primary PCI and increases shock, stroke, and mortality.
Early stent thrombosis was associated with small stent diameter, failure to use glycoprotein inhibitors, and bivalirudin use.
Minimizing stent thrombosis may require the use of imaging and aggressive antithrombotic therapy
The quest for a “diabetic” stent
Authors: Khan Asaad A. , Dangas George D. 
Published: April 2018

Key Points

Patients with diabetes mellitus and extensive coronary artery disease generally had worse outcomes with early generation drug eluting stents (DES) as compared to coronary artery bypass grafting.
Initial results with Amphilimus eluting coronary stent in patients with diabetes have been promising in small studies
The data from Sardella et al. should be used, in conjunction with previous clinical studies with this DES type, as hypothesis generating for a large multicenter randomized trial to aid in our quest to find the “new diabetic stent.”
TAVR technique tries to go higher than bicuspid valve hurdles
Authors: Burzotta Francesco , Trani Carlo 
Published: April 2018

Key Points

Aortic stenosis developed in bicuspid valves is commonly characterized by a complex anatomy
TAVR may be considered for high risk patients with bicuspid valve stenosis but procedure is usually technically challenging
High (supra‐annular) implantation of self‐expandable TAVR prostheses may be a valuable option for selected patients with bicuspid valve stenosis
Heteroatomic Zn‐MWW Zeolite Developed for Catalytic Dehydrogenation Reactions: A Combined Experimental and DFT Study
Authors: Yan Wenjin , Xi Shibo , Du Yonghua , Schreyer Martin K. , Tan Sze Xing , Liu Yan , Borgna Armando 
Published: April 2018

AbstractTo incorporate divalent transition metals into molecular sieve frameworks remains a great challenge in zeolite chemistry. In this study, Zn was successfully incorporated inside the MWW zeolite framework, namely Zn‐MWW (Zn−Si), through hydrothermal synthesis. A combined DFT and X‐ray absorption near edge structure (XANES) simulation was applied to unravel the location of Zn inside the structure, indicating that the most plausible Zn position is T5 with two sodium cations close to the neighboring oxygen to neutralize the charge of the zeolite. The as‐synthesized material exhibits superior catalytic performance for 1‐butene oxidative dehydrogenation with CO2 compared with MCM‐22 and ITQ‐1 supported ZnO. The 1,3‐butadiene (BD) selectivity is doubled at similar 1‐butene conversions. On the other hand, more than 51 % acetaldehyde is produced during ethanol conversion on the Zn‐MWW zeolite, whereas MCM‐22 mainly gives ethylene. The remarkable performance is associated with the efficient combination of acidity and redox properties owing to the successful insertion of atomic Zn inside the MWW framework, as demonstrated by XRD, FTIR, 29Si MAS NMR, XANES analysis, and DFT simulations.
Gulf‐Selective Postsynthetic Functionalization of a Soluble Hexabenzoovalene
Authors: Baumgärtner Kevin , Rominger Frank , Mastalerz Michael 
Published: April 2018

AbstractThe interest in 2D‐annulated polycyclic aromatic hydrocarbons (PAHs) has risen in recent years due to promising applications in using PAHs for organic electronics. The larger the PAHs, the more insoluble they are, making their characterization and especially selective functionalization difficult. Triptycene end‐capping has been introduced to circumvent the problem of low solubility of a hexabenzoovalene (HBO). Additionally, the tendency to form single‐crystals for X‐ray diffraction is preserved. The good solubility of the HBO makes it possible to selectively difunctionalize the compound in the “gulf” region to change electronic properties of the π‐system, which has been investigated photophysically as well as electrochemically.
3D Hierarchical Microballs Constructed by Intertwined MnO@N‐doped Carbon Nanofibers towards Superior Lithium‐Storage Properties
Authors: Li Yi‐Jing , Fan Chao‐Ying , Li Huan‐Huan , Huang Ke‐Cheng , Zhang Jing‐Ping , Wu Xing‐Long 
Published: April 2018

AbstractMnO is a promising high‐capacity anode material for lithium‐ion batteries (LIBs), but pristine material suffers short cycle life and poor rate capability, thus hindering the practical application. In this work, a new type of porous MnO microballs stringed with N‐doped porous carbon (3DHB‐MnO@NC) with a well‐connected hierarchical three‐dimensional network structure was prepared by the facile self‐template method. The 3DHB‐MnO@NC electrode can effectively promote the ion/electron transfer and buffer the large volume change of electrode during the electrochemical reaction. As the anode for LIBs, the 3DHB‐MnO@NC possesses outstanding cycling performance (1247.7 mA h g−1 after 90 cycles at 200 mA g−1) and good rate capabilities (949.6 mA h g−1 after 450 cycles at 1000 mA g−1). The facile self‐template method of the prepared 3DHB‐MnO@NC composite paves a new way for practical applications of MnO in high performance LIBs.
Epoxide Hydrolase Conformational Heterogeneity for the Resolution of Bulky Pharmacologically Relevant Epoxide Substrates
Authors: Serrano‐Hervás Eila , Casadevall Guillem , Garcia‐Borràs Marc , Feixas Ferran , Osuna Sílvia 
Published: April 2018

AbstractThe conformational landscape of Bacillus megaterium epoxide hydrolase (BmEH) and how it is altered by mutations that confer the enzyme the ability to accept bulky epoxide substrates has been investigated. Extensive molecular dynamics (MD) simulations coupled to active site volume calculations have unveiled relevant features of the enzyme conformational dynamics and function. Our long‐timescale MD simulations identify key conformational states not previously observed by means of X‐ray crystallography and short MD simulations that present the loop containing one of the catalytic residues, Asp239, in a wide‐open conformation, which is likely involved in the binding of the epoxide substrate. Introduction of mutations M145S and F128A dramatically alters the conformational landscape of the enzyme. These singly mutated variants can accept bulky epoxide substrates due to the disorder induced by mutation in the α‐helix containing the catalytic Tyr144 and some parts of the lid domain. These changes impact the enzyme active site, which is substantially wider and more complementary to the bulky pharmacologically relevant epoxide substrates.
Efficiently Photocontrollable or Not? Biological Activity of Photoisomerizable Diarylethenes
Authors: Komarov Igor V. , Afonin Sergii , Babii Oleg , Schober Tim , Ulrich Anne S. 
Published: April 2018

AbstractDiarylethene derivatives, the biological activity of which can be reversibly changed by irradiation with light of different wavelengths, have shown promise as scientific tools and as candidates for photocontrollable drugs. However, examples demonstrating efficient photocontrol of their biological activity are still relatively rare. This concept article discusses the possible reasons for this situation and presents a critical analysis of existing data and hypotheses in this field, in order to extract the design principles enabling the construction of efficient photocontrollable diarylethene‐based molecules. Papers addressing biologically relevant interactions between diarylethenes and biomolecules are analyzed; however, in most published cases, the efficiency of photocontrol in living systems remains to be demonstrated. We hope that this article will encourage further discussion of design principles, primarily among pharmacologists, synthetic and medicinal chemists.
Die Wahrheit über Michael Jacksons Tod
Authors: Spieler Florian 
Published: April 2018

ZusammenfassungDas ausgezeichnete Seminar „Chemie und Theater“ schlägt eine Brücke zwischen den Schulfächern Chemie und dramatischem Spiel. In selbst geschriebenen Szenen verpacken die 15 Schülerinnen und Schüler die Chemie der Schule neu und innovativ. Ob beim „Tanz der Moleküle“, dem „Nightlife der Elemente“ oder dem „Tod des King of Pop“, jede Szene ist in sich ein Stück kreativer Chemieunterricht.
A multiobjective optimization procedure for the electrode design of cochlear implants
Authors: Ramos‐de‐Miguel Ángel , Escobar José M. , Greiner David , Ramos‐Macías Ángel 
Published: April 2018

AbstractThis paper presents a new procedure to design optimal electrodes for cochlear implants. The main objective of this study is to find a set of electrode designs that maximize the focalization and minimize the power consumption simultaneously. To achieve that, a criterion to measure the ability of focalization of an electrode is proposed. It is presented a procedure to determine (1) the electrical potential induced by an electrode by solving the Laplace equation through the finite element method; (2) the response of a neuron to an applied field using NEURON, a compartmentalized cell model; (3) the optimization to find the best electrode designs according to power consumption and focalization by 2 evolutionary multiobjective methods based on the non‐dominated sorting genetic algorithm II: a straight multiobjective approach and a seeded multiobjective approach. An electrode design formed by 2 conductive rings with a possible difference of potential between them is proposed. It is analyzed that the response of the neuron is determined by the shape and the difference of the potential between the electrode rings. Our procedure successfully achieves a nondominated set of optimum electrode designs improving a standard electrode in both objectives, as designs with better focalization allow to include extra electrodes in the cochlear implant, and designs with lower power consumption extend the length of the battery.