bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoelectrochemical H2 Evolution with a Hydrogenase Immobilized on a TiO2‐Protected Silicon Electrode
Authors: Lee Chong‐Yong , Park Hyun S. , Fontecilla‐Camps Juan C. , Reisner Erwin 
Published: April 2016

AbstractThe combination of enzymes with semiconductors enables the photoelectrochemical characterization of electron‐transfer processes at highly active and well‐defined catalytic sites on a light‐harvesting electrode surface. Herein, we report the integration of a hydrogenase on a TiO2‐coated p‐Si photocathode for the photo‐reduction of protons to H2. The immobilized hydrogenase exhibits activity on Si attributable to a bifunctional TiO2 layer, which protects the Si electrode from oxidation and acts as a biocompatible support layer for the productive adsorption of the enzyme. The p‐Si|TiO2|hydrogenase photocathode displays visible‐light driven production of H2 at an energy‐storing, positive electrochemical potential and an essentially quantitative faradaic efficiency. We have thus established a widely applicable platform to wire redox enzymes in an active configuration on a p‐type semiconductor photocathode through the engineering of the enzyme–materials interface.
The Benzyl Moiety in a Quinoxaline‐Based Scaffold Acts as a DNA Intercalation Switch
Authors: Mahata Tridib , Kanungo Ajay , Ganguly Sudakshina , Modugula Eswar Kalyan , Choudhury Susobhan , Pal Samir Kumar , Basu Gautam , Dutta Sanjay 
Published: April 2016

AbstractQuinoxaline antibiotics intercalate dsDNA and exhibit antitumor properties. However, they are difficult to synthesize and their structural complexity impedes a clear mechanistic understanding of DNA binding. Therefore design and synthesis of minimal‐intercalators, using only part of the antibiotic scaffold so as to retain the key DNA‐binding property, is extremely important. Reported is a unique example of a monomeric quinoxaline derivative of a 6‐nitroquinoxaline‐2,3‐diamine scaffold which binds dsDNA by two different modes. While benzyl derivatives bound DNA in a sequential fashion, with intercalation as the second event, nonbenzyl derivatives showed only the first binding event. The benzyl intercalation switch provides important insights about molecular architecture which control specific DNA binding modes and would be useful in designing functionally important monomeric quinoxaline DNA binders and benchmarking molecular simulations.
Homolytic Cleavage of a B−B Bond by the Cooperative Catalysis of Two Lewis Bases: Computational Design and Experimental Verification
Authors: Wang Guoqiang , Zhang Honglin , Zhao Jiyang , Li Wei , Cao Jia , Zhu Chengjian , Li Shuhua 
Published: April 2016

AbstractDensity functional theory (DFT) investigations revealed that 4‐cyanopyridine was capable of homolytically cleaving the B−B σ bond of diborane via the cooperative coordination to the two boron atoms of the diborane to generate pyridine boryl radicals. Our experimental verification provides supportive evidence for this new B−B activation mode. With this novel activation strategy, we have experimentally realized the catalytic reduction of azo‐compounds to hydrazine derivatives, deoxygenation of sulfoxides to sulfides, and reduction of quinones with B2(pin)2 at mild conditions.
Hierarchical NiCo2O4 Hollow Microcuboids as Bifunctional Electrocatalysts for Overall Water‐Splitting
Authors: Gao Xuehui , Zhang Hongxiu , Li Quanguo , Yu Xuegong , Hong Zhanglian , Zhang Xingwang , Liang Chengdu , Lin Zhan 
Published: April 2016

AbstractBifunctional electrocatalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline electrolyte may improve the efficiency of overall water splitting. Nickel cobaltite (NiCo2O4) has been considered a promising electrode material for the OER. However, NiCo2O4 that can be used as an electrocatalyst in HER has not been studied yet. Herein, we report self‐assembled hierarchical NiCo2O4 hollow microcuboids for overall water splitting including both the HER and OER reactions. The NiCo2O4 electrode shows excellent activity toward overall water splitting, with 10 mA cm−2 water‐splitting current reached by applying just 1.65 V and 20 mA cm−2 by applying just 1.74 V across the two electrodes. The synthesis of NiCo2O4 microflowers confirms the importance of structural features for high‐performance overall water splitting.
Enzyme Shielding in an Enzyme‐thin and Soft Organosilica Layer
Authors: Correro M. Rita , Moridi Negar , Schützinger Hansjörg , Sykora Sabine , Ammann Erik M. , Peters E. Henrik , Dudal Yves , Corvini Philippe F.‐X. , Shahgaldian Patrick 
Published: April 2016

AbstractThe fragile nature of most enzymes is a major hindrance to their use in industrial processes. Herein, we describe a synthetic chemical strategy to produce hybrid organic/inorganic nanobiocatalysts; it exploits the self‐assembly of silane building blocks at the surface of enzymes to grow an organosilica layer, of controlled thickness, that fully shields the enzyme. Remarkably, the enzyme triggers a rearrangement of this organosilica layer into a significantly soft structure. We demonstrate that this change in stiffness correlates with the biocatalytic turnover rate, and that the organosilica layer shields the enzyme in a soft environment with a markedly enhanced resistance to denaturing stresses.
N‐Heterocyclic Carbenes as Promotors for the Rearrangement of Phosphaketenes to Phosphaheteroallenes: A Case Study for OCP to OPC Constitutional Isomerism
Authors: Li Zhongshu , Chen Xiaodan , Benkő Zoltán , Liu Liu Leo , Ruiz David A. , Peltier Jesse L. , Bertrand Guy , Su Chen‐Yong , Grützmacher Hansjörg 
Published: April 2016

AbstractThe concept of isomerism is essential to chemistry and allows defining molecules with an identical composition but different connectivity (bonds) between their atoms (constitutional isomers) and/or a different arrangement in space (stereoisomers). The reaction of phosphanyl ketenes, (NHP)−P=C=O (NHP=N‐heterocyclic phosphenium) with N‐heterocyclic carbenes (NHCs) leads to phosphaheteroallenes (NHP)−O−P=C=NHC in which the PCO unit has been isomerized to OPC. Based on the isolation of several intermediates and DFT calculations, a mechanism for this fundamental isomerisation process is proposed.
Allosterische optische Steuerung eines Klasse‐B‐G‐Protein‐gekoppelten Rezeptors
Authors: Broichhagen Johannes , Johnston Natalie R. , von Ohlen Yorrick , Meyer‐Berg Helena , Jones Ben J. , Bloom Stephen R. , Rutter Guy A. , Trauner Dirk , Hodson David J. 
Published: April 2016

AbstractDie allosterische Regulation von G‐Protein‐gekoppelten Rezeptoren (GPCRs) erhöht deren Arzneimittelspezifität und ermöglicht so neue therapeutische Ansätze. Dennoch ist die heutige Wirkstoffentwicklung gehemmt, da die allosterische Bindestelle nur unzureichend präzise kontrollierbar ist. Hier beschreiben wir Design, Synthese und Anwendung von PhotoETP, einem lichtabhängigen positiven allosterischen Regulator des Klasse‐B‐GPCR GLP‐1R (“glucagon‐like peptide‐1 receptor”), der an der Aufrechterhaltung der Glukose‐Homöostase beteiligt ist. PhotoETP ermöglicht die von GLP‐1 und dessen Metaboliten abhängige Potenzierung von Ca2+‐, cAMP‐ und Insulin‐Antworten nach Bestrahlung von Zellen und Pankreasgewebe mit blauem Licht. PhotoETP bietet somit eine Vorlage für die Entwicklung von niedermolekularen allosterischen Photoschaltern für Klasse‐B‐GPCRs, und es könnte nützlich dabei sein, die positive Kooperativität des GLP‐1R zu verstehen.
Computer‐Assisted Synthetic Planning: The End of the Beginning
Authors: Szymkuć Sara , Gajewska Ewa P. , Klucznik Tomasz , Molga Karol , Dittwald Piotr , Startek Michał , Bajczyk Michał , Grzybowski Bartosz A. 
Published: April 2016

AbstractExactly half a century has passed since the launch of the first documented research project (1965 Dendral) on computer‐assisted organic synthesis. Many more programs were created in the 1970s and 1980s but the enthusiasm of these pioneering days had largely dissipated by the 2000s, and the challenge of teaching the computer how to plan organic syntheses earned itself the reputation of a “mission impossible”. This is quite curious given that, in the meantime, computers have “learned” many other skills that had been considered exclusive domains of human intellect and creativity—for example, machines can nowadays play chess better than human world champions and they can compose classical music pleasant to the human ear. Although there have been no similar feats in organic synthesis, this Review argues that to concede defeat would be premature. Indeed, bringing together the combination of modern computational power and algorithms from graph/network theory, chemical rules (with full stereo‐ and regiochemistry) coded in appropriate formats, and the elements of quantum mechanics, the machine can finally be “taught” how to plan syntheses of non‐trivial organic molecules in a matter of seconds to minutes. The Review begins with an overview of some basic theoretical concepts essential for the big‐data analysis of chemical syntheses. It progresses to the problem of optimizing pathways involving known reactions. It culminates with discussion of algorithms that allow for a completely de novo and fully automated design of syntheses leading to relatively complex targets, including those that have not been made before. Of course, there are still things to be improved, but computers are finally becoming relevant and helpful to the practice of organic‐synthetic planning. Paraphrasing Churchill's famous words after the Allies’ first major victory over the Axis forces in Africa, it is not the end, it is not even the beginning of the end, but it is the end of the beginning for the computer‐assisted synthesis planning. The machine is here to stay.
Modular Bidentate Hybrid NHC‐Thioether Ligands for the Stabilization of Palladium Nanoparticles in Various Solvents
Authors: Rühling Andreas , Schaepe Kira , Rakers Lena , Vonhören Benjamin , Tegeder Patricia , Ravoo Bart Jan , Glorius Frank 
Published: April 2016

AbstractThe synthesis of four different bidentate hybrid NHC‐thioether ligands is presented. The corresponding palladium nanoparticles are stable in various solvents, depending on the ligand used, and show high chemoselectivity in the hydrogenation of olefins. The solubility of the nanoparticles can be switched multiple times depending on the pH value of the solvent. XPS analysis (which shows a subtle shift in the binding energy) was identified as a convenient tool to establish the binding mode of NHC ligands.
Specific Enzymatic Halogenation—From the Discovery of Halogenated Enzymes to Their Applications In Vitro and In Vivo
Authors: Weichold Veit , Milbredt Daniela , van Pée Karl‐Heinz 
Published: April 2016

AbstractDuring the last 20 years, focus has shifted from haloperoxidases to flavin‐dependent and non‐heme‐iron halogenases because of their proven involvement in the biosynthesis of halogenated metabolites in different organisms and the regioselectivity of their reactions. During the first 10–12 years, the main research topics were the detection of halogenases as well as the elucidation of three‐dimensional structures and reaction mechanisms. This Review mainly deals with studies on halogenating enzymes published between 2010 and 2015. It focusses on the elucidation of the involvement of halogenating enzymes in halometabolite biosynthesis, application of halogenases in in vivo and in vitro systems, in vivo modification of biosynthetic pathways in bacteria and plants, improvement of enzyme stability, broadening of substrate specificity, and the combination of biocatalysis with chemical synthesis to produce new compounds.
Structure and Metabolic‐Flow Analysis of Molecular Complexity in a 13C‐Labeled Tree by 2D and 3D NMR
Authors: Komatsu Takanori , Ohishi Risa , Shino Amiu , Kikuchi Jun 
Published: April 2016

AbstractImproved signal identification for biological small molecules (BSMs) in a mixture was demonstrated by using multidimensional NMR on samples from 13C‐enriched Rhododendron japonicum (59.5 atom%) cultivated in air containing 13C‐labeled carbon dioxide for 14 weeks. The resonance assignment of 386 carbon atoms and 380 hydrogen atoms in the mixture was achieved. 42 BSMs, including eight that were unlisted in the spectral databases, were identified. Comparisons between the experimental values and the 13C chemical shift values calculated by density functional theory supported the identifications of unlisted BSMs. Tracing the 13C/12C ratio by multidimensional NMR spectra revealed faster and slower turnover ratios of BSMs involved in central metabolism and those categorized as secondary metabolites, respectively. The identification of BSMs and subsequent flow analysis provided insight into the metabolic systems of the plant.
Activation of Methane Promoted by Adsorption of CO on Mo2C2− Cluster Anions
Authors: Liu Qing‐Yu , Ma Jia‐Bi , Li Zi‐Yu , Zhao Chongyang , Ning Chuan‐Gang , Chen Hui , He Sheng‐Gui 
Published: April 2016

AbstractAtomic clusters are being actively studied for activation of methane, the most stable alkane molecule. While many cluster cations are very reactive with methane, the cluster anions are usually not very reactive, particularly for noble metal free anions. This study reports that the reactivity of molybdenum carbide cluster anions with methane can be much enhanced by adsorption of CO. The Mo2C2− is inert with CH4 while the CO addition product Mo2C3O− brings about dehydrogenation of CH4 under thermal collision conditions. The cluster structures and reactions are characterized by mass spectrometry, photoelectron spectroscopy, and quantum chemistry calculations, which demonstrate that the Mo2C3O− isomer with dissociated CO is reactive but the one with non‐dissociated CO is unreactive. The enhancement of cluster reactivity promoted by CO adsorption in this study is compared with those of reported systems of a few carbonyl complexes.
Controlled‐Potential Electromechanical Reshaping of Cartilage
Authors: Hunter Bryan M. , Kallick Jeremy , Kissel Jessica , Herzig Maya , Manuel Cyrus , Protsenko Dmitri , Wong Brian J. F. , Hill Michael G. 
Published: April 2016

AbstractAn alternative to conventional “cut‐and‐sew” cartilage surgery, electromechanical reshaping (EMR) is a molecular‐based modality in which an array of needle electrodes is inserted into cartilage held under mechanical deformation by a jig. Brief (ca. 2 min) application of an electrochemical potential at the water‐oxidation limit results in permanent reshaping of the specimen. Highly sulfated glycosaminoglycans within the cartilage matrix provide structural rigidity to the tissue through extensive ionic‐bonding networks; this matrix is highly permselective for cations. Our studies indicate that EMR results from electrochemical generation of localized, low‐pH gradients within the tissue: fixed negative charges in the proteoglycan matrix are protonated, resulting in chemically induced stress relaxation of the tissue. Re‐equilibration to physiological pH restores the fixed negative charges, and yields remodeled cartilage that retains a new shape approximated by the geometry of the reshaping jig.
Designer Micelles Accelerate Flux Through Engineered Metabolism in E. coli and Support Biocompatible Chemistry
Authors: Wallace Stephen , Balskus Emily P. 
Published: April 2016

AbstractSynthetic biology has enabled the production of many value‐added chemicals via microbial fermentation. However, the problem of low product titers from recombinant pathways has limited the utility of this approach. Methods to increase metabolic flux are therefore critical to the success of metabolic engineering. Here we demonstrate that vitamin E‐derived designer micelles, originally developed for use in synthetic chemistry, are biocompatible and accelerate flux through a styrene production pathway in Escherichia coli. We show that these micelles associate non‐covalently with the bacterial outer‐membrane and that this interaction increases membrane permeability. In addition, these micelles also accommodate both heterogeneous and organic‐soluble transition metal catalysts and accelerate biocompatible cyclopropanation in vivo. Overall, this work demonstrates that these surfactants hold great promise for further application in the field of synthetic biotechnology, and for expanding the types of molecules that can be readily accessed from renewable resources via the combination of microbial fermentation and biocompatible chemistry.
Nickel‐Catalyzed Difluoroalkylation of (Hetero)Arylborons with Unactivated 1‐Bromo‐1,1‐difluoroalkanes
Authors: Xiao Yu‐Lan , Min Qiao‐Qiao , Xu Chang , Wang Ruo‐Wen , Zhang Xingang 
Published: April 2016

AbstractA nickel‐catalyzed cross‐coupling between (hetero)arylborons and unactivated 1‐bromo‐1,1‐difluoroalkanes has been developed. The use of two ligands (a bidentate bipyridine‐based ligand, 4,4′‐ditBu‐bpy, and a monodentate pyridine‐based ligand, DMAP) offers a highly efficient nickel‐based catalytic system to prepare difluoroalkylated arenes which have important applications in medicinal chemistry.
Structural Polymorphism and Thin Film Transistor Behavior in the Fullerene Framework Molecule 5,6;11,12‐di‐o‐Phenylenetetracene
Authors: Wombacher Tobias , Gassmann Andrea , Foro Sabine , von Seggern Heinz , Schneider Jörg J. 
Published: April 2016

AbstractThe molecular structure of the hydrocarbon 5,6;11,12‐di‐o‐phenylenetetracene (DOPT), its material characterization and evaluation of electronic properties is reported for the first time. A single‐crystal X‐ray study reveals two different motifs of intramolecular overlap with herringbone‐type arrangement displaying either face‐to‐edge or co‐facial face‐to‐face packing depicting intensive π–π interactions. Density functional theory (DFT) calculations underpin that a favorable electronic transport mechanism occurs by a charge hopping process due to a π‐bond overlap in the DOPT polymorph with co‐facial arene orientation. The performance of polycrystalline DOPT films as active organic semiconducting layer in a state‐of‐the‐art organic field effect transistor (OFET) device was evaluated and proves to be film thickness dependent. For 40 nm layer thickness it displays a saturation hole mobility (μhole) of up to 0.01 cm2 V−1 s−1 and an on/off‐ratio (Ion/Ioff) of 1.5×103.
Concise Synthesis of a Pateamine A Analogue with In Vivo Anticancer Activity Based on an Iron‐Catalyzed Pyrone Ring Opening/Cross‐Coupling
Authors: Zhuo Chun‐Xiang , Fürstner Alois 
Published: April 2016

AbstractThe marine macrolide pateamine A and its non‐natural sibling DMDA‐Pat A are potent translation inhibitors targeting the eukaryotic initiation factor 4A (eIF4A), an enzyme with RNA helicase activity. Although essential for every living cell, this protein target seems “drugable” since DMDA‐Pat A has previously been shown to exhibit remarkable in vivo activity against two different melanoma mouse models. The novel entry into this promising compound presented herein is shorter and significantly more productive than the literature route. Key to success was the masking of the signature Z,E‐configured dienoate subunit of DMDA‐Pat A in the form of a 2‐pyrone ring, which was best crafted by a gold‐catalyzed cyclization. While the robustness of the heterocycle facilitated the entire assembly stage, the highly isomerization‐prone seco‐Z,E‐dienoic acid could be unlocked in due time for macrolactonization by an unconventional iron‐catalyzed ring opening/cross coupling. Moreover, the crystal structure analysis of an advanced intermediate gave first insights into the conformation of the macrodilactone framework of the pateamine family, which is thought to be critical for eliciting the desired biological response.
Preparation of hydrogel impregnated antimicrobial polyurethane foam for absorption of radionuclide contaminated blood and biological fluids
Authors: Kaur Avneet , Chattopadhyay Sruti , Jain Swati , Tyagi Amit , Singh Harpal 
Published: April 2016

ABSTRACTMulti‐purpose polyacrylamide (PAM) and polyacrylamide‐co‐sodiumpolyacrylate (PAM‐co‐NaPA) impregnated polyurethane foams (PUF) loaded with iodine have been prepared by in situ free radical polymerization. The prepared hydrogel networks displayed higher capacity for absorbing biological fluids as compared to regular PUF sheets and cotton matrices used in hospitals for maintaining hygiene conditions in cases of blood spillage and leakages. PAM‐impregnated‐PUF showed 910, 605, and 172% absorption in water, saline, and blood, respectively, whereas PAM‐co‐NaPA‐impregnated‐PUF showed absorption of 1545, 1395, and 269% in water, saline, and blood, respectively in 24 h. Exposure to nuclear, biological, and chemical (NBC) environment has become a grave predicament in today's world necessitating prevention of radiological contaminations especially in medical facilities. PAM‐co‐NaPA‐impregnated‐PUF displayed 97% absorption of Tc99 from whole blood whereas PUF sheets were highly hydrophobic and showed only 1% absorption of Tc99 from whole blood. It was also demonstrated that modified foams have long‐term broad‐spectrum antimicrobial properties due to sustain release of ionic iodine. Thus, PAM‐co‐NaPA‐impregnated‐PUF sheets have strong potential to be used as matrices for carrying the injured patients, from field conditions to hospitals expose to NBC environment. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43625.
Healing of polymeric artificial muscle reinforced ionomer composite by resistive heating
Authors: Zhang Pengfei , Ayaugbokor Ukeamezhim , Ibekwe Samuel , Jerro Dwayne , Pang Su‐Seng , Mensah Patrick , Li Guoqiang 
Published: April 2016

ABSTRACTIn this study, structural‐scale crack healing of artificial muscle reinforced ionomer composite was investigated following the close‐then‐heal (CTH) healing strategy. Structural‐scale crack of 3 mm deep and 1 mm wide in notched beam specimens was first closed by actuation of the embedded polymeric artificial muscles made of fishing lines, followed by intrinsic healing of the ionomer matrix. The healing process was triggered by resistive heating of embedded carbon fibers by DC power. It is found that, with 0.7% by volume of polymeric artificial muscles, the wide‐opened cracks are effectively closed, and the closed cracks in the ionomer composite are effectively and repeatedly healed, with a healing efficiency of over 80%. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43660.
Relaxation behavior and activation energy of relaxation for polyimide and polyimide–graphene nanocomposite
Authors: Marashdeh Wajeeh F. , Longun Jimmy , Iroh Jude O. 
Published: April 2016

ABSTRACTThe relaxation behavior of polyimide and its nanocomposite containing 10 wt % of graphene was studied by using the dynamic mechanical spectrometer. Dynamic mechanical analysis of polyimide and its composite was performed as a function of temperature and frequency in the temperature range of 25–480 °C and frequency range between 0.05 and 100 Hz. The effect of increasing frequency of testing from 0.05 to 100 Hz is a significant shift from the glass transition temperature, Tg, to higher temperature from 360 °C at 0.05 Hz to 420 °C at 100 Hz. The tan δ peak height for both α and β transitions decreased with increasing test frequency from 0.24 at 0.05 Hz to 0.08 at 100 Hz, due to increasing restriction to chain motion. At any given testing frequency, the Tg for the composite was shown to be higher than that for the matrix by about 5–10 °C. The Arrhenius equation was used to calculate the activation energy for both α and β transitions. The activation for α and β transitions for the composite and polyimide matrix were determined to be 688 and 537 kJ/mol and 313 and 309 kJ/mol, respectively, indicating that a significant increase in the energy barrier to chain relaxation occurred as a result of reinforcement of polyimide with low weight fraction of graphene. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43684.