bluuebunny/crossref_metadata_2025_split huggingface dataset:
Palladium(0)‐Catalyzed Cross‐Coupling of 1,1‐Diboronates with Vinyl Bromides and 1,1‐Dibromoalkenes
Authors: Li Huan , Zhang Zhikun , Shangguan Xianghang , Huang Shan , Chen Jun , Zhang Yan , Wang Jianbo 
Published: September 2014

AbstractPalladium‐catalyzed cross‐coupling reactions of 1,1‐diboronates with vinyl bromides and dibromoalkenes were found to afford 1,4‐dienes and allenes, respectively. These reactions utilize the high reactivities of both 1,1‐diboronates and allylboron intermediates generated in the initial coupling.
Supramolecular Transcription of Guanosine Monophosphate into Mesostructured Silica
Authors: Bueno‐Alejo Carlos J. , Villaescusa Luis A. , Garcia‐Bennett Alfonso E. 
Published: September 2014

AbstractThere is large interest in replicating biological supramolecular structures in inorganic materials that are capable of mimicking biological properties. The use of 5‐guanosine monophosphate in the presence of Na+ and K+ ions as a supramolecular template for the synthesis of well‐ordered mesostructured materials is reported here. Mesostructured particles with the confined template exhibit high structural order at both meso‐ and atomic scales, with a lower structural symmetry in the columnar mesophase. Although a chiral space group can not be deduced from X‐ray diffraction, analysis by electron microscopy and circular dichroism confirms a chiral stacking arrangement along the c‐axis. Guanosine monophosphate based mesophases thus illustrate the possibility for specific molecular imprinting of mesoporous materials by genetic material and the potential for higher definition in molecular recognition.
Translating Bacterial Detection by DNAzymes into a Litmus Test
Authors: Tram Kha , Kanda Pushpinder , Salena Bruno J. , Huan Shuangyan , Li Yingfu 
Published: September 2014

AbstractMicrobial pathogens pose serious threats to public health and safety, and results in millions of illnesses and deaths as well as huge economic losses annually. Laborious and expensive pathogen tests often represent a significant hindrance to implementing effective front‐line preventative care, particularly in resource‐limited regions. Thus, there is a significant need to develop low‐cost and easy‐to‐use methods for pathogen detection. Herein, we present a simple and inexpensive litmus test for bacterial detection. The method takes advantage of a bacteria‐specific RNA‐cleaving DNAzyme probe as the molecular recognition element and the ability of urease to hydrolyze urea and elevate the pH value of the test solution. By coupling urease to the DNAzyme on magnetic beads, the detection of bacteria is translated into a pH increase, which can be readily detected using a litmus dye or pH paper. The simplicity, low cost, and broad adaptability make this litmus test attractive for field applications, particularly in the developing world.
Carbon Nanofibers Decorated with Molybdenum Disulfide Nanosheets: Synergistic Lithium Storage and Enhanced Electrochemical Performance
Authors: Zhou Fei , Xin Sen , Liang Hai‐Wei , Song Lu‐Ting , Yu Shu‐Hong 
Published: September 2014

AbstractTraditional lithium‐ion batteries that are based on layered Li intercalation electrode materials are limited by the intrinsically low theoretical capacities of both electrodes and cannot meet the increasing demand for energy. A facile route for the synthesis of a new type of composite nanofibers, namely carbon nanofibers decorated with molybdenum disulfide sheets (CNFs@MoS2), is now reported. A synergistic effect was observed for the two‐component anode, triggering new electrochemical processes for lithium storage, with a persistent oxidation from Mo (or MoS2) to MoS3 in the repeated charge processes, leading to an ascending capacity upon cycling. The composite exhibits unprecedented electrochemical behavior with high specific capacity, good cycling stability, and superior high‐rate capability, suggesting its potential application in high‐energy lithium‐ion batteries.
One‐Step Multicomponent Self‐Assembly of a First‐Generation Sierpiński Triangle: From Fractal Design to Chemical Reality
Authors: Sarkar Rajarshi , Guo Kai , Moorefield Charles N. , Saunders Mary Jane , Wesdemiotis Chrys , Newkome George R. 
Published: September 2014

AbstractA novel terpyridine‐based architecture that mimics a first‐generation Sierpiński triangle has been synthesized by multicomponent assembly and features tpyCdIItpy connectivity (tpy=terpyridine). The key terpyridine ligands were synthesized by the Suzuki cross‐coupling reaction. Mixing two different terpyridine‐based ligands and CdII in a precise stoichiometric ratio (1:1:3) produced the desired fractal architecture in near‐quantitative yield. Characterization was accomplished by NMR spectroscopy, mass spectrometry, and transmission electron microscopy.
Herkunft und Verbleib von Elektronen und Protonen bei der Bildung des intermetalloiden Clusters [Sm@Ga3−xH3−2xBi10+x]3− (x=0, 1)
Authors: Weinert Bastian , Müller Fabian , Harms Klaus , Clérac Rodolphe , Dehnen Stefanie 
Published: September 2014

AbstractDie Reaktion von [GaBi3]2− mit [Sm(C5Me4H)3] führte zur Bildung des ersten protonierten ternären intermetalloiden Clusters [Sm@Ga3−xH3−2xBi10+x]3− (1; x=0,1). Die Existenz von Ga‐H‐Bindungen und der Transfer von Elektronen und Protonen während der Bildung von 1 wurde durch Kombination verschiedener experimenteller und quantenchemischer Methoden beleuchtet, was auch die Rolle des Lösungsmittels 1,2‐Diaminoethan als Brønsted‐Säure unterstrich. Als organisches Nebenprodukt wurde das bisher nicht bekannte Octamethylfulven (2) erhalten, das durch eine C‐C‐Kupplung aus (C5Me4H)− hervorging.
Switchable Amplification of Vibrational Circular Dichroism as a Probe of Local Chiral Structure
Authors: Domingos Sérgio R. , Sanders Hans J. , Hartl František , Buma Wybren J. , Woutersen Sander 
Published: September 2014

AbstractA new method to detect the vibrational circular dichroism (VCD) of a localized part of a chiral molecular system is reported. A local VCD amplifier was implemented, and the distance dependence of the amplification was investigated in a series of peptides. The results indicate a characteristic distance of 2.0±0.3 bonds, which suggests that the amplification is a localized phenomenon. The amplifier can be covalently coupled to a specific part of a molecule, and can be switched ON and OFF electrochemically. By subtracting the VCD spectra obtained when the amplifier is in the ON and OFF states, the VCD of the local environment of the amplifier can be separated from the total VCD spectrum. Switchable local VCD amplification thus makes it possible to “zoom in” on a specific part of a chiral molecule.
Chemical Probes for the Functionalization of Polyketide Intermediates
Authors: Riva Elena , Wilkening Ina , Gazzola Silvia , Li W. M. Ariel , Smith Luke , Leadlay Peter F. , Tosin Manuela 
Published: September 2014

AbstractA library of functionalized chemical probes capable of reacting with ketosynthase‐bound biosynthetic intermediates was prepared and utilized to explore in vivo polyketide diversification. Fermentation of ACP mutants of S. lasaliensis in the presence of the probes generated a range of unnatural polyketide derivatives, including novel putative lasalocid A derivatives characterized by variable aryl ketone moieties and linear polyketide chains (bearing alkyne/azide handles and fluorine) flanking the polyether scaffold. By providing direct information on microorganism tolerance and enzyme processing of unnatural malonyl‐ACP analogues, as well as on the amenability of unnatural polyketides to further structural modifications, the chemical probes constitute invaluable tools for the development of novel mutasynthesis and synthetic biology.
Single‐Chain Magnetic Behavior in a Hetero‐Tri‐Spin Complex Mediated by Supramolecular Interactions with TCNQF.− Radicals
Authors: Wang Zhao‐Xi , Zhang Xuan , Zhang Yuan‐Zhu , Li Ming‐Xing , Zhao Hanhua , Andruh Marius , Dunbar Kim R. 
Published: September 2014

AbstractThe self‐assembly of organic TCNQF.− radicals (2‐fluoro‐7,7,8,8‐tetracyano‐p‐quinodimethane) and the anisotropic [Tb(valpn)Cu]3+ dinuclear cations produced a single‐chain magnet (SCM) involving stacking interactions of TCNQF.− radicals (H2valpn is the Schiff base from the condensation of o‐vanillin with 1,3‐diaminopropane). Static and dynamic magnetic characterizations reveal that the effective energy barrier for the reversal of the magnetization in this hetero‐tri‐spin SCM is significantly larger than the barrier of the isolated single‐molecule magnet based on the {TbCu} dinuclear core.
Solvent Effects in Acid‐Catalyzed Biomass Conversion Reactions
Authors: Mellmer Max A. , Sener Canan , Gallo Jean Marcel R. , Luterbacher Jeremy S. , Alonso David Martin , Dumesic James A. 
Published: September 2014

AbstractReaction kinetics were studied to quantify the effects of polar aprotic organic solvents on the acid‐catalyzed conversion of xylose into furfural. A solvent of particular importance is γ‐valerolactone (GVL), which leads to significant increases in reaction rates compared to water in addition to increased product selectivity. GVL has similar effects on the kinetics for the dehydration of 1,2‐propanediol to propanal and for the hydrolysis of cellobiose to glucose. Based on results obtained for homogeneous Brønsted acid catalysts that span a range of pKa values, we suggest that an aprotic organic solvent affects the reaction kinetics by changing the stabilization of the acidic proton relative to the protonated transition state. This same behavior is displayed by strong solid Brønsted acid catalysts, such as H‐mordenite and H‐beta.
Hexagonal Transition‐Metal Chalcogenide Nanoflakes with Pronounced Lateral Quantum Confinement
Authors: Miró Pere , Han Jae Hyo , Cheon Jinwoo , Heine Thomas 
Published: September 2014

AbstractTransition‐metal chalcogenide (TMC) nanoflakes of composition MX2(where M=Ti, Zr and Hf; X=S and Se) crystallize preferentially in equilateral hexagons and exhibit a pronounced lateral quantum confinement. The hexagonal shape of octahedral (1T) TMC nanoflakes is the result of charge localization at the edges/vertices and the resulting Coulomb repulsion. Independent of their size, all nanoflakes have the MnX2n−2stoichiometry and thus an unoxidized metal center which results in dopant states. These states become relevant for small nanoflakes and lead to metallic character, but for larger nanoflakes (>6 nm) the 2D monolayer properties dominate. Finally, coordination of Lewis bases at the nanoflake edges has no significant effect on the electronic structure of these species confirming the viability of colloidal synthetic approaches.
Cu–Al Spinel Oxide as an Efficient Catalyst for Methanol Steam Reforming
Authors: Xi Hongjuan , Hou Xiaoning , Liu Yajie , Qing Shaojun , Gao Zhixian 
Published: September 2014

AbstractCu–Al spinel oxide, which contains a small portion of the CuO phase, has been successfully used in methanol steam reforming (MSR) without prereduction. The omission of prereduction not only avoids the copper sintering prior to the catalytic reaction, but also slows down the copper‐sintering rate in MSR. During this process, the CuO phase can initiate MSR at a lower temperature, and CuAl2O4 releases active copper gradually. The catalyst CA2.5‐900, calcined at 900 °C with n(Al)/n(Cu)=2.5, has a higher CuAl2O4 content, higher BET surface area, and smaller CuAl2O4 crystal size. Its activity first increases and then decreases during MSR. Furthermore, both fresh and regenerated CA2.5‐900 showed better catalytic performance than the commercial Cu–Zn–Al catalyst.
Cleavage and Formation of Molecular Dinitrogen in a Single System Assisted by Molybdenum Complexes Bearing Ferrocenyldiphosphine
Authors: Miyazaki Takamasa , Tanaka Hiromasa , Tanabe Yoshiaki , Yuki Masahiro , Nakajima Kazunari , Yoshizawa Kazunari , Nishibayashi Yoshiaki 
Published: September 2014

AbstractThe NN bond of molecular dinitrogen bridging two molybdenum atoms in the pentamethylcyclopentadienyl molybdenum complexes that bear ferrocenyldiphosphine as an auxiliary ligand is homolytically cleaved under visible light irradiation at room temperature to afford two molar molybdenum nitride complexes. Conversely, the bridging molecular dinitrogen is reformed by the oxidation of the molybdenum nitride complex at room temperature. This result provides a successful example of the cleavage and formation of molecular dinitrogen induced by a pair of two different external stimuli using a single system assisted by molybdenum complexes bearing ferrocenyldiphosphine under ambient conditions.
Two‐Component Supramolecular Gels Derived from Amphiphilic Shape‐Persistent Cyclo[6]aramides for Specific Recognition of Native Arginine
Authors: He Youzhou , Xu Min , Gao Rongzhao , Li Xiaowei , Li Fengxue , Wu Xuedan , Xu Dingguo , Zeng Huaqiang , Yuan Lihua 
Published: September 2014

AbstractA unique supramolecular two‐component gelation system was constructed from amphiphilic shape‐persistent cyclo[6]aramides and diethylammonium chloride (or triethylammonium chloride). This system has the ability to discriminate native arginine from 19 other amino acids in a specific fashion. Cyclo[6]aramides show preferential binding for the guanidinium residue over ammonium groups. This specificity was confirmed by both experimental results and theoretical simulations. These results demonstrated a new modular displacement strategy, exploring the use of species‐binding hydrogen‐bonded macrocyclic foldamers for the construction of two‐component gelation systems for selective recognition of native amino acids by competitive host–guest interactions. This strategy may be amenable to developing a variety of functional two‐component gelators for specific recognition of various targeted organic molecular species.
Enzymatic Polyketide Chain Branching To Give Substituted Lactone, Lactam, and Glutarimide Heterocycles
Authors: Heine Daniel , Bretschneider Tom , Sundaram Srividhya , Hertweck Christian 
Published: September 2014

AbstractPolyketides typically result from head‐to‐tail condensation of acyl thioesters to produce highly functionalized linear chains. The biosynthesis of the phytotoxin rhizoxin, however, involves a polyketide synthase (PKS) module that introduces a δ‐lactone chain branch through Michael addition of a malonyl extender to an α,β‐unsaturated intermediate unit. To evaluate the scope of the branching module, polyketide mimics were synthesized and their biotransformation by the reconstituted PKS module from the Rhizopus symbiont Burkholderia rhizoxinica was monitored in vitro. The impact of the type and configuration of the δ‐substituents was probed and it was found that amino‐substituted surrogates yield the corresponding lactams. A carboxamide analogue was transformed into a glutarimide unit, which can be found in many natural products. Our findings illuminate the biosynthesis of glutarimide‐bearing polyketides and also demonstrate the utility of this branching module for synthetic biology.
Luminescence, Stability, and Proton Response of an Open‐Shell (3,5‐Dichloro‐4‐pyridyl)bis(2,4,6‐trichlorophenyl)methyl Radical
Authors: Hattori Yohei , Kusamoto Tetsuro , Nishihara Hiroshi 
Published: September 2014

AbstractA luminescent open‐shell organic radical with high chemical stability was synthesized. (3,5‐Dichloro‐4‐pyridyl)bis(2,4,6‐trichlorophenyl)methyl radical (PyBTM) was photoluminescent under various conditions. Fluorescence quantum yields of 0.03, 0.26, and 0.81 (the highest value reported for a stable organic radical) were obtained in chloroform, in poly(methyl methacrylate) film at room temperature, and in an EPA matrix (diethyl ether:isopentane:ethanol) at 77 K, respectively. The photostability of PyBTM is up to 115 times higher than that of the tris(2,4,6‐trichlorophenyl)methyl radical, a previously reported luminescent radical. The pyridine moiety of PyBTM acts as a proton coordination site, thereby allowing for control of the electronic and optical properties of the radical by protonation and deprotonation.
Simultaneous Detection of Single Attoliter Droplet Collisions by Electrochemical and Electrogenerated Chemiluminescent Responses
Authors: Dick Jeffrey E. , Renault Christophe , Kim Byung‐Kwon , Bard Allen J. 
Published: September 2014

AbstractWe provide evidence of single attoliter oil droplet collisions at the surface of an ultra‐microelectrode (UME) by the observation of simultaneous electrochemical current transients (i–t curves) and electrogenerated chemiluminescent (ECL) transients in an oil/water emulsion. An emulsion system based on droplets of toluene and tri‐n‐propylamine (2:1 v/v) emulsified with an ionic liquid and suspended in an aqueous continuous phase was formed by ultrasonification. When an ECL luminophore, such as rubrene, is added to the emulsion droplet, stochastic events can be tracked by observing both the current blips from oxidation at the electrode surface and the ECL blips from the follow‐up ECL reaction, which produces light. This report provides a means of studying fundamental aspects of electrochemistry using the attoliter oil droplet and offers complementary analytical techniques for analyzing discrete collision events, size distribution of emulsion systems, and individual droplet electroactivity.
A CXCR4‐Targeted Site‐Specific Antibody–Drug Conjugate
Authors: Kularatne Sumith A. , Deshmukh Vishal , Ma Jennifer , Tardif Virginie , Lim Reyna K. V. , Pugh Holly M. , Sun Ying , Manibusan Anthony , Sellers Aaron J. , Barnett Richard S. , Srinagesh Shailaja , Forsyth Jane S. , Hassenpflug Wolf , Tian Feng , Javahishvili Tsotne , Felding‐Habermann Brunhilde , Lawson Brian R. , Kazane Stephanie A. , Schultz Peter G. 
Published: September 2014

AbstractA chemically defined anti‐CXCR4–auristatin antibody–drug conjugate (ADC) was synthesized that selectively eliminates tumor cells overexpressing the CXCR4 receptor. The unnatural amino acid p‐acetylphenylalanine (pAcF) was site‐specifically incorporated into an anti‐CXCR4 immunoglobulin G (IgG) and conjugated to an auristatin through a stable, non‐cleavable oxime linkage to afford a chemically homogeneous ADC. The full‐length anti‐CXCR4 ADC was selectively cytotoxic to CXCR4+ cancer cells in vitro (half maximal effective concentration (EC50)≈80–100 pM). Moreover, the anti‐CXCR4 ADC eliminated pulmonary lesions from human osteosarcoma cells in a lung‐seeding tumor model in mice. No significant overt toxicity was observed but there was a modest decrease in the bone‐marrow‐derived CXCR4+ cell population. Because CXCR4 is highly expressed in a majority of metastatic cancers, a CXCR4–auristatin ADC may be useful for the treatment of a variety of metastatic malignancies.
In vitro toxicity evaluation of hydrogel–carbon nanotubes composites on intestinal cells
Authors: Bellingeri Romina , Alustiza Fabrisio , Picco Natalia , Acevedo Diego , Molina Maria Alejandra , Rivero Rebeca , Grosso Carolina , Motta Carlos , Barbero Cesar , Vivas Adriana 
Published: September 2014

ABSTRACTComposite materials based on carbon nanotubes (CNT) and polymeric hydrogels have become the subject matter of major interest for use as carriers in drug delivery research. The aim of this study was to evaluate the in vitro cytotoxicity of the hydrogel–carbon nanotube–chitosan (hydrogel–CNT–CH) composites on intestinal cells. Oxidized CNT were wrapped with chitosan (CH), Fourier transform infrared (FT‐IR) analysis suggest that oxidized CNT interact with CH. Transmission electron microscopy (TEM) images show a CH layer lying around CNT. Chitosan wrapped CNT were incorporated to poly (acrylamide‐co‐acrylic acid) hydrogels. Swelling behavior in buffers at different pH were evaluated and revealed a significantly lower swelling when it is exposed to a acid buffer solution (pH 2.2). Mechanical properties were evaluated by measurements of elasticity and the material with CNT showed better mechanical properties. The incorporation and liberation of Egg Yolk Immunoglobulin from hydrogel–CNT–CH were also assessed and it revealed an improved performance. To evaluate the effect of these nanocomposites on cellular redox balance, intestinal cells were exposed to hydrogel–CNT–CH composites and antioxidant enzymes were assessed. Cytotoxicity and apoptosis were also evaluated. Hydrogel–CNT–CH composites induce no oxidative stress and there were no evidence of cytotoxicity or cell death. These preliminary findings suggest that hydrogel–CNT–CH composites show improved properties and good biocompatibility in vitro making these biomaterials promising systems for drug delivery purposes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41370.
Effect of montmorillonite on the rheological properties of dually crosslinked guar gum‐based hydrogels
Authors: Branca Caterina , Crupi Cristina , D'Angelo Giovanna , Khouzami Khaoula , Rifici Simona , Visco Annamaria , Wanderlingh Ulderico 
Published: September 2014

ABSTRACTOne strategy to create chemical and physical cross‐links simultaneously is to introduce into the chemical network hydrogen bonding with clay nanofillers. Understanding the relaxation mechanisms of these systems is crucially important and has drawn the extensive interest of many scientists. In this work, the influence of different amounts of montmorillonite on the structural and rheological properties of guar gum hydrogels was investigated. Depending on the clay content, different nanostructures were identified by X‐ray diffraction (XRD) and their effect on the rheological properties of the dual hydrogels was studied. From stress and frequency sweep tests it emerged that all the samples exhibit a weak gel behavior and showed a maximum for G″ that can be ascribed to the breaking and reforming of transient physical crosslinks. This relaxation mode is more pronounced for the hydrogel for which a minimum in the swelling degree was observed. On the basis of these results, a model structure was proposed according to which the clay sheets act as effective multifunctional cross‐linkers. The more homogeneously dispersed are the clay platelets, the higher is the density of physical crosslinks. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41373.
Compatibility of cassava starch films as nitric oxide carrier for potential medical device
Authors: de Fazio Aguiar Helena , Júnior Antonio Carlos Roveda , de Jesus Piva Renan , Onoda Kevin Akira , Miyakawa Ayumi Aurea , Krieger Jose Eduardo , Franco Douglas Wagner , Tadini Carmen Cecilia 
Published: September 2014

ABSTRACTFilms prepared with bioabsorbable materials (cassava starch, glycerol, and carboxymethyl cellulose (CMC)) can be used as an external support in the myocardial revascularization surgery, releasing nitric oxide (NO) during the tissue regeneration. In the present study, these materials submitted to in vitro degradation tests under physiological conditions, presented the reduction of 38% of weight loss by the modification of native starch using sodium trimetaphosphate (STMP) (15 g/100g of starch). The CMC addition of 10 g/100g of cassava starch increased 119% of the tensile strength of the films in comparison with films prepared without CMC. It was verified that the ruthenium complex trans‐[Ru(NH3)4(isn)(NO)](BF4)3 incorporated in the starch based films behave similarly as in aqueous solution, releasing NO by photochemical reaction. Macrophage cells were detected in in vivo degradation tests in rats around the implant after 1 and 7 days, and complete biodegradation was observed after 30 days. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41382.