bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enzymatic Formation of a Skipped Methyl‐Substituted Octaprenyl Side Chain of Longestin (KS‐505a): Involvement of Homo‐IPP as a Common Extender Unit
Authors: Ozaki Taro , Shinde Sandip S. , Gao Lei , Okuizumi Ryo , Liu Chengwei , Ogasawara Yasushi , Lei Xiaoguang , Dairi Tohru , Minami Atsushi , Oikawa Hideaki 
Published: March 2018

AbstractLongestin (KS‐505a), a specific inhibitor of phosphodiesterase, is a meroterpenoid that consists of a unique octacyclic terpene skeleton with branched methyl groups at unusual positions (C1 and C12). Biochemical analysis of Lon23, a methyltransferase involved in the biosynthesis of longestin, demonstrated that it methylates homoisopentenyl diphosphate (homo‐IPP) to afford (3Z)‐3‐methyl IPP. This compound, along with IPP, is selectively accepted as extender units by Lon22, a geranylgeranyl diphosphate (GGPP) synthase homologue, to yield dimethylated GGPP (dmGGPP). The absolute configuration of dmGGPP was determined to be (4R,12R) by degradation and chiral GC analysis. These findings allowed us to propose an enzymatic sequence for key steps of the biosynthetic pathway of the unusual homoterpenoid longestin.
Redox‐Divergent Synthesis of Fluoroalkylated Pyridines and 2‐Pyridones through Cu‐Catalyzed N−O Cleavage of Oxime Acetates
Authors: Bai Dachang , Wang Xueli , Zheng Guangfan , Li Xingwei 
Published: March 2018

AbstractCu‐catalyzed redox‐divergent [3+3] coupling of oxime esters with β‐CF3 enones and acrylates is described. This redox‐neutral coupling with enones and acrylates affords trifluoromethylated pyridines and pyridones, respectively. Under reductive conditions, difluoromethylated pyridines, difluoromethlated pyridones, and trifluoromethylated dihydropyridones are obtained. The reactions occur under mild conditions with broad substrate scope and regio/redox selectivity.
How Changing the Bridgehead Can Affect the Properties of Tripodal Ligands
Authors: Plajer Alex J. , Colebatch Annie L. , Rizzuto Felix J. , Pröhm Patrick , Bond Andrew D. , García‐Rodríguez Raúl , Wright Dominic S. 
Published: March 2018

AbstractAlthough a multitude of studies have explored the coordination chemistry of classical tripodal ligands containing a range of main‐group bridgehead atoms or groups, it is not clear how periodic trends affect ligand character and reactivity within a single ligand family. A case in point is the extensive family of neutral tris‐2‐pyridyl ligands E(2‐py)3 (E=C−R, N, P), which are closely related to archetypal tris‐pyrazolyl borates. With the 6‐methyl substituted ligands E(6‐Me‐2‐py)3 (E=As, Sb, Bi) in hand, the effects of bridgehead modification alone on descending a single group in the periodic table were assessed. The primary influence on coordination behaviour is the increasing Lewis acidity (electropositivity) of the bridgehead atom as Group 15 is descended, which not only modulates the electron density on the pyridyl donor groups but also introduces the potential for anion selective coordination behaviour.
Accessing Frustrated Lewis Pair Chemistry from a Spectroscopically Stable and Classical Lewis Acid‐Base Adduct
Authors: Johnstone Timothy C. , Wee Gabriel N. J. H. , Stephan Douglas W. 
Published: March 2018

AbstractB(C6F5)3 and P(MeNCH2CH2)3N form a classical Lewis adduct, (C6F5)3BP(MeNCH2CH2)3N. Although (C6F5)3BP(MeNCH2CH2)3N does not exhibit spectroscopic evidence of dissociation into its constituent acid and base, products of frustrated Lewis pair (FLP) addition reactions are seen with PhNCO, PhCH2N3, PhNSO, and CO2. Computational studies show that thermal access to the dissociated acid and base permits FLP reactivity to proceed. These results demonstrate that FLP reactivity extends across the entire continuum of equilibria governing Lewis acid‐base adducts.
Eisenkatalysierte C‐O/C‐O‐Bindungsmetathese von aliphatischen Ethern
Authors: Biberger Tobias , Makai Szabolcs , Lian Zhong , Morandi Bill 
Published: March 2018

AbstractMetathesereaktionen von Alkenen und Alkinen sind sicherlich die bestentwickelten Klassen von Metathesereaktionen für den Aufbau molekularer Komplexität. Demgegenüber ist das Verhalten von Einfachbindungen in Bezug auf Metathesereaktionen recht wenig erforscht, vor allem im Hinblick auf präparativ wichtige Ringschlussreaktionen. Hier wird eine Eisen‐katalysierte Ringschlussmetathese von aliphatischen Diethern vorgestellt, die für den raschen Aufbau von Tetrahydrofuranen, Tetrahydropyranen, Morpholinen und Dioxanen angewendet werden kann. Diese Transformation verläuft offenbar über cyclische Oxonium‐Intermediate.
Valency‐Controlled Framework Nucleic Acid Signal Amplifiers
Authors: Liu Qi , Ge Zhilei , Mao Xiuhai , Zhou Guobao , Zuo Xiaolei , Shen Juwen , Shi Jiye , Li Jiang , Wang Lihua , Chen Xiaoqing , Fan Chunhai 
Published: March 2018

AbstractWeak ligand–receptor recognition events are often amplified by recruiting multiple regulatory biomolecules to the action site in biological systems. However, signal amplification in in vitro biomimetic systems generally lack the spatiotemporal regulation in vivo. Herein we report a framework nucleic acid (FNA)‐programmed strategy to develop valence‐controlled signal amplifiers with high modularity for ultrasensitive biosensing. We demonstrated that the FNA‐programmed signal amplifiers could recruit nucleic acids, proteins, and inorganic nanoparticles in a stoichiometric manner. The valence‐controlled signal amplifier enhanced the quantification ability of electrochemical biosensors, and enabled ultrasensitive detection of tumor‐relevant circulating free DNA (cfDNA) with sensitivity enhancement of 3–5 orders of magnitude and improved dynamic range.
Electrooxidative Ruthenium‐Catalyzed C−H/O−H Annulation by Weak O‐Coordination
Authors: Qiu Youai , Tian Cong , Massignan Leonardo , Rogge Torben , Ackermann Lutz 
Published: March 2018

AbstractElectrocatalysis has been identified as a powerful strategy for organometallic catalysis, and yet electrocatalytic C−H activation is restricted to strongly N‐coordinating directing groups. The first example of electrocatalytic C−H activation by weak O‐coordination is presented, in which a versatile ruthenium(II) carboxylate catalyst enables electrooxidative C−H/O−H functionalization for alkyne annulations in the absence of metal oxidants; thereby exploiting sustainable electricity as the sole oxidant. Mechanistic insights provide strong support for a facile organometallic C−H ruthenation and an effective electrochemical reoxidation of the key ruthenium(0) intermediate.
Copper‐Mediated Reversible Deactivation Radical Polymerization in Aqueous Media
Authors: Jones Glen R. , Anastasaki Athina , Whitfield Richard , Engelis Nikolaos , Liarou Evelina , Haddleton David M. 
Published: March 2018

AbstractKey advances within the past 10 years have transformed copper‐mediated radical polymerization from a technique which was not very tolerant of protic media into a range of closely related processes capable of controlling the polymerization of a wide range of monomers in pure water at ppm catalyst loadings. This approach has afforded water‐soluble macromolecules of desired molecular weight, architecture, and chemical functionality, with applications ranging from drug delivery to oil processing. In this Review we highlight and critically evaluate the synthetic methods that have been developed to control radical polymerization in water by using copper complexes as well as identify future areas of interest and challenges still to be overcome.
Iron‐Catalyzed Ring‐Closing C−O/C−O Metathesis of Aliphatic Ethers
Authors: Biberger Tobias , Makai Szabolcs , Lian Zhong , Morandi Bill 
Published: March 2018

AbstractAmong all metathesis reactions known to date in organic chemistry, the metathesis of multiple bonds such as alkenes and alkynes has evolved into one of the most powerful methods to construct molecular complexity. In contrast, metathesis reactions involving single bonds are scarce and far less developed, particularly in the context of synthetically valuable ring‐closing reactions. Herein, we report an iron‐catalyzed ring‐closing metathesis of aliphatic ethers for the synthesis of substituted tetrahydropyrans and tetrahydrofurans, as well as morpholines and polycyclic ethers. This transformation is enabled by a simple iron catalyst and likely proceeds via cyclic oxonium intermediates.
Mapping the Relationship between Glycosyl Acceptor Reactivity and Glycosylation Stereoselectivity
Authors: van der Vorm Stefan , van Hengst Jacob M. A. , Bakker Marloes , Overkleeft Herman S. , van der Marel Gijsbert A. , Codée Jeroen D. C. 
Published: March 2018

AbstractThe reactivity of both coupling partners—the glycosyl donor and acceptor—is decisive for the outcome of a glycosylation reaction, in terms of both yield and stereoselectivity. Where the reactivity of glycosyl donors is well understood and can be controlled through manipulation of the functional/protecting‐group pattern, the reactivity of glycosyl acceptor alcohols is poorly understood. We here present an operationally simple system to gauge glycosyl acceptor reactivity, which employs two conformationally locked donors with stereoselectivity that critically depends on the reactivity of the nucleophile. A wide array of acceptors was screened and their structure–reactivity/stereoselectivity relationships established. By systematically varying the protecting groups, the reactivity of glycosyl acceptors can be adjusted to attain stereoselective cis‐glucosylations.
Novel interpenetrating 3D network polyaniline/phenolic aerogel with combined thermal and electrical performances
Authors: Yao Rui , Yao Zhengjun , Zhou Jintang 
Published: March 2018

ABSTRACTA novel interpenetrating three‐dimensional (3D) network polyaniline/phenolic (AP/RF) aerogel was prepared via a three‐step method. Micro‐, thermal, and electrical analyses were conducted for analyzing the pore morphology, thermal, and electrical performance of the aerogel. From the experimental results, AP/RF aerogel prepared by a three‐step compound method and freeze‐drying exhibited an interpenetrating 3D network structure with nanopores. In addition, compared with single AP aerogel, AP/RF aerogel had lower heat conductivity and higher heat‐resistance. What's more, it exhibited superior electrical performance as compared with that of RF aerogel. In general, AP/RF aerogel with low heat conductivity [0.022 W/(m K)], high heat resistance, electrical conductivity (0.09 S/cm), and specific capacitance (420 F/g) exhibited more excellent thermal and electrical comprehensive performance than single AP or RF aerogels. It will have good application prospect in the fields of electrical components. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45953.
Dynamic rheological behavior of poly(ether ketone ketone) from solid state to melt state
Authors: Coulson Mike , Quiroga Cortés Luis , Dantras Eric , Lonjon Antoine , Lacabanne Colette 
Published: March 2018

ABSTRACTHigh performance thermoplastic poly(ether ketone ketone) (PEKK) polymers with various meta phenyl links ratio were investigated by dynamical mechanical analysis. Analyses were carried out in a wide range of temperature from solid state (torsion rectangular mode) to the melt state (torsion parallel plates mode) as function of thermal history and environmental conditions. In the solid state, this study was focused on the secondary relaxations in the vitreous state. A complementary investigation conducted with different poly(aryl ether ketones) allowed us to propose a molecular interpretation of PEKK sub‐vitreous relaxations. In the molten state, storage modulus (G′), loss modulus (G″), storage viscosity (η′), and loss viscosity (η″) were studied to determine zero shear‐rate viscosity (η0) and thermal activation energy Ea. Master curves were built and the shift factor aT was determined. Thermal activation energies were extracted from an Arrhenius model on the shift factor temperature's dependency. Finally, Ea and η0 were determined thanks to the dynamic viscosity fit with Cross model and Cole–Cole representation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46456.
Development of antimicrobial‐loaded polyurethane films for drug‐eluting catheters
Authors: Barde Mehul , Davis Montoia , Rangari Shivani , Mendis Hajeewaka C. , De La Fuente Leonardo , Auad Maria L. 
Published: March 2018

ABSTRACTTo prepare antibacterial, polymeric catheters for preventing catheter‐induced infections, sulfathiazole was loaded into polyurethane by solubilizing with solvents and the resultant films were cast. Fourier transform infrared spectroscopy confirmed the presence of sulfathiazole in the drug‐loaded polyurethane films. The thermal and mechanical properties of the films were assessed using differential scanning calorimetry and dynamic mechanical analysis. The drug‐loaded films were immersed in constantly stirred, deionized water at 37 °C for in vitro drug release study. The experimental data obtained from the in vitro drug release study were fit into mathematical models. Antibacterial efficiency of released sulfathiazole was evaluated by Escherichia coli growth inhibition test. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46467.
Vesicular and micellar self‐assembly of stimuli‐responsive poly(N‐isopropyl acrylamide‐b‐9‐anthracene methyl methacrylate) amphiphilic diblock copolymers
Authors: Pawar Kishor , Kutcherlapati S. N. Raju , Yeole Niranjan , Hundiwale Dilip , Jana Tushar 
Published: March 2018

ABSTRACTDually responsive amphiphilic diblock copolymers consisting of hydrophilic poly(N‐isopropyl acrylamide) [poly(NIPAAm)] and hydrophobic poly(9‐anthracene methyl methacrylate) were synthesized by reversible addition fragmentation chain‐transfer (RAFT) polymerization with 3‐(benzyl sulfanyl thiocarbonyl sulfanyl) propionic acid as a chain‐transfer agent. In the first step, the poly(NIPAAm) chain was grown to make a macro‐RAFT agent, and in the second step, the chain was extended by hydrophobic 9‐anthryl methyl methacrylate to yield amphiphilic poly(N‐isopropyl acrylamide‐b‐9‐anthracene methyl methacrylate) block copolymers. The formation of copolymers with three different hydrophobic block lengths and a fixed hydrophilic block was confirmed from their molecular weights. The self‐assembly of these copolymers was studied through the determination of the lower critical solution temperature and critical micelle concentration of the copolymers in aqueous solution. The self‐assembled block copolymers displayed vesicular morphology in the case of the small hydrophobic chain, but the morphology gradually turned into a micellar type when the hydrophobic chain length was increased. The variations in the length and chemical composition of the blocks allowed the tuning of the block copolymer responsiveness toward both the pH and temperature. The resulting self‐assembled structures underwent thermally induced and pH‐induced morphological transitions from vesicles to micelles and vice versa in aqueous solution. These dually responsive amphiphilic diblock copolymers have potential applications in the encapsulation of both hydrophobic and hydrophilic drug molecules, as evidenced from the dye encapsulation studies. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46474.
Synthesis of a novel sulfonated poly(amide‐imide) and its application in preparation of ultrafiltration PES membranes as a modifier
Authors: Rezania Jafar , Vatanpour Vahid , Hayatipour Moahammad , Shockravi Abbas , Ehsani Morteza 
Published: March 2018

ABSTRACTSulfonated poly(amide‐imide) (SPAI) copolymer was synthesized, characterized, and blended into poly(ether sulfone) (PES)/dimethylacetamide casting solutions to prepare ultrafiltration membranes. Different weight ratios of the copolymer (0–10 wt %) were mixed in the PES casting solution. The analyses of contact angle and attenuated total reflection‐Fourier transform infrared spectra were used to study hydrophilicity and physicochemical properties of the membrane surface, respectively. The membranes were further characterized by scanning electron microscopy images, ultrafiltration performance, and fouling analyses. The outcomes showed that addition of the SPAI in the PES matrix improved considerably the membranes hydrophilicity. Moreover, with increasing SPAI concentration, the porosity, flux recovery ratio, and pure water permeability of the modified membranes were improved. The pure water flux was increased from 3.6 to 12.4 kg/m2 h by increasing 2 wt % SPAI. The antifouling property of the modified PES membranes against bovine serum albumin, tested by a dead‐end filtration setup revealed that bovine serum albumin rejection of the obtained membrane was also enhanced and the antifouling properties of the blending membranes were improved. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46477.
Enhanced CO2 separation performance by PVA/PEG/silica mixed matrix membrane
Authors: Barooah Mridusmita , Mandal Bishnupada 
Published: March 2018

ABSTRACTThis article focused on segregation of low concentration CO2 from CO2/N2 mixture gas by implementing high‐performance facilitated transport mixed matrix membranes (MMMs) in large‐scale carbon capture techniques. These advanced, novel CO2‐selective membrane materials were developed by embedding silica nanoparticles at different loading into the poly(vinyl alcohol) (PVA)/poly(ethylene glycol) (PEG) matrix using solution casting. In situ sol–gel technique was applied for the synthesis of the hydrophilic SiO2 nanoparticles. The compatibility of filler‐polymer matrix plays a crucial role in the optimization of the membrane performance. The dispersion and interaction of the filler into the polymer matrix were confirmed by thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy, X‐ray diffraction, field emission scanning electron microscopy, contact angle tests, and swelling ratio analysis. Field emission scanning electron microscopy analysis of the synthesized MMMs established the homogeneous dispersion of the fillers in the polymer matrix. Owing to its good compatibility with PVA/PEG matrix, the inclusion of fillers significantly increased the overall separation efficiency of CO2 within the membrane. Compared to pristine PVA/PEG membrane, PVA/PEG/silica membrane with 3.34 wt % silica loading showed pronounced improvement in its gas separation properties with 78% augmentation in CO2 permeability and 45% enhancement in CO2/N2 selectivity for fixed conditions pertaining to sweep side water flow rate of 0.04 mL/min and 100 °C temperature. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46481.
The use of amylose‐rich starch nanoparticles in emulsion polymerization
Authors: Cummings Shidan , Cunningham Michael , Dubé Marc A. 
Published: March 2018

ABSTRACTRegenerated starch nanoparticles (RSNPs) produced from dent corn, an amylose‐rich source of starch, are added to an emulsion polymerization. To reduce or eliminate the challenges of polymerizing in the presence of amylose‐rich starch, a seeded, semibatch, monomer‐starved approach is used. To prevent the accumulation of water soluble amylose in the aqueous phase, reaction with a hydrophobic compatibilizing monomer, butyl acrylate, is used prior to the primary butyl acrylate/methyl methacrylate/acrylic acid feed. In addition, an elevated initiator concentration is used in the seed stage to reduce the molecular weight of the soluble starch and promote grafting. The procedure yields a 100.0 cp latex with 40 wt % solids, 25 wt % RSNP loading, and 40 wt % incorporation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46485.
Electrospinning polymer blend of PLA and PBAT: Electrospinnability–solubility map and effect of polymer solution parameters toward application as antibiotic‐carrier mats
Authors: Khatsee Sarunphat , Daranarong Donraporn , Punyodom Winita , Worajittiphon Patnarin 
Published: March 2018

ABSTRACTElectrospinning of a biodegradable polymer blend of poly(lactic acid) (PLA) and poly(butylene adipate‐co‐terephthalate) (PBAT) is reported for the first time. Effects of several solution parameters on electrospinning are explored, including types of single and binary solvents, binary solvent mixing ratio, polymer blend concentration, polymer blending ratio, and loading content of tetrabutyl titanate as a compatibilizer. An electrospinnability–solubility map of the PLA/PBAT blend is firstly developed for the facile selection of a suitable binary solvent system, thus simplifying the laborious, time‐consuming, trial‐and‐error process. A particular binary solvent system derived from good and non‐solvent serves as the most suitable medium for the successful preparation of homogeneous bead‐free electrospun PLA/PBAT nanofibers. It is revealed that the compatibilizer acts not only as a diameter size tuner for the PLA/PBAT fibers but also as a mechanical property enhancer for the immiscible PLA/PBAT electrospun mats. Moreover, the antibacterial activity of the drug‐loaded PLA/PBAT fibrous mats suggests their potential application as antibiotic‐carrier mats. Preparation of the composite mats comprising bead‐free fibers with an average size at sub‐micrometer scale is also demonstrated, additionally promoting the possibility of using the PLA/PBAT‐based electrospun mats as a matrix of various additives for a wide range of applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46486.
Crystallization kinetics study of dynamically vulcanized PA6/NBR/HNTs nanocomposites by nonisothermal differential scanning calorimetry
Authors: Paran Seyed Mohammad Reza , Vahabi Henri , Ducos Franck , Formela Krzysztof , Zarrintaj Payam , Laachachi Abdelghani , Lopez Cuesta José‐Marie , Saeb Mohammad Reza 
Published: March 2018

ABSTRACTInvestigation of crystallization behavior and kinetics of thermoplastic elastomer nanocomposites was the subject of limited works because of complexities associated with semiexperimental modeling of such phenomenon in a system containing components having completely different behavior in the molten state. Nonisothermal crystallization kinetics of dynamically vulcanized PA6/NBR/HNTs thermoplastic elastomer nanocomposites was mathematically modeled applying well‐known Avrami, Ozawa, and Mo theoretical models to the differential scanning calorimetry data gathered at various cooling rates. It was found that HNTs contribute as nucleating agents to the crystallization kinetics and cause acceleration of crystallization. Activation energy of the crystallization was calculated by correlating the crystallization peak temperature with the cooling rate using Kissinger model. It was found that Mo equation could properly describe nonisothermal crystallization kinetics of the PA6/NBR/HNTs thermoplastic elastomer nanocomposites. This was recognized from the obtained parameters of Mo equation in terms of HNTs loading level, which suggested a higher rate for dynamic crystallization. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46488.