bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure‐Based Rational Design of Prodrugs To Enable Their Combination with Polymeric Nanoparticle Delivery Platforms for Enhanced Antitumor Efficacy
Authors: Wang Hangxiang , Xie Haiyang , Wu Jiaping , Wei Xuyong , Zhou Lin , Xu Xiao , Zheng Shusen 
Published: September 2014

AbstractDrug‐loaded nanoparticles (NPs) are of particular interest for efficient cancer therapy due to their improved drug delivery and therapeutic index in various types of cancer. However, the encapsulation of many chemotherapeutics into delivery NPs is often hampered by their unfavorable physicochemical properties. Here, we employed a drug reform strategy to construct a small library of SN‐38 (7‐ethyl‐10‐hydroxycamptothecin)‐derived prodrugs, in which the phenolate group was modified with a variety of hydrophobic moieties. This esterification fine‐tuned the polarity of the SN‐38 molecule and enhanced the lipophilicity of the formed prodrugs, thereby inducing their self‐assembly into biodegradable poly(ethylene glycol)‐block‐poly(d,l‐lactic acid) (PEG‐PLA) nanoparticulate structures. Our strategy combining the rational engineering of prodrugs with the pre‐eminent features of conventionally used polymeric materials should open new avenues for designing more potent drug delivery systems as a therapeutic modality.
Analyse des Ubiquitincodes durch proteasebeständige Ubiquitinketten mit definierter Verknüpfung
Authors: Schneider Tatjana , Schneider Daniel , Rösner Daniel , Malhotra Saurav , Mortensen Franziska , Mayer Thomas U. , Scheffner Martin , Marx Andreas 
Published: September 2014

AbstractUbiquitylierung ist eine komplexe posttranslationale Modifikation, und die Deregulierung dieses Signalweges ist mit verschiedenen menschlichen Erkrankungen assoziiert. Ubiquitylierung kommt in unterschiedlichen Varianten vor: Neben Monoubiquitylierung werden auch Ubiquitinketten mit verschiedenartiger Verknüpfungen an Substratproteinen gebildet. Das Schicksal der ubiquitylierten Proteine wird dabei durch den Verknüpfungstyp der konjugierten Ubiquitinkette bestimmt. Der zugrundeliegende Mechanismus ist bisher nur dürftig charakterisiert. Wir zeigen hier ein neues Konzept, basierend auf Kodonerweiterung und Klick‐Chemie‐vermittelter Polymerisation, um Ubiquitinketten mit definierten Verknüpfungen herzustellen, die widerstandsfähig gegenüber ubiquitinspezifischen Proteasen sind und natürliche Funktionen haben. Das Potenzial dieser künstlichen Ketten für die Analyse des Ubiquitincodes wird durch verknüpfungsspezifische Auswirkungen auf den Verlauf des Zellzyklus gezeigt.
Engineering Catalyst Microenvironments for Metal‐Catalyzed Hydrogenation of Biologically Derived Platform Chemicals
Authors: Schwartz Thomas J. , Johnson Robert L. , Cardenas Javier , Okerlund Adam , Da Silva Nancy A. , Schmidt‐Rohr Klaus , Dumesic James A. 
Published: September 2014

AbstractIt is shown that microenvironments formed around catalytically active sites mitigate catalyst deactivation by biogenic impurities that are present during the production of biorenewable chemicals from biologically derived species. Palladium and ruthenium catalysts are inhibited by the presence of sulfur‐containing amino acids; however, these supported metal catalysts are stabilized by overcoating with poly(vinyl alcohol) (PVA), which creates a microenvironment unfavorable for biogenic impurities. Moreover, deactivation of Pd catalysts by carbon deposition from the decomposition of highly reactive species is suppressed by the formation of bimetallic PdAu nanoparticles. Thus, a PVA‐overcoated PdAu catalyst was an order of magnitude more stable than a simple Pd catalyst in the hydrogenation of triacetic acid lactone, which is the first step in the production of biobased sorbic acid. A PVA‐overcoated Ru catalyst showed a similar improvement in stability during lactic acid hydrogenation to propylene glycol in the presence of methionine.
Photomobile Polymer Materials with Crosslinked Liquid‐Crystalline Structures: Molecular Design, Fabrication, and Functions
Authors: Ube Toru , Ikeda Tomiki 
Published: September 2014

AbstractCrosslinked liquid‐crystalline polymer materials that macroscopically deform when irradiated with light have been extensively studied in the past decade because of their potential in various applications, such as microactuators and microfluidic devices. The basic motions of these materials are contraction–expansion and bending–unbending, which are observed mainly in polysiloxanes and polyacrylates that contain photochromic moieties. Other sophisticated motions such as twisting, oscillation, rotation, and translational motion have also been achieved. In recent years, efforts have been made to improve the photoresponsive and mechanical properties of this novel class of materials through the modification of molecular structures, development of new fabrication methods, and construction of composite structures. Herein, we review structures, functions, and working mechanisms of photomobile materials and recent advances in this field.
Exploring Weak Ligand–Protein Interactions by Long‐Lived NMR States: Improved Contrast in Fragment‐Based Drug Screening
Authors: Buratto Roberto , Mammoli Daniele , Chiarparin Elisabetta , Williams Glyn , Bodenhausen Geoffrey 
Published: September 2014

AbstractLigands that have an affinity for protein targets can be screened very effectively by exploiting favorable properties of long‐lived states (LLS) in NMR spectroscopy. In this work, we describe the use of LLS for competitive binding experiments to measure accurate dissociation constants of fragments that bind weakly to the ATP binding site of the N‐terminal ATPase domain of heat shock protein 90 (Hsp90), a therapeutic target for cancer treatment. The LLS approach allows one to characterize ligands with an exceptionally wide range of affinities, since it can be used for ligand concentrations [L] that are several orders of magnitude smaller than the dissociation constantsKD. This property makes the LLS method particularly attractive for the initial steps of fragment‐based drug screening, where small molecular fragments that bind weakly to a target protein must be identified, which is a difficult task for many other biophysical methods.
Enantioselective Synthesis of Piperidines through the Formation of Chiral Mixed Phosphoric Acid Acetals: Experimental and Theoretical Studies
Authors: Sun Zhankui , Winschel Grace A. , Zimmerman Paul M. , Nagorny Pavel 
Published: September 2014

AbstractAn enantioselective intramolecular chiral phosphoric acid‐catalyzed cyclization of unsaturated acetals has been utilized for the synthesis of functionalized chiral piperidines. The chiral enol ether products of these cyclizations undergo subsequent in situ enantioenrichment through acetalization of the minor enantiomer. A new computational reaction exploration method was utilized to elucidate the mechanism and stereoselectivity of this transformation. Rather than confirming the originally postulated cyclization proceeding directly through a vinyl oxocarbenium ion, simulations identified an alternative two‐step mechanism involving the formation of a mixed chiral phosphate acetal, which undergoes a concerted, asynchronous SN2′‐like displacement to yield the product with stereoselectivity in agreement with experimental observations.
Organic Dicarboxylate Negative Electrode Materials with Remarkably Small Strain for High‐Voltage Bipolar Batteries
Authors: Ogihara Nobuhiro , Yasuda Tomomi , Kishida Yoshihiro , Ohsuna Tetsu , Miyamoto Kaito , Ohba Nobuko 
Published: September 2014

AbstractAs advanced negative electrodes for powerful and useful high‐voltage bipolar batteries, an intercalated metal–organic framework (iMOF), 2,6‐naphthalene dicarboxylate dilithium, is described which has an organic‐inorganic layered structure of π‐stacked naphthalene and tetrahedral LiO4 units. The material shows a reversible two‐electron‐transfer Li intercalation at a flat potential of 0.8 V with a small polarization. Detailed crystal structure analysis during Li intercalation shows the layered framework to be maintained and its volume change is only 0.33 %. The material possesses two‐dimensional pathways for efficient electron and Li+ transport formed by Li‐doped naphthalene packing and tetrahedral LiO3C network. A cell with a high potential operating LiNi0.5Mn1.5O4 spinel positive and the proposed negative electrodes exhibited favorable cycle performance (96 % capacity retention after 100 cycles), high specific energy (300 Wh kg−1), and high specific power (5 kW kg−1). An 8 V bipolar cell was also constructed by connecting only two cells in series.
Identification of Hypoxic Cells Using an Organotellurium Tag Compatible with Mass Cytometry
Authors: Edgar Landon J. , Vellanki Ravi N. , Halupa Adrienne , Hedley David , Wouters Bradly G. , Nitz Mark 
Published: September 2014

AbstractMass cytometry (MC) offers unparalleled potential for the development of highly parameterized assays for characterization of single cells within heterogeneous populations. Current reagents compatible with MC analysis employ antibody‐metal‐chelating polymer conjugates to report on the presence of biomarkers. Here, we expand the utility of MC by developing the first activity‐based probe designed specifically for use with the technology. A compact MC‐detectable telluroether is linked to a bioreductively sensitive 2‐nitroimidazole scaffold, thereby generating a probe sensitive to cellular hypoxia. The probe exhibits low toxicity and is able to selectively label O2‐deprived cells. A proof‐of‐concept experiment employing metal‐bound DNA intercalators demonstrates that a heterogeneous mixture of cells with differential exposure to O2 can be effectively discriminated by the quantity of tellurium‐labeling. The organotellurium reagents described herein provide a general approach to the development of a large toolkit of MC‐compatible probes for activity‐based profiling of single cells.
Palladium(0)‐Catalyzed Heck Reaction/CH Activation/Amination Sequence with Diaziridinone: A Facile Approach to Indolines
Authors: Zheng Huaiji , Zhu Yingguang , Shi Yian 
Published: September 2014

AbstractIndolines are important moieties present in various biologically significant molecules and have attracted considerable attention in synthetic chemistry. This paper describes a Heck reaction/CH activation/amination sequence for forming indolines using di‐tert‐butyldiaziridinone. The reaction process likely proceeds via a pallada(II)cycle, which is converted into an indoline by oxidative addition to the diaziridinone and two subsequent CN bond formations.
Towards Chemical Communication between Gated Nanoparticles
Authors: Giménez Cristina , Climent Estela , Aznar Elena , Martínez‐Máñez Ramón , Sancenón Félix , Marcos M. Dolores , Amorós Pedro , Rurack Knut 
Published: September 2014

AbstractThe design of comparatively simple and modularly configurable artificial systems able to communicate through the exchange of chemical messengers is, to the best of our knowledge, an unexplored field. As a proof‐of‐concept, we present here a family of nanoparticles that have been designed to communicate with one another in a hierarchical manner. The concept involves the use of capped mesoporous silica supports in which the messenger delivered by a first type of gated nanoparticle is used to open a second type of nanoparticle, which delivers another messenger that opens a third group of gated nanoobjects. We believe that the conceptual idea that nanodevices can be designed to communicate with one another may result in novel applications and will boost further advances towards cooperative systems with complex behavior as a result of the communication between simple abiotic individual components.
Concise and Enantioselective Total Synthesis of (−)‐Mehranine, (−)‐Methylenebismehranine, and Related Aspidosperma Alkaloids
Authors: Mewald Marius , Medley Jonathan William , Movassaghi Mohammad 
Published: September 2014

AbstractWe report an efficient and highly stereoselective strategy for the synthesis of Aspidosperma alkaloids based on the transannular cyclization of a chiral lactam precursor. Three new stereocenters are formed in this key step with excellent diastereoselectivity due to the conformational bias of the cyclization precursor, leading to a versatile pentacyclic intermediate. A subsequent stereoselective epoxidation followed by a mild formamide reduction enabled the first total synthesis of the Aspidosperma alkaloids (−)‐mehranine and (+)‐(6S,7S)‐dihydroxy‐N‐methylaspidospermidine. A late‐stage dimerization of (−)‐mehranine mediated by scandium trifluoromethanesulfonate completed the first total synthesis of (−)‐methylenebismehranine.
A Straightforward Approach towards Cyclic Photoactivatable Tubulysin Derivatives
Authors: Hoffmann Judith , Kazmaier Uli 
Published: September 2014

AbstractThe development of a new photolabile protecting group containing an additional allyl functionality allows the synthesis of cyclic photoactivatable natural products. Cyclization occurs between the allyl moiety in the protecting group and a second double bond in the target molecule by means of ring‐closing metathesis. Cyclization should increase the metabolic stability towards proteases. On the other hand, the conformational change should cause diminished biological activity. As illustrated for tubulysin derivatives, cyclic and photoactivatable drug candidates can easily be obtained in only two steps from simple building blocks through Ugi reaction and ring‐closing metathesis. The photolabile protecting group is introduced by means of the isocyanide component during the Ugi reaction.
Selective Formation of Metastable Ferrihydrite in the Chiton Tooth
Authors: Gordon Lyle M. , Román Jessica K. , Everly R. Michael , Cohen Michael J. , Wilker Jonathan J. , Joester Derk 
Published: September 2014

AbstractMetastable precursors are thought to play a major role in the ability of organisms to create mineralized tissues. Of particular interest are the hard and abrasion‐resistant teeth formed by chitons, a class of rock‐grazing mollusks. The formation of chiton teeth relies on the precipitation of metastable ferrihydrite (Fh) in an organic scaffold as a precursor to magnetite. In vitro synthesis of Fh under physiological conditions has been challenging. Using a combination of X‐ray absorption and electron paramagnetic resonance spectroscopy, we show that, prior to Fh formation in the chiton tooth, iron ions are complexed by the organic matrix. In vitro experiments demonstrate that such complexes facilitate the formation of Fh under physiological conditions. These results indicate that acidic molecules may be integral to controlling Fh formation in the chiton tooth. This biological approach to polymorph selection is not limited to specialized proteins and can be expropriated using simple chemistry.
Improving energy efficiency of distillation using heat pump assisted columns
Authors: Reddy C. C. S. , Fang Y. , Rangaiah G. P. 
Published: September 2014

ABSTRACTDistillation is a widely used separation technique in process industries, although it requires substantial energy inputs. In this study on improving the energy efficiency, both compression and absorption type heat pumps along with feed preheat are analyzed for two common distillation processes of a typical petroleum refinery, to recover waste heat at lower temperatures by upgrading it to useful temperature levels. The heat pumps are also coupled with intermediate heat exchangers (HEXs) to improve cost savings further. The case studies in this investigation are sour water stripper and the C4 separation unit consisting of a deisobutanizer and debutanizer; these include distillation with a partial condenser and separation of compounds having wide boiling points, which have not been studied earlier. Results from these case studies indicate that heat pumps can generally achieve attractive cost savings and that further addition of intermediate HEXs usually worsens the payback, mainly due to additional capital cost. However, intermediate HEXs are beneficial for cases where heat pump application between condenser and reboiler is not economical or feasible, especially in the case of distillation operations requiring very high temperature lifts. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.
Phosphorus adsorption onto an industrial acidified laterite by‐product: equilibrium and thermodynamic investigation
Authors: Glocheux Yoann , Méndez Pasarín Martin , Albadarin Ahmad B. , Mangwandi Chirangano , Chazarenc Florent , Walker Gavin M. 
Published: September 2014

ABSTRACTThe present research investigates the uptake of phosphate ions from aqueous solutions using acidified laterite (ALS), a by‐product from the production of ferric aluminium sulfate using laterite. Phosphate adsorption experiments were performed in batch systems to determine the amount of phosphate adsorbed as a function of solution pH, adsorbent dosage and thermodynamic parameters per fixed P concentration. Kinetic studies were also carried out to study the effect of adsorbent particle sizes. The maximum removal capacity of ALS observed at pH 5 was 3.68 mg P g−1. It was found that as the adsorbent dosage increases, the equilibrium pH decreases, so an adsorbent dosage of 1.0 g L−1 of ALS was selected. Adsorption capacity (qm) calculated from the Langmuir isotherm was found to be 2.73 mg g−1. Kinetic experimental data were mathematically well described using the pseudo first‐order model over the full range of the adsorbent particle size. The adsorption reactions were endothermic, and the process of adsorption was favoured at high temperature; the ΔG and ΔH values implied that the main adsorption mechanism of P onto ALS is physisorption. The desorption studies indicated the need to consider a NaOH 0.1 M solution as an optimal solution for practical regeneration applications. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.
A study of the effect of injection pressure on the combustion, performance, and emission characteristics of cardanol biofuel blend fuelled compression ignition engine
Authors: Dinesha P. , Mohanan P. 
Published: September 2014

AbstractThe use of biodiesel along with other alternative fuel sources is expected to address the twin problems of pollution and energy security. This study investigates the effect of injection pressure (IP) on the performance, combustion, and emission characteristics of a four‐stroke single cylinder direct injection diesel engine fuelled with a biofuel, namely cardanol‐methanol‐diesel blend (B20M10). The results are compared with baseline diesel operations under standard operating conditions. The biofuel blend B20M10 (20% cardanol, 10% methanol, and 70% diesel) is used as fuel, and the combustion, performance, and emission characteristics are investigated at IP levels of 180, 200, and 220 bar. The test results show that the optimum fuel IP is 220 bar with B20M10. At this optimized pressure, a reduction in CO, HC, and smoke emissions with an increase in the oxides of nitrogen (NOx) and brake thermal efficiency (BTE) are noticed compared with 180 and 200 bar B20M10 operations. When compared with diesel (180 bar IP), B20M10 blend at 220 bar IP gives marginally lower BTE and lower CO and HC emissions, but oxides of nitrogen and smoke are slightly more. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.
Effects of the film thickness on the morphology, structure, and crystal orientation behavior of poly(chloro‐p‐xylylene) films
Authors: Tan Kaiyuan , Zhang Hao , Wen Maoping , Du Ziwei 
Published: September 2014

ABSTRACTPoly(chloro‐p‐xylylene) (PPXC) films with a thickness range encompassing more than three orders of magnitude (from 102 nm to 102 μm) were prepared on Si substrates by the chemical vapor deposition method under the same conditions. The effect of the film thickness (d) on the morphology, crystal structure, and crystal orientation behavior of the PPXC films was studied. The average roughness of the root mean square (rms) of the films increased with increasing d according to a power law (rms ≈ dβ, where β is an exponent that depends on the film growth process over time and β = 0.240±0.005, as probed by atomic force microscopy), and the monomer diffusion and relaxation of polymer were suggested as the primary factors governing this morphological evolution. The X‐ray diffraction results indicate that both the crystallinity and crystal size of PPXC increased with increasing d due to the surface confinement effect between the film and the substrate, which retarded the crystallization process. The X‐ray pole figures suggested that the (020) fiber textures with the b axis parallel to the Si substrate normal existed in the PPXC films; these fiber textures, mainly composed of edge‐on crystal lamellae, were thermodynamically favored. The Herman's orientation factor of the fiber textures increased gradually as d grew; this indicated that stronger (020) fiber textures with higher concentrations of edge‐on lamellae existed in the thicker PPXC films. This thickness dependence of the crystal orientation behavior was interpreted to be caused by the strong adhesion between the polymer chains and the substrate. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41394.
Multinuclear solid‐state NMR investigation of the moisture distribution in PEEK‐PBI and PEKK‐PBI blends
Authors: Pope Jacqueline C. , Sue Hung‐Jue , Bremner Tim , Blümel Janet 
Published: September 2014

ABSTRACTBlends of polyaryletherketones (PAEK), such as polyetheretherketones (PEEK) and polyetherketoneketones (PEKK), with polybenzimidazole (PBI) are of commercial interest due to their improved high‐temperature stability and wear properties. The changes of PBI and its PEEK‐ and PEKK‐blends (50 : 50 wt %) after immersing them in liquid H2O and D2O, and exposing them to D2O steam at elevated temperatures and pressures are investigated by multinuclear solid‐state NMR and IR spectroscopy. Macroscopic morphological and chemical changes on the molecular scale, which take place upon high‐temperature steam‐treatment and the extent and reversibility of moisture uptake have been investigated. Interactions and reactions of water, steam, and aqueous solutions of LiCl and ZnBr2 with the functional groups of the polymer components have been studied using D2O in combination with IR, 1H wideline, 2H, 7Li, and 79Br MAS, as well as 13C and 15N CP/MAS NMR spectroscopy. Different locations and types of water and protons in the blends have been described and PBI has been proven to be mainly responsible for water and salt uptake into the blends. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41421.
Studies on luminescence from a cerium‐doped strontium stannate phosphor
Authors: Karabulut Yüksel , Ayvacikli Mehmet , Canimoglu Adil , Garcia Guinea Javier , Can Nurdogan 
Published: September 2014

AbstractThe crystal structure and morphology of Ce3+‐doped SrSnO3 materials prepared using the solid‐state reaction method were extensively characterized using experimental techniques. X‐Ray diffraction results show that the cerium substitution of strontium does not change the structure of the strontium stannate. Raman spectroscopy was used to investigate the microstructures and lattice vibrations. Environmental scanning electron microscopy images showed that phosphors aggregate and their particles form irregular shapes. SrSnO3 exhibits an intense green emission with a broad band originating from the 5d1 → 4f1 transition of cerium. It was observed that, after exposure to beta‐irradiation, the glow curve of this material has two broad thermoluminescence peaks, one centered at ~ 127°C and the other at ~ 245°C for a heating rate of 5 K/s. The kinetic parameters, which include the frequency factor and the activation energy of the material, were calculated using Chen's method, after beta‐irradiation. The fading and reusability of the phosphor were also studied and it was found that the phosphor is suitable for radiation dosimetry. Copyright © 2014 John Wiley & Sons, Ltd.