bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immobilization of the Gas Signaling Molecule H2S by Radioisotopes: Detection, Quantification, and In Vivo Imaging
Authors: Sarkar Swarbhanu , Ha Yeong Su , Soni Nisarg , An Gwang Il , Lee Woonghee , Kim Min Hwan , Huynh Phuong Tu , Ahn Heesu , Bhatt Nikunj , Lee Yong Jin , Kim Jung Young , Park Kwon Moo , Ishii Isao , Kang Shin‐Geol , Yoo Jeongsoo 
Published: July 2016

AbstractHydrogen sulfide (H2S) has multifunctional roles as a gas signaling molecule in living systems. However, the efficient detection and imaging of H2S in live animals is very challenging. Herein, we report the first radioisotope‐based immobilization technique for the detection, quantification, and in vivo imaging of endogenous H2S. Macrocyclic 64Cu complexes that instantly reacted with gaseous H2S to form insoluble 64CuS in a highly sensitive and selective manner were prepared. The H2S concentration in biological samples was measured by a thin‐layer radiochromatography method. When 64Cu–cyclen was injected into mice, an elevated H2S concentration in the inflamed paw was clearly visualized and quantified by Cerenkov luminescence and positron emission tomography (PET) imaging. PET imaging was also able to pinpoint increased H2S levels in a millimeter‐sized infarcted lesion of the rat heart.
Total Synthesis of the Hamigerans
Authors: Li Xiaojun , Xue Dongsheng , Wang Cheng , Gao Shuanhu 
Published: July 2016

AbstractThe first total synthesis of hamigerans D, G, L, and N–Q has been accomplished. A convergent approach was used to build the basic tricarbocyclic ring system bearing a 5‐6‐6 structure. A sequence of oxidative cleavage, homologation, and ring regeneration provided access to the 5‐7‐6 skeleton of hamigeran G. Based on the biogenetic hypothesis, elegant and highly efficient biomimetic transformations of hamigeran G into hamigerans D, N–Q, and L were achieved.
Synthesis and Disassembly/Reassembly of Giant Ring‐Shaped Polyoxotungstate Oligomers
Authors: Minato Takuo , Suzuki Kosuke , Yamaguchi Kazuya , Mizuno Noritaka 
Published: July 2016

AbstractThe disassembly and reassembly of giant molecules are essential processes in controlling the structure and function of biological and artificial systems. In this work, the disassembly and reassembly of a giant ring‐shaped polyoxometalate (POM) without isomerization of the monomeric units is reported. The reaction of a hexavacant lacunary POM that is soluble in organic solvents, [P2W12O48]14−, with manganese cations gave the giant ring‐shaped POM [{γ‐P2W12O48Mn4(C5H7O2)2(CH3CO2)}6]42−. This POM is a hexamer of manganese‐substituted {P2W12O48Mn4} units, and its inner cavity was larger than any of those previously reported for ring‐shaped polyoxotungstates. It was disassembled into monomeric units in acetonitrile, and the removal of the capping organic ligands on the manganese cations led to reassembly into a tetrameric ring‐shaped POM, [{γ‐P2W12O48Mn4(H2O)6}4(H2O)4]24−.
Lewis Acid Catalyzed Selective Reactions of Donor–Acceptor Cyclopropanes with 2‐Naphthols
Authors: Kaicharla Trinadh , Roy Tony , Thangaraj Manikandan , Gonnade Rajesh G. , Biju Akkattu T. 
Published: July 2016

AbstractLewis acid‐catalyzed reactions of 2‐substituted cyclopropane 1,1‐dicarboxylates with 2‐naphthols is reported. The reaction exhibits tunable selectivity depending on the nature of Lewis acid employed and proceed as a dearomatization/rearomatization sequence. With Bi(OTf)3 as the Lewis acid, a highly selective dehydrative [3+2] cyclopentannulation takes place leading to the formation of naphthalene‐fused cyclopentanes. Interestingly, engaging Sc(OTf)3 as the Lewis acid, a Friedel–Crafts‐type addition of 2‐naphthols to cyclopropanes takes place, thus affording functionalized 2‐naphthols. Both reactions furnished the target products in high regioselectivity and moderate to high yields.
Sequenz‐spezifischer Einbau von Enzym‐Nukleotid‐Chimären durch DNA‐Polymerasen
Authors: Welter Moritz , Verga Daniela , Marx Andreas 
Published: July 2016

AbstractDurch Erkennung von Form und Geometrie des naszierenden Nukleotidpaars stellen DNA‐Polymerasen die hohe Selektivität der DNA‐Replikation sicher. Man geht davon aus, dass DNA‐Polymerasen mit hoher Replikationsgenauigkeit hierzu ein genau angepasstes aktives Zentrum enthalten, das nur geringe Abweichungen von den kanonischen Basenpaarungen toleriert. Dennoch ist bekannt, dass DNA‐Polymerasen Nukleotide mit kleinen Modifikationen als Substrate akzeptieren, was von wesentlicher Bedeutung für zahlreiche grundlegende biotechnologische Anwendungen ist. Hier wird nun gezeigt, dass selbst DNA‐Polymerasen, die eine hohe Replikationsgenauigkeit aufweisen, in der Lage sind, eine Nukleotid‐Chimäre, die mit einem großen Protein wie der Meerrettichperoxidase modifiziert ist, als Substrat zu nutzen, obwohl diese “Fracht” um ein Hundertfaches größer ist als das natürliche Substrat. Wir nutzten diese Eigenschaft, um ein Testsystem zu entwickeln, das den Nachweis von DNA und RNA in Einzelbasenauflösung mit bloßem Auge ermöglicht.
Kontrolle der Kinetik von Iminaustauschreaktionen mit Photoschaltern zur lichtgesteuerten Modulation der Selbstheilung in Polysiloxannetzwerken
Authors: Kathan Michael , Kovaříček Petr , Jurissek Christoph , Senf Antti , Dallmann Andre , Thünemann Andreas F. , Hecht Stefan 
Published: July 2016

AbstractEs wurden mehrere aldehydsubstituierte Photoschalter entwickelt, deren Reaktivität gegenüber Aminen ferngesteuert werden kann. Ein thermisch stabiles, difunktionelles Diarylethen, das in seiner ringgeschlossenen Form eine um den Faktor zehn erhöhte Reaktivität gegenüber Aminen aufweist, wurde als photoschaltbarer Vernetzer für ein kommerziell erhältliches, aminofunktionalisiertes Polysiloxan eingesetzt. Die Selbstheilungsgeschwindigkeit und viskoelastischen Eigenschaften dieses gummiartigen Materials können somit reversibel mit Licht moduliert werden.
Catalytic Asymmetric Synthesis of Cyclopentyl β‐Amino Esters by [3+2] Cycloaddition of Enecarbamates with Electrophilic Metalloenolcarbene Intermediates
Authors: Deng Yongming , Yglesias Matthew V. , Arman Hadi , Doyle Michael P. 
Published: July 2016

AbstractChiral cyclopentyl β‐amino esters are formed catalytically by [3+2] cycloaddition reactions of enecarbamates with electrophilic metalloenolcarbenes in high yield with up to 98 % ee and excellent diastereocontrol. Use of β‐silyl‐substituted enoldiazoacetates with a chiral dirhodium catalyst and trans‐β‐arylvinylcarbamates are optimal for this transformation, which occurs with hydrogen‐bond association between the vinylcarbamate and the intermediate metalloenolcarbene. Reductive conversion of the protected amino esters forms highly functionalized cyclopentyl β‐amino acids and 3‐aminocyclopentanones.
Combining Neopentyllithium with Potassium tert‐Butoxide: Formation of an Alkane‐Soluble Lochmann–Schlosser Superbase
Authors: Benrath Philipp , Kaiser Maximilian , Limbach Thomas , Mondeshki Mihail , Klett Jan 
Published: July 2016

AbstractMixtures of alkyllithium and heavier alkali‐metal alkoxides are often used to form alkyl compounds of heavier alkali metals, but these mixtures are also known for their high reactivity in deprotonative metalation reactions. These organometallic mixtures are often called LiC–KOR superbases, but despite many efforts their constitution remains unknown. Herein we present mixed alkali‐metal alkyl/alkoxy compounds produced by reaction of neopentyllithium with potassium tert‐butoxide. The key to success was the good solubility and temperature‐stability of neopentyl alkali‐metal compounds, leading to hexane‐soluble mixtures, which allowed handling at ambient temperatures and isolation by crystallization. The compounds in solid state and in solution were identified by X‐ray crystallography and NMR spectroscopy as mixtures of lithium/potassium neopentyl/tert‐butoxy aggregates of varying compositions LixKyNpz(OtBu)x+y−z.
Unveiling (−)‐Englerin A as a Modulator of L‐Type Calcium Channels
Authors: Rodrigues Tiago , Sieglitz Florian , Somovilla Víctor J. , Cal Pedro M. S. D. , Galione Antony , Corzana Francisco , Bernardes Gonçalo J. L. 
Published: July 2016

AbstractThe voltage‐dependent L‐type Ca2+channel was identified as a macromolecular target for (−)‐englerin A. This finding was reached by using an unprecedented ligand‐based prediction platform and the natural product piperlongumine as a pharmacophore probe. (−)‐Englerin A features high substructure dissimilarity to known ligands for voltage‐dependent Ca2+ channels, selective binding affinity for the dihydropyridine site, and potent modulation of calcium signaling in muscle cells and vascular tissue. The observed activity was rationalized at the atomic level by molecular dynamics simulations. Experimental confirmation of this hitherto unknown macromolecular target expands the bioactivity space for this natural product and corroborates the effectiveness of chemocentric computational methods for prioritizing target‐based screens and identifying binding counterparts of complex natural products.
Deformylation Reaction by a Nonheme Manganese(III)–Peroxo Complex via Initial Hydrogen‐Atom Abstraction
Authors: Barman Prasenjit , Upadhyay Pranav , Faponle Abayomi S. , Kumar Jitendra , Nag Sayanta Sekhar , Kumar Devesh , Sastri Chivukula V. , de Visser Sam P. 
Published: July 2016

AbstractMetal–peroxo intermediates are key species in the catalytic cycles of nonheme metalloenzymes, but their chemical properties and reactivity patterns are still poorly understood. The synthesis and characterization of a manganese(III)–peroxo complex with a pentadentate bispidine ligand system and its reactivity with aldehydes was studied. Manganese(III)–peroxo can react through hydrogen‐atom abstraction reactions instead of the commonly proposed nucleophilic addition reaction. Evidence of the mechanism comes from experiments which identify a primary kinetic isotope effect of 5.4 for the deformylation reaction. Computational modeling supports the established mechanism and identifies the origin of the reactivity preference of hydrogen‐atom abstraction over nucleophilic addition.
MgI2‐chemoselective cleavage for removal of amino acid protecting groups: A fresh vision for peptide synthesis
Authors: Berthet Mathéo , Martinez Jean , Parrot Isabelle 
Published: July 2016

AbstractIn the field of peptide synthesis, the key to a successful access to synthetic targets lies on a pertinent combination of protecting groups. Their choice is directed by their selective removal conditions. We present here the behavior of some of the most used protecting groups in peptide chemistry under experimental cleavage conditions, combining MgI2 with MW irradiation, using 2‐Me‐THF as a green solvent. In these experimental conditions, the benzyloxycarbonyl protecting group as well as the Merrifield resin can be re‐considered in peptide chemistry.
In vitro metabolism of specific CYP2D and CYP3A opioid substrates using rat liver S9 fractions and mass spectrometry reveal a severe metabolic impairment with increasing age
Authors: Salmin Sabrin Fuad , Giroux Marie‐Chantal , Vachon Pascal , Beaudry Francis 
Published: July 2016

AbstractCodeine and oxycodone are opioids used to alleviate pain. The outcome of the treatment is ultimately related to their metabolism by Cytochromes P450 (CYPs). Depending on the drugs used, alterations in the metabolism of drugs by CYPs can lead to severe consequences including alterations in their efficacy, safety and toxicity. The objectives of this study were to develop a novel HPLC–MS/MS method capable of quantifying codeine and oxycodone along with specific metabolites using an isotopic dilution strategy and study the rate of formation of morphine (CYP2D), norcodeine (CYP3A), oxymorphone (CYP2D) and noroxycodone (CYP3A). The chromatographic separation was achieved using a Biobasic C18 100 × 1 mm column combined with an isocratic mobile phase composed of methanol and 10 mm ammonium acetate (40:60) at a flow rate of 75 μL/min. The mass spectrometer was operating in scan mode MS/MS and the analytical range was set at 10–10 000 nm. The precision (RSD) and accuracy (RE) observed were 4.4–11.5 and −9.1–6.1% respectively. Liver S9 fractions from 3‐, 6‐, 12‐ and 18‐month‐old male Sprague–Dawley rats were prepared and Michaelis–Menten parameters were determined. The derived maximum enzyme velocity suggested a rapid saturation of the CYP2D and CYP3A active sites in the liver S9 fractions of 18‐month‐old rats. Moreover, metabolic stabilities of codeine and oxycodone in rat liver S9 fractions were significantly greater for the 18‐month‐old rats. This study suggests that there is an impairment of CYP2D and CYP3A metabolism in aging rats.
Exploring the capabilities of fluorometric online monitoring on chinese hamster ovary cell cultivations producing a monoclonal antibody
Authors: Schwab Karen , Amann Thomas , Schmid Jakob , Handrick René , Hesse Friedemann 
Published: July 2016

Online monitoring of Chinese hamster ovary fed‐batch cell cultures via two‐dimensional fluorescence spectroscopy (2DFS) was evaluated in this work. Particular attention was directed toward different process strategies regarding the use of nutrient‐rich feed media and temperature shifts. These intentionally performed process manipulations broadened the variances in the obtained fluorescence spectra and this was suspected to hamper the generation of reliable soft sensors. Principal component analysis of the obtained fluorescence data showed that temperature shift and feeding strategy had a considerable impact on the fluorescence signals. Partial least square regression models were calculated for the prediction of glucose, lactate, monoclonal antibody (mAb), and viable cell concentrations (VCC). It was aimed to integrate all 2DFS datasets in the respective calibration models regardless of the process‐strategy‐dependent diversity. Contrary to the expectations, it was feasible to calibrate soft sensors for the online prediction of glucose (7 latent variables (LVs),
= 0.97, rout mean squared error of prediction (RMSEP) = 1.1 g L−1), lactate (5 LV;
= 0.96; RMSEP = 0.5 g L−1) and mAb concentrations (4 LV;
= 0.99; RMSEP = 11.4 mg L−1). Feeding and temperature shifts had the highest impact on the VCC model (3 LV;
= 0.94; RMSEP 3.8 × 105 mL−1), nevertheless the prediction of VCC from the fed‐batch 2DFS data was feasible. The results strongly indicate that variances in the datasets due to the process strategy can be tolerated to some extent by the respective soft sensors. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1592–1600, 2016
Enzymatic Resolution by a d‐Lactate Oxidase Catalyzed Reaction for (S)‐2‐Hydroxycarboxylic Acids
Authors: Sheng Binbin , Xu Jing , Ge Yongsheng , Zhang Shuo , Wang Danqi , Gao Chao , Ma Cuiqing , Xu Ping 
Published: July 2016

AbstractOxidase‐catalyzed kinetic resolution is important for the production of enantiopure 2‐hydroxycarboxylic acids (2‐HAs), which are versatile building blocks for the synthesis of many significant compounds. However, in contrast to that of (R)‐2‐HAs, the production of (S)‐2‐HA is challenging because of the lack of related oxidases. Herein, suitable enzymes were screened systematically through the analysis of numerous putative d‐lactate oxidase sequences and identification of several required properties. Finally, a d‐lactate oxidase from Gluconobacter oxydans 621H with advantageous characteristics, such as good solubility, broad substrate spectrum, and high stereoselectivity, was selected to resolve 2‐HAs into (S)‐2‐HAs. A variety of (S)‐2‐HAs was produced successfully using this d‐lactate oxidase with excellent enantiomeric excess values (>99 %). The presented screening criteria and approach for target biocatalysis suggested a guideline for the production of optically active chemicals such as (S)‐2‐HAs.
Functionalization of Pyrene To Prepare Luminescent Materials—Typical Examples of Synthetic Methodology
Authors: Feng Xing , Hu Jian‐Yong , Redshaw Carl , Yamato Takehiko 
Published: July 2016

AbstractPyrene‐based π‐conjugated materials are considered to be an ideal organic electro‐luminescence material for application in semiconductor devices, such as organic light‐emitting diodes (OLEDs), organic field‐effect transistors (OFETs) and organic photovoltaics (OPVs), and so forth. However, the great drawback of employing pyrene as an organic luminescence material is the formation of excimer emission, which quenches the efficiency at high concentration or in the solid‐state. Thus, in order to obtain highly efficient optical devices, scientists have devoted much effort to tuning the structure of pyrene derivatives in order to realize exploitable properties by employing two strategies, 1) introducing a variety of moieties at the pyrene core, and 2) exploring effective and convenient synthetic strategies to functionalize the pyrene core. Over the past decades, our group has mainly focused on synthetic methodologies for functionalization of the pyrene core; we have found that formylation/acetylation or bromination of pyrene can selectly lead to functionalization at K‐region by Lewis acid catalysis. Herein, this Minireview highlights the direct synthetic approaches (such as formylation, bromination, oxidation, and de‐tert‐butylation reactions, etc.) to functionalize the pyrene in order to advance research on luminescent materials for organic electronic applications. Further, this article demonstrates that the future direction of pyrene chemistry is asymmetric functionalization of pyrene for organic semiconductor applications and highlights some of the classical asymmetric pyrenes, as well as the latest breakthroughs. In addition, the photophysical properties of pyrene‐based molecules are briefly reviewed. To give a current overview of the development of pyrene chemistry, the review selectively covers some of the latest reports and concepts from the period covering late 2011 to the present day.
Regioselective, Solvent‐ and Metal‐Free Chalcogenation of Imidazo[1,2‐a]pyridines by Employing I2/DMSO as the Catalytic Oxidation System
Authors: Rafique Jamal , Saba Sumbal , Rosário Alisson R. , Braga Antonio L. 
Published: July 2016

AbstractHighly efficient molecular‐iodine‐catalyzed chalcogenations (S and Se) of imidazo[1,2‐a]pyridines were achieved by using diorganoyl dichalcogenides under solvent‐free conditions. This approach afforded the desired products that had been chalcogenated regioselectively at the C3 position in up to 96 % yield by using DMSO as an oxidant, in the absence of a metal catalyst, and under an inert atmosphere. This mild, green approach allowed the preparation of different types of chalcogenated imidazo[1,2‐a]pyridines with structural diversity. Furthermore, the current protocol was also extended to other N‐heterocyclic cores.
New Found Hope for Antibiotic Discovery: Lipid II Inhibitors
Authors: Ng Vivian , Chan Weng C. 
Published: July 2016

AbstractResearch into antibacterial agents has recently gathered pace in light of the disturbing crisis of antimicrobial resistance. The development of modern tools offers the opportunity of reviving the fallen era of antibacterial discovery through uncovering novel lead compounds that target vital bacterial cell components, such as lipid II. This paper provides a summary of the role of lipid II as well as an overview and insight into the structural features of macrocyclic peptides that inhibit this bacterial cell wall component. The recent discovery of teixobactin, a new class of lipid II inhibitor has generated substantial research interests. As such, the significant progress that has been achieved towards its development as a promising antibacterial agent is discussed.
An Unprecedented Two‐Fold Nested Super‐Polyrotaxane: Sulfate‐Directed Hierarchical Polythreading Assembly of Uranyl Polyrotaxane Moieties
Authors: Mei Lei , Wu Qun‐yan , Yuan Li‐yong , Wang Lin , An Shu‐wen , Xie Zhen‐ni , Hu Kong‐qiu , Chai Zhi‐fang , Burns Peter C. , Shi Wei‐qun 
Published: July 2016

AbstractThe hierarchical assembly of well‐organized submoieties could lead to more complicated superstructures with intriguing properties. We describe herein an unprecedented polyrotaxane polythreading framework containing a two‐fold nested super‐polyrotaxane substructure, which was synthesized through a uranyl‐directed hierarchical polythreading assembly of one‐dimensional polyrotaxane chains and two‐dimensional polyrotaxane networks. This special assembly mode actually affords a new way of supramolecular chemistry instead of covalently linked bulky stoppers to construct stable interlocked rotaxane moieties. An investigation of the synthesis condition shows that sulfate can assume a vital role in mediating the formation of different uranyl species, especially the unique trinuclear uranyl moiety [(UO2)3O(OH)2]2+, involving a notable bent [O=U=O] bond with a bond angle of 172.0(9)°. Detailed analysis of the coordination features, the thermal stability as well as a fluorescence, and electrochemical characterization demonstrate that the uniqueness of this super‐polyrotaxane structure is mainly closely related to the trinuclear uranyl moiety, which is confirmed by quantum chemical calculations.
The Effect of KOH Treatment on the Chemical Structure and Electrocatalytic Activity of Reduced Graphene Oxide Materials
Authors: Kim Sujin , Choi Kwangrok , Shim Yeonjun , Lee Seungjun , Park Sungjin 
Published: July 2016

AbstractReduced graphene oxide (rG‐O)‐based materials have great potential as metal‐free electrocatalysts for the oxygen reduction reaction (ORR) owing to their electrical and electrochemical properties and large surface area. Long‐term durability and chemical stability of the catalysts in the presence of electrolytes such as aqueous KOH solution are important for their use in practical applications. In this study, three types of rG‐O and rG‐O‐K (rG‐O after reaction with KOH) materials were synthesized. The chemical structures, surface areas, and catalytic ORR performances of the rG‐O materials were compared with those of the corresponding rG‐O‐K materials. The onset potentials of the rG‐O materials for electrocatalytic reduction of oxygen are almost the same as those of the corresponding rG‐O‐K materials; however, the current density and the number of transferred electrons are significantly reduced. These data show that the catalytic ORR performance of rG‐O‐based materials can be altered by KOH.
H2 separation using tubular stainless steel supported natural clinoptilolite membranes
Authors: Farjoo Afrooz , Kuznicki Steven M. 
Published: July 2016

AbstractDisk membranes generated from high‐purity natural clinoptilolite mineral rock have shown promising hydrogen separation performance. To scale up production of these types of membranes for industrial gas separation, a coating strategy was devised. A mixture of natural clinoptilolite and aluminum silicate was deposited on the inner surface of porous stainless steel tubes by the slip casting technique. Phase composition and morphology of the coating materials were investigated using X‐ray diffraction. The performance was evaluated for a range of gases using single gas permeation tests at different temperatures and pressures. Introduction of the second layer significantly improved the performance of the membrane system. The experiments on the double‐layered membranes measured a hydrogen permeance of 1.65 × 10−7 mol · m−2 · s−1 · Pa−1 at 300 °C. H2/CO2 and H2/C2H6 single gas selectivity was 10.2 and 8.45 respectively at 25 °C and feed pressure of 110 kPa. These results show that natural zeolite coated stainless steel tubular membranes have high potential for large‐scale gas separation at high temperature requirements.