bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transcranial Doppler versus transthoracic echocardiography for the detection of patent foramen ovale in patients with cryptogenic cerebral ischemia: A systematic review and diagnostic test accuracy meta‐analysis
Authors: Katsanos Aristeidis H. , Psaltopoulou Theodora , Sergentanis Theodoros N. , Frogoudaki Alexandra , Vrettou Agathi‐Rosa , Ikonomidis Ignatios , Paraskevaidis Ioannis , Parissis John , Bogiatzi Chrysa , Zompola Christina , Ellul John , Triantafyllou Nikolaos , Voumvourakis Konstantinos , Kyritsis Athanassios P. , Giannopoulos Sotirios , Alexandrov Anne W. , Alexandrov Andrei V. , Tsivgoulis Georgios 
Published: February 2016

ObjectivePatent foramen ovale (PFO) can be detected in up to 43% of patients with cryptogenic cerebral ischemia undergoing investigation with transesophageal echocardiography (TEE). The diagnostic value of transthoracic echocardiography (TTE) in the detection of PFO in patients with cryptogenic ischemic stroke or transient ischemic attack has not been compared with that of transcranial Doppler (TCD) using a comprehensive meta‐analytical approach.MethodsWe performed a systematic literature review to identify all prospective observational studies of patients with cryptogenic cerebral ischemia that provided both sensitivity and specificity measures of TTE, TCD, or both compared to the gold standard of TEE.ResultsOur literature search identified 35 eligible studies including 3,067 patients. The pooled sensitivity and specificity for TCD was 96.1% (95% confidence interval [CI] = 93.0–97.8%) and 92.4% (95% CI = 85.5–96.1%), whereas the respective measures for TTE were 45.1% (95% CI = 30.8–60.3%) and 99.6% (95% CI = 96.5–99.9%). TTE was superior in terms of higher positive likelihood ratio values (LR+ = 106.61, 95% CI = 15.09–753.30 for TTE vs LR+ = 12.62, 95% CI = 6.52–24.43 for TCD; p = 0.043), whereas TCD demonstrated lower negative likelihood values (LR− = 0.04, 95% CI = 0.02–0.08) compared to TTE (LR− = 0.55, 95% CI = 0.42–0.72; p < 0.001). Finally, the area under the summary receiver operating curve (AUC) was significantly greater (p < 0.001) in TCD (AUC = 0.98, 95% CI = 0.97–0.99) compared to TTE studies (AUC = 0.86, 95% CI = 0.82–0.89).InterpretationTCD is more sensitive but less specific compared to TTE for the detection of PFO in patients with cryptogenic cerebral ischemia. The overall diagnostic yield of TCD appears to outweigh that of TTE. Ann Neurol 2016;79:625–635
Synthetisch gewonnene Naturstofffragmente in der Wirkstoffentwicklung
Authors: Crane Erika A. , Gademann Karl 
Published: February 2016

AbstractDie organische Chemie mit ihrer einzigartigen Fähigkeit zur maßgeschneiderten Herstellung von Naturstoff‐Analoga ist ein ausgezeichnetes Mittel, um das volle Potenzial von Naturstoffen bei der Wirkstoffentwicklung auszuschöpfen. In diesem Aufsatz stellen wir eine Strategie vor, die auf von Naturstoffen abgeleiteten Fragmenten basiert, die sich durch eine substanzielle Verringerung des Molekulargewichts, reduzierte strukturelle Komplexität und kürzere Synthesesequenzen zu ihrer Herstellung auszeichnen, während ihre für die Anwendung entscheidenden Eigenschaften wie biochemische Potenz und Selektivität beibehalten oder sogar verstärkt werden. Dies wird anhand von Beispielen aus verschiedenen Stadien des Arzneistoffentwicklungsprozesses bis hin zur klinischen Anwendung erläutert. Darüber hinaus kann die hier beschriebene Strategie durch neuartige Techniken wie die Entwicklung von Antikörper‐Wirkstoff‐Konjugaten oder Genome Mining unterstützt werden. Das Zusammenspiel dieser Ansätze birgt das Potenzial zur Entwicklung der nächsten Generation naturstoffinspirierter Wirkstoffmoleküle.
Thiophene‐S,S‐dioxidized Indophenine: A Quinoid‐Type Building Block with High Electron Affinity for Constructing n‐Type Polymer Semiconductors with Narrow Band Gaps
Authors: Deng Yunfeng , Sun Bin , He Yinghui , Quinn Jesse , Guo Chang , Li Yuning 
Published: February 2016

AbstractThree thiophene‐S,S‐dioxidized indophenine (IDTO) isomers, 3 a (E,E,E), 3 b (Z,E,E), and 3 c (Z,E,Z), were synthesized by oxidation of an indophenine compound. 3 b and 3 c could be converted into the most‐stable 3 a by heating at 110 °C. An IDTO‐containing conjugated polymer, PIDTOTT, was prepared using 3 a as a comonomer through a Stille coupling reaction, and it possesses a narrow band gap and low energy levels. In organic field effect transistors (OFETs), PIDTOTT exhibited unipolar n‐type semiconductor characteristics with unexpectedly high electron mobility (up to 0.14 cm2 V−1 s−1), despite its rather disordered chain packing.
Monolayer Filaments versus Multilayer Stacking of Bent‐Core Molecules
Authors: Matraszek Joanna , Topnani Neha , Vaupotič Natasa , Takezoe Hideo , Mieczkowski Jozef , Pociecha Damian , Gorecka Ewa 
Published: February 2016

AbstractBent‐core materials exhibiting lamellar crystals (B4 phase), when dissolved in organic solvents, formed gels with helical ribbons made of molecular monolayers and bilayers, whereas strongly deformed stacks of 5–6 layers were found in the bulk samples. The width and pitch of the helical filaments were governed by molecular length; they both increased with terminal‐chain elongation. It was also found that bulk samples were optically active, in contrast to the corresponding gels, which lacked optical activity. The optical activity of samples originated from the internal structure of the crystal layers rather than from the helicity of the filaments. A theoretical model predicts a strong increase in optical activity as the number of layers in the stack increases and its saturation for few layers, thus explaining the smaller optical activity for gels than for bulk samples. A strong increase and redshift in fluorescence was detected in gels as compared to the sol state.
Bifunctional Brønsted Base Catalyzes Direct Asymmetric Aldol Reaction of α‐Keto Amides
Authors: Echave Haizea , López Rosa , Palomo Claudio 
Published: February 2016

AbstractThe first enantioselective direct cross‐aldol reaction of α‐keto amides with aldehydes, mediated by a bifunctional ureidopeptide‐based Brønsted base catalyst, is described. The appropriate combination of a tertiary amine base and an aminal, and urea hydrogen‐bond donor groups in the catalyst structure promoted the exclusive generation of the α‐keto amide enolate which reacted with either non‐enolizable or enolizable aldehydes to produce highly enantioenriched polyoxygenated aldol adducts without side‐products resulting from dehydration, α‐keto amide self‐condensation, aldehyde enolization, and isotetronic acid formation.
An Intrinsically Disordered Peptide Facilitates Non‐Endosomal Cell Entry
Authors: Medina Scott H. , Miller Stephen E. , Keim Allison I. , Gorka Alexander P. , Schnermann Martin J. , Schneider Joel P. 
Published: February 2016

AbstractMany cell‐penetrating peptides (CPPs) fold at cell surfaces, adopting α‐ or β‐structure that enable their intracellular transport. However, the same structural folds that facilitate cellular entry can also elicit potent membrane‐lytic activity, limiting their use in delivery applications. Further, a distinct CPP can enter cells through many mechanisms, often leading to endosomal entrapment. Herein, we describe an intrinsically disordered peptide (CLIP6) that exclusively employs non‐endosomal mechanisms to cross cellular membranes, while being remarkably biocompatible and serum‐stable. We show that a single anionic glutamate residue is responsible for maintaining the disordered bioactive state of the peptide, defines its mechanism of cellular entry, and is central to its biocompatibility. CLIP6 can deliver membrane‐impermeable cargo directly to the cytoplasm of cells, suggesting its broad utility for delivery of drug candidates limited by poor cell permeability and endosomal degradation.
Catalytic Promiscuity of Transaminases: Preparation of Enantioenriched β‐Fluoroamines by Formal Tandem Hydrodefluorination/Deamination
Authors: Cuetos Aníbal , García‐Ramos Marina , Fischereder Eva‐Maria , Díaz‐Rodríguez Alba , Grogan Gideon , Gotor Vicente , Kroutil Wolfgang , Lavandera Iván 
Published: February 2016

AbstractTransaminases are valuable enzymes for industrial biocatalysis and enable the preparation of optically pure amines. For these transformations they require either an amine donor (amination of ketones) or an amine acceptor (deamination of racemic amines). Herein transaminases are shown to react with aromatic β‐fluoroamines, thus leading to simultaneous enantioselective dehalogenation and deamination to form the corresponding acetophenone derivatives in the absence of an amine acceptor. A series of racemic β‐fluoroamines was resolved in a kinetic resolution by tandem hydrodefluorination/deamination, thus giving the corresponding amines with up to greater than 99 % ee. This protocol is the first example of exploiting the catalytic promiscuity of transaminases as a tool for novel transformations.
Intramolecular Singlet Fission in Oligoacene Heterodimers
Authors: Sanders Samuel N. , Kumarasamy Elango , Pun Andrew B. , Steigerwald Michael L. , Sfeir Matthew Y. , Campos Luis M. 
Published: February 2016

AbstractWe investigate singlet fission (SF) in heterodimers comprising a pentacene unit covalently bonded to another acene as we systematically vary the singlet and triplet pair energies. We find that these energies control the SF process, where dimers undergo SF provided that the resulting triplet pair energy is similar or lower in energy than the singlet state. In these systems the singlet energy is determined by the lower‐energy chromophore, and the rate of SF is found to be relatively independent of the driving force. However, triplet pair recombination in these heterodimers follows the energy gap law. The ability to tune the energies of these materials provides a key strategy to study and design new SF materials—an important process for third‐generation photovoltaics.
Guest‐Induced Breathing Effect in a Flexible Molecular Crystal
Authors: Sheng Yujie , Chen Qibin , Yao Junyao , Lu Yunxiang , Liu Honglai , Dai Sheng 
Published: February 2016

AbstractBy introducing a flexible component into a molecular building block, we present an unprecedented alkyl‐decorated flexible crystalline material with a breathing behavior. Its selective adsorption is derived from the breathing effect induced by a guest triggered alkyl transformation. This feature allows the crystal to take up 2.5 mmol g−1 of chloroform with high adsorption selectivity (CHCl3/EA >2000 for example), implying a potential application in sorption separation and chemical sensors.
A Rhizavidin Monomer with Nearly Multimeric Avidin‐Like Binding Stability Against Biotin Conjugates
Authors: Lee Jeong Min , Kim Jung A. , Yen Tzu‐Chi , Lee In Hwan , Ahn Byungjun , Lee Younghoon , Hsieh Chia‐Lung , Kim Ho Min , Jung Yongwon 
Published: February 2016

AbstractDeveloping a monomeric form of an avidin‐like protein with highly stable biotin binding properties has been a major challenge in biotin‐avidin linking technology. Here we report a monomeric avidin‐like protein—enhanced monoavidin—with off‐rates almost comparable to those of multimeric avidin proteins against various biotin conjugates. Enhanced monoavidin (eMA) was developed from naturally dimeric rhizavidin by optimally maintaining protein rigidity during monomerization and additionally shielding the bound biotin by diverse engineering of the surface residues. eMA allowed the monovalent and nonperturbing labeling of head‐group‐biotinylated lipids in bilayer membranes. In addition, we fabricated an unprecedented 24‐meric avidin probe by fusing eMA to a multimeric cage protein. The 24‐meric avidin and eMA were utilized to demonstrate how artificial clustering of cell‐surface proteins greatly enhances the internalization rates of assembled proteins on live cells.
Ein P‐H‐funktionalisiertes Al/P‐basiertes frustriertes Lewis‐Paar: Substrataktivierung und selektiver Wasserstofftransfer
Authors: Keweloh Lukas , Klöcker M Sc. Hans , Würthwein Ernst‐Ulrich , Uhl Werner 
Published: February 2016

AbstractDie Hydoaluminierung eines sekundären Alkinylphosphans ergab ein neuartiges P‐H‐funktionalisiertes FLP. Die reaktive P‐H‐Gruppe beeinflusst nicht die typischen FLP‐Eigenschaften, der Aktivierung der Substrate folgt aber in einer neuartigen Reaktionsweise die Übertragung eines Wasserstoffatoms unter Bildung ungewöhnlicher Phosphaharnstoff‐, Iminophosphan‐ oder Phosphanyltriazen‐Derivate.
Modifizierte Nukleotide für die Diskriminierung zwischen Cytosin und dem epigenetischen Marker 5‐Methylcytosin
Authors: von Watzdorf Janina , Leitner Kim , Marx Andreas 
Published: February 2016

Abstract5‐Methyl‐2′‐desoxycytosin, der häufigste epigenetische DNA‐Marker in eukaryotischen Zellen, spielt eine Schlüsselrolle in der Genregulierung und beeinflusst somit zahlreiche zelluläre Prozesse, wie Entwicklung und Karzinogenese. Daher kann die Detektion von 5mC als wichtiger Biomarker in der Diagnostik fungieren. Wir beschreiben hier, dass modifizierte dGTP‐Analoga, wie auch modifizierte Primer, in der Lage sind, die An‐ oder Abwesenheit einer einzigen Methylierung von C zu detektieren, obwohl diese Modifizierung nicht direkt mit der Watson‐Crick‐Basenpaarung interferiert. Durch das Testen vieler verschiedener Nukleotidgerüste haben wir festgestellt, dass O6‐modifizierte 2′‐Desoxyguanosinanaloga zwischen C und 5mC diskriminieren. Diese modifizierten Nukleotide können in der positionsspezifischen Detektion von 5mC, z. B. bei Echtzeit‐PCR‐Methoden, Anwendung finden.
Synthetic Strategies toward Natural Products Containing Contiguous Stereogenic Quaternary Carbon Atoms
Authors: Büschleb Martin , Dorich Stéphane , Hanessian Stephen , Tao Daniel , Schenthal Kyle B. , Overman Larry E. 
Published: February 2016

AbstractStrategies for the total synthesis of complex natural products that contain two or more contiguous stereogenic quaternary carbon atoms in their intricate structures are reviewed with 12 representative examples. Emphasis has been put on methods to create quaternary carbon stereocenters, including syntheses of the same natural product by different groups, thereby showcasing the diversity of thought and individual creativity. A compendium of selected natural products containing two or more contiguous stereogenic quaternary carbon atoms and key reactions in their total or partial syntheses is provided in the Supporting Information.
Nanomechanics of Poly(catecholamine) Coatings in Aqueous Solutions
Authors: Lim Chanoong , Huang Jun , Kim Sunjin , Lee Haeshin , Zeng Hongbo , Hwang Dong Soo 
Published: February 2016

AbstractMussel‐inspired self‐polymerized catecholamine coatings have been widely utilized as a versatile coating strategy that can be applied to a variety of substrates. For the first time, nanomechanical measurements and an evaluation of the contribution of primary amine groups to poly(catecholamine) coatings have been conducted using a surface‐forces apparatus. The adhesive strength between the poly(catecholamine) layers is 30‐times higher than that of a poly(catechol) coating. The origin of the strong attraction between the poly(catecholamine) layers is probably due to surface salt displacement by the primary amine, π–π stacking (the quadrupole–quadrupole interaction of indolic crosslinks), and cation–π interactions (the monopole–quadrupole interaction between positively charged amine groups and the indolic crosslinks). The contribution of the primary amine group to the catecholamine coating is vital for the design and development of mussel‐inspired catechol‐based coating materials.
Total Syntheses of (+)‐Grandilodine C and (+)‐Lapidilectine B and Determination of their Absolute Stereochemistry
Authors: Nakajima Masaya , Arai Shigeru , Nishida Atsushi 
Published: February 2016

AbstractEnantioselective total syntheses of the Kopsia alkaloids (+)‐grandilodine C and (+)‐lapidilectine B were accomplished. A key intermediate, spirodiketone, was synthesized in 3 steps and converted into the chiral enone by enantioselective deprotonation followed by oxidation with up to 76 % ee. Lactone formation was achieved through stereoselective vinylation followed by allylation and ozonolysis. The total synthesis of (+)‐grandilodine C was achieved by palladium‐catalyzed intramolecular allylic amination and ring‐closing metathesis to give 8‐ and 5‐membered heterocycles, respectively. Selective reduction of a lactam carbonyl gave (+)‐lapidilectine B. The absolute stereochemistry of both natural products was thereby confirmed. These syntheses enable the scalable preparation of the above alkaloids for biological studies.
Enantioselective Cyanosilylation of Ketones with Lithium(I) Dicyanotrimethylsilicate(IV) Catalyzed by a Chiral Lithium(I) Phosphoryl Phenoxide
Authors: Hatano Manabu , Yamakawa Katsuya , Kawai Tomoaki , Horibe Takahiro , Ishihara Kazuaki 
Published: February 2016

AbstractA highly enantioselective cyanosilylation of ketones was developed by using a chiral lithium(I) phosphoryl phenoxide aqua complex as an acid/base cooperative catalyst. The pentacoordinate silicate generated in situ from Me3SiCN/LiCN acts as an extremely reactive cyano reagent. Described is a 30 gram scale reaction and the synthesis of the key precursor to (+)‐13‐hydroxyisocyclocelabenzine.
Cobalt(III)‐Catalyzed Redox‐Neutral Synthesis of Unprotected Indoles Featuring an N−N Bond Cleavage
Authors: Lerchen Andreas , Vásquez‐Céspedes Suhelen , Glorius Frank 
Published: February 2016

AbstractA redox‐neutral cobalt(III)‐catalyzed synthetic approach for the direct synthesis of unprotected indoles showcasing an N−N bond cleavage is reported. The herein newly introduced Boc‐protected hydrazines establish a beneficial addition to the limited portfolio of oxidizing directing groups for cobalt(III) catalysis. Moreover, the developed catalytic methodology tolerates a good variety of functional groups.
Halogen‐Bond‐Templated [2+2] Photodimerization in the Solid State: Directed Synthesis and Rare Self‐Inclusion of a Halogenated Product
Authors: Sinnwell Michael A. , MacGillivray Leonard R. 
Published: February 2016

AbstractA ditopic halogen‐bond acceptor organizes a diiodooctafluorostilbene for a [2+2] photodimerization reaction to take place between two stilbene molecules in the solid state. The resultant cyclobutane product is functionalized with halogen atoms and undergoes self‐assembly to form a channel‐type host–guest compound that exhibits a very rare form of self‐inclusion.
Experimental and Theoretical Evidence for an Agostic Interaction in a Gold(III) Complex
Authors: Rekhroukh Feriel , Estévez Laura , Bijani Christian , Miqueu Karinne , Amgoune Abderrahmane , Bourissou Didier 
Published: February 2016

AbstractThe first agostic interaction in a gold complex is described. The presence of a bonding C−H⋅⋅⋅Au interaction in a cationic “tricoordinate” gold(III) complex was suggested by DFT calculations and was subsequently confirmed by NMR spectroscopy at low temperature. The agostic interaction was analyzed computationally using NBO and QTAIM analyses (NBO=natural bond orbital; QTAIM=quantum theory of atoms in molecules).
Morphology and dynamical mechanical properties of poly ether ketone ketone (PEKK) with meta phenyl links
Authors: Quiroga Cortés Luis , Caussé Nicolas , Dantras Eric , Lonjon Antoine , Lacabanne Colette 
Published: February 2016

ABSTRACTPoly ether ketone ketone (PEKK) with different proportion of meta phenyl links were investigated by combining differential scanning calorimetry and dynamic mechanical analysis. The influence of the Terephthalyl/Isophthalyl isomers (T/I) ratio on the vitreous phase is mild, the shift of the glass transition is limited to a few degrees and the vitreous G′ is only sensitive to the content of the crystalline phase. Contrarily, the increase of meta isomers is responsible for a significant decrease of the melting temperature (Tm) by 60 °C, which considerably facilitates processing. The modification of interchain interactions in the crystalline phase might be implied. A series of thermal protocols evidenced that the difference of crystallization behavior is also dependent upon the T/I isomer ratio. A time and temperature dependence of annealing on the double melting behavior of PEKK was observed. Regarding the mechanical behavior, the observed reinforcing effect due to the crystalline phase was more prominent in the rubbery state than in the glassy state. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2016,133, 43396.
Improving properties of silicone rubber composites using macromolecular silane coupling agent (MMSCA)
Authors: Mei Honggang , Chen Guowen , Zhu Qingzeng , Dong Peng , Zhao Dannan , Ahmed Raza Waqas 
Published: February 2016

ABSTRACTTwo types of vinyl silicone oil (VSO), allyl‐capped hyperbranched polycarbosilane (HBP), and triethoxysilane (TES) were employed to synthesize macromolecular silane coupling agent (MMSCA) by hydrosilylation. VSOs, HBP, and the hydrosilylated products were used as crosslinker, respectively, to improve weak mechanical properties of silicone rubber (SR). Structures of the crosslinkers were studied by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR). Crosslinking density test and scanning electron microscope (SEM) observation showed an increased interaction between silicone rubber and fumed silica by the use of MMSCA. Mechanical properties of the resulted composites using MMSCAs were increased to varying degrees compared with those possessing crosslinkers without ethoxy group. MMSCAs were effective for further property enhancements of composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2016,133, 43415.
Morphological features and crystallization behavior of the conductive composites of poly(trimethylene terephthalate)/graphene nanosheets
Authors: Huang Chien‐Lin , Wang Yu‐Jyun , Fan Yang‐Chun 
Published: February 2016

ABSTRACTPoly(trimethylene terephthalate) (PTT) composites filled with well‐dispersed graphene nanosheets (GNSs) were prepared through a coagulation method. The effects of increased GNS concentration on variations in the structure and properties of the PTT matrix, such as its electrical conductivity, crystallization kinetics, melting behavior, and crystal morphology, were investigated. Several analytical techniques were used, including electrical conductivity measurement, differential scanning calorimetry, Fourier transform infrared spectroscopy, wide‐angle X‐ray diffraction, polarized light microscopy, transmission electron microscopy (TEM), and thermo‐gravimetric analysis (TGA). Electrical conductivity increased from 1.8 × 10−17S/cm for neat PTT to 0.33 ± 0.23 S/cm for PTT/GNS composites with 2.97 vol % GNS content. Percolation scaling laws were applied, and then threshold concentration and exponent were determined. In the case wherein liquid nitrogen was used to quench the melt, a mesomorphic phase was formed despite the extremely short crystallization time after adding high GNS contents. PTT crystallization rate increased with the gradual addition of GNSs. The enhanced crystallization kinetics was attributed to the high nucleation ability of GNSs to induce epitaxially grown lamellae on their surfaces, as revealed by TEM. PTT nuclei were randomly developed on the GNS surface to form the lamellae. However, crystallinity reached its maximum value near the electrical percolation threshold because the PTT chain mobility was confined after the GNS–GNS network formed. The growth of PTT banded spherulites in the bulk was still observed for composites with high GNS content, and TGA results revealed that the GNS‐filled PTT composites had excellent thermal stability. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2016,133, 43419.