bluuebunny/crossref_metadata_2025_split huggingface dataset:
Donor‐Promiskuität einer thermostabilen Transketolase durch gelenkte Evolution – effektive Komplementierung der 1‐Desoxy‐d‐ xylulose‐5‐phosphat‐Synthase‐Aktivität
Authors: Saravanan Thangavelu , Junker Sebastian , Kickstein Michael , Hein Sascha , Link Marie‐Kristin , Ranglack Jan , Witt Samantha , Lorillière Marion , Hecquet Laurence , Fessner Wolf‐Dieter 
Published: April 2017

AbstractEnzyme, die asymmetrische C‐C‐Verknüpfungen katalysieren, sind typischerweise hoch spezifisch für ihre nukleophilen Donorsubstrate. Mittels strukturbasierter gerichteter Evolution konnten neue Enzymvarianten der thermostabilen Transketolase aus Geobacillus stearothermophilus erzeugt werden, die anstelle ihrer natürlichen Substrate, wie polyhydroxylierte Ketosephosphate oder Hydroxypyruvat, auch Pyruvat und dessen höhere aliphatische Homologe als Nukleophile für den Acyltransfer verwenden können. Die Einfachvariante H102T war am besten geeignet, 3‐Methyl‐2‐oxobutyrat als Donor zu verwerten, während die Doppelvariante H102L/H474S die höchste katalytische Effizienz für Pyruvat als Donorsubstrat aufwies. Die letztgenannte Variante war in der Lage, den auxotrophen Defekt eines Deletionsstamms von Escherichia coli zu komplementieren, dem das dxs‐Gen für den ersten Schritt in die Terpenoid‐Biosynthese fehlt. Dies eröffnet die Möglichkeit zur weiteren Enzymoptimierung mithilfe eines Wachstumsselektionstests.
Superconductivity Induced by Oxygen Doping in Y2O2Bi
Authors: Cheng Xiyue , Gordon Elijah E. , Whangbo Myung‐Hwan , Deng Shuiquan 
Published: April 2017

AbstractWhen doped with oxygen, the layered Y2O2Bi phase becomes a superconductor. This finding raises questions about the sites for doped oxygen, the mechanism of superconductivity, and practical guidelines for discovering new superconductors. We probed these questions in terms of first‐principles calculations for undoped and O‐doped Y2O2Bi. The preferred sites for doped O atoms are the centers of Bi4 squares in the Bi square net. Several Bi 6p x/y bands of Y2O2Bi are raised in energy by oxygen doping because the 2p x/y orbitals of the doped oxygen make antibonding possible with the 6p x/y orbitals of surrounding Bi atoms. Consequently, the condition necessary for the “flat/steep” band model for superconductivity is satisfied in O‐doped Y2O2Bi.
HDPE composites strengthened–toughened synergistically by l‐aspartic acid functionalized graphene/carbon nanotubes hybrid nanomaterials
Authors: Bian J. , Wang G. , Lin H. L. , Zhou X. , Wang Z. J. , Xiao W. Q. , Zhao X. W. 
Published: April 2017

ABSTRACTEthylenediamine (EDA) covalently functionalized graphene sheets (GS‐EDA) and acidized carbon nanotubes (MWNTs‐COOH) were first prepared, followed by synthesizing l‐aspartic acid functionalized GS‐EDA/MWNTs‐COOH (LGC) hybrid nanomaterials by using l‐aspartic acid as a bridging agent. Then nanocomposites of high density polyethylene‐g‐maleic anhydride (HDPE‐g‐MAH) synergistic strengthening–toughening using LGC hybrids were prepared via melt compounding method. The surface structure of filler was characterized by using infrared (FTIR) and Raman spectrum. The synergistic strengthening–toughening effects of LGC hybrids on the HDPE‐g‐MAH were investigated by scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), thermal gravimetric analysis (TGA), tensile, and impact tests. FTIR showed that EDA has been grafted on the graphene sheets, and COOH group has been introduced into MWNTs. The l‐aspartic acid connected GS‐EDA and MWNTs‐COOH through chemical bonds. SEM observations showed that LGC hybrids were homogeneously dispersed in HDPE‐g‐MAH nanocomposites. Tensile and impact tests indicated that the mechanical properties of nanocomposites were improved obviously when LGC hybrid nanomaterials were incorporated simultaneously. DMA analysis indicated that the storage modulus of composites was higher than that of pure HDPE‐g‐MAH matrix. TGA results revealed that the maximum decomposition temperature of HDPE‐g‐MAH composites containing 0.75 wt % of LGC showed 11.5 °C higher than that of HDPE‐g‐MAH matrix. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45055.
Mechanical properties of carbon fiber reinforced bisphenol A dicyanate ester composites modified with multiwalled carbon nanotubes
Authors: Mei Hui , Xia Junchao , Zhang Ding , Li Haiqing , Bai Qianglai , Cheng Laifei 
Published: April 2017

ABSTRACTA novel electrophoretic deposition (EPD) method was employed for grafting multiwalled carbon nanotubes (MWCNTs) on carbon fibers, which, after impregnation with bisphenol A dicyanate ester (BADCy), synergistically reinforced BADCy matrix composites (CNT‐C/BADCy). The effect of MWCNT presence on the mechanical properties of the composites was investigated. Composite tensile strength increased by 45.2% for an EPD duration of 2 min, while flexural strength exhibited a decreasing trend with EPD duration. Optical microscopy revealed that the existence of MWCNTs enhanced the fiber‐matrix interface while a large number of CNTs were observed to have pulled‐out from the matrix, a finding which explained the observed tensile strength increase in terms of energy dissipation by the specific toughening mechanism. The flexural strength decrease of the composites with CNTs as compared to specimens without nanotubes was found linked to the increased stress concentration in the BADCy matrix due to tube presence which weakens the adhesion between carbon fabrics. In a word, carbon nanotubes will enhance the micro interface and weaken the macro interface of the composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45100.
Morphometry, Microstructure, and Wear Pattern of Neornithischian Dinosaur Teeth From the Upper Cretaceous Iharkút Locality (Hungary)
Authors: Virág Attila , Ősi Attila 
Published: April 2017

ABSTRACTTeeth of iguanodontian ornithopods and ceratopsians could be remarkably similar, thus the referral of isolated dental material to particular neornithischian clades can be highly problematic. These groups are represented by the rhabdodontid Mochlodon vorosi and the basal coronosaurian Ajkaceratops kozmai in the Upper Cretaceous Csehbánya Formation at Iharkút (western Hungary). Whereas teeth of Mochlodon are common elements at the locality, no dental material belonging to Ajkaceratops was identified until now. Here we used mathematical statistical approaches, as well as tooth wear and dental microstructure analysis in order to decide whether the teeth previously referred to Mochlodon can be treated as a homogenous sample, or some remains belong rather to Ajkaceratops. According to our results, there was a striking morphological and structural convergence between the teeth of both taxa. However, the wear study revealed the existence of two different patterns within the sample. One is characterized by straight and parallel microstriations that suggest orthal movements during the jaw closure. This pattern was associated with Mochlodon. The other pattern appeared only on a few teeth, and it can be differentiated by its distinctive curved microstriations that indicate circumpalinal chewing. Because curved striations have never been described in ornithopods, but are found in several neoceratopsians, this pattern was associated here with Ajkaceratops. Here we present the first teeth that can provisionally be referred to the latter genus. We believe that the methodology discussed in this article will facilitate distinguishing ceratopsian and ornithopod teeth in other localities as well. Anat Rec, 300:1439–1463, 2017. © 2017 Wiley Periodicals, Inc.
Antibodies to Cyclic Citrullinated Peptides in Patients With Juvenile Idiopathic Arthritis and Patients With Rheumatoid Arthritis: Shared Expression of the Inherently Autoreactive 9G4 Idiotype
Authors: Peckham Hannah , Cambridge Geraldine , Bourke Lauren , Sen Debajit , Radziszewska Anna , Leandro Maria , Ioannou Yiannis 
Published: April 2017

ObjectiveAntibodies to cyclic citrullinated peptides (anti‐CCP) in rheumatoid arthritis (RA) can express the inherently autoreactive gene VH4–34, detected using the rat monoclonal antibody 9G4. Patients with the polyarticular subtype of juvenile idiopathic arthritis (JIA) share some but not all of the features of adult patients with RA. This study was undertaken to compare serologic findings for rheumatoid factor (RF), anti‐CCP, and 9G4‐expressing anti‐CCP in a large JIA cohort with a cohort of adult RA patients.MethodsSerum from 88 patients with polyarticular JIA, 29 patients with enthesitis‐related arthritis, 38 patients with extended oligoarthritis, 31 adolescent controls, 35 patients with RA, and 30 adult controls were tested for RF, for IgG, IgA, and IgM anti‐CCP, and for 9G4‐expressing anti‐CCP by enzyme‐linked immunosorbent assay. Total serum 9G4‐positive IgM was also measured.ResultsOf 65 patients with RF‐negative polyarticular JIA, 4 (6.2%) were IgG anti‐CCP positive. Sera from 20 of 23 patients with RF‐positive polyarticular JIA (87.0%), 24 of 35 patients with RA (68.6%), and 1 patient with extended oligoarthritis contained IgG anti‐CCP. IgA and IgM anti‐CCP levels were lower in the adolescent group (P < 0.01). Levels of 9G4‐expressing anti‐CCP were higher in patients with RF‐positive polyarticular JIA than in those with RF‐negative polyarticular JIA (P < 0.0001). Median levels of 9G4‐expressing anti‐CCP in patients with RF‐positive polyarticular JIA and those with RA did not differ. Expression of 9G4 on serum total IgM was greater in patients with RF‐positive polyarticular JIA than other adolescent groups (P < 0.01), but similar to adult RF‐positive RA.ConclusionIn healthy individuals, 9G4‐positive B cells comprise 5–10% of the peripheral blood pool but serum immunoglobulins utilizing VH4–34 are disproportionately low. The idiotope recognized by 9G4 was detected on anti‐CCP antibodies in >80% of patients with RF‐positive polyarticular JIA. VH4–34 usage by anti‐CCP in both JIA and RA patients suggest elicitation of these autoantibodies through shared pathogenic B cell selection processes.
Model moist bias in the middle and upper troposphere during DEEPWAVE
Authors: Yang Yang , Moore Stuart , Uddstrom Michael , Turner Richard , Carey‐Smith Trevor 
Published: April 2017

AbstractData from 279 dropsonde profiles collected during the Deep Propagating Gravity Wave Experiment (DEEPWAVE) over New Zealand between 4 June and 20 July 2014 were used to verify the relative humidity (RH) fields simulated by regional configurations of the UK Met Office Unified Model (MetUM) in the troposphere. Significant RH biases (predictions up to 28% too high) were found in the middle and upper troposphere during this period. This RH bias was found to be mainly caused by the errors in the simulated‐specific humidity. It is demonstrated here that evaporation from the lower boundary (mainly sea surface) is not a factor leading to the moist bias. A similar magnitude of moist bias was also found in the Global UM (the global configuration of the MetUM) and from a preliminary inspection is also very likely to occur in ERA‐interim and NCEP‐GFS reanalyses. This study suggests that the moist bias is very likely not a regional or a model specific issue.
Long‐term variations in sunspot magnetic field–area relation
Authors: Nagovitsyn Y. A. , Pevtsov A. A. , Osipova A. A. 
Published: April 2017

BackgroundSeveral recent studies indicated possible long‐term variations of physical properties of sunspots.Materials and MethodsUsing observations of sunspot magnetic field strengths (H) from the Crimean Astrophysical Observatory and area (S) of sunspots from the Kislovodsk Mountain Astronomical Station of Pulkovo Observatory, we investigate the changes in the relation between H and S over the period of about two solar cycles (1994– 2013). The data were fitted by H = A + B log S, where A = (778 ± 46) and B = (778 ± 25).ResultsWe show that the correlation between H and S varies with the phase of solar cycle, and A coefficient decreases significantly after year 2001, while B coefficient does not change significantly. Furthermore, our data confirm the presence of two distinct populations in the distribution of sunspots (small sunspots with weaker field strength and large sunspots with stronger field). We show that the relative contribution of each component to the distribution of sunspots by their area changes with the phase of solar cycle and on longer‐than‐cycle periods.ConclusionWe interpret these changes as a signature of a long‐term (centennial) variations in the properties of sunspots.
Autarkie – Tendenzen der solarthermischen Selbstversorgung
Authors: Goeke Johannes , Krükel Felix 
Published: April 2017

AbstractUnter Autarkie in Gebäuden versteht man im Allgemeinen die Selbstversorgung mit elektrischer Energie und Wärme. Der Beitrag konzentriert sich allein auf die Wärmeversorgung und stellt eine Untersuchung vor, der frei verfügbare Daten über teilweise selbstversorgende Gebäude zugrunde liegen. Im Wesentlichen wird hier die Teilautarkie bzw. der Autarkiegrad der Selbstversorgung von Gebäuden mit Wärme betrachtet, da komplett selbstversorgende Gebäude bisher kaum realisiert wurden. Der Autarkiegrad bezieht sich dabei sowohl auf die Erzeugung von Wärmeenergie als auch auf deren Verbrauch in den Bilanzgrenzen des Gebäudes. Die Auswertung betrachtet die entscheidenden Größen wie den Wärmebedarf, die solare Wärmeproduktion in Form der Kollektorfläche der Solarpanels und den maximalen Energieinhalt von Warmwasserspeichern. Damit ein Vergleich unabhängig von der Gebäudegröße gemacht werden kann, werden aus diesen Daten Relationen (Autarky Performance Indicators) gebildet und zum Autarkiegrad in Beziehung gesetzt. Dabei werden Tendenzen bezüglich der Kollektorflächen und den Speicherinhalten im Verlauf der Trendlinien des Autarkiegrades sichtbar.
Robust MOFs of “tsg” Topology Based on Trigonal Prismatic Organic and Metal Cluster SBUs: Single Crystal to Single Crystal Postsynthetic Metal Exchange and Selective CO2 Capture
Authors: Chandrasekhar Pujari , Savitha Govardhan , Moorthy Jarugu Narasimha 
Published: April 2017

AbstractThe self‐assembly of a rigid and trigonal prismatic triptycene‐hexaacid H6THA with Co(NO3)2 or Mn(NO3)2 leads to isostructural metal‐organic frameworks (MOFs) that are sustained by 6‐connecting metal cluster [M3(μ3‐O)(COO)6] secondary building units (SBUs). The Co‐ and Mn‐MOFs, constructed from organic and metal‐cluster building blocks that are both trigonal prismatic, correspond to the heretofore unknown “tsg” topology. Due to the rigidity and concave attributes of H6THA, the networks in the Co‐ and Mn‐MOFs are highly porous and undergo 3‐fold interpenetration. The interpenetration imparts permanent microporosity and high thermal stability to the MOFs to permit postsynthetic metal exchange (PSME) and gas sorption. The PSME occurs in a single crystal to single crystal fashion when the crystals of Co‐ or Mn‐MOFs are immersed in a solution of Cu(NO3)2 in MeOH/H2O. Further, the isostructural robust MOFs exhibit significant gas sorption and remarkable selectivity for CO2 over N2 (ca. 100 fold) at ambient conditions. In fact, the postsynthetically‐engineered Cu‐THA exhibits better CO2 sorption than Co‐THA and Mn‐THA. A composite of effects that include pore dimensions (ca. 0.7 nm), unsaturated metal centers, and basic environments conferred by the quinoxaline nitrogen atoms appears to be responsible for the observed high CO2 capture and selectivity. The high symmetry and structural attributes of the organic linker seemingly dictate adoption of the trigonal‐prismatic metal cluster SBU by the metal ions in the MOFs.
Reversible Folding of a β‐Hairpin Peptide by a Metal‐Chelating Amino Acid
Authors: Reutzel Jan , Diogo Timm M. , Geyer Armin 
Published: April 2017

Abstract5‐(1‐Hydroxy‐pyridin‐2(1H)‐onyl)‐l‐alanine (Hop) is a N‐hydroxy‐1,2‐pyridone functionalized α‐amino acid with the desired metal‐chelating properties of DOPA (3,4‐dihydroxy phenylalanine) but without its unwanted redox activity. The Fmoc‐protected amino acid Fmoc‐l‐Hop(tBu)‐OH (11) was synthesized from glycine phosphonate followed by enzymatic hydrolysis of the methyl ester yielding the Hop l‐isomer in 96 % ee. The amino acid 11 is used in automated peptide synthesis for the assembly of a 14mer β‐hairpin peptide with the sequence [dsb1, 14]H‐CHXETGKHGHKLVC‐OH (X=W, l‐Hop). While the 10 π electron containing indole side chain of l‐Trp in peptide 14 completes the formation of a hydrophobic cluster and results in 90 % folding, the folded fraction is significantly decreased to approximately 30 % for the 6 π electron l‐Hop side chain in peptide 16. Metal chelation of Ga3+ reconstitutes the folding of 16 to above 60 % due to the formation of the Ga(16)3 trimer. The chelation process of 16 is monitored by NMR spectroscopy and the subsequent release of Ga3+ by a competitive metal chelator exemplifies the reversible oligomerization of peptide epitopes by metal chelation, bearing the opportunity to synthesize protein‐sized aggregates on the basis of reversible chemistry in water.
Advances in Phosphasilene Chemistry
Authors: Nesterov Vitaly , Breit Nora C. , Inoue Shigeyoshi 
Published: April 2017

AbstractHeavier alkene analogues possess unique electronic properties and reactivity, encouraging multidisciplinary research groups to utilize them in the rational design of novel classes of compounds and materials. Phosphasilenes are heavier imine analogues, containing highly reactive Si=P double bonds. Recent achievements in this field are closely related to the progress in the chemistry of stable low‐coordinate silicon compounds. In this Review, we have attempted to summarize in a comprehensive way the available data on the structures, syntheses, electronic and chemical properties of these compounds, with an emphasis on recent achievements.
Self‐Exfoliated Metal‐Organic Nanosheets through Hydrolytic Unfolding of Metal‐Organic Polyhedra
Authors: Garai Bikash , Mallick Arijit , Das Anuja , Mukherjee Rabibrata , Banerjee Rahul 
Published: April 2017

AbstractFew‐layers thick metal‐organic nanosheets have been synthesized using water‐assisted solid‐state transformation through a combined top‐down and bottom‐up approach. The metal‐organic polyhedra (MOPs) convert into metal‐organic frameworks (MOFs) which subsequently self‐exfoliate into few‐layered metal‐organic nanosheets. These MOP crystals experience a hydrophobicity gradient with the inner surface during contact with water because of the existence of hydrophobic spikes on their outer surface. When the amount of water available for interaction is higher, the resultant layers are not stacked to form bulk materials; instead few‐layered nanosheets with high uniformity were obtained in high yield. The phenomenon has resulted high yield production of uniformly distributed layered metal‐organic nanosheets from three different MOPs, showing its general adaptability.
Modular Synthesis of Diverse Natural Product‐Like Macrocycles: Discovery of Hits with Antimycobacterial Activity
Authors: Dow Mark , Marchetti Francesco , Abrahams Katherine A. , Vaz Luis , Besra Gurdyal S. , Warriner Stuart , Nelson Adam 
Published: April 2017

AbstractA modular synthetic approach was developed in which variation of the triplets of building blocks used enabled systematic variation of the macrocyclic scaffolds prepared. The approach was demonstrated in the synthesis of 17 diverse natural product‐like macrocyclic scaffolds of varied (12–20‐membered) ring size. The biological relevance of the chemical space explored was demonstrated through the discovery of a series of macrocycles with significant antimycobacterial activity.
Effects of N‐Oxidation on Heteroaromatic Macrocycles: Synthesis, Electronic Structures, Spectral Properties, and Reactivities of Tetraazaporphyrin meso‐N‐Oxides
Authors: Toriumi Naoyuki , Yanagi Shunsuke , Muranaka Atsuya , Hashizume Daisuke , Uchiyama Masanobu 
Published: April 2017

AbstractHeteroaromatic N‐oxides such as pyridine and quinoline N‐oxides are well studied in organic chemistry, and N‐oxide formation has long been utilized for tuning the reactivities of heteroaromatics. However, the scope of aromatic N‐oxidation is still restricted to relatively small azine or azole skeletons, and there has been little investigation of the photophysical/chemical effects of N‐oxidation on larger heteroaromatic systems. Here, the synthesis and unique properties of new macrocyclic heteroaromatic N‐oxides, tetraazaporphyrin (TAP) meso‐N‐oxides, are reported. N‐Oxidation of TAP reduced the 18π‐aromaticity of the TAP ring compared with that of the parent TAP owing to the cross‐conjugated resonance structure. The optical properties of TAPs were significantly changed by N‐oxidation: the N‐oxides did not exhibit azaporphyrin‐like but instead porphyrin‐like optical properties, that is, weak Q absorption bands, strong Soret absorption bands, and weak fluorescence. These features can be explained by the near‐degenerate frontier molecular orbitals resulting from N‐oxide formation. Singlet oxygen quantum yields were greatly increased to almost quantitative levels by N‐oxidation. The N‐oxides showed near‐IR‐responsive photoredox properties and were suitable as both oxidants and sensitizers for oxidation reactions. Protonation of the N‐oxides restored TAP‐like intense Q bands and red fluorescence, offering a potential design strategy for fluorescence switches.
Facile Synthesis of Cellulose Acetate Ultrafiltration Membrane with Stimuli‐Responsiveness to pH and Temperature Using the Additive of F127‐b‐PDMAEMA
Authors: Li Naixu , Yin Jun , Wei Lingfei , Shen Quanhao , Tian Wei , Li Jing , Chen Yong , Jin Jing , Teng Hongcheng , Zhou Jiancheng 
Published: April 2017

AbstractWe fabricate a novel cellulose acetate (CA) ultrafiltration membrane modified by block copolymer F127‐b‐ PDMAEMA, which is synthesized using F127 and DMAEMA via the ARGET ATRP method. Compared to conventional ultrafiltration membranes, the incorporation of both F127 and PDMAEMA can not only readily increase the hydrophilicity of the membrane, but also exhibit stimuli‐responsiveness to temperature and pH. Fourier transform infrared spectroscopy (FT‐IR), nuclear magnetic resonance spectroscopy (NMR), and gel permeation chromatography (GPC) are employed to analyze the structure of the F127‐b‐PDMAEMA. The membrane properties are evaluated via scanning electron microscope (SEM) imaging, porosity test, automatic target recognition Fourier transform infrared spectroscopy (ATR‐FTIR), water contact angle test and permeation test. The results indicate that the F127‐b‐PDMAEMA is an excellent pore agent, which contributes to an enhancement of the membrane in sensitivity to temperature and pH. The modified membrane also exhibits lower water contact angle (64.5°), which is attributed to the good anti‐fouling performance and high water permeation.
Direct Visualization of Model Membrane Remodeling by α‐Synuclein Fibrillization
Authors: Chaudhary Himanshu , Subramaniam Vinod , Claessens Mireille M. A. E. 
Published: April 2017

AbstractThe interaction of α‐synuclein (αS) with membranes is thought to be critical in the etiology of Parkinson's disease. Besides oligomeric αS aggregates that possibly form membrane pores, the aggregation of αS into amyloid fibrils has been reported to disrupt membranes. The mechanism by which aggregation affects the integrity of membranes is, however, unknown. Here, we show that whereas mature αS fibrils only weakly adhere to POPC/POPG giant unilamellar vesicles (GUVs), fibrillization of αS on the membrane results in large‐scale membrane remodeling. Fibrils that grow on the vesicle surface stiffen the membrane and make the initially spherical membrane become polyhedral. Additionally, membrane‐attached fibrils extract lipids. The lipid extraction and membrane remodeling of growing fibrils can consume the complete bilayer surface and results in loss of vesicle content. These observations suggest that there are several mechanisms by which growing fibrils can disrupt membrane function.