bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spontaneous Sequestration of Proteins into Liquid Crystalline Microdroplets
Authors: Naveenkumar Parinamipura M. , Mann Stephen , Sharma Kamendra P. 
Published: December 2018

AbstractIn this work a facile method for fabricating protein‐sequestered liquid crystal (LC) emulsion droplets based on the uptake of surface‐engineered protein–polymer surfactant (PS) core–shell bioconjugates is described. Uptake of myoglobin‐PS, bovine serum albumin‐PS, Zn‐porphyrin myoglobin‐PS, horseradish peroxidase‐PS, and glucose oxidase‐PS occurs without structural or functional degradation, and gives rise to sequestration within the interior or at the surface of 4‐cyano‐4′‐pentylbiphenyl (5CB) nematic droplets depending on the surface modification of the protein‐PS bioconjugates. Differences in uptake behavior are used to achieve the spontaneous positional assembly of multiple proteins in the LC phase, and the use of spatially separated glucose oxidase‐PS and horseradish peroxidase‐PS bioconjugates is demonstrated to produce 5CB based droplets capable of housing an enzyme cascade reaction. This method opens a pathway for the development of bioactive liquid crystal droplets and can have potential applications in the optical sensing of biomolecular substrates.
Tunable Emissions of Upconversion Fluorescence for Security Applications
Authors: Yao Weijing , Tian Qingyong , Wu Wei 
Published: December 2018

AbstractThe rampant appearance of counterfeiting has a serious adverse effect on every aspect in the global markets. Thus, the development of high‐tech security strategies has become an urgent challenge. Recently, lanthanide ions (Ln3+) doped materials open new avenues for concealing factual data and shield against counterfeiting because of their unique optical characteristics of color‐tunable emissions under near‐infrared excitation. The present review surveys the recent advances in Ln3+‐doped upconversion crystals (UCCs) as fluorescent functional inks toward designable and high‐level anti‐counterfeiting patterns and graphical encoding. The great achievements of fabrication of versatile security patterns can be ascribed to the combination of the single or multiple colorful UCCs with polymers, additives, and solvents. Moreover, the crucial factors including underlying mechanisms, synthetic methods of upconversion fluorescence materials, and the diverse printing technologies employed for patterning the fluorescence images have been highlighted, and the corresponding challenges and opportunities in this promising research area are presented. This review will help providing a fundamental understanding and guidance to rational design fluorescence optical labels based on Ln3+‐doped UCCs for broadening their applications in high‐level security fields.
Molecular Design of β‐Sheet Peptide for the Multi‐Modal Analysis of Disease
Authors: Cao Hongyan , Wang Yunyun , Gao Yuan , Deng Xinli , Cong Yulong , Liu Ye , Jiang Xingyu 
Published: December 2018

AbstractIntermolecular forces constrain peptide conformation. However, the role of each intermolecular force in constraining peptide conformation remains poorly understood. In this work, we show that aromatic–aromatic interactions drive peptides into β‐sheets, and the hydrophobic effect determines the assembly speed of peptides. By using intermolecular forces to artificially control the assembly of β‐sheets, a multi‐modal analytical system was developed that allows five readouts and dual qualitative–quantitative analysis, and satisfies both point‐of‐care testing (POCT) and laboratory‐based testing. For Mycoplasma Pneumoniae diagnosis, this system eradicates misdiagnosis (from 30 % to 0 %) and broadens the linear range by three‐fold, both of which are critical for guiding therapy. This work not only illustrates exact roles of intermolecular forces in driving the formation of β‐sheets, but also provides a guideline for the construction of a multi‐modal analytical system for disease diagnosis.
Metal‐Helix Frameworks from Short Hybrid Peptide Foldamers
Authors: Misra Rajkumar , Saseendran Abhijith , Dey Sanjit , Gopi Hosahudya N. 
Published: December 2018

AbstractThe potential of structured peptides has not been explored much in the design of metal‐organic frameworks (MOFs). This is partly due to the difficulties in obtaining stable secondary structures from the short α‐peptide sequences. Here we report the design, crystal conformations, coordination site dependent different silver coordinated frameworks of short α,γ‐hybrid peptide 12‐helices consisting of terminal pyridyl moieties and the utility of metal‐helix frameworks in the adsorption of CO2. Upon silver ion coordination the 12‐helix terminated by the 3‐pyridyl derivatives adopted a 2:2 macrocyclic structure, while the 12‐helix terminated by the 4‐pyridyl derivatives displayed remarkable porous metal‐helix frameworks. Both head‐to‐tail intermolecular H‐bonds of the 12‐helix and metal ion coordination have played an important role in stabilizing the ordered metal‐helix frameworks. The studies described here open the door to design a new class of metal‐organic‐frameworks from peptide foldamers.
Facile Conversion of syn‐[FeIV(O)(TMC)]2+ into the anti Isomer via Meunier's Oxo–Hydroxo Tautomerism Mechanism
Authors: Prakash Jai , Sheng Yuan , Draksharapu Apparao , Klein Johannes E. M. N. , Cramer Christopher J. , Que Lawrence 
Published: December 2018

AbstractThe syn and anti isomers of [FeIV(O)(TMC)]2+ (TMC=tetramethylcyclam) represent the first isolated pair of synthetic non‐heme oxoiron(IV) complexes with identical ligand topology, differing only in the position of the oxo unit bound to the iron center. Both isomers have previously been characterized. Reported here is that the syn isomer [FeIV(Osyn)(TMC)(NCMe)]2+ (2) converts into its anti form [FeIV(Oanti)(TMC)(NCMe)]2+ (1) in MeCN, an isomerization facilitated by water and monitored most readily by 1H NMR and Raman spectroscopy. Indeed, when H218O is introduced to 2, the nascent 1 becomes 18O‐labeled. These results provide compelling evidence for a mechanism involving direct binding of a water molecule trans to the oxo atom in 2 with subsequent oxo–hydroxo tautomerism for its incorporation as the oxo atom of 1. The nonplanar nature of the TMC supporting ligand makes this isomerization an irreversible transformation, unlike for their planar heme counterparts.
Catalytic Asymmetric Epoxidation of Aldehydes with Two VANOL‐Derived Chiral Borate Catalysts
Authors: Gupta Anil K. , Yin Xiaopeng , Mukherjee Munmun , Desai Aman A. , Mohammadlou Aliakbar , Jurewicz Kelsee , Wulff William D. 
Published: December 2018

AbstractA highly diastereo‐ and enantioselective method for the epoxidation of aldehydes with α‐diazoacetamides has been developed with two different borate ester catalysts of VANOL. Both catalytic systems are general for aromatic, aliphatic, and acetylenic aldehydes, giving high yields and inductions for nearly all cases. One borate ester catalyst has two molecules of VANOL and the other only one VANOL. Catalysts generated from BINOL and VAPOL are ineffective catalysts. An application is shown for access to the side‐chain of taxol.
Alkyne Versus Ynamide Reactivity: Regioselective Radical Cyclization of Yne‐Ynamides
Authors: Dutta Shubham , Mallick Rajendra K. , Prasad Rangu , Gandon Vincent , Sahoo Akhila K. 
Published: December 2018

AbstractYnamides are typically more reactive than simple alkynes and olefins. However, a serendipitous observation revealed a rare case where the reactivity of simple alkynes exceeds that of ynamides. This led to the development of a unique sulfur‐radical‐triggered cyclization of yne‐tethered ynamides, which involves attack of the alkyne by a thiyl radical followed by cyclization with the ynamide. A wide range of novel 4‐thioaryl pyrroles that could tolerate common functional moieties and N‐protecting groups were expediently constructed by this strategy. The current method contrasts with the typical cyclization of yne‐ynamides, which involves the attack of the alkyne moiety by the ynamide core. Control experiments and DFT calculations supported the participation of the sulfur radical in the reaction and the regioselective cyclization. The synthetic potential of the substituted pyrroles is also discussed.
Conductive Fused Porphyrin Tapes on Sensitive Substrates by a Chemical Vapor Deposition Approach
Authors: Bengasi Giuseppe , Baba Kamal , Frache Gilles , Desport Jessica , Gratia Paul , Heinze Katja , Boscher Nicolas D. 
Published: December 2018

AbstractOxidative polymerization of nickel(II) 5,15‐diphenyl porphyrin and nickel(II) 5,15‐bis(di‐3,5‐tert‐butylphenyl) porphyrin by oxidative chemical vapor deposition (oCVD) yields multiply fused porphyrin oligomers in thin film form. The oCVD technique enables one‐step formation, deposition, and p‐doping of conjugated poly(porphyrins) coatings without solvents or post‐treatments. The decisive reactions and side reactions during the oCVD process are shown by high‐resolution mass spectrometry. Owing to the highly conjugated structure of the fused tapes, the thin films exhibit an electrical conductivity of 3.6×10−2 S cm−1 and strong absorption in the visible to near‐infrared spectral region. The formation of smooth conjugated poly(porphyrins) coatings, even on sensitive substrates, is demonstrated by deposition and patterning on glass, silicon, and paper. Formation of conductive poly(porphyrins) thin films could enable the design of new optoelectronic devices using the oCVD approach.
Distributed delay‐dependent filtering for Markovian jump systems interconnected over an undirected graph with time‐delay
Authors: Xue Xiaojuan , Xu Li , Xu Huiling 
Published: December 2018

AbstractIn this paper, the problems of delay‐dependent stochastic stability analysis and distributed filter synthesis are considered for Markovian jump systems interconnected over an undirected graph with state time‐invariant delay. A sufficient condition for the well‐posedness, delay‐dependent stochastic stability and contractiveness of the plant is developed in terms of linear matrix inequalities (LMIs). The distributed filter synthesis aims to design a distributed filter inheriting the structure of the plant such that the filtering error systems is well‐posed, delay‐dependent stochastically stable and contractive. Specifically, a corresponding sufficient condition to guarantee the filtering error system contractive is first presented by a set of nonlinear matrix inequalities. Next, for coupling these nonlinear matrix inequalities, a sufficient condition on the existence of such a distributed filter is proposed via a series of finite‐dimensional LMIs. Finally, a numerical simulation is presented to demonstrate the effectiveness of the proposed approach.
Structure‐guided design combined with evolutionary diversity led to the discovery of the xylose‐releasing exo‐xylanase activity in the glycoside hydrolase family 43
Authors: Zanphorlin Letícia Maria , de Morais Mariana Abrahão Bueno , Diogo José Alberto , Domingues Mariane Noronha , de Souza Flávio Henrique Moreira , Ruller Roberto , Murakami Mario Tyago 
Published: December 2018

AbstractRational design is an important tool for sculpting functional and stability properties of proteins and its potential can be much magnified when combined with in vitro and natural evolutionary diversity. Herein, we report the structure‐guided design of a xylose‐releasing exo‐β‐1,4‐xylanase from an inactive member of glycoside hydrolase family 43 (GH43). Structural analysis revealed a nonconserved substitution (Lys247) that results in the disruption of the hydrogen bond network that supports catalysis. The mutation of this residue to a conserved serine restored the catalytic activity and crystal structure elucidation of the mutant confirmed the recovery of the proper orientation of the catalytically relevant histidine. Interestingly, the tailored enzyme can cleave both xylooligosaccharides and xylan, releasing xylose as the main product, being the first xylose‐releasing exo‐β‐1,4‐xylanase reported in the GH43 family. This enzyme presents a unique active‐site topology when compared with closely related β‐xylosidases, which is the absence of a hydrophobic barrier at the positive‐subsite region, allowing the accommodation of long substrates. Therefore, the combination of rational design for catalytic activation along with naturally occurring differences in the substrate binding interface led to the discovery of a novel activity within the GH43 family. In addition, these results demonstrate the importance of solvation of the β‐propeller hollow for GH43 catalytic function and expand our mechanistic understanding about the diverse modes of action of GH43 members, a key and polyspecific carbohydrate‐active enzyme family abundant in most plant cell‐wall‐degrading microorganisms.
Anti‐Inflammatory Effect of Novel 7‐Substituted Coumarin Derivatives through Inhibition of NF‐κB Signaling Pathway
Authors: Mu Chaoyu , Wu Mingfei , Li Zeng 
Published: December 2018

AbstractA series of novel 7‐substituted coumarin derivatives were synthesized and evaluated. Biological screening results obtained by the evaluation of the compounds’ inhibition against LPS‐induced IL‐6 and TNF‐α release in RAW 264.7 cells indicated that most compounds exhibited potent anti‐inflammatory activity. Among them, N‐(3‐methoxybenzyl)‐2‐[(2‐oxo‐2H‐chromen‐7‐yl)oxy]acetamide (2d) showed the best activity. The potential targets of title compound 2d were reversely screened with the molecular modeling software, Discovery Studio 2017 R2. Screening and molecule docking results showed that 2d could bind to the active site (NLS Polypeptide) of NF‐κB p65, and this binding affinity was confirmed by surface plasmon resonance (SPR) analysis. Furthermore, Western blot assay showed that 2d remarkably blocked the NF‐κB signaling pathway in vitro. Collectively, all these findings suggested that compound 2d might be a promising lead compound worthy of further pursuit.
Involvement of β‐Alkylation Machinery and Two Sets of Ketosynthase‐Chain‐Length Factors in the Biosynthesis of Fogacin Polyketides in Actinoplanes missouriensis
Authors: Sato Kei , Katsuyama Yohei , Yokota Kousuke , Awakawa Takayoshi , Tezuka Takeaki , Ohnishi Yasuo 
Published: December 2018

AbstractFogacin and two novel fogacin derivatives, fogacins B and C, were isolated from the rare actinomycete Actinoplanes missouriensis. Biosynthesis of fogacin C apparently requires β alkylation of a polyketide chain. The fogacin biosynthetic type II polyketide synthase (PKS) gene cluster contains a hydroxymethylglutaryl‐coenzyme A synthase (HCS) cassette, which is usually responsible for β alkylation in the type I PKS system. Another characteristic of the fog cluster is that it encodes two sets of ketosynthase (KS) and chain‐length factor (CLF). Inactivation of either of the two KS genes in A. missouriensis and heterologous expression of the HCS cassette with either of the two KS‐CLF genes in Streptomyces albus indicated that each KS‐CLF had a different starter substrate specificity: one preferred an unusual β‐alkylated starter and the other preferred a normal acetyl starter. This study expands knowledge of HCS cassette‐dependent β alkylation into the type II PKS system and provides a natural example of combinatorial biosynthesis for producing diverse polyketides from different starter substrates.
Armeniaspirol Antibiotic Biosynthesis: Chlorination and Oxidative Dechlorination Steps Affording Spiro[4.4]non‐8‐ene
Authors: Fu Chengzhang , Xie Feng , Hoffmann Judith , Wang Qiushui , Bauer Armin , Brönstrup Mark , Mahmud Taifo , Müller Rolf 
Published: December 2018

AbstractArmeniaspirols are potent antibiotics containing an unusual spiro[4.4]non‐8‐ene moiety. Herein, we describe the cloning and functional analysis of the armeniaspirol biosynthetic gene cluster. Gene‐inactivation studies and subsequent isolation of previously unknown biosynthetic intermediates shed light on intriguing biosynthetic details. Remarkably, deletion of ams15, which encodes a protein bearing a flavin‐binding domain, led to the accumulation of several non‐spiro intermediates with various numbers of chlorine substitutions on the pyrrole moiety. The di‐ and trichloropyrrole species were converted by Streptomyces albus expressing Ams15 into mono‐ and dichlorinated spiro derivatives, respectively. In addition, in vitro conversion of these non‐spiro intermediates into des‐N‐methyl spiro intermediates by the cell lysate of the same recombinant strain proved Ams15 to be responsible for spiro formation through oxidative dehalogenation.
Hollow Structured Carbon@FeSe Nanocomposite as a Promising Anode Material for Li‐Ion Batteries
Authors: Chen Yu , Shao Jie , Lin Xiaoyu , Gu Yuanyuan , Holze Rudolf , Yun Yuanxing , Qu Qunting , Zheng Honghe 
Published: December 2018

AbstractCarbon@FeSe nanocomposites with homogeneous hollow microspherical and nanotubular structures are prepared using sulfonated polystyrene microspheres and sulfonated poly(divinylbenzene) nanotubes as both the template and carbon source. Benefiting from their hollow core‐shell and hierarchical micro/nanostructures, the carbon@FeSe nanocomposites as the anode material of Li‐ion batteries exhibit high capacities with a steady discharge plateau of 1.5 V (vs. Li/Li+), stable cycling performance (700 mAh g−1 in the 200th cycle at 800 mA g−1), and good rate behavior (620 mAh g−1 at 16 A g−1). The steady discharge plateau of carbon@FeSe, together with its high capacity, renders it a promising anode material for Li‐ion batteries.
4“‐O‐Alkylated α‐Galactosylceramide Analogues as iNKT‐Cell Antigens: Synthetic, Biological, and Structural Studies
Authors: Janssens Jonas , Bitra Aruna , Wang Jing , Decruy Tine , Venken Koen , van der Eycken Johan , Elewaut Dirk , Zajonc Dirk M. , van Calenbergh Serge 
Published: December 2018

AbstractInvariant natural killer T‐cells (iNKT) are a glycolipid‐responsive subset of T‐lymphocytes that fulfill a pivotal role in the immune system. The archetypical synthetic glycolipid, α‐galactosylceramide (α‐GalCer), whose molecular framework is inspired by a group of amphiphilic natural products, remains the most studied antigen for iNKT‐cells. Nonetheless, the potential of α‐GalCer as an immunostimulating agent is compromised by the fact that this glycolipid elicits simultaneous secretion of Th1‐ and Th2‐cytokines. This has incited medicinal chemistry efforts to identify analogues that are able to perturb the Th1/Th2 balance. In this work, we present the synthesis of an extensive set of 4“‐O‐alkylated α‐GalCer analogues, which were evaluated in vivo for their cytokine induction. We have found that conversion of the 4”‐OH group to ether moieties decreases the immunogenic potential in mice relative to α‐GalCer. Yet, the benzyl‐modified glycolipids are able to produce a distinct pro‐inflammatory immune response. The crystal structures suggest an extra hydrophobic interaction between the benzyl moiety and the α2‐helix of CD1d.
Where have all the tree diameters grown? Patterns in Fagus sylvatica L. diameter growth on their run to the upper canopy
Authors: Janík David , Vrška Tomáš , Hort Libor , Unar Pavel , Král Kamil 
Published: December 2018

AbstractThe diameter growth of a tree reflects the success of that tree in competition. We investigated patterns of Fagus sylvatica diameter growth in the Žofín Forest Dynamics Plot, which is part of Smithsonian's Forest Global Earth Observatory as a research plot representing European natural mixed temperate forests. We focused primarily on the spatial patterns of beech diameter growth from the viewpoint of the most successful individuals in different ontogenetic stages. We analyzed the reaction of trees along a gradient of disturbance intensity as well as the effects of neighborhood competition. We used stem maps of trees with a diameter at breast height (dbh) ≥ 10 cm carried out in 1997 and 2012. Various types of the pair correlation function were applied to the data to describe the tree density variability. Tree spatial pattern analyses were performed on six 1.5‐ha square plots. Our results show an increasing trend of general increment growth in the interval between dbh 10 cm and dbh 40 cm. Average increment first peaked between dbh 40–42 cm with values higher than 5 mm/year, after which the absolute average increment slightly decreased and stagnated; dbh increment again increased only after dbh 79 cm, but with a much wider range of confidence intervals. An analysis of the variability in diameter growth at intermediate spatial scales showed that disturbance events influence diameter growth differently in connection with dbh. Diameter growth in thinner trees was strongly positively correlated with disturbance intensity, while disturbance had no effect on the variability in diameter growth in larger trees. The spatial pattern of elite‐growth recruits differed from the generally clustered pattern of recruits, with mutual negative interactions up to 2 m. Elite‐growth small‐sized trees (dbh 10–19 cm) showed a positive association with dead individuals in the same size category. In contrast, elite‐growth medium‐sized trees (dbh 20–39 cm) had no positive associations at all. At the same time, negative correlations with canopy beeches were observed across all categories. In conclusion, current tree spatial patterns of trees and their diameter growth are the results of multiple interactions accumulated over the long term with high inertia.
Variability in fire‐induced change to vegetation physiognomy and biomass in semi‐arid savanna
Authors: Singh Jenia , Levick Shaun R. , Guderle Marcus , Schmullius Christiane , Trumbore Susan E. 
Published: December 2018

AbstractFire plays an intrinsic role in shaping the biophysical attributes of savanna ecosystems. Savanna fires limit vegetation biomass below their climatically determined potential, but the magnitude of this effect and how it varies across heterogeneous landscapes are poorly understood. In this study, we explore woody tree structure and canopy characteristics across a fire manipulation experiment that has been maintained for 63 yr in South Africa's Kruger National Park. Our study design assessed three late dry‐season fire regimes (biennial, triennial, and unburnt) across a precipitation gradient (737–496 mm/yr) spanning four different landscapes with a mixture of sandy and clay soils. We used terrestrial laser scanning (TLS) to quantify tree height, canopy cover, and aboveground carbon storage across the experimental treatments. Vegetation physiognomy was influenced by the interaction between landscape and fire frequency. In the absence of fire, woody height, cover, and biomass increased with increasing rainfall. The presence of fire acted to reduce structure and biomass as expected, but the magnitude of this effect increased with increasing rainfall. We found minimal difference between the effects of biennial or triennial burning—except at the wettest site where the triennial fire plots had half the biomass of those burnt biennially. The rainfall dependent fire–vegetation relationships shown here provide empirical quantification of top‐down constraint by fire and highlight the challenges of predicting responses to disturbances in these inherently heterogeneous ecosystems. Robust quantification of 3D structure and dynamics through TLS will be useful for constraining carbon stock models and predicting trajectories of change under future climate and land‐use conditions.