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Now showing items 129 - 144 of 402

  • Molecular characterization of class 3 integrons from Delftia spp.v

    Xu, Hai   Davies, Julian  

    Two environmental strains, Delftia acidovorans C17 and Delftia tsuruhatensis A90, were found to carry class 3 integrons, which have seldom been reported and then only from pathogens in which they are associated with antibiotic resistance genes. The Detftia integrons comprised a highly conserved class 3 integrase gene, upstream and oppositely oriented from a set of three or four gene cassettes that encoded unidentified functions. The A90 integron had one more gene cassette than the C17 integron, but the two were otherwise the same; furthermore, they were located within regions of sequence identity in both strains and linked to chromosomal genes. A screen of other Delftia and related strains did not reveal the presence of additional class 3 integrons. The observations suggest that these integrons were horizontally transferred to Delftia as part of a larger region and reside as chromosomal elements that probably predate transposon dissemination, as has been proposed for certain class 1I integrons.
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  • A novel FC17/CESA4 mutation causes increased biomass saccharification and lodging resistance by remodeling cell wall in rice

    Li, Fengcheng   Liu, Sitong   Xu, Hai   Xu, Quan  

    BackgroundRice not only produces grains for human beings, but also provides large amounts of lignocellulose residues, which recently highlighted as feedstock for biofuel production. Genetic modification of plant cell walls can potentially enhance biomass saccharification; however, it remains a challenge to maintain a normal growth with enhanced lodging resistance in rice.ResultsIn this study, rice (Oryza sativa) mutant fc17, which harbors the substitution (F426S) at the plant-conserved region (P-CR) of cellulose synthase 4 (CESA4) protein, exhibited slightly affected plant growth and 17% higher lodging resistance compared to the wild-type. More importantly, the mutant showed a 1.68-fold enhancement in biomass saccharification efficiency. Cell wall composition analysis showed a reduction in secondary wall thickness and cellulose content, and compensatory increase in hemicelluloses and lignin content. Both X-ray diffraction and calcofluor staining demonstrated a significant reduction in cellulose crystallinity, which should be a key factor for its high saccharification. Proteomic profiling of wild-type and fc17 plants further indicated a possible mechanism by which mutation induces cellulose deposition and cell wall remodeling.ConclusionThese results suggest that CESA4 P-CR site mutation affects cell wall features especially cellulose structure and thereby causes enhancement in biomass digestion and lodging resistance. Therefore, CESA4 P-CR region is promising target for cell wall modification to facilitate the breeding of bioenergy rice.
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  • Solution-Processed Sensing Textiles with Adjustable Sensitivity and Linear Detection Range Enabled by Twisting Structure

    Hui, Zengyu   Chen, Ruyi   Chang, Jin   Gong, Yujiao   Zhang, Xianwang   Xu, Hai   Sun, Yue   Zhao, Yue   Wang, Lumin   Zhou, Ruicong   Ju, Feng   Chen, Qiang   Zhou, Jinyuan   An, Jianing   Sun, Gengzhi   Huang, Wei  

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  • Quantifying the dependence of cyanobacterial growth to nutrient for the eutrophication management of temperate-subtropical shallow lakes

    Zou, Wei   Zhu, Guangwei   Cai, Yongjiu   Xu, Hai   Zhu, Mengyuan   Gong, Zhijun   Zhang, Yunlin   Qin, Boqiang  

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  • Hai‐Chao Xu

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  • Determination of critical concentrations by synchronous fluorescence spectrometry

    Yu, Daoyong   Huang, Fang   Xu, Hai  

    We demonstrate that by using constant wavelength synchronous fluorescence spectrometry (CW-SFS) critical concentrations of some types of aggregation can be quantified. Detection of aggregation associated with hydrogen bonding in Chlorin e(6) and Triton X-100 suggest that CW-SFS may be a technique that can explore aggregation at much lower levels (dimer, trimer, oligomer, etc.)
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  • Synthesis and properties of perylene diimide dyes bearing unsymmetrical and symmetrical phenoxy substituents at bay positions

    Zhao, Hang   Zhang, Ying-ying   Xu, Hai   He, Ze-min   Zhang, Zhen-Lin   Zhang, Hai-quan  

    Perylene diimide dyes bearing symmetrical and unsymmetrical phenoxy substituents at the bay positions (N,N'-diethylhexyl-1-bromo-7-pentafluorophenoxy-substituted perylene diimide and 1,7-diphenoxy-substituted perylene diimide) were prepared. H-1 NMR analysis indicated that these compounds contain a small quantity of the 1,6-regioisomer, and yield intramolecular hydrogen bonds. Furthermore, their photophysical, electrochemical, aggregation, and thermal properties were studied. It was found that their photophysical properties, structure, aggregation, and thermal stability in the solid state depend on the structure of the phenoxy substituent. (C) 2015 Elsevier Ltd. All rights reserved.
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  • Controlled Growth of 1D MoSe2 Nanoribbons with Spatially Modulated Edge States

    Cheng, Fang   Xu, Hai   Xu, Wentao   Zhou, Pinjia   Martin, Jens   Loh, Kian Ping  

    Two-dimensional (2D) transition metal dichalcogenides (TMDCs) possess interesting one-dimensional (1D) properties at its edges and inversion domain boundaries, where properties markedly different from the 2D basal plane, such as 1D metallicity and charge density waves, can be observed. Although 2D TMDCs crystals are widely grown by chemical vapor deposition (CVD), the fabrication of 1D TMDCs ribbons is challenging due to the difficulty to confine growth in only one dimension. Here we report the controlled growth of MoSe2 nanoribbons with an aspect ratio >100 by using prepatterned Se reconstructions on Au(100). Using scanning tunneling microscope and spectroscopy (STM/STS), the atomic and electronic structure of MoSe2 nanoribbons are studied. The ultranarrow ribbons show metallic behavior, while wider ribbons show a crossover from metallic to semiconducting behavior going from the edge to the center of the ribbon. The observed conductance modulations of the ultranarrow ribbons are attributed to 1D Moire pattern. Remarkably, it shows a different periodicity compared with the 2D Moire pattern in wider ribbons indicating that the ID system is softened due to the high ratio of edge to basal plane bonds. Further, we demonstrated that the nanoribbons are stable against ambient conditions, which suggests that ID TMDCs can be exploited for further applications.
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  • Tuning the Emission Color of Iridium(III) Complexes with Ancillary Ligands: A Combined Experimental and Theoretical Study RID C-4837-2009

    Gu, Xin   Fei, Teng   Zhang, Houyu   Xu, Hai   Yang, Bing   Ma, Yuguang   Liu, Xiaodong  

    A series of iridium(III) complexes [Ir(dfppy)(2)(L(boolean AND)X)] {dfppy = 2-(2,4-difluorophenyl)pyridine, L(boolean AND)X = acac, FIr(acac); dbm, FIr(dbm); natfac, FIr(natfac); acac = acetylacetonate, dbm = dibenzoylmethanane, natfac = 1-naphthoyl-3,3,3-trifluoroacetone} have been synthesized and characterized by elemental analysis, NMR and IR spectroscopy, and mass spectrometry. The cyclic voltammetric, absorption, and emission properties of these complexes have been systematically investigated. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations have been performed to investigate the ground- and excited-state properties of these complexes to provide an insight into their structural, electronic, and optical properties. The results of this work provide further evidence regarding how and to what extent the substituents on the ancillary ligand L(boolean AND)X influence the emission properties of [Ir(dfppy)(2)(L(boolean AND)X)] complexes. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
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  • High cell selectivity and low-level antibacterial resistance of designed amphiphilic peptide G(IIKK)(3)I-NH(2).

    Chen, Cuixia   Hu, Jing   Zeng, Ping   Chen, Yucan   Xu, Hai   Lu, Jian R  

    On the basis of cell cultures involving bacterial strains (Escherichia coli 5alpha and Bacillus subtilis 168) and a mammalian cell line (NIH 3T3), the potent antibacterial activity and distinct selectivity from designed amphiphilic peptides G(IIKK)nI-NH2 (n =3D 2-4) have been demonstrated. This work extends these studies to multidrug resistant pathogens (ESBL-producing E. coli) and primary human cells (HDFa), followed by the in vivo mouse model investigation of ESBL-producing bacterial infection. G(IIKK)3I-NH2 exhibits high antibacterial activity against the pathogenic strain both in vitro and in vivo while displaying low toxicity toward the primary cells and the mice. Peptide molecules can kill bacteria by selectively interacting with bacterial membranes, causing structural disruptions. Furthermore, multidrug resistant ESBL-producing bacteria do not develop resistance after multiple treatments with G(IIKK)3I-NH2. The high cellular selectivity, low toxicity toward mammalian hosts and noninducing bacterial resistance indicate great potential for developing the peptides as anti-infection agents. =20
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  • A comprehensive survey on isoleucine biosynthesis pathways in seven epidemic Leptospira interrogans reference strains of China.

    Zou, Ying   Guo, Xiaokui   Picardeau, Mathieu   Xu, Hai   Zhao, Guoping  

    Previous studies have indicated that different species of Leptospira synthesize isoleucine via either pyruvate and/or threonine pathways. Seven epidemic Leptospira interrogans reference strains from China belonging to different serovars, together with three saprophytic strains of Leptospira biflexa and Leptospira meyeri, were analysed. The isoleucine biosynthesis properties were studied firstly by measuring the key enzymes of the two pathways, citramalate synthase (CimA, CE4.1.3.-) and threonine deaminase (IlvA, CE4.2.1.16), from cell extracts of the bacteria. Meanwhile, alpha-isopropylmalate synthase (LeuA, CE4.2.1.12), the key enzyme of leucine biosynthesis, was also measured as a control. It was found that all L. interrogans strains synthesized isoleucine via the pyruvate pathway exclusively, but L. biflexa and L. meyeri used both pathways. Dot-Blot and PCR amplification of both cimA and ilvA genes in the corresponding strains provided additional evidence consistent with the data of enzymatic assays. Although it is evident that leptospires' isoleucine biosynthesis may preferentially adapt either to the pyruvate pathway exclusively for pathogens or to the combination of both pyruvate and threonine pathways for saprophytes, broader sampling with careful genomospecies identification is needed for a solid conclusion.
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  • Polarization recovery and auto-compensation in quantum key distribution network - art. no. 630513

    Ma, Lijun   Xu, Hai   Tang, Xiao  

    A Quantum Key Distribution (QKD) network can allow multi-user communication via secure key. Moreover, by actively switching communication nodes, one can achieve high key transmission rate for the selected nodes. However, the polarization properties of different fiber path are different and these properties also randomly drift over time. Therefore, polarization recovery after the switching and auto-compensation during key transmission are critical for the QKD network. In this work, we use programmable polarization controllers to implement polarization recovery and auto-compensation in the QKD network. We will also discuss its time limitation and future improvement.
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  • Comparisons of plant-type characteristics and yield components in filial generations of Indica x Japonica crosses grown in different regions in China

    Jin, Feng   Wang, Hetong   Xu, Hai   Liu, Tiansheng   Tang, Liang   Wang, Xiaoxue   Jiang, Yijun   Yang, Li   Li, Maobai   Sui, Ming   Lang, Xidong   Xua, Zhengjin   Chen, Wenfu  

    ldeotype breeding plays a significant role in increasing rice yields. A number of representative plant-type models have been developed based on environmental conditions and yield potential. Identifying the effects of the ecological environment on plant-type models will provide insight into rice ideotype breeding, and will be useful to optimize cultivation management. The aim of this study was to analyze the effects of different ecological conditions on plant-type traits and yields, and to identify the relationships between plant-type models and yield components in different ecological environments. Two populations of filial generations Indica x Japonica rice were grown in Liaoning, Sichuan, Shanghai, and Guangdong in 2012. The grain yield showed a downward trend from high latitude to low latitude. The traits of the plant-types differed markedly among the four regions. Plant height was significantly greater in Sichuan and Liaoning than in Shanghai and Guangdong. Based on panicle length, the four regions were ranked as follows (longest panicle length to shortest) Shanghai > Sichuan > Guangdong > Liaoning. For flag leaf length, the ranking order was as follows (longest to shortest): Shanghai > Guangdong > Sichuan > Liaoning; for flag leaf width (widest to narrowest): Sichuan > Liaoning > Shanghai > Guangdong. The flag leaf angle was larger in Liaoning and Guangdong than in Shanghai and Sichuan. Panicle curvature was significantly influenced by genetic factors. The long-flag-leaf, curved-panicle type with characteristics of the super hybrid plant-type model showed significant vigor in Guangdong, Sichuan, and Shanghai. The short-flag-leaf, erect-panicle plant-type was more adaptable to the environmental conditions in Liaoning. There were strong correlations between some plant-type traits and yield components. However, the strengths and directions of the correlations were not completely consistent because of the different populations in different ecological environments. In ideotype breeding practice, the criteria should be regionalized based on local climatic and cultivation conditions. Such breeding should consider not only traits of "space", but also specific geoecotypes. (C) 2013 Published by Elsevier B.V.
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  • Intrinsic defect formation in peptide self-assembly

    Deng, Li   Zhao, Yurong   Xu, Hai   Wang, Yanting  

    In contrast to extensively studied defects in traditional materials, we report here a systematic investigation of the formation mechanism of intrinsic defects in self-assembled peptide nanostructures. The Monte Carlo simulations with our simplified dynamic hierarchical model revealed that the symmetry breaking of layer bending mode at the two ends during morphological transformation is responsible for intrinsic defect formation, whose microscopic origin is the mismatch between layer stacking along the side-chain direction and layer growth along the hydrogen bond direction. Moreover, defect formation does not affect the chirality of the self-assembled structure, which is determined by the initial steps of the peptide self-assembly process. (C) 2015 Author(s).
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  • Climate changes reconstructed from a glacial lake in High Central Asia over the past two millennia

    Lan, Jianghu   Xu, Hai   Sheng, Enguo   Yu, Keke   Wu, Huixian   Zhou, Kangen   Yan, Dongna   Ye, Yuanda   Wang, Tianli  

    Climatic changes in Arid Central Asia (ACA) over the past two millennia have been widely concerned. However, less attention has been paid to those in the High Central Asia (HCA), where the Asian water tower nurtures the numerous oases by glacier and/or snow melt. Here, we present a new reconstruction of the temperature and precipitation change over the past two millennia based on grain size of a well-dated glacial lake sediment core in the central of southern Tianshan Mountains. The results show that the glacial lake catchment has experienced cold-wet climate conditions during the Dark Age Cold Period (similar to 300-600 AD; DACP) and the Little Ice Age (similar to 1300-1870 AD; LIA), whereas warm-dry conditions during the Medieval Warm Period (similar to 700-1270 AD; MWP). Integration of our results with those of previously published lake sediment records, stalagmite delta O-18 records, ice core net accumulation rates, tree-ring based temperature reconstructions, and mountain glacier activities suggest that there has a broadly similar hydroclimatic pattern over the HCA areas on centennial time scale during the past two millennia. Comparison between hydroclimatic pattern of the HCA and that of the ACA areas suggests a prevailing 'warm-dry and cold-wet' hydroclimatic pattern over the whole westerlies-dominated central Asia areas during the past two millennia. We argue that the position and intensity of the westerlies, which are closely related to the phase of the North Atlantic Oscillation (NAO), and the strength of the Siberian High pressure (SH), could have jointly modulated the late Holocene central Asia hydroclimatic changes. (C) 2017 Elsevier Ltd and INQUA. All rights reserved.
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  • Peptide-Induced DNA Condensation into Virus-Mimicking Nanostructures

    Cao, Meiwen   Wang, Yu   Zhao, Wenjing   Qi, Ruilian   Han, Yuchun   Wu, Rongliang   Wang, Yilin   Xu, Hai  

    A series of surfactant-like peptides have been designed for inducing DNA condensation, which are all comprised of the same set of amino acids in different sequences. Results from experiments and molecular dynamics simulations show that the peptide's self-assembly and DNA-interaction behaviors can be well manipulated through sequence variation. With optimized pairing modes between the beta-sheets, the peptide of I(3)V(3)A(3)G(3)K(3) can induce efficient DNA condensation into virus-mimicking structures. The condensation involves two steps; the peptide molecules first bind onto the DNA chain through electrostatic interactions and then self-associate into beta-sheets under hydrophobic interactions and hydrogen bonding. In such condensates, the peptide beta-sheets act as scaffolds to assist the ordered arrangement of DNA, mimicking the very nature of the virus capsid in helping DNA packaging. Such a hierarchy affords an extremely stable structure to attain the highly condensed state and protect DNA against enzymatic degradation. Moreover, the condensate size can be well tuned by the DNA length. The condensates with smaller sizes and narrow size distribution can deliver DNA efficiently into cells. The study helps not only for probing into the DNA packaging mechanism in virus but also delineating the role of peptide self-assembly in DNA condensation, which may lead to development of peptide-based gene vectors for therapeutic applications.
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