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Now showing items 129 - 144 of 236

  • Fusion and leakage of catanionic surfactant vesicles induced by alpha-helical peptides:the effect of membrane charge

    Wang, Dong   Cao, Yueying   Chen, Cuixia   Cao, Meiwen   Sun, Yawei   Wang, Jiqian   Xu, Hai  

    Leakage and fusion of vesicles have triggered great interest because they are important steps in the transportation of materials in living systems. In this paper, we have shown a process of vesicle leakage and fusion induced by a type of alpha-helical peptide through the adsorption of peptide molecules on or their absorption in the membrane of vesicles. The fusion process was monitored by dynamic light scattering and cryogenic transmission electron microscopy, and the leakage process was tested with fluorescence dequenching of carboxyfluorescein molecules. The mechanism of leakage and fusion was deduced through circular dichroism and zeta-potential measurements. It was found that the positively charged peptides could only interact with negatively charged vesicles and that the interaction between peptides and negative vesicles depended on the charge density of the membrane. This study could enhance the understanding of the transport of materials in vivo and promote potential applications in drug delivery systems.
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  • Mapping quantitative trait loci associated with starch paste viscosity in rice (Oryza sativa L.) under different environmental conditions

    Yao, Xiaoyun   Wang, Jiayu   Liu, Jin   Zhang, Jia   Ren, Chunyuan   Ma, Dianrong   Xu, Hai   Xu, Zhengjin  

    A recombinant inbred line (RIL) population consisting of 153 lines derived from a cross between indica Zhongyouzao8' and japonica Toyonishiki' rice was used to detect stable quantitative trait loci (QTL) for rapid visco analyser (RVA) characteristics under four environmental conditions. We identified 93 QTL for RVA profiles, and four pleiotropic regions harbouring stably expressed QTL were detected on chromosomes 2, 6, 7 and 11. These newly identified and stable QTL will facilitate further research into the genetic mechanism regulating RVA profiles. Amylose content (AC) was correlated with RVA traits. AC and RVA traits were unaffected by indica-japonica subspecies differentiation, suggesting that RVA profiles were mainly influenced by the Wx gene. The RIL population was divided into two subpopulations according to Wx genotypes. A total of 106 QTL associated with RVA profiles were detected in the subpopulations. These QTL differed from those detected in the whole population in terms of their genomic location, number, logarithm of odds values and amount of phenotypic variance explained. Using this strategy, we detected QTL with minor effects and eliminated false due to the Wx gene.
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  • Climate change and soil erosion in a small alpine lake basin on the Loess Plateau,China

    Yu, Keke   Xu, Hai   Lan, Jianghu   Sheng, Enguo   Liu, Bin   Wu, Huixian   Tan, Liangcheng   Yeager, Kevin M.  

    Multi-proxy indices retrieved from sediments in Lake Chaonaqiu, an alpine lake on the western Loess Plateau (LP) of China, were used to reconstruct a precipitation history over the last similar to 300 years. The results correlate well with records from tree rings and historical documents in neighboring regions. We show that the lake oscillated between two states, i.e. wetter climatic conditions, which favored denser vegetation cover, and promoted weaker catchment soil erosion; and drier climatic conditions, which lead to less vegetation coverage, correlate with stronger surface soil erosion. Several intensive soil erosion events were identified in the sediment cores, and most of these occurred during decadal/multi-decadal dry periods, and correlate well with flood events documented in historical literature. The results of this study show that soil erosion by flood events is particularly intense during dry periods, and further highlights the role of vegetation cover in the conservation of water and soil in small lake basins on the Chinese LP. Copyright (c) 2016 John Wiley & Sons, Ltd.
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  • Two-dimensional tessellation by molecular tiles constructed from halogen-halogen and halogen-metal networks

    Cheng, Fang   Wu, Xue-Jun   Hu, Zhixin   Lu, Xuefeng   Ding, Zijing   Shao, Yan   Xu, Hai   Ji, Wei   Wu, Jishan  

    Molecular tessellations are often discovered serendipitously, and the mechanisms by which specific molecules can be tiled seamlessly to form periodic tessellation remain unclear. Fabrication of molecular tessellation with higher symmetry compared with traditional Bravais lattices promises potential applications as photonic crystals. Here, we demonstrate that highly complex tessellation can be constructed on Au(111) from a single molecular building block, hexakis(4-iodophenyl)benzene (HPBI). HPBI gives rise to two self-assembly phases on Au(111) that possess the same geometric symmetry but different packing densities, on account of the presence of halogen-bonded and halogen-metal coordinated networks. Subdomains of these phases with self-similarity serve as tiles in the periodic tessellations to express polygons consisting of parallelograms and two types of triangles. Our work highlights the important principle of constructing multiple phases with self-similarity from a single building block, which may constitute a new route to construct complex tessellations.
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  • Complexation and Dynamic Switching Properties of Fluorophore-Appended Resorcin[4]arene Cavitands

    Shirtcliff, Laura D.   Xu, Hai   Diederich, Francois  

    Fluorophore-appended resorcin[4]arene-based cavitands having pyrene (2) and anthracene (3) moieties attached to the rims were prepared by short synthetic routes. Both undergo reversible temperature- and acid- (CF(3)COOD) induced vase -> kite switching as evidenced by (1)H NMR spectroscopy. The (1)H NMR spectra also suggest that suitably sized solvents, such as [D(8)]toluene, efficiently solvate the cavity, reducing the conformational flexibility. In [D(12)]mesitylene, both cavitands undergo remarkably stable host-guest inclusion complexation with cycloalkanes. The larger cavity of 3 preferentially hosts cyclohexane, whereas the smaller cavity of 2 forms the most stable complex with cyclopentane. The propensity for the cavitands to facilitate pi-pi stacking between the chromophores was confirmed by both (1)H NMR and fluorescence spectroscopy. The interchromophoric interaction is strongly solvent-dependent: pi-pi stacking between the pyrene moieties of 2 is not as efficient in [D(8)]toluene, as it solvates the inner cavity and prevents the two chromophores from approaching each other. Fluorescence studies revealed an unexpectedly large conformational flexibility of the cavitand structures both in the vase and kite forms, which was further confirmed by molecular dynamics simulations. Excimer formation is most preferred in [D(12)]mesitylene when the cavities are empty, whereas efficient solvation or guest binding in the interior spaces reduces the propensity for excimer formation. The observed high conformational flexibility of the cavitands in solution explains previous differences from the behavior of related systems in the solid state. This study shows that the rigid, perfect vase and kite geometries found for bridged resorcin[4]arene cavitands in the solid state are largely a result of crystal packing effects and that the conformational flexibility of the structures in solution is rather high.
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  • Microstructure Design of Carbonaceous Fibers: A Promising Strategy toward High芒聙聬Performance Weaveable/Wearable Supercapacitors

    Yu, Chenyang   An, Jianing   Zhou, Ruicong   Xu, Hai   Zhou, Jinyuan   Chen, Qiang   Sun, Gengzhi   Huang, Wei  

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  • Warming favors subtropical lake cyanobacterial biomass increasing

    Yan, Dongna   Xu, Hai   Lan, Jianghu   Yang, Ming   Wang, Fushun   Hou, Weiguo   Zhou, Kangen   An, Zhisheng  

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  • Comparison of dual-source ct coronary angiography and conventional coronary angiography for detecting coronary artery disease

    Xu, Yi   Tang, Lijun   Zhu, Xiaomei   Xu, Hai   Tang, Jinhua   Yang, Zhijian   Wang, Liansheng   Wang, Dehang  

    To evaluate the diagnostic accuracy of dual-source CT coronary angiography for detecting coronary artery stenosis. From February 2008 to January 2009, dual-source CT coronary CT angiography (DSCT-CCTA) and conventional coronary angiography (CAG) were both performed in 84 patients who had either clinical symptoms or a high risk of coronary artery disease. The diagnostic accuracy of DSCT-CCTA was evaluated by comparing it with that of CAG, which was regarded as the gold standard for making the diagnosis of coronary artery disease. Occlusion or stenosis of various degrees was revealed by DSCT-CCTA in 244 segments of 84 patients. Compared to CAG, segment-based sensitivity, specificity, positive predictive value and negative predictive value of DSCT-CCTA were 97.4, 97.8, 92.2 and 100%, respectively. The diagnostic accuracy of DSCT-CCTA for the detection of coronary artery stenosis was 96.5%. The paired chi(2) tests revealed no significant difference between DSCT-CCTA and CAG for making the diagnosis of coronary artery disease (P = 0.076). The diagnostic performance of DSCT-CCTA is generally as accurate as that of CAG. Thus, DSCT-CCTA is a reliable non-invasive method for detecting coronary artery stenosis.
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  • Gelatin modified ultrathin silk fibroin films for enhanced proliferation of cells.

    Yang, Luyuan   Yaseen, Mohammed   Zhao, Xiubo   Coffey, Paul   Pan, Fang   Wang, Yuming   Xu, Hai   Webster, John   Lu, Jian R  

    Silk fibroin (SF) films were modified with gelatin (G) to explore if such SF/G films could enhance the surface biocompatibility of silk as cell growth biomaterials. Ultrathin films were coated from aqueous SF solutions pre-mixed with different amounts of G. It was found that the SF/G blended films after methanol treatment were highly stable in physiological conditions. The incorporation of G smoothed the surface morphology of the SF/G films formed. Surface-exposed RGD sequences were successfully identified on the SF/G films through specific recognition of an integrin-mimicking peptide (bearing the sequence of CWDDGWLC). Cell culture experiments with 3T3 fibroblasts demonstrated that SF/G films with 1.2-20% (w/w) G gave clear improvement in promoting cell attachment and proliferation over pure SF films. Films containing 10-20% (w/w) of G showed cell attachment and growth even superior to the pure G films. The differences as observed from this study suggest that due to the lack of mechanical strength associated with its high solubility, G could not work alone as a cell growth scaffold. The enhanced cellular responses from the blended SF/G films must result from improvement in film stability arising from SF and in cytocompatibility arising from G. The results thus indicate the potential of the SF/G blends in tissue engineering and biomedical engineering where physical and biological properties could be manipulated via mixing either as bulk biomaterials or for coating purposes. =20
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  • Beta-MnO2 3D nanostructures: mineralizer-assisted synthesis, characterization, and growth mechanism.

    Zhou, Fu   Zhao, Xuemei   Yuan, Cunguang   Xu, Hai  

    The beta-MnO2 three-dimensional (3D) nanostructures were synthesized in large area by a mineralizer-assisted hydrothermal route. KNO3 was introduced as inorganic mineralizer to direct the growth of beta-MnO2 3D nanostructures from Mn(NO3)2 solutions. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Possible growth mechanism of beta-MnO2 3D nanostructures was proposed based on comparative experiments, indicating that KNO3 mineralizer and the concentration of Mn(NO3)2 solution were the two decisive factors in the fabrication of beta-MnO2 3D nanostructures.
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  • Surface Physical Activity and Hydrophobicity of Designed Helical Peptide Amphiphiles Control Their Bioactivity and Cell Selectivity

    Chen, Cuixia   Yang, Cheng   Chen, Yucan   Wang, Fang   Mu, Quanmeng   Zhang, Jing   Li, Zongyi   Pan, Fang   Xu, Hai   Lu, Jian Ren  

    G(IKK)(3)I-NH2 has been recently shown to be highly effective at killing bacteria and inhibiting cancer cell growth while remaining benign to normal host mammalian cells. The aim of this work is to evaluate how residue substitutions of Ala (A), Val (V), Glu (E), and Lys (K) for the N-terminal Gly (G) or C-terminal Ile (I) of G(ILKK)(3)I-NH2 affect the physiochemical properties and bioactivity of the variants. All substitutions caused the reduction of peptide hydrophobicity, while N-terminal substitutions had a less noticeable effect on the surface activity and helix-forming ability than C-terminal substitutions. N-terminal variants held potent anticancer activity but exhibited reduced hemolytic activity; these actions were related to the maintenance of their moderate surface pressures (12-16 mN m(-1)), while their hydrophobicity was reduced. Thus, N-terminal substitutions enhanced the cell selectivity of the mutants relative.to the control peptide G(IIKK)(3)I-NH2. In contrast, C-terminal variants exhibited lower anticancer activity and much lower hemolytic activity,except for G(IIKK)(3)V-NH2. These featutes were correlated well with their lower surface pressures (<=3D 10 mN m(-1)) and decreased hydrophobicity. In Spite of its very low helical content, the C-terminal variant G(IIKK)(3)V-NH2 still displayed potent anticancer activity while retaining high hemolytic activity as well, again correlating well with its relatively high surface pressure and hydrophobicity. These results together indicated that surface activity governs the anticancer activity of the peptides, but hydrophobicity influences their hemolytic activity. In contrast, helicity appears to be poorly correlated to their bioactivity. This work has demonstrated that N-terminal modifications provide a useful strategy to optimize the anticancer activity of helical anticancer peptides (ACPs) against its potential toxicity to mammalian host cells.
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  • Long-Term Satellite Observations of Microcystin Concentrations in Lake Taihu during Cyanobacterial Bloom Periods.

    Shi, Kun   Zhang, Yunlin   Xu, Hai   Zhu, Guangwei   Qin, Boqiang   Huang, Changchun   Liu, Xiaohan   Zhou, Yongqiang   Lv, Heng  

    Microcystins (MCs) produced by cyanobacteria pose a serious threat to public health. Intelligence on MCs distributions in freshwater is therefore critical for environmental agencies, water authorities, and public health organizations. We developed and validated an empirical model to quantify MCs in Lake Taihu during cyanobacterial bloom periods using the atmospherically Rayleigh-corrected moderate resolution imaging spectroradiometer (MODIS-Aqua) (Rrc) products and in situ data by means of chlorophyll a concentrations (Chla). First, robust relationships were constructed between MCs and Chla (r =3D 0.91; p < 0.001; t-test) and between Chla and a spectral index derived from Rrc (r =3D -0.86; p < 0.05; t-test). Then, a regional algorithm to analyze MCs in Lake Taihu was constructed by combining the two relationships. The model was validated and then applied to an 11-year series of MODIS-Aqua data to investigate the spatial and temporal distributions of MCs. MCs in the lake were markedly variable both spatially and temporally. Cyanobacterial bloom scums, temperature, wind, and light conditions probably affected the temporal and spatial distribution of MCs in Lake Taihu. The findings demonstrate that remote sensing reconnaissance in conjunction with in situ monitoring can greatly aid MCs assessment in freshwater. =20
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  • Identification and Characterization of New Resistance-Conferring SGI1s (Salmonella Genomic Island 1) in Proteus mirabilis

    Bie, Luyao   Fang, Meng   Li, Zhiqiang   Wang, Mingyu   Xu, Hai  

    Salmonella genomic island 1 (SGI1) is a resistance-conferring chromosomal genomic island that contains an antibiotic resistance gene cluster. The international spread of SGI1-containing strains drew attention to the role of genomic islands in the dissemination of antibiotic resistance genes in Salmonella and other Gram-negative bacteria. In this study, five SGI1 variants conferring multidrug and heavy metal resistance were identified and characterized in Proteus mirabilis strains: SGI1-PmCAU, SGI1-PmABB, SGI1-PmJN16, SGI1-PmJN40, and SGI1-PmJN48. The genetic structures of SGI1-PmCAU and SGI1-PmABB were identical to previously reported SGI1s, while structural analysis showed that SGI1-PmJN16, SGI1-PmJN40, and SGI1-PmJN48 are new SGI1 variants. SGI1-PmJN16 is derived from SGI1-Z with the MDR region containing a new gene cassette array dfrA12-orfF-aadA2-qacE Delta 1-sul1-chrA-orf1. SGI1-PmJN40 has an unprecedented structure that contains two right direct repeat sequences separated by a transcriptional regulator-rich DNA fragment, and is predicted to form two different extrachromosomal mobilizable DNA circles for dissemination. SGI1-PmJN48 lacks a common ORF S044, and its right junction region exhibits a unique genetic organization due to the reverse integration of a P. mirabilis chromosomal gene cluster and the insertion of part of a P. mirabilis plasmid, making it the largest known SGI1 to date (189.1 kb). Further mobility functional analysis suggested that these SGIs can be excised from the chromosome for transfer between bacteria, which promotes the horizontal transfer of antibiotic and heavy metal resistance genes. The identification and characterization of the new SGI1 variants in this work suggested the diversity of SGI1 structures and their significant roles in the evolution of bacteria.
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  • Aggregation-induced emission fluorescent probe for monitoring endogenous alkaline phosphatase in living cells

    Li, Yaqian   Xie, Ruihua   Pang, Xiao   Zhou, Zile   Xu, Hai   Gu, Biao   Wu, Cuiyan   Li, Haitao   Zhang, Youyu  

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  • An ESIPT-based fluorescent probe for the detection of phosgene in the solution and gas phases

    Wu, Cuiyan   Xu, Hai   Li, Yaqian   Xie, Ruihua   Li, Peijuan   Pang, Xiao   Zhou, Zile   Gu, Biao   Li, Haitao   Zhang, Youyu  

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  • A new membrane based process to isolate immunoglobulin from chicken egg yolk

    Yang, Juan   Xu, Hai   Lu, Junren   Cui, Zhanfeng  

    Although the importance of eggs as a source of specific antibodies has been well recognised, the generation of egg yolk immunoglobulins (IgY) is rarely chosen due to the peculiar composition of egg yolk and the lack of specific affinity ligands. In this work, we report a novel membrane based two-stage ultrafiltration process to isolate IgY from egg yolk. The effects of solution pH, ionic strength, stirring speed and permeate flux on the transmission of proteins were quantified using the pulsed sample injection technique and parameter scanning ultrafiltration. Under optimised conditions, the purity of immunoglobulin obtained was greater than 93% after the two-stage ultrafiltration process and the recovery of immunoglobulin from the feedstock was close to 87%. The resulting immunoglobulin product was then analysed by Isoelectric Focusing (IEF), SDS-PAGE and Circular Dichroism (CD), to confirm its isoelectric point, molecular weight and molecular secondary structure. (C) 2010 Elsevier Ltd. All rights reserved.
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