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Now showing items 97 - 112 of 236

  • Relationship between the structural conformation of monoclonal antibody layers and antigen binding capacity RID A-1690-2011

    Xu, Hai   Zhao, Xiubo   Lu, Jian R.   Williams, David E.  

    Neutron reflection has been used to determine the pH-dependent structural conformation of monoclonal antibody layers adsorbed at the hydrophilic silicon oxide/solution interface, within the pH range 4-8, over which the silicon oxide surface carried weak negative charges and the net charge on the antibody reversed. The depth resolution achieved, by use of D2O as solvent to enhance the neutron contrast of the adsorbed antibody layer, was around 2-3 A. The results have been correlated with the ellipsometric measurement of antigen binding capacity (AgBC). The antibody was a mouse monoclonal anti-hCG (human chorionic gonadotropin) directed against the beta subunit of hCG, with molecular weight of 150 000 and isoelectric point around pH 6.0. At pH 4, the adsorbed antibody could be described as a single layer 40 angstrom thick, consistent with an almost perfect flat-on orientation with all three fragments (Fc, Fab) lying flat on the surface. With increasing pH, the antibody layer swelled (65 A at pH 6, 75 A at pH 8) and could be described as three sublayers of different protein density, consistent with some twisting of molecules so that some fragments became more loosely attached to the surface. At pH 8, the repulsive interaction between protein and surface was reflected in a significantly decreased total adsorbed amount. The dominant effect acting to increase AgBC was decreased surface packing density. The effect of the conformational changes revealed at different pH was less important. The results have shown that within the flat-on orientation adopted by the adsorbed antibody, steric hindrance is the main constraint on binding, restricting the access of the antigen to active sites within the antibody layer.
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  • Solar activity and the westerlies dominate decadal hydroclimatic changes over arid Central Asia

    Yan, Dongna   Xu, Hai   Lan, Jianghu   Zhou, Kangen   Ye, Yuanda   Zhang, Jixiao   An, Zhisheng   Yeager, Kevin M.  

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  • Cilostazol Promotes Angiogenesis and Increases Cell Proliferation After Myocardial Ischemia–Reperfusion Injury Through a cAMP-Dependent Mechanism

    Li, Jiangjin   Xiang, Xiaoli   Xu, Hai   Shi, Yafei  

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  • Effects of Microcystis on Hypothalamic-Pituitary-Gonadal-Liver Axis in Nile Tilapia (Oreochromis niloticus)

    Chen, Jiazhang   Meng, Shunlong   Xu, Hai   Zhang, Zhen   Wu, Xiangyang  

    In the present study, Nile tilapia (Oreochromis niloticus) were used to assess the endocrine disruption potential of Microcytis aeruginosa. Male Nile tilapia were exposed to lyophilized M. aeruginosa or purified microcystin-LR (8.3 mu g/L) for 28 days. The levels of serum hormones (17 beta-estradiol and testosterone) and transcripts of selected genes in the hypothalamus-pituitary-gonadal-liver axis were analyzed. The results showed that serum hormones were significantly up-regulated, and transcripts of 13 genes (GHRH, PACAP, GH, GHR1, GHR2, IGF1, IGF2, CYP19a, CYP19b, 3 beta-HSD1, 20 beta-HSD, 17 beta-HSD1 and 17 beta-HSD8) were significantly altered after Microcytis exposure. These results indicate that fish reproduction can be altered in a Microcystis bloom-contaminated aquatic environment.
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  • Sedentism and plant cultivation in northeast China emerged during affluent conditions

    Shelach-Lavi, Gideon   Teng, Mingyu   Goldsmith, Yonaton   Wachtel, Ido   Stevens, Chris J.   Marder, Ofer   Wan, Xiongfei   Wu, Xiaohong   Tu, Dongdong   Shavit, Roi   Polissar, Pratigya   Xu, Hai   Fuller, Dorian Q.   Yang, Xiaoyan  

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  • An efficient Co-N/C electrocatalyst for oxygen reduction facilely prepared by tuning cobalt species content

    Liu, Hao   Yi, Shijie   Wu, Yunfeng   Wu, Han   Zhou, Jinrong   Liang, Wenjie   Cai, Jianfeng   Xu, Hai  

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  • Diphenylamine-substituted cruciform oligo(phenylene vinylene)s: Enhanced one- and two-photon excited fluorescence in the solid state

    He, Feng   Tian, Leilei   Tian, Xiaoyu   Xu, Hai   Wang, Yinghui   Xie, Weijie   Hanif, Muddasir   Xia, Jialiang   Shen, Fengzhong   Yang, Bing   Li, Feng   Ma, Yuguang   Yang, Yanqiang   Shen, Jiacong  

    1,4-di(4'-N,N-diphenylaminostyryl)benzene (DPA-DSB) is a well known compound with a large two-photon absorption (TPA) section and strong fluorescence in solution. However, the ease with which it crystallizes results in the formation of discontinuous crystalline phases during vacuum deposition processes, thereby greatly limiting its applicability in solid-state devices. A cruciform dimer of DPA-DSB, 2,5,2',5'-tetra(4'-N,N-diphenylaminostyryl)biphenyl (DPA-TSB) is reported, wherein two DPA-DSB molecules are linked through a central biphenyl bond. The DPA-TSB molecules take on a cruciform configuration because of the steric crowding around the central biphenyl core, which has the effect of efficiently suppressing crystalline and intermolecular interactions. ne neat DPA-TSB solid shows strong green-blue fluorescence because of both steady-state absorption as well as TPA. The DPA-TSB solid exhibits a photoluminescence (PL) efficiency (eta(solid)) of 29% and a solid-state two-photon action cross section (delta eta(solid)) of 954 GM (1 GM = 1 x 10(-50) cm(4) s photon(-1) molecule(-1)), which is much greater than for the model compound DPA-DSB (eta(solid) = 16% and delta eta(solid) = 150 GM, where delta is the TPA cross section and eta is the fluorescence quantum yield). Based on its high PL efficiency, good film-forming ability, and strong TPA, DPA-TSB seems to be a good candidate for applications in solid-state optical devices.
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  • Surface-Limited Superconducting Phase Transition on 1T-TaS2

    Wang, Ziying   Sun, Yi-Yang   Abdelwahab, Ibrahim   Cao, Liang   Yu, Wei   Ju, Huanxin   Zhu, Junfa   Fu, Wei   Chu, Leiqiang   Xu, Hai   Loh, Kian Ping  

    Controlling superconducting phase transition on a two-dimensional (2D) material is of great fundamental and technological interest from the viewpoint of making 2D resistance-free electronic circuits. Here, we demonstrate that a 1T-to-2H phase transition can be induced on the topmost monolayer of bulk (<100 nm thick) 1T-TaS2 by thermal annealing. The monolayer 2H-TaS2 on bulk 1T-TaS2 exhibits a superconducting transition temperature (T-c) of 2.1 K, which is significantly enhanced compared to that of bulk 2H-TaS2. Scanning tunneling microscopy measurements reveal a 3 X 3 charge density wave (CDW) in the phase-switched monolayer at 4.5 K. The enhanced Tc is explained by the suppressed 3 X 3 CDW and a charge-transfer doping from the IT substrate. We further show that the monolayer 2H-TaS2 could be switched back to 1T phase by applying a voltage pulse. The observed surface-limited superconducting phase transition offers a convenient way to prepare robust 2D superconductivity on bulk 1T-TaS2 crystal, thereby bypassing the need to exfoliate monolayer samples.
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  • Domino Aryne Annulation via a Nucleophilic-Ene Process

    Xu, Hai   He, Jia   Shi, Jiarong   Tan, Liang   Qiu, Dachuan   Luo, Xiaohua   Li, Yang  

    1,2-Benzdiyne equivalents possess the unique property that they can react with two arynophiles through iteratively generated 1,2- and 2,3-aryne intermediates. Upon rational modification on the second leaving group of these aryne precursors, a domino aryne annulation approach was developed through a nucleophilic-ene reaction sequence. Various benzo-fused N-heterocyclic frameworks were achievable under transition metal-free conditions with a broad substrate scope.
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  • The impact of endocrine-disrupting chemicals on oxidative stress and innate immune response in zebrafish embryos

    Xu, Hai   Yang, Ming   Qiu, Wenhui   Pan, Chenyuan   Wu, Minghong  

    Bisphenol A (BPA) and nonylphenol (NP) are well known endocrine-disrupting chemicals (EDCs) ubiquitous in the aquatic environment and are an ecotoxicological risk for the health of aquatic organisms. Limited attention has been given to the immunotoxicity of these chemicals. The present study revealed a concentration-dependent increase of reactive oxygen species content and an induced expression of redox-sensitive transcription factors in zebrafish embryos after exposure to various concentrations of BPA, NP, and BPA/NP mixture for 4h to 168h postfertilization. Transcription of genes related to the immune response, including IFN, IL1, IL10, Mx, TNF, CC-chemokine, and CXCL-clc, were significantly up-regulated on exposure to EDCs. A significant induction of concentrations of proinflammatory mediator, nitric oxide, accompanied by an increase in the activity of nitric oxide synthase (NOS) and an upregulation of inducible NOS gene expression, was detected in zebrafish embryos on exposures to EDCs. To elucidate the potential mechanisms by which BPA and NP activate the innate immune response, expression profiles of genes related to the Toll-like receptors (TLRs) signaling pathway were examined. Expressions of TLR3, TRIF, MyD88, SARM, IRAK4, and TRAF6 were altered on exposure to EDCs. The authors' results demonstrate that exposure to BPA and NP significantly affects the expression of genes related to immune response in zebrafish embryos following oxidative stress. Environ Toxicol Chem 2013;32:1793-1799. (c) 2013 SETAC
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  • Dynamic Adsorption and Structure of Interfacial Bilayers Adsorbed from Lipopeptide Surfactants at the Hydrophilic Silicon/Water Interface: Effect of the Headgroup Length RID A-1690-2011

    Jia, Donghui   Tao, Kai   Wang, Jiqian   Wang, Chengdong   Zhao, Xiubo   Yaseen, Mohammed   Xu, Hai   Que, Guohe   Webster, John R. P.   Lu, Jian R.  

    Lipopeptides are an important group of biosurfactants expressed by microorganisms. Because they are well-known for being biocompatible, biodegradable, and highly surface active, they are attractive for a wide range of applications. Natural lipopeptide surfactants are however impure; it is hence difficult to use them for exploring the structure function relation. In this work, a series of cationic lipopeptide surfactants, C(14)K(n) (n = 1-4), where C denotes the myristic acyl chain and K denotes lysine (Lys), have been synthesized, and their interfacial behavior has been characterized by studying their adsorption at the silicon/water interface (bearing a thin native oxide layer) using spectroscopic ellipsometry and neutron reflection (NR). The, dynamic adsorption was marked by an initial fast step within the first 2-3 min followed by a slow molecular relaxation process over the subsequent 20-30 min. The initial rate of time-dependent adsorption and the equilibrated adsorbed amount showed a steady decrease with increasing n, indicating the impact of the molecular size, structure, and charge. NR revealed the formation of sandwiched bilayers from C(14)K(n), similar to conventional surfactants such as nonionic C(12)E(6) and cationic C(16)TAB. However, the electrostatic attraction between K and the silica surface caused confinement of the K groups, forcing the head segments into a predominantly flat-on conformation. This characteristic structural feature was confirmed by the almost constant thickness of the headgroup regions ranging from 8 to 11 angstrom as determined from NR combined with partial deuterium labeling to the acyl tail. An increase in area per molecular pair with n resulted,directly from increasing the footprint. As a result, the hydrophobic back-to-back tail mixing and acyl chain tilting rose with n. The extent of chain-head intermixing became so intensified that the C(14)K(4) bilayer could be approximated to a uniform layer distribution.
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  • Sensitive detection of thiacloprid in environmental and food samples by enhanced chemiluminescent enzyme immunoassay

    Liu, Zhen J.   Wei, Xi   Xu, Hai   Li, Ming   Zhu, Gang B.   Xue, Yong L.   Zhang, Zhen   Zhao, Guan D.   Du, Dao L.  

    A fast and sensitive enhanced chemiluminescent enzyme immunoassay (ECL-EIA) was developed based on horseradish peroxidase detected with a luminol-based substrate for neonicotinoid insecticide thiacloprid in environmental and food samples. Toward this goal, a variety conditions of chemiluminescent substrate solution including the reacting buffer, the concentrations of p-iodophenol, luminol and H2O2 were optimized. Under the optimal conditions, the sensitivity (the 50% inhibitory concentration value) was 1.80 ng mL(-1). The ECL-EIA was 5.5 times more sensitive compared to the colorimetric-EIA. The average recoveries of thiacloprid from ten spiked samples were estimated to range from 79.7 to 119%, with relative standard deviations of 4.2 to 11.2%. The dissipation of thiacloprid applied to real tomato samples was monitored with the ECL-EIA and HPLC methods. The ECL-EIA results agreed well with the HPLC results (R-2 =3D 0.993). These results suggested that the thiacloprid in the samples could be simply, rapidly and accurately detected by ECL-EIA.
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  • Bacterial plasmid-mediated quinolone resistance genes in aquatic environments in China

    Yan, Lei   Liu, Dan   Wang, Xin-Hua   Wang, Yunkun   Zhang, Bo   Wang, Mingyu   Xu, Hai  

    Emerging antimicrobial resistance is a major threat to human's health in the 21st century. Understanding and combating this issue requires a full and unbiased assessment of the current status on the prevalence of antimicrobial resistance genes and their correlation with each other and bacterial groups. In aquatic environments that are known reservoirs for antimicrobial resistance genes, we were able to reach this goal on plasmid-mediated quinolone resistance (PMQR) genes that lead to resistance to quinolones and possibly also to the co-emergence of resistance to beta-lactams. Novel findings were made that qepA and aac-(6')-Ib genes that were previously regarded as similarly abundant with qnr genes are now dominant among PMQR genes in aquatic environments. Further statistical analysis suggested that the correlation between PMQR and beta-lactam resistance genes in the environment is still weak, that the correlations between antimicrobial resistance genes could be weakened by sufficient wastewater treatment, and that the prevalence of PMQR has been implicated in environmental, pathogenic, predatory, anaerobic, and more importantly, human symbiotic bacteria. This work provides a comprehensive analysis of PMQR genes in aquatic environments in Jinan, China, and provides information with which combat with the antimicrobial resistance problem may be fought.
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  • Late Holocene hydroclimatic variation in central Asia and its response to mid-latitude Westerlies and solar irradiance

    Lan, Jianghu   Zhang, Jin   Cheng, Peng   Ma, Xiaolin   Ai, Li   Chawchai, Sakonvan   Zhou, Kang鈥檈n   Wang, Tianli   Yu, Keke   Sheng, Enguo   Kang, Shugang   Zang, Jingjie   Yan, Dongna   Wang, Yaqin   Tan, Liangcheng   Xu, Hai  

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  • Transcriptomic analysis reveals potential mechanisms of toxicity in a combined exposure to dibutyl phthalate and diisobutyl phthalate in zebrafish (Danio rerio) ovary

    Chen, Hui   Feng, Weiwei   Chen, Kun   Qiu, Xuchun   Xu, Hai   Mao, Guanghua   Zhao, Ting   Ding, Yangyang   Wu, Xiangyang  

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  • Different effects of DEP1 on vascular bundle- and panicle-related traits under indica and japonica genetic backgrounds

    Xu, Quan   Liu, Tiansheng   Bi, Wenjing   Wang, Yuanzheng   Xu, Hai   Tang, Liang   Sun, Jian   Xu, Zhengjin  

    Rice (Oryza sativa L.) is a major food for more than half of the world's population and serves as a model monocot plant. DEP1 (dense and erect panicle 1), corresponding to an erect-panicle architecture, may bring the third breakthrough in rice breeding after the introduction of the semi-dwarf trait and the application of heterosis in hybrid rice. The aim of this study was to determine the effects of DEP1 on yield components and vascular bundle-related traits under indica and japonica genetic backgrounds. We analyzed a series of recombinant inbred lines, which were derived from a cross between the japonica variety SN265 with an erect panicle and the indica variety R99 with a curved panicle. The results showed that effects of the DEP1/dep1 allele were much stronger than the effects of the indica/japonica genetic background on vascular bundle-related traits and yield components. As the frequency of indica alleles increased, the grain yield per plant and the harvest index significantly increased in lines with the dep1 allele. Among the indica-type lines, those with the dep1 allele showed superior values for almost all of the vascular bundle-related traits and yield components. Our results provide new insights into the use of a high-yield-related gene derived from japonica in the indica genetic background.
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