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Now showing items 97 - 112 of 446

  • Controlled silica deposition on self-assembled peptide nanostructures via varying molecular structures of short amphiphilic peptides.

    Wang, Shengjie   Xue, Junyi   Zhao, Yurong   Du, Mingxuan   Deng, Li   Xu, Hai   Lu, Jian R  

    Cationic amphiphilic peptides are highly similar to native silaffins and silicateins for biosilicification in terms of their composition, amphiphilicity, and self-assembling propensity. To understand the relationship between organic molecular structures, molecular self-assembly and silica morphogenesis during biosilicification, we have prepared a series of short self-assembling peptide amphiphiles (I3-5K, I4K2, I3-4R, and I4R2) and investigated their capability to mediate silicification under ambient conditions. I3K self-assembled into tubular nanofibrils while I4K1-2 and I5K formed solid nanofibrils in aqueous solution with their outer diameters decreasing as the number of hydrophobic or hydrophilic amino acid residues increased. Changes in molecular structure thus altered their self-assembled geometries, and the exposed surfaces and surface lysine densities under different geometries then played different mediating roles in silicification, leading to different silica deposition patterns and final silica nanostructures. The templating capacity was weakened or lost when lysine was replaced by arginine, despite the fact that I3-4R and I4R2 self-assembled into nanofibrils and nanoribbons under similar conditions. =20
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  • Proteomic profile and toxicity pathway analysis in zebrafish embryos exposed to bisphenol A and di-n-butyl phthalate at environmentally relevant levels

    Dong, Xing   Qiu, Xuchun   Meng, Shunlong   Xu, Hai   Wu, Xiangyang   Yang, Ming  

    Bisphenol A (BPA) and di-n-butyl phthalate (DBP) are well-known endocrine-disrupting chemicals (EDCs) that have human health risks. Chronic exposure to BPA and DBP increases the occurrence of human disease. Despite the potential for exposure in embryonic development, the mechanism of action of BPA and DBP on vertebrate development and disease still remains unclear. In the present study, we identified proteins and protein networks that are perturbed by BPA and DBP during zebrafish (Danio rerio) development. Zebrafish embryos were exposed to environmentally relevant levels of BPA (10 mu g/L) and DBP (50 mu g/L) for 96 h. By iTRAQ labeling quantitative proteomics, a set of 26 and 41 differentially expressed proteins were identified in BPA- and DBP-treated zebrafish embryos, respectively. Integrated toxicity analysis predicted that these proteins function in common regulatory networks that are significantly associated with developmental and metabolic disorders. Exposure to low concentrations of BPA and DBP has potential health risks in zebrafish embryos. Our results also show that BPA and DBP significantly up-regulate the expression levels of multiple network proteins, providing valuable information about the molecular actions of BPA and DBP on the developmental systems. (C) 2017 Elsevier Ltd. All rights reserved.
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  • Influence of Acyl Chain Saturation on the Membrane-Binding Activity of a Short Antimicrobial Peptide

    Ciumac, Daniela   Campbell, Richard A.   Clifton, Luke A.   Xu, Hai   Fragneto, Giovanna   Lu, Jian R.  

    Different bacterial types and their living environments can lead to different saturations in the chains of their membrane lipids. Such structural differences may influence the efficacy of antibiotics that target bacterial membranes. In this work, the effects of acyl chain saturation on the binding of an antimicrobial peptide G4 have been examined as a function of the packing density of lipid monolayers by combining external reflection Fourier transform infrared (ER-FTIR) spectroscopy and neutron reflection (NR) measurements. Langmuir monolayers were formed from 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DPPG) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol)(POPG), respectively, with the initial surface pressures controlled at 8 and 28 mN/m. A reduction in the order of the acyl chains associated with the increase in the layer thickness upon G4 binding was revealed from ER-FTIR spectroscopy, with peptide binding reaching equilibration faster in POPG than in DPPG monolayers. Whereas the dynamic DPPG-binding process displayed a steady increase in the amide I band area, the POPG-binding process showed little change in the amide area after the initial period. The peptide amide I area from ER-FTIR spectroscopy could be linearly correlated with the adsorbed G4 amount from NR, irrespective of time, initial pressure, or chain saturation, with clearly more peptide incorporated into the DPPG monolayer. Furthermore, NR revealed that although the peptide was associated with both POPG and DPPG lipid monolayers, it was more extensively distributed in the latter, showing that acyl chain saturation clearly promoted peptide binding and structural disruption.
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  • Why Lake Taihu continues to be plagued with cyanobacterial blooms through 10 years (2007-2017) efforts

    Qin, Boqiang   Paerl, Hans W.   Brookes, Justin D.   Liu, Jianguo   Jeppesen, Erik   Zhu, Guangwei   Zhang, Yunlin   Xu, Hai   Shi, Kun   Deng, Jianming  

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  • The diversity of glycosylation of cellobiohydrolase I from Trichoderma reesei determined with mass spectrometry

    Wang, Mingyu   Ma, Yanan   Li, Ling   Wang, Bianfang   Wei, Xin   Zhang, Mengge   Wang, Juan   Cui, Qingyu   Li, Zhiqiang   Xu, Hai  

    Cellulases are glycosylated enzymes that have wide applications in fields like biofuels. It has been widely accepted that glycosylation of cellulases impact their performance. Trichoderma reesei is the most important cellulase-producer and cellobiohydrolase I (CBHI) is the most important cellulase from T. reesei. Therefore, the glycosylation of T. reesei CBHI has been a focus of research. However, investigations have been focused on N-glycosylation of three of the four potential glycosylation sites, as well as O-glycosylation on the linker region, while a full picture of glycosylation of T. reesei CBHI is still needed. In this work, with extensive mass spectrometric investigations on CBHI from two T. reesei strains grown under three conditions, several new discoveries were made: 1) N45 and N64 are N-glycosylated with high mannose type glycans; 2) the catalytic domain of CBHI is extensively O-glycosylated with hexoses and N-acetylhexosamines; 3) experimental evidence on the mannosylation of carbohydrate binding domain (other than the linker adjacent region) was found. With structural analysis, we found several glycosylation sites (such as T383, S8, and S46) are located at the openings of the substrate binding tunnel, and potentially involve in the binding of cellulose. These investigations provide a full and comprehensive picture on the glycosylation of CBHI from T. reesei, which benefits the engineering of CBHI by raising potential sites for modification. (C) 2018 Elsevier Inc. All rights reserved.
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  • Modified CAR T cells targeting membrane-proximal epitope of mesothelin enhances the antitumor function against large solid tumor

    Zhang, Zhiwei   Jiang, Duqing   Yang, Huan   He, Zhou   Liu, Xiangzhen   Qin, Wenxia   Li, Linfang   Wang, Chao   Li, Yang   Li, He   Xu, Hai   Jin, Huajun   Qian, Qijun  

    Mesothelin (MSLN) is an attractive antigen for chimeric antigen receptor (CAR) T therapy and the epitope selection within MSLN is essential. In this study, we constructed two types of CARs targeting either region I of MSLN (meso1 CAR, also known as a membrane-distal region) or region III of MSLN (meso3 CAR, also known as a membraneproximal region) using a modified piggyBac transposon system. We reported that, compared with meso1 CAR T cells, meso3 CAR T cells express higher levels of CD107a upon activation and produce increased levels of interleukin-2, TNF-alpha, and IFN-gamma against multiple MSLN-expressing cancer cells in vitro. In a real-time cell analyzer system and a three-dimensional spheroid cancer cell model, we also demonstrated that meso3 CAR T cells display an enhanced killing effect compared with that of meso1 CAR T cells. More importantly, in a gastric cancer NSG mice model, meso3 CAR T cells mediated stronger antitumor responses than meso1 CAR T cells did. We further identified that meso3 CAR T cells can effectively inhibit the growth of large ovarian tumors in vivo. Collectively, our study provides evidences that meso3 CAR T-cell therapy performs as a better immunotherapy than meso1 CAR Tcell therapy in treating MSLN-positive solid tumors.
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  • Linalool inhibits cigarette smoke-induced lung inflammation by inhibiting NF-kappaB activation.

    Ma, Jianqun   Xu, Hai   Wu, Jun   Qu, Changfa   Sun, Fenglin   Xu, Shidong  

    Linalool, a natural compound that exists in the essential oils of several aromatic plants species, has been reported to have anti-inflammatory effects. However, the effects of linalool on cigarette smoke (CS)-induced acute lung inflammation have not been reported. In the present study, we investigated the protective effects of linalool on CS-induced acute lung inflammation in mice. Linalool was given i.p. to mice 2h before CS exposure daily for five consecutive days. The numbers of macrophages and neutrophils in bronchoalveolar lavage fluid (BALF) were measured. The production of TNF-alpha, IL-6, IL-1beta, IL-8 and MCP-1 were detected by ELISA. The expression of NF-kappaB was detected by Western blotting. Our results showed that treatment of linalool significantly attenuated CS-induced lung inflammation, coupled with inhibited the infiltration of inflammatory cells and TNF-alpha, IL-6, IL-1beta, IL-8 and MCP-1 production. Meanwhile, treatment of linalool inhibited CS-induced lung MPO activity and pathological changes. Furthermore, linalool suppressed CS-induced NF-kappaB activation in a dose-dependent manner. In conclusion, our results demonstrated that linalool protected against CS-induced lung inflammation through inhibiting CS-induced NF-kappaB activation. Copyright =C2=A9 2015 Elsevier B.V. All rights reserved.
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  • pi-Conjugated dithieno[3,2-b:2 ',3 '-d]pyrrole (DTP) oligomers for organic thin-film transistors

    Lin, Gaobo   Qin, Yunke   Guan, Ying-Shi   Xu, Hai   Xu, Wei   Zhu, Daoben  

    Two new molecules with acceptor-donor-donor-acceptor (A-D-D-A) configuration bearing coplanar electron-donating dithieno[3,2-b: 2',3'-d] pyrrole (DTP) as the donor unit and the electron-withdrawing dicyanovinylene as the acceptor block, DTP-L and DTP-S, were synthesized. The introduction of two branched alkyl chains with different lengths at the N-position of DTP led to different transport properties with the longer alkyl chains (DTP-L) showing hole mobility of up to 0.12 cm(2) V-1 s(-1) with on/off ratios of 106 without being subjected to annealing, and the one with short alkyl chains (DTP-S) exhibiting very poor hole mobility of 7.0 x 10(-4) cm(2) V-1 s(-1). The poor performance of DTP-S films was mainly caused by a less ordered film and low crystallinity.
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  • Stress Relaxation Properties and Microscopic Deformation Structure in Bending of the C7025 and C7035 Alloy

    Xiao, Xiangpeng   Xu, Hai   Huang, Jian   Wang, Junfeng   Zhang, Jianbo  

    Stress relaxation tests in cantilever bending were performed on the C7025 and C7035 alloys at 298 K and 393 K, respectively. The effect of stress-relief treatments on stress relaxation properties was investigated. The structural changes associated with the stress relaxation process were examined using transmission electron microscopy. The stress relaxation curve fits well to empirical formula sigma* =3D [K'ln(t + alpha(0)) + C](-n) for stress relaxation. The curves can be split into two stages. The stress drops fast at first and then it gets slower in the second stage, and tends towards a certain limited value after a long time. The curve and microstructure reveal that the C7035 alloy has a lower rate of stress relaxation and a higher anti-stress relaxation capacity than the C7025. The first reason is that the movement of vacancies required by spinodal decomposition is inhibited, and the quantity of cobalt-containing vacancies decreases dramatically in the C7035 alloy. The other reason is that the precipitated phases became uniformly diffused in the C7035 alloy. The precipitate phase is uniformly distributed in the grain boundaries and the matrix, during the relaxed condition, and thus the dislocation movement is blocked by the precipitate.
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  • Molecular Beam Epitaxy of Highly Crystalline Monolayer Molybdenum Disulfide on Hexagonal Boron Nitride

    Fu, Deyi   Zhao, Xiaoxu   Zhang, Yu-Yang   Li, Linjun   Xu, Hai   Jang, A-Rang   Yoon, Seong In   Song, Peng   Poh, Sock Mui   Ren, Tianhua   Ding, Zijing   Fu, Wei   Shin, Tae Joo   Shin, Hyeon Suk   Pantelides, Sokrates T.   Zhou, Wu   Loh, Kian Ping  

    Atomically thin molybdenum disulfide (MoS2), a direct-band-gap semiconductor, is promising for applications in electronics and optoelectronics, but the scalable synthesis of highly crystalline film remains challenging. Here we report the successful epitaxial growth of a continuous, uniform, highly crystalline monolayer MoS2 film on hexagonal boron nitride (h-BN) by molecular beam epitaxy. Atomic force microscopy and electron microscopy studies reveal that MoS2 grown on h-BN primarily consists of two types of nucleation grains (0 aligned and 60 degrees antialigned domains). By adopting a high growth temperature and ultralow precursor flux, the formation of 60 degrees antialigned grains is largely suppressed. The resulting perfectly aligned grains merge seamlessly into a highly crystalline film. Large-scale monolayer MoS2 film can be grown on a 2 in. h-BN/sapphire wafer, for which surface morphology and Raman mapping confirm good spatial uniformity. Our study represents a significant step in the scalable synthesis of highly crystalline MoS2 films on atomically flat surfaces and paves the way to large-scale applications.
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  • Rational Design of Short Peptide-Based Hydrogels with MMP-2 Responsiveness for Controlled Anticancer Peptide Delivery.

    Chen, Cuixia   Zhang, Yu   Hou, Zhe   Cui, Xuejing   Zhao, Yurong   Xu, Hai  

    Molecular self-assembly makes it feasible to harness the structures and properties of advanced materials via initial molecular design. To develop short peptide-based hydrogels with stimuli responsiveness, we designed here short amphiphilic peptides by engineering protease cleavage site motifs into self-assembling peptide sequences. We demonstrated that the designed Ac-I3SLKG-NH2 and Ac-I3SLGK-NH2 self-assembled into fibrillar hydrogels and that the Ac-I3SLKG-NH2 hydrogel showed degradation in response to MMP-2 but the Ac-I3SLGK-NH2 hydrogel did not. The cleavage of Ac-I3SLKG-NH2 into Ac-I3S and LKG-NH2 was found to be mechanistically responsible for the enzymatic degradation. Finally, when an anticancer peptide G(IIKK)3I-NH2 (G3) was entrapped into Ac-I3SLKG-NH2 hydrogels, its release was revealed to occur in a "cell-demanded" way in the presence of HeLa cells that overexpress MMP-2, therefore leading to a marked inhibitory effect on their growth on the gels.=20
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  • Designed Antimicrobial and Antitumor Peptides with High Selectivity RID A-1690-2011

    Hu, Jing   Chen, Cuixia   Zhang, Shengzhong   Zhao, Xichen   Xu, Hai   Zhao, Xiubo   Lu, Jian R.  

    We report a new class of cationic amphiphilic peptides with short sequences, G(IIKK)(n)I-NH(2) (n = 1-4), that can kill Gram-positive and Gram-negative bacteria as effectively as several well-known antimicrobial peptides and antibiotics. In addition, some of these peptides possess potent antitumor activities against cancer cell lines. Moreover, their hemolytic activities against human red blood cells (hRBCs) remain remarkably low even at some 10-fold bactericidal minimum inhibitory concentrations (MICs). When bacteria or tumor cells are cocultured with NIH 3T3 fibroblast cells, G(IIKK)(3)I-NH(2) showed fast and strong selectivity against microbial or tumor cells, without any adverse effect on NIH 3T3 cells. The high selectivity and associated features are attributed to two design tactics: the use of Ile residues rather than Leu and the perturbation of the hydrophobic face of the helical structure with the insertion of a positively charged Lys residue. This class of simple peptides hence offers new opportunities in the development of cost-effective and highly selective antimicrobial and antitumor peptide-based treatments.
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  • Interactions between Yersinia pestis V-antigen (LcrV) and human Toll-like receptor 2 (TLR2) in a modelled protein complex and potential mechanistic insights

    Wei, Tiandi   Gong, Jing   Qu, Guojing   Xu, Hai  

    Background Yersinia pestis, the etiological pathogen of plague, is capable of repressing the immune response of white blood cells to evade phagocytosis. The V-antigen (LcrV) was found to be involved in this process by binding to human Toll-like Receptor 2 (TLR2). The detailed mechanism behind this LcrV and TLR2 mediated immune response repression, however, is yet to be fully elucidated due to the lack of structural information. Results In this work, with protein structure modelling, we were able to construct a structure model of the heterotetramer of Y. pestis LcrV and human TLR2. Molecular dynamics simulation suggests the stability of this structure in aquatic environment. The LcrV model has a dumbbell-like structure with two globule domains (G1 at N-terminus and G2 away from membrane) connected with a coiled-coil linker (CCL) domain. The two horseshoe-shape TLR2 subunits form a V-shape structure, are not in direct contact with each other, and are held together by the LcrV homodimer. In this structure model, both the G1 and CCL domains are involved in the formation of LcrV homodimer, while all three domains are involved in LcrV-TLR2 binding. A mechanistic model was proposed based on this heterotetrameric structure model: The LcrV homodimer separates the TLR2 subunits to inhibit the dimerization of TLR2 and subsequent signal transfer for immune response; while LcrV could also inhibit the formation of heterodimers of TLR2 with other TLRs, and leads to immune response repression. Conclusions A heterotetrameric structure of Y. pestis LcrV and human TLR2 was modelled in this work. Analysis of this modelled structure showed its stability in aquatic environments and the role of LcrV domains and residues in protein-protein interaction. A mechanistic model for the role of LcrV in Y. pestis pathogenesis is raised based on this heterotetrameric structure model. This work provides a hypothesis of LcrV function, with which further experimental validation may elucidate the role of LcrV in human immune response repression.
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  • Structure of DNA helicase RepA in complex with sulfate at 1.95 ANG resolution implicates structural changes to an 'open' form.

    Xu, Hai   Straeter, Norbert   Schroeder, Werner   Boettcher, Christoph   Ludwig, Kai  

    The structure of a new crystal form (space group C2), grown at pH 8.0 and diffracting to 1.95 ANG resolution, of the replicative homo-hexameric DNA helicase RepA encoded by plasmid RSF1010 is reported. In contrast to previous crystals grown at pH 6.0 in space group P21 (Niedenzu et al., 2001), only one half (a trimer) of the RepA hexamer occupies the asymmetric unit of the space-group C2 crystals. The new crystal packing explains the pH-dependent hexamer-hexamer association mechanism of RepA. The C-terminus 264VLERQRKS-KGVPRGEA279, which could not be modelled in the previous structure, is clearly defined in the present electron density except for the last four amino acids. Sulfate anions occupy the six ATPase active sites of RepA at positions where the product phosphates are supposed to bind. Binding of sulfate anions induces conformational changes both at the ATPase active sites and throughout the whole molecular structure. In agreement with electron microscopy, the above studies implicate structural changes to an 'open' form that may occur upon binding and hydrolysis of nucleotide 5'-triphosphates and could be essential for DNA duplex-unwinding activity.
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  • Dual-source CT coronary angiography involving injection protocol with iodine load tailored to patient body weight and body mass index: estimation of optimal contrast material dose

    Zhu, Xiaomei   Zhu, Yinsu   Xu, Hai   Yang, Guanyu   Tang, Lijun   Xu, Yi  

    Background: Body mass index (BMI) has a positive linear influence on arterial attenuation at coronary CT angiography involving injection protocol with dose linearly tailored to body weight (BW). Excessive contrast material may inadvertently be given in heavier patients when the dose is determined by BW only. Purpose: To investigate the effect of injection protocol with dose of contrast material (CM) tailored to BW and BMI on coronary arterial attenuation, contrast-to-noise ratio, and image noise at dual-source CT coronary angiography (DSCT-CA). Material and Methods: A total of 233 consecutive patients (mean age, 60.2 years) undergoing DSCT-CA were included. Image acquisition protocol was standardized (120 kV, 380 mAs, and retrospective electrocardiograph-triggered DSCT-CA). CM dosage calculation was randomly categorized into groups: a BW group and a BW-BMI group. CM flow rate in both groups was calculated as dosage divided by scan time plus 8 s. Correlations between BW, BMI, and attenuations of ascending aorta (AA) above coronary ostia, left main coronary artery (LM), proximal right coronary artery (RCA), left anterior descending (LAD), and left circumflex artery (LCX), contrast to noise ratio of LM (LMCNR) and RCA (RCA(CNR)), and image noise were evaluated with simple linear regression for two groups individually. Results: In BW group, attenuations of AA and coronary arteries showed positive linear correlations to BW and BMI. In contrast, no relationships were found in BW-BMI group. LMCNR and RCA(CNR) were inversely determined by BW and BMI in both groups. Image noise increased with BW and BMI increasing in two groups. Conclusion: BMI has a positive linear influence on arterial attenuation with fixed iodine per BW. The injection protocol with CM dose tailored to BW and BMI is reasonable during DSCT-CA.
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  • Engineering T7 bacteriophage as a potential DNA vaccine targeting delivery vector.

    Xu, Hai   Bao, Xi   Wang, Yiwei   Xu, Yue   Deng, Bihua   Lu, Yu   Hou, Jibo  

    BACKGROUND: DNA delivery with bacteriophage by surface-displayed mammalian cell penetrating peptides has been reported. Although, various phages have been used to facilitate DNA transfer by surface displaying the protein transduction domain of human immunodeficiency virus type 1 Tat protein (Tat peptide), no similar study has been conducted using T7 phage.; METHODS: In this study, we engineeredT7 phage as a DNA targeting delivery vector to facilitate cellular internalization. We constructed recombinant T7 phages that displayed Tat peptide on their surface and carried eukaryotic expression box (EEB) as a part of their genomes (T7-EEB-Tat).; RESULTS: We demonstrated that T7 phage harboring foreign gene insertion had packaged into infective progeny phage particles. Moreover, when mammalian cells that were briefly exposed to T7-EEB-Tat, expressed a significant higher level of the marker gene with the control cells infected with the wide type phage without displaying Tat peptides.; CONCLUSION: These data suggested that the potential of T7 phage as an effective delivery vector for DNA vaccine transfer.=20
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