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Now showing items 225 - 236 of 236

  • Hierarchical processes in beta-sheet peptide self-assembly from the microscopic to the mesoscopic level

    Deng, Li   Xu, Hai  

    Under appropriate physicochemical conditions, short peptide fragments and their synthetic mimics have been shown to form elongated cross-beta nanostructures through self-assembly. The self-assembly process and the resultant peptide nanostructures are not only related to neurodegenerative diseases but also provide inspiration for the development of novel bionanomaterials. Both experimental and theoretical studies on peptide self-assembly have shown that the self-assembly process spans multiple time and length scales and is hierarchical. beta-sheet self-assembly consists of three sub-processes from the microscopic to the mesoscopic level: beta-sheet locking, lateral stacking, and morphological transformation. Detailed atomistic simulation studies have provided insight into the early stages of peptide nanostructure formation and the interplay between different non-covalent interactions at the microscopic level. This review gives a brief introduction of the hierarchical peptide self-assembly process and focuses on the roles of various non-covalent interactions in the sub-processes based on recent simulation, experimental, and theoretical studies.
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  • Rational design, properties and applications of biosurfactants: a short review of recent advances

    Liu, Kang   Sun, Yawei   Cao, Meiwen   Wang, Jiqian   Lu, Jian R.   Xu, Hai  

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  • Bisphenol S-induced chronic inflammatory stress in liver via peroxisome proliferator-activated receptor γ using fish in vivo and in vitro models

    Qiu, Wenhui   Yang, Ming   Liu, Jingyu   Xu, Hai   Luo, Shusheng   Wong, Minghung   Zheng, Chunmiao  

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  • Chemistry and materials based on 5,5 '-bibenzo[c][1,2,5]thiadiazole

    Xue, Shanfeng   Liu, Suijun   He, Feng   Yao, Liang   Gu, Cheng   Xu, Hai   Xie, Zengqi   Wu, Hongbin   Ma, Yuguang  

    D-A compounds constructed from a novel building block 5,5 '-bibenzo[c][1,2,5] thiadiazole (BBTz) possess a special configuration of swivel cruciform, which exhibits promising potential in the solution-processed small molecule optoelectronic devices, e.g. OSCs and OLEDs.
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  • Molecular origin of the self-assembled morphological difference caused by varying the order of charged residues in short peptides.

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

    In order to understand how microscopic molecular interactions between short peptides determine their mesoscopic self-assembled morphology, we studied the microscopic assembled structures of the short peptides I4K2 and KI4K, which have the same amino acid composition but different sequences, by using all-atom replica exchange molecular dynamics simulation. We found that, at room temperature, the difference in amino acid sequence does not apparently alter their strong propensity of forming beta-sheets but does strongly affect their assembled stable structures and their appearance probabilities. These differences result from the competition between the electrostatic and hydrophobic interactions among the side chains of the molecules, which are linked up by hydrogen bonds formed between neighboring peptide backbones. Our simulation results not only reveal the molecular origin of the self-assembled morphological difference between I4K2 and KI4K but also demonstrate in general the subtle balance between electrostatic, hydrophobic, and hydrogen bonding interactions in short-peptide self-assembly. =20
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  • Assessment of immunotoxicity of dibutyl phthalate using live zebrafish embryos.

    Xu, Hai   Dong, Xing   Zhang, Zhen   Yang, Ming   Wu, Xiangyang   Liu, Hongcui   Lao, Qiaocong   Li, Chunqi  

    This study set out to understand the immune-toxic effects of dibutyl phthalate (DBP) using transgenic, albino or AB line zebrafish. Zebrafish embryos were exposed to different concentrations of DBP, and the immune cells formation, phagocytosis ability were measured after a short-term exposure to DBP for 6 h post-fertilization (hpf) to 72 or 96 hpf. Exposure to DBP was found to inhibit the neutrophils and macrophage formation in a concentration-dependent manner. The ability of macrophage phagocytosis was all decreased after exposure to DBP, indicating the occurrence of immunotoxicity. The respiratory burst was induced, and the transcription levels of T/B cell-related genes rag1/2 were up-regulated. The overall results indicate that DBP in aquatic environment greatly influence the immune system in fish, and zebrafish embryos can serve as a reliable model for the developmental immunotoxicity of toxic-chemicals. Copyright =C2=A9 2015 Elsevier Ltd. All rights reserved.
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  • Structural Features of Micelles of Zwitterionic Dodecyl-phosphocholine (C=E2=82=81=E2=82=82PC) Surfactants Studied by Small-Angle Neutron Scattering.

    Pambou, Elias   Crewe, John   Yaseen, Mohammed   Padia, Faheem N   Rogers, Sarah   Wang, Dong   Xu, Hai   Lu, Jian R  

    Small-angle neutron scattering (SANS) was used to investigate the size and shape of zwitterionic dodecyl phosphocholine (C12PC) micelles formed at various concentrations above its critical micelle concentration (CMC =3D 0.91 mM). The predominant spherical shape of micelles is revealed by SANS while the average micellar size was found to be broadly consistent with the hydrodynamic diameters determined by dynamic light scattering (DLS). Cryogenic tunneling electron microscopy (cryo-TEM) shows a uniform distribution of structures, proposing micelle monodispersity ( Supporting Information ). H/D substitution was utilized to selectively label the chain, head, or entire surfactant so that structural distributions within the micellar assembly could be investigated using fully protonated, head-deuterated, and tail-deuterated PC surfactants in D2O and fully deuterated surfactants in H2O. Using the analysis software we have developed, the four C12PC contrasts at a given concentration were simultaneously analyzed using various core-shell models consisting of a hydrophobic core and a shell representing hydrated polar headgroups. Results show that at 10 mM, C12PC micelles can be well represented by a spherical core-shell model with a core radius and shell thicknesses of 16.9 =C2=B1 0.5 and 10.2 =C2=B1 2.0 A (total radius 27.1 =C2=B1 2.0 A), respectively, with a surfactant aggregation number of 57 =C2=B1 5. As the concentration was increased, the SANS data revealed an increase in core-shell mixing, characterized by the emergence of an intermediate mixing region at the spherical core-shell interface. C12PC micelles at 100 mM were found to have a core radius and shell thicknesses of 19.6 =C2=B1 0.5 and 7.8 =C2=B1 2.0 A, with an intermediate mixing region of 3.0 =C2=B1 0.5 A. Further reduction in the shell thickness with concentration was also observed, coupled with an increased mixing of the core and shell regions and a reduction in miceller hydration, suggesting that concentration has a significant influence on surfactant packing and aggregation within micelles. =20
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  • Fabrication of Patterned Thermoresponsive Microgel Strips on Cell-Adherent Background and Their Application for Cell Sheet Recovery

    Xia, Yongqing   Tang, Ying   Wu, Han   Zhang, Jing   Li, Zongyi   Pan, Fang   Wang, Shengjie   Wang, Xiaojuan   Xu, Hai   Lu, Jian Ren  

    Interfaces between materials and cells play a critical role in cell biomedical applications. Here, a simple, robust, and cost-effective method is: developed to fabricate patterned thermoresponsive poly(N-isopropylacrylamide-co-styrene) microgel strips on a polyethyleneiinine-precoated, non-thermoresponsive cell-adherent glass coverslip. The aim is to investigate whether cell sheets could be harvested from these cell-adherent surfaces patterned with thermoresponsive strips comprised of the microgels. We hypothesize that if the cell-to-cell interaction is strong enough to retain the whole cell sheet from disintegration, the cell segments growing-Ton the thermoresponsive strips may drag the cell segments growing on the. cell-adherent gaps to detach, ending with a whole freestanding and transferable cell sheet. Critical value concerning the width of the thermoresponsive strip and its ratio to the non-thermoresponsive gap may exist for cell sheet recovery from this type of surface pattern. To obtain this critical value, a series of strip patterns with various widths of thermoresponsive strip and non-thermoresponsive gap were prepared using negative microcontact printing technology, with COS7 fibroblast cells being used to test the growth and detachment, The results unraveled that COS7 cells preferentially attached-and proliferated on the cell adherent, non-thermoresponsive gaps to form. patterned cell layers and that they subsequently proliferated to cover the microgel strips to form a confluent cell layer. Intact COS7 cell sheets could be recovered when the width of the thermoresponsive strip is no smaller than that of the non-thermoresponsive gap. Other cells such as HeLa, NIH3T3, 293E, and L929 could grow similarly; that is,,they showed initial preference to the non-thermoresponsive gaps and then migrated to cover the entire patterned surface. However, it was difficult to detach them as cell sheets due to the weak interactions within the-cell layers formed. In contrast, when COS7 and HeLa cells were cultured successively, they formed the cocultured cell layer that could be detached together. These freestanding patterned cell sheets could lead to the development, of more elaborate tumor models for drug targeting and interrogation.
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  • Purification,characterization and potential applications of a novel halotolerant metalloprotease from marine bacterium Vibrio sp LA-05

    Zhang, Hong   Li, Hui   Lang, Dietmar A.   Xu, Hai   Zhu, Hu  

    BACKGROUND Many reported proteases showed low activity and stability under harsh operating conditions, e.g. high pH, salinity and surfactants, which hinders expansion of their applications in industry. Here, a novel halotolerant metalloprotease from marine bacterium Vibrio sp. LA-05 endowed with superior properties was purified and characterized, and its industrial application also evaluated. RESULTS CONCLUSION The protease was active and stable at 25-40 degrees C and pH 6.0-10.0. Moreover, it was remarkably stable in high salt solution, tolerant to denaturing agents, organic solvents, surfactants and bleaching agents, and quite compatible and stable with many commercial detergents. Its residual activities were above 22% even after co-incubation with 20% NaCl for 480 h. Except Ariel and Tide, the residual activities were all above 55% after co-incubation with five other liquid detergents for 240 h. The corresponding theoretical analyses show that it is a metalloprotease containing 1 mol of zinc ion per mole of protease, the mature active protease predominantly in alpha-helix form consists of 321 amino acids, and the central zinc ion along with 11 other conserved and crucial amino acid residues forms the catalytic domain. These excellent properties indicated that the protease has considerable potential as a bio-additive in the application of detergent formulations. (c) 2018 Society of Chemical Industry
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  • An ultrasensitive competitive immunosensor using silica nanoparticles as an enzyme carrier for simultaneous impedimetric detection of tetrabromobisphenol A bis(2-hydroxyethyl) ether and tetrabromobisphenol A mono(hydroxyethyl) ether.

    Zhang, Zhen   Dong, Shuaibing   Ge, Daohan   Zhu, Nuanfei   Wang, Kun   Zhu, Gangbing   Xu, Wanzhen   Xu, Hai  

    Based on our produced polyclonal antibody capable of recognizing tetrabromobisphenol A bis(2-hydroxyethyl) ether (TBBPA-DHEE) and tetrabromobisphenol A mono(hydroxyethyl) ether (TBBPA-MHEE) (cross-reactivity, 100% for TBBPA DHEE; 98.7% for TBBPA MHEE), an important derivative and byproduct of tetrabromobisphenol A (TBBPA), respectively, a novel ultrasensitive competitive immunosensor was established using an electrochemical impedimetric strategy for the simultaneous detection of both chemicals. A significantly amplified electrochemical impedance spectroscopy (EIS) for quantitative target analysis was obtained through (i) the biocatalytic precipitation of 4-chloro-1-naphthol (CN) on the electrode surface triggered by horseradish peroxidase (HRP) and (ii) increased amounts of the enzyme with HRP-loaded silica nanoparticles carrying poly-brushes (SiO2@PAA) as labels, achieving a remarkable improvement in catalytic performance. Under the optimized conditions, the immunosensor showed satisfactory accuracy (recovery, 84.6-118%) and a good linear range (0.21- 111.31ng/mL) with a limit of detection (LOD) of 0.08ng/mL (S/N =3D 3) for TBBPA DHEE and TBBPA MHEE. In addition, the proposed approach was used to analyse real environmental water samples, and our results indicated that this immunosensor had great potential for the determination of the trace pollutants in aquatic environments. Copyright =C2=A9 2018 Elsevier B.V. All rights reserved.
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  • Proteomics analysis of zebrafish brain following chronically exposed to bisphenol A

    Wu, Xiangyang   Lu, Chongwei   Dong, Xing   Zhang, Zhen   Yang, Ming   Xu, Hai  

    Bisphenol A, a plastic monomer and plasticizer, is a well-known endocrine disrupter, widely present in the aquatic environment, but little is known regarding its neurotoxicity in fish. Herein, we investigated its effects on male zebrafish brain. Zebrafish were exposed to 10 mu g/L BPA for 45 days. An isobaric tags for relative and absolute quantitation approach coupled with nano high-performance liquid chromatography-tandem mass spectrometry analysis was employed to detect and identify differentially expressed proteins. A total of 46 proteins was identified and categorized into functional classes that mostly included metabolism and transport, cytoplasm and organelle, ion and nucleotide binding, indicating that bisphenol A toxicity in fish brain is complex. The biological pathways of starch and sucrose metabolism, calcium signaling, and aminoacyl-tRNA biosynthesis were also induced. Proteomic analyses add new perspectives to bisphenol A neurotoxicity in aquatic organisms.
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  • Tuning of peptide assembly through force balance adjustment.

    Cao, Meiwen   Cao, Changhai   Zhang, Lijuan   Xia, Daohong   Xu, Hai  

    Controlled self-assembly of amphiphilic tripeptides into distinct nanostructures is achieved via a controlled design of the molecular architecture. The tripeptide Ac-Phe-Phe-Lys-CONH2 (FFK), hardly soluble in water, forms long amyloid-like tubular structures with the aid of beta-sheet hydrogen bonding and aromatic pi-pi stacking. Substitution of phenylalanine (F) with tyrosine (Y), that is, only a subtle structural variation in adding a hydroxyl group to the phenyl ring, results in great change in molecular self-assembly behavior. When one F is substituted with Y, the resulting molecules of FYK and YFK self-assemble into long thinner fibrils with high propensity for lateral association. When both Fs are substituted with Y, the resulting YYK molecule forms spherical aggregates. Introduction of hydroxyl groups into the molecule modifies aromatic interactions and introduces hydrogen bonding. Moreover, since the driving forces for peptide self-assembly including hydrogen bonding, electrostatic repulsion, and pi-pi stacking have high interdependence with each other, changes in aromatic interaction induce a Domino effect and cause a shift of force balance to a new state. This leads to significant variations in self-assembly behavior. Copyright 2013 Elsevier Inc. All rights reserved.
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