The Experts below are selected from a list of 11712 Experts worldwide ranked by ideXlab platform
Liangguo Yan - One of the best experts on this subject based on the ideXlab platform.
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edta modified β cyclodextrin chitosan for rapid removal of pb ii and acid red from aqueous solution
Journal of Colloid and Interface Science, 2018Co-Authors: Yaoguang Wang, Qin Wei, Liangguo Yan, Tao YanAbstract:Abstract EDTA modified β-cyclodextrin/chitosan (CDCS-EDTA) was fabricated successfully by a two-step method and applied to remove Pb(II) and anionic dye acid red 73 (AR). CDCS-EDTA was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and zeta potential analysis. The effects of experimental parameters including adsorbent dose, contact time and pH value on the adsorption efficiency of CDCS-EDTA for the pollutants were investigated. The maximum adsorption capacities were 114.8 mg g−1 for Pb(II) and 754.6 mg g−1 for AR under the optimal conditions. 93.4% of Pb(II) and 92.1% of AR could be adsorbed within 5 min, and the adsorptions reached equilibrium rapidly within 20 min and 10 min for Pb(II) and AR, respectively. A possible adsorption mechanism had been proposed that chelation of EDTA and Electrostatic Attraction of hydroxyl and amino groups dominated the adsorption of Pb(II), while the adsorption of AR mainly by the formation of inclusion complex with cyclodextrin cavities and Electrostatic Attraction with functional groups. For these two pollutants, the adsorption kinetic and isotherm data fitted well with the pseudo-second-order model and the Langmuir model, respectively. Thermodynamic studies implied that the adsorption process of Pb(II) and AR were spontaneous. Furthermore, the excellent regeneration performance indicated that CDCS-EDTA has a promising application in water treatment.
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fabrication of hyperbranched polyamine functionalized graphene for high efficiency removal of pb ii and methylene blue
Chemical Engineering Journal, 2016Co-Authors: Zhongping Yang, Limei Cui, Huu Hao Ngo, Yaoguang Wang, Qin Wei, Liangguo YanAbstract:Abstract Multifunctional hyperbranched polyamine modified graphene oxide (HPA-GO) was successfully prepared and characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), zeta potential and scanning electron microscope (SEM) analyses. HPA-GO exhibited excellent adsorption performance for the removal of a heavy metal (Pb(II)) and a dye (methylene blue (MB)). The equilibrium adsorption capacity was 819.7 mg g −1 for Pb(II) and 740.7 mg g −1 for MB under the optimal conditions. The pseudo-second order equation and the Langmuir model exhibited good correlation with the adsorption kinetic and isotherm data, respectively, for these two pollutants. The thermodynamic results (Δ G H > 0, Δ S > 0) implied that the adsorption process of Pb(II) and MB was feasible, endothermic and spontaneous in nature. A possible adsorption mechanism has been proposed where chelation and Electrostatic Attraction dominated the adsorption of Pb(II) and π–π stacking interactions and Electrostatic Attraction dominated the adsorption of MB. In addition, the excellent reproducibility endowed HPA-GO with the potential for application in water treatment.
Gideon Schreiber - One of the best experts on this subject based on the ideXlab platform.
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regular articleexperimental assignment of the structure of the transition state for the association of barnase and barstar1
Journal of Molecular Biology, 2001Co-Authors: Christian Frisch, Alan R Fersht, Gideon SchreiberAbstract:Association of a protein complex follows a two step reaction mechanism, with the first step being the formation of an encounter complex which evolves into the final complex. Here we present new experimental data for the association of the bacterial ribonuclease barnase and its polypeptide inhibitor barstar which shed light on the thermodynamics and structure of the transition state and preceding encounter complex of association at diminishing Electrostatic Attraction. We show that the activation entropy at the transition state is close to zero, with the activation enthalpy being equal to the free energy of binding. This observation was independent of the magnitude of the mutual Electrostatic Attraction, which were altered by mutagenesis or by addition of salt. The low activation entropy implies that the transition state is mostly solvated at all ionic strengths. The structure of the transition state was probed by measuring pairwise interaction energies using double-mutant-cycles. While at low ionic strength all proximal charge-pairs form contacts, at high salt only a subset of these interactions are maintained. More specifically, charge-charge interactions between partially buried residues are lost, while exposed charged residues maintain their ability to form specific interactions even at the highest salt concentration. Uncharged residues do not interact at any ionic strength. The results presented here suggest that the barnase-barstar binding sites are correctly aligned during the transition state even at diminishing Electrostatic Attraction, although specific short range interactions of uncharged residues are not yet formed. Furthermore, most of the interface desolvation (which contributes to the entropy of the system) has not yet occurred. This picture seems to be valid at low and high salt. However, at high salt, interactions of the activated complex are limited to a more restricted set of residues which are easier approached during diffusion, prior to final docking. This suggest that the steering region at high salt is more limited, albeit maintaining its specificity.
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experimental assignment of the structure of the transition state for the association of barnase and barstar
Journal of Molecular Biology, 2001Co-Authors: Christian Frisch, Alan R Fersht, Gideon SchreiberAbstract:Abstract Association of a protein complex follows a two step reaction mechanism, with the first step being the formation of an encounter complex which evolves into the final complex. Here we present new experimental data for the association of the bacterial ribonuclease barnase and its polypeptide inhibitor barstar which shed light on the thermodynamics and structure of the transition state and preceding encounter complex of association at diminishing Electrostatic Attraction. We show that the activation entropy at the transition state is close to zero, with the activation enthalpy being equal to the free energy of binding. This observation was independent of the magnitude of the mutual Electrostatic Attraction, which were altered by mutagenesis or by addition of salt. The low activation entropy implies that the transition state is mostly solvated at all ionic strengths. The structure of the transition state was probed by measuring pairwise interaction energies using double-mutant-cycles. While at low ionic strength all proximal charge-pairs form contacts, at high salt only a subset of these interactions are maintained. More specifically, charge-charge interactions between partially buried residues are lost, while exposed charged residues maintain their ability to form specific interactions even at the highest salt concentration. Uncharged residues do not interact at any ionic strength. The results presented here suggest that the barnase-barstar binding sites are correctly aligned during the transition state even at diminishing Electrostatic Attraction, although specific short range interactions of uncharged residues are not yet formed. Furthermore, most of the interface desolvation (which contributes to the entropy of the system) has not yet occurred. This picture seems to be valid at low and high salt. However, at high salt, interactions of the activated complex are limited to a more restricted set of residues which are easier approached during diffusion, prior to final docking. This suggest that the steering region at high salt is more limited, albeit maintaining its specificity.
Toshikazu Nosaka - One of the best experts on this subject based on the ideXlab platform.
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nanotweezers consisting of carbon nanotubes operating in an atomic force microscope
Applied Physics Letters, 2001Co-Authors: Seiji Akita, Yoshikazu Nakayama, Syotaro Mizooka, Yuichi Takano, Takashi Okawa, Yu Miyatake, Sigenori Yamanaka, Masashi Tsuji, Toshikazu NosakaAbstract:We have developed nanotweezers consisting of carbon nanotubes that will operate in an atomic force microscope. The two nanotubes were attached on the metal electrodes patterned on a conventional Si tip and their fixations were made by carbon deposition. These processes were made under the view of a scanning electron microscope. The application of a dc voltage to the two nanotube arms induces their movement to approach each other. The numerical simulation by taking into account the balance between the Electrostatic Attraction and the bending moment of the nanotubes well explains the motion of the nanotube arms.
Yaoguang Wang - One of the best experts on this subject based on the ideXlab platform.
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edta modified β cyclodextrin chitosan for rapid removal of pb ii and acid red from aqueous solution
Journal of Colloid and Interface Science, 2018Co-Authors: Yaoguang Wang, Qin Wei, Liangguo Yan, Tao YanAbstract:Abstract EDTA modified β-cyclodextrin/chitosan (CDCS-EDTA) was fabricated successfully by a two-step method and applied to remove Pb(II) and anionic dye acid red 73 (AR). CDCS-EDTA was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and zeta potential analysis. The effects of experimental parameters including adsorbent dose, contact time and pH value on the adsorption efficiency of CDCS-EDTA for the pollutants were investigated. The maximum adsorption capacities were 114.8 mg g−1 for Pb(II) and 754.6 mg g−1 for AR under the optimal conditions. 93.4% of Pb(II) and 92.1% of AR could be adsorbed within 5 min, and the adsorptions reached equilibrium rapidly within 20 min and 10 min for Pb(II) and AR, respectively. A possible adsorption mechanism had been proposed that chelation of EDTA and Electrostatic Attraction of hydroxyl and amino groups dominated the adsorption of Pb(II), while the adsorption of AR mainly by the formation of inclusion complex with cyclodextrin cavities and Electrostatic Attraction with functional groups. For these two pollutants, the adsorption kinetic and isotherm data fitted well with the pseudo-second-order model and the Langmuir model, respectively. Thermodynamic studies implied that the adsorption process of Pb(II) and AR were spontaneous. Furthermore, the excellent regeneration performance indicated that CDCS-EDTA has a promising application in water treatment.
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fabrication of hyperbranched polyamine functionalized graphene for high efficiency removal of pb ii and methylene blue
Chemical Engineering Journal, 2016Co-Authors: Zhongping Yang, Limei Cui, Huu Hao Ngo, Yaoguang Wang, Qin Wei, Liangguo YanAbstract:Abstract Multifunctional hyperbranched polyamine modified graphene oxide (HPA-GO) was successfully prepared and characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), zeta potential and scanning electron microscope (SEM) analyses. HPA-GO exhibited excellent adsorption performance for the removal of a heavy metal (Pb(II)) and a dye (methylene blue (MB)). The equilibrium adsorption capacity was 819.7 mg g −1 for Pb(II) and 740.7 mg g −1 for MB under the optimal conditions. The pseudo-second order equation and the Langmuir model exhibited good correlation with the adsorption kinetic and isotherm data, respectively, for these two pollutants. The thermodynamic results (Δ G H > 0, Δ S > 0) implied that the adsorption process of Pb(II) and MB was feasible, endothermic and spontaneous in nature. A possible adsorption mechanism has been proposed where chelation and Electrostatic Attraction dominated the adsorption of Pb(II) and π–π stacking interactions and Electrostatic Attraction dominated the adsorption of MB. In addition, the excellent reproducibility endowed HPA-GO with the potential for application in water treatment.
Qin Wei - One of the best experts on this subject based on the ideXlab platform.
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edta modified β cyclodextrin chitosan for rapid removal of pb ii and acid red from aqueous solution
Journal of Colloid and Interface Science, 2018Co-Authors: Yaoguang Wang, Qin Wei, Liangguo Yan, Tao YanAbstract:Abstract EDTA modified β-cyclodextrin/chitosan (CDCS-EDTA) was fabricated successfully by a two-step method and applied to remove Pb(II) and anionic dye acid red 73 (AR). CDCS-EDTA was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and zeta potential analysis. The effects of experimental parameters including adsorbent dose, contact time and pH value on the adsorption efficiency of CDCS-EDTA for the pollutants were investigated. The maximum adsorption capacities were 114.8 mg g−1 for Pb(II) and 754.6 mg g−1 for AR under the optimal conditions. 93.4% of Pb(II) and 92.1% of AR could be adsorbed within 5 min, and the adsorptions reached equilibrium rapidly within 20 min and 10 min for Pb(II) and AR, respectively. A possible adsorption mechanism had been proposed that chelation of EDTA and Electrostatic Attraction of hydroxyl and amino groups dominated the adsorption of Pb(II), while the adsorption of AR mainly by the formation of inclusion complex with cyclodextrin cavities and Electrostatic Attraction with functional groups. For these two pollutants, the adsorption kinetic and isotherm data fitted well with the pseudo-second-order model and the Langmuir model, respectively. Thermodynamic studies implied that the adsorption process of Pb(II) and AR were spontaneous. Furthermore, the excellent regeneration performance indicated that CDCS-EDTA has a promising application in water treatment.
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fabrication of hyperbranched polyamine functionalized graphene for high efficiency removal of pb ii and methylene blue
Chemical Engineering Journal, 2016Co-Authors: Zhongping Yang, Limei Cui, Huu Hao Ngo, Yaoguang Wang, Qin Wei, Liangguo YanAbstract:Abstract Multifunctional hyperbranched polyamine modified graphene oxide (HPA-GO) was successfully prepared and characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), zeta potential and scanning electron microscope (SEM) analyses. HPA-GO exhibited excellent adsorption performance for the removal of a heavy metal (Pb(II)) and a dye (methylene blue (MB)). The equilibrium adsorption capacity was 819.7 mg g −1 for Pb(II) and 740.7 mg g −1 for MB under the optimal conditions. The pseudo-second order equation and the Langmuir model exhibited good correlation with the adsorption kinetic and isotherm data, respectively, for these two pollutants. The thermodynamic results (Δ G H > 0, Δ S > 0) implied that the adsorption process of Pb(II) and MB was feasible, endothermic and spontaneous in nature. A possible adsorption mechanism has been proposed where chelation and Electrostatic Attraction dominated the adsorption of Pb(II) and π–π stacking interactions and Electrostatic Attraction dominated the adsorption of MB. In addition, the excellent reproducibility endowed HPA-GO with the potential for application in water treatment.