The Experts below are selected from a list of 28446 Experts worldwide ranked by ideXlab platform
Chuanxian Ding - One of the best experts on this subject based on the ideXlab platform.
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mechanism of apatite formation on wollastonite coatings in simulated body fluids
Biomaterials, 2004Co-Authors: Chuanxian DingAbstract:Abstract The formation mechanism of apatite on the Surface of wollastonite coating was examined. Plasma-sprayed wollastonite coatings were soaked in a lactic acid solution (pH=2.4) to result in the dissolution of calcium from the coating to form silanol (Si–OH) on the Surface. Some calcium-drained samples were soaked in a trimethanol aminomethane solution (pH=10) for 24 h to create a Negatively Charged Surface with the functional group (Si–O − ). These samples before and after treatment in a trimethanol aminomethane solution were immersed in simulated body fluids (SBF) to investigate the precipitation of apatite on the coating Surface. The results indicate that the increase of calcium in the SBF solution is not the critical factor affecting the precipitation of apatite on the Surface of the wollastonite coating and the apatite can only form on a Negatively Charged Surface with the functional group (Si–O − ). The mechanism of apatite formation on the wollastonite coating is proposed. After the wollastonite coatings are immersed into the SBF, calcium ions initially exchange with H + leading to the formation of silanol (Si–OH) on the Surface of the layer and increase in the pH value at the coating–SBF interface. Consequently, a Negatively Charged Surface with the functional group (Si–O − ) forms on the Surface. Due to the Negatively Charged Surface, Ca 2+ ions in the SBF solution are attracted to the interface between the coating and solution, thereby increasing the ionic activity of the apatite at the interface to the extent that apatite precipitates on the coating Surface.
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mechanism of apatite formation on wollastonite coatings in simulated body fluids
Biomaterials, 2004Co-Authors: Xuanyong Liu, Chuanxian Ding, Paul K ChuAbstract:The formation mechanism of apatite on the Surface of wollastonite coating was examined. Plasma-sprayed wollastonite coatings were soaked in a lactic acid solution (pH=2.4) to result in the dissolution of calcium from the coating to form silanol (triple bond Si-OH) on the Surface. Some calcium-drained samples were soaked in a trimethanol aminomethane solution (pH=10) for 24h to create a Negatively Charged Surface with the functional group (triple bond Si-O(-)). These samples before and after treatment in a trimethanol aminomethane solution were immersed in simulated body fluids (SBF) to investigate the precipitation of apatite on the coating Surface. The results indicate that the increase of calcium in the SBF solution is not the critical factor affecting the precipitation of apatite on the Surface of the wollastonite coating and the apatite can only form on a Negatively Charged Surface with the functional group (triple bond Si-O(-)). The mechanism of apatite formation on the wollastonite coating is proposed. After the wollastonite coatings are immersed into the SBF, calcium ions initially exchange with H(+) leading to the formation of silanol (triple bond Si-OH) on the Surface of the layer and increase in the pH value at the coating-SBF interface. Consequently, a Negatively Charged Surface with the functional group (triple bond Si-O(-)) forms on the Surface. Due to the Negatively Charged Surface, Ca(2+) ions in the SBF solution are attracted to the interface between the coating and solution, thereby increasing the ionic activity of the apatite at the interface to the extent that apatite precipitates on the coating Surface.
Jiři Skvarla - One of the best experts on this subject based on the ideXlab platform.
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accumulation of counterions and coions evaluated by cryogenic xps as a new tool for describing the structure of electric double layer at the silica water interface
Physical Chemistry Chemical Physics, 2017Co-Authors: Andrey Shchukarev, Maria Kaňuchova, I Brezani, Jiři SkvarlaAbstract:We introduce a new method of evaluating the structure of electric double layer (EDL) at the native solid/liquid interface using cryogenic X-ray photoelectron spectroscopy technique. This method is based on evaluating the atomic concentration ratio of counterions and co-ions of supporting electrolyte at the close-to-in situ state Surface of colloid particles by the cryo-XPS and comparing it with analogous ratio predicted by EDL models. For silica colloids in aqueous KCl solutions at pH 6 to 8 it has been found that the latter ratio is higher than unity, as expected for the Negatively Charged Surface of silica, but does not correspond with the prediction of the basic Gouy–Chapman EDL model for the ideal interface. However, it agrees with that deduced from experiments on electrolytic coagulation kinetics of analogous silica colloids by applying a simple EDL model of swellable ion-permeable (Donnanian) polyelectrolyte gel layer. It turns out that the traditional Stern layer-based concept of EDL at solid/liquid interfaces is not justified for metal oxides at least in KCl solutions.
Jian Zhou - One of the best experts on this subject based on the ideXlab platform.
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multiscale simulations of protein g b1 adsorbed on Charged self assembled monolayers
Langmuir, 2013Co-Authors: Jie Liu, Chenyi Liao, Jian ZhouAbstract:The orientation of an antibody plays an important role in the development of immunosensors. Protein G is an antibody binding protein, which specifically targets the Fc fragment of an antibody. In this work, the orientation of prototypical and mutated protein G B1 adsorbed on positively and Negatively Charged self-assembled monolayers was studied by parallel tempering Monte Carlo and all-atom molecular dynamics simulations. Both methods present generally similar orientation distributions of protein G B1 for each kind of Surface. The root-mean-square deviation, DSSP, gyration radius, eccentricity, dipole moment, and superimposed structures of protein G B1 were analyzed. Moreover, the orientation of binding antibody was also predicted in this work. Simulation results show that with the same orientation trends, the mutant exhibits narrower orientation distributions than does the prototype, which was mainly caused by the stronger dipole of the mutant. Both kinds of proteins adsorbed on Charged Surfaces were induced by the competition of electrostatic interaction and vdW interaction; the electrostatic interaction energy dominated the adsorption behavior. The protein adsorption was also largely affected by the distribution of Charged residues within the proteins. Thus, the prototype could adsorb on a Negatively Charged Surface, although it keeps a net charge of -4 e. The mutant has imperfect opposite orientation when it adsorbed on oppositely Charged Surfaces. For the mutant on a carboxyl-functionalized self-assembled monolayer (COOH-SAM), the orientation was the same as that inferred by experiments. While for the mutant on amine-functionalized self-assembled monolayer (NH2-SAM), the orientation was induced by the competition between attractive interactions (led by ASP40 and GLU56) and repulsive interactions (led by LYS10); thus, the perfect opposite orientation could not be obtained. On both Surfaces, the adsorbed protein could retain its native conformation. The desired orientation of protein G B1, which would increase the efficiency of binding antibodies, could be obtained on a Negatively Charged Surface adsorbed with the prototype. Further, we deduced that with the packing density of 12,076 protein G B1 domain per μm(2), the efficiency of the binding IgG would be maximized. The simulation results could be applied to control the orientation of protein G B1 in experiments and to provide a better understanding to maximize the efficiency of antibody binding.
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molecular simulation studies of the orientation and conformation of cytochrome c adsorbed on self assembled monolayers
Journal of Physical Chemistry B, 2004Co-Authors: Jian Zhou, Jie Zheng, Shaoyi JiangAbstract:Cytochrome c (Cyt-c) is an important membrane electron-transfer protein. To maximize its electron transfer, adsorbed Cyt-c should have a preferred orientation with its heme ring close and perpendicular to the Surface. Moreover, the adsorbed Cyt-c should keep its native conformation. In this work, the orientation and conformation of Cyt-c adsorbed on carboxyl-terminated self-assembled monolayers (SAMs) are investigated by a combined Monte Carlo and molecular dynamics simulation approach. The root-mean-square deviation, radius of gyration, eccentricity, dipole moment, heme orientation, and superimposed structures of Cyt-c were calculated. Simulation results show that the desired orientation of Cyt-c with its heme group perpendicular to the Surface could be obtained on a Negatively Charged Surface. The direction of the dipole of Cyt-c, contributed significantly by both lysine residues near the Surface and glutamic acid residues far away from the Surface, determines the final orientation of Cyt-c adsorbed on ...
Michael Kappl - One of the best experts on this subject based on the ideXlab platform.
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interaction of cationic hydrophobic surfactants at Negatively Charged Surfaces investigated by atomic force microscopy
Langmuir, 2009Co-Authors: Cathy E Mcnamee, Hansjurgen Butt, Ko Higashitani, Ivan U Vakarelski, Michael KapplAbstract:Atomic force microscopy was used to study the adsorption of the surfactant octadecyl trimethyl ammonium chloride (C18TAC) at a low concentration (0.03 mM) to Negatively Charged Surfaces in water. Atomic force microscopy tips were functionalized with dimethyloctadecyl(3-tripropyl)ammonium chloride (C18TAC-si) or N-trimethoxysilylpropyl-N,N,N-trimethylammomium chloride (hydrophilpos-si) to facilitate imaging of the adsorbed surfactant without artifacts. Tapping mode images and force measurements revealed C18TAC patches, identified as partial surfactant bilayers or hemimicelles. The forces controlling the adsorption process of the C18TAC to a Negatively Charged Surface were investigated by measuring the forces between a C18TAC-si or a hydrophilpos-si tip and a silica Surface in the presence of varying concentrations of either NaCl or NaNO3. Screening of forces with an increasing NaCl concentration was observed for the C18TAC-si and hydrophilpos-si tips, proving an electrostatic contribution. Screening was al...
Paul K Chu - One of the best experts on this subject based on the ideXlab platform.
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mechanism of apatite formation on wollastonite coatings in simulated body fluids
Biomaterials, 2004Co-Authors: Xuanyong Liu, Chuanxian Ding, Paul K ChuAbstract:The formation mechanism of apatite on the Surface of wollastonite coating was examined. Plasma-sprayed wollastonite coatings were soaked in a lactic acid solution (pH=2.4) to result in the dissolution of calcium from the coating to form silanol (triple bond Si-OH) on the Surface. Some calcium-drained samples were soaked in a trimethanol aminomethane solution (pH=10) for 24h to create a Negatively Charged Surface with the functional group (triple bond Si-O(-)). These samples before and after treatment in a trimethanol aminomethane solution were immersed in simulated body fluids (SBF) to investigate the precipitation of apatite on the coating Surface. The results indicate that the increase of calcium in the SBF solution is not the critical factor affecting the precipitation of apatite on the Surface of the wollastonite coating and the apatite can only form on a Negatively Charged Surface with the functional group (triple bond Si-O(-)). The mechanism of apatite formation on the wollastonite coating is proposed. After the wollastonite coatings are immersed into the SBF, calcium ions initially exchange with H(+) leading to the formation of silanol (triple bond Si-OH) on the Surface of the layer and increase in the pH value at the coating-SBF interface. Consequently, a Negatively Charged Surface with the functional group (triple bond Si-O(-)) forms on the Surface. Due to the Negatively Charged Surface, Ca(2+) ions in the SBF solution are attracted to the interface between the coating and solution, thereby increasing the ionic activity of the apatite at the interface to the extent that apatite precipitates on the coating Surface.
