The Experts below are selected from a list of 16023 Experts worldwide ranked by ideXlab platform
Christopher J Mundy - One of the best experts on this subject based on the ideXlab platform.
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visualization of aluminum ions at the mica water interface links hydrolysis state to surface potential and Particle Adhesion
Journal of the American Chemical Society, 2020Co-Authors: Benjamin A Legg, Marcel D Baer, Jaehun Chun, Gregory K Schenter, Shifeng Huang, Yuanzhong Zhang, Christopher J MundyAbstract:When hydrolyzable cations such as aluminum interact with solid–water interfaces, macroscopic interfacial properties (e.g., surface charge and potential) and interfacial phenomena (e.g., Particle Adhesion) become tightly linked with the microscopic details of ion adsorption and speciation. We use in situ atomic force microscopy to directly image individual aluminum ions at a mica–water interface and show how adsorbate populations change with pH and aluminum activity. Complementary streaming potential measurements then allow us to build a triple layer model (TLM) that links surface potentials to adsorbate populations, via equilibrium binding constants. Our model predicts that hydrolyzed species dominate the mica–water interface, even when unhydrolyzed species dominate the solution. Ab initio molecular dynamics (AIMD) simulations confirm that aluminum hydrolysis is strongly promoted at the interface. The TLM indicates that hydrolyzed adsorbates are responsible for surface-potential inversions, and we find strong correlations between hydrolyzed adsorbates and Particle-Adhesion forces, suggesting that these species mediate Adhesion by chemical bridging.
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visualization of aluminum ions at the mica water interface links hydrolysis state to surface potential and Particle Adhesion
Journal of the American Chemical Society, 2020Co-Authors: Benjamin A Legg, Marcel D Baer, Jaehun Chun, Gregory K Schenter, Shifeng Huang, Yuanzhong Zhang, Christopher J MundyAbstract:When hydrolyzable cations such as aluminum interact with solid–water interfaces, macroscopic interfacial properties (e.g., surface charge and potential) and interfacial phenomena (e.g., Particle ad...
Richard A Firtel - One of the best experts on this subject based on the ideXlab platform.
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requirement of a vasodilator stimulated phosphoprotein family member for cell Adhesion the formation of filopodia and chemotaxis in dictyostelium
Journal of Biological Chemistry, 2002Co-Authors: Chang Y Chung, Deborah Wessels, Stephen Stephens, Margaret A. Titus, David R Soll, Richard A FirtelAbstract:Abstract We have examined the function of a member of the vasodilator-stimulated phosphoprotein family of proteins (DdVASP) inDictyostelium. Ddvasp null cells lack filopodia, whereas targeting DdVASP to the plasma membrane with a myristoyl tag results in a significant increase in filopodia. The proline-rich domain-Ena/VASP homology 2 structure is required for both actin polymerization activity and filopodia formation.Ddvasp null cells exhibit a chemotaxis defect, which appears to be due to a defect in the ability of the cells to properly adhere to the substratum and to suppress lateral pseudopod extension. We demonstrate that during chemotaxis, the anterior ∼50% of the cell lifts from the substratum and remains elevated for up to 1 min. These defects lead to a significant decrease in chemotaxis efficiency. DdVASP localizes to the leading edge in migrating cells and to the tips of filopodia. In addition, Ddvasp null cells have a defect in Particle Adhesion but internalize Particles normally. Our results provide new insights into the function of DdVASP in controlling the actin cytoskeleton during chemotaxis and filopodia formation.
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requirement of a vasodilator stimulated phosphoprotein family member for cell Adhesion the formation of filopodia and chemotaxis in dictyostelium
Journal of Biological Chemistry, 2002Co-Authors: Young-hoon Han, Deborah Wessels, Stephen Stephens, Margaret A. Titus, Chang Y Chung, David R Soll, Richard A FirtelAbstract:We have examined the function of a member of the vasodilator-stimulated phosphoprotein family of proteins (DdVASP) in Dictyostelium. Ddvasp null cells lack filopodia, whereas targeting DdVASP to the plasma membrane with a myristoyl tag results in a significant increase in filopodia. The proline-rich domain-Ena/VASP homology 2 structure is required for both actin polymerization activity and filopodia formation. Ddvasp null cells exhibit a chemotaxis defect, which appears to be due to a defect in the ability of the cells to properly adhere to the substratum and to suppress lateral pseudopod extension. We demonstrate that during chemotaxis, the anterior approximately 50% of the cell lifts from the substratum and remains elevated for up to 1 min. These defects lead to a significant decrease in chemotaxis efficiency. DdVASP localizes to the leading edge in migrating cells and to the tips of filopodia. In addition, Ddvasp null cells have a defect in Particle Adhesion but internalize Particles normally. Our results provide new insights into the function of DdVASP in controlling the actin cytoskeleton during chemotaxis and filopodia formation.
Benjamin A Legg - One of the best experts on this subject based on the ideXlab platform.
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visualization of aluminum ions at the mica water interface links hydrolysis state to surface potential and Particle Adhesion
Journal of the American Chemical Society, 2020Co-Authors: Benjamin A Legg, Marcel D Baer, Jaehun Chun, Gregory K Schenter, Shifeng Huang, Yuanzhong Zhang, Christopher J MundyAbstract:When hydrolyzable cations such as aluminum interact with solid–water interfaces, macroscopic interfacial properties (e.g., surface charge and potential) and interfacial phenomena (e.g., Particle Adhesion) become tightly linked with the microscopic details of ion adsorption and speciation. We use in situ atomic force microscopy to directly image individual aluminum ions at a mica–water interface and show how adsorbate populations change with pH and aluminum activity. Complementary streaming potential measurements then allow us to build a triple layer model (TLM) that links surface potentials to adsorbate populations, via equilibrium binding constants. Our model predicts that hydrolyzed species dominate the mica–water interface, even when unhydrolyzed species dominate the solution. Ab initio molecular dynamics (AIMD) simulations confirm that aluminum hydrolysis is strongly promoted at the interface. The TLM indicates that hydrolyzed adsorbates are responsible for surface-potential inversions, and we find strong correlations between hydrolyzed adsorbates and Particle-Adhesion forces, suggesting that these species mediate Adhesion by chemical bridging.
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visualization of aluminum ions at the mica water interface links hydrolysis state to surface potential and Particle Adhesion
Journal of the American Chemical Society, 2020Co-Authors: Benjamin A Legg, Marcel D Baer, Jaehun Chun, Gregory K Schenter, Shifeng Huang, Yuanzhong Zhang, Christopher J MundyAbstract:When hydrolyzable cations such as aluminum interact with solid–water interfaces, macroscopic interfacial properties (e.g., surface charge and potential) and interfacial phenomena (e.g., Particle ad...
Maria M. Santore - One of the best experts on this subject based on the ideXlab platform.
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the impact of nanoscale chemical features on micron scale Adhesion crossover from heterogeneity dominated to mean field behavior
Journal of Colloid and Interface Science, 2009Co-Authors: Ranojoy Duffadar, Surachate Kalasin, Jeffrey M Davis, Maria M. SantoreAbstract:Abstract This work explores the impact of nanoscale surface heterogeneity, small relative to the effective contact area between two surfaces, on pairwise colloid-scale interactions. Polycation-based positive patches, of order 10 nm in diameter, arranged randomly and lying flat on otherwise negative substrates, were used to create surfaces whose competing attractive and repulsive features determined the net interactions with opposing surfaces. Lab experiments and simulations of the Adhesion of gently flowing dilute negative microParticles varied Particle size (0.5–2 μm), ionic strength (κ−1 = 1–12 nm) and the density of heterogeneity on the collectors. Limiting behaviors from heterogeneity-controlled at high ionic strength to mean-field-like interactions at low ionic strength are reported. When heterogeneities are important, pairwise interactions are more attractive than predicted by average surface properties (e.g. per DLVO), and an Adhesion threshold, describing the minimum average density of cationic features needed for single Particle capture (Adhesion), depends strongly on Debye length. In the opposite limit, the threshold becomes insensitive to the Debye length, and the average surface character approximates the interactions. An analytical treatment, reduced to a simple scaling argument predicts a −1/2 power-law dependence of the Adhesion threshold on Debye length and Particle size. A slightly stronger Particle size dependence in experiments and simulations results from hydrodynamic contributions along with slight scaling differences in electrostatic, van der Waals, and hydrodynamic forces. An analogy to biological ligands is made for the heterogeneity-dominated limit: it is discovered, for this particular system, that engagement of as few as 20–100 cationic patches dictates Particle Adhesion (with details depending on flow, Particle size, and ionic strength), similar to reports for selectin-mediated rolling of white blood cells during the inflammatory pathway. Also discovered is a heterogeneity-dependent crossover in the effect of ionic strength on Particle capture, where added salt promotes Particle Adhesion in most cases but stabilizes the Particles when the heterogeneity becomes relatively dense.
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micrometer scale Adhesion on nanometer scale patchy surfaces Adhesion rates Adhesion thresholds and curvature based selectivity
Langmuir, 2007Co-Authors: Maria M. Santore, Natalia KozlovaAbstract:Using a model system based on electrostatics, we probe interactions between spherical Particles (negative silica) and planar surfaces that present randomly placed discrete attractive regions, 10 nm in size, in a repulsive background (silica flats carrying cationic surface constructs). Experiments measure the Adhesion rates of Particles onto the patchy collecting surfaces from flowing dispersions, as a function of the surface loading of the attractive patches, for different Particle sizes (0.5 and 1 μm diameter spheres) and different ionic strengths. Surfaces densely populated with patches, such that they present net electrostatic attractions to approaching Particles, capture Particles at the transport-limited (maximum) rate. Surfaces sparsely loaded with attractive patches (which present a repulsive mean field to approaching Particles) are usually still adhesive, but the Particle Adhesion rate depends on Particle size, ionic strength, and patch loading. Most significant is an Adhesion threshold, a critica...
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manipulation of micrometer scale Adhesion by tuning nanometer scale surface features
Langmuir, 2006Co-Authors: Natalia Kozlova, Maria M. SantoreAbstract:This article demonstrates how the Adhesion rates of micrometer-scale Particles on a planar surface can be manipulated by nanometer-scale features on the latter. Here, ∼500-nm-diameter spherical silica Particles carrying a substantial and relatively uniform negative charge experienced competing attractions and repulsions as they approached and attempted to adhere to a negative planar silica surface carrying flat 11-nm-diameter patches of concentrated positive charge. The average spacing of these patches profoundly influenced the Particle Adhesion. For dense positive patch spacing on the planar collector, the Particle Adhesion was rapid, and the fundamental Adhesion kinetics were masked by Particle transport to the interface. For patch densities corresponding to a planar surface with net zero charge, Particle Adhesion was still rapid. Adhesion kinetics were observably reduced for patch spacings exceeding 20 nm and become slower with increased patch spacing. Ultimately, above a critical or threshold average ...
Yuanzhong Zhang - One of the best experts on this subject based on the ideXlab platform.
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visualization of aluminum ions at the mica water interface links hydrolysis state to surface potential and Particle Adhesion
Journal of the American Chemical Society, 2020Co-Authors: Benjamin A Legg, Marcel D Baer, Jaehun Chun, Gregory K Schenter, Shifeng Huang, Yuanzhong Zhang, Christopher J MundyAbstract:When hydrolyzable cations such as aluminum interact with solid–water interfaces, macroscopic interfacial properties (e.g., surface charge and potential) and interfacial phenomena (e.g., Particle Adhesion) become tightly linked with the microscopic details of ion adsorption and speciation. We use in situ atomic force microscopy to directly image individual aluminum ions at a mica–water interface and show how adsorbate populations change with pH and aluminum activity. Complementary streaming potential measurements then allow us to build a triple layer model (TLM) that links surface potentials to adsorbate populations, via equilibrium binding constants. Our model predicts that hydrolyzed species dominate the mica–water interface, even when unhydrolyzed species dominate the solution. Ab initio molecular dynamics (AIMD) simulations confirm that aluminum hydrolysis is strongly promoted at the interface. The TLM indicates that hydrolyzed adsorbates are responsible for surface-potential inversions, and we find strong correlations between hydrolyzed adsorbates and Particle-Adhesion forces, suggesting that these species mediate Adhesion by chemical bridging.
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visualization of aluminum ions at the mica water interface links hydrolysis state to surface potential and Particle Adhesion
Journal of the American Chemical Society, 2020Co-Authors: Benjamin A Legg, Marcel D Baer, Jaehun Chun, Gregory K Schenter, Shifeng Huang, Yuanzhong Zhang, Christopher J MundyAbstract:When hydrolyzable cations such as aluminum interact with solid–water interfaces, macroscopic interfacial properties (e.g., surface charge and potential) and interfacial phenomena (e.g., Particle ad...