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Timothy L Cover - One of the best experts on this subject based on the ideXlab platform.
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Acid Activation of helicobacter pylori vacuolating cytotoxin vaca results in toxin internalization by eukaryotic cells
Molecular Microbiology, 2000Co-Authors: Mark S Mcclain, Wayne P Schraw, Vittorio Ricci, Patrice Boquet, Timothy L CoverAbstract:Helicobacter pylori VacA is a secreted toxin that induces multiple structural and functional alterations in eukaryotic cells. Exposure of VacA to either Acidic or alkaline pH (‘Activation’) results in structural changes in the protein and a marked enhancement of its cell-vacuolating activity. However, the mechanism by which Activation leads to increased cytotoxicity is not well understood. In this study, we analysed the binding and internalization of [125I]-VacA by HeLa cells. We detected no difference in the binding of untreated and activated [125I]-VacA to cells. Binding of Acid-activated [125I]-VacA to cells at 4°C was not saturable, and was only partially inhibited by excess unlabelled toxin. These results suggest that VacA binds either non-specifically or to an abundant, low-affinity receptor on HeLa cells. To study internalization of VacA, we used a protease protection assay. Analysis by SDS–PAGE and autoradiography indicated that the intact 87 kDa toxin was internalized in a time-dependent process at 37°C but not at 4°C. Furthermore, internalization of the intact toxin was detected only if VacA was Acid or alkaline activated before being added to cells. The internalization of activated [125I]-VacA was not substantially inhibited by the presence of excess unlabelled toxin, but was blocked if cells were depleted of cellular ATP by the addition of sodium azide and 2-deoxy-d-glucose. These results indicate that Acid or alkaline pH-induced structural changes in VacA are required for VacA entry into cells, and that internalization of the intact 87 kDa toxin is required for VacA cytotoxicity.
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Acid Activation of helicobacter pylori vacuolating cytotoxin vaca results in toxin internalization by eukaryotic cells
Molecular Microbiology, 2000Co-Authors: Mark S Mcclain, Wayne P Schraw, Vittorio Ricci, Patrice Boquet, Timothy L CoverAbstract:Helicobacter pylori VacA is a secreted toxin that induces multiple structural and functional alterations in eukaryotic cells. Exposure of VacA to either Acidic or alkaline pH ('Activation') results in structural changes in the protein and a marked enhancement of its cell-vacuolating activity. However, the mechanism by which Activation leads to increased cytotoxicity is not well understood. In this study, we analysed the binding and internalization of [125I]-VacA by HeLa cells. We detected no difference in the binding of untreated and activated [125I]-VacA to cells. Binding of Acid-activated [125I]-VacA to cells at 4 degrees C was not saturable, and was only partially inhibited by excess unlabelled toxin. These results suggest that VacA binds either non-specifically or to an abundant, low-affinity receptor on HeLa cells. To study internalization of VacA, we used a protease protection assay. Analysis by SDS-PAGE and autoradiography indicated that the intact 87 kDa toxin was internalized in a time-dependent process at 37 degrees C but not at 4 degrees C. Furthermore, internalization of the intact toxin was detected only if VacA was Acid or alkaline activated before being added to cells. The internalization of activated [125I]-VacA was not substantially inhibited by the presence of excess unlabelled toxin, but was blocked if cells were depleted of cellular ATP by the addition of sodium azide and 2-deoxy-D-glucose. These results indicate that Acid or alkaline pH-induced structural changes in VacA are required for VacA entry into cells, and that internalization of the intact 87 kDa toxin is required for VacA cytotoxicity.
Mark S Mcclain - One of the best experts on this subject based on the ideXlab platform.
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Acid Activation of helicobacter pylori vacuolating cytotoxin vaca results in toxin internalization by eukaryotic cells
Molecular Microbiology, 2000Co-Authors: Mark S Mcclain, Wayne P Schraw, Vittorio Ricci, Patrice Boquet, Timothy L CoverAbstract:Helicobacter pylori VacA is a secreted toxin that induces multiple structural and functional alterations in eukaryotic cells. Exposure of VacA to either Acidic or alkaline pH (‘Activation’) results in structural changes in the protein and a marked enhancement of its cell-vacuolating activity. However, the mechanism by which Activation leads to increased cytotoxicity is not well understood. In this study, we analysed the binding and internalization of [125I]-VacA by HeLa cells. We detected no difference in the binding of untreated and activated [125I]-VacA to cells. Binding of Acid-activated [125I]-VacA to cells at 4°C was not saturable, and was only partially inhibited by excess unlabelled toxin. These results suggest that VacA binds either non-specifically or to an abundant, low-affinity receptor on HeLa cells. To study internalization of VacA, we used a protease protection assay. Analysis by SDS–PAGE and autoradiography indicated that the intact 87 kDa toxin was internalized in a time-dependent process at 37°C but not at 4°C. Furthermore, internalization of the intact toxin was detected only if VacA was Acid or alkaline activated before being added to cells. The internalization of activated [125I]-VacA was not substantially inhibited by the presence of excess unlabelled toxin, but was blocked if cells were depleted of cellular ATP by the addition of sodium azide and 2-deoxy-d-glucose. These results indicate that Acid or alkaline pH-induced structural changes in VacA are required for VacA entry into cells, and that internalization of the intact 87 kDa toxin is required for VacA cytotoxicity.
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Acid Activation of helicobacter pylori vacuolating cytotoxin vaca results in toxin internalization by eukaryotic cells
Molecular Microbiology, 2000Co-Authors: Mark S Mcclain, Wayne P Schraw, Vittorio Ricci, Patrice Boquet, Timothy L CoverAbstract:Helicobacter pylori VacA is a secreted toxin that induces multiple structural and functional alterations in eukaryotic cells. Exposure of VacA to either Acidic or alkaline pH ('Activation') results in structural changes in the protein and a marked enhancement of its cell-vacuolating activity. However, the mechanism by which Activation leads to increased cytotoxicity is not well understood. In this study, we analysed the binding and internalization of [125I]-VacA by HeLa cells. We detected no difference in the binding of untreated and activated [125I]-VacA to cells. Binding of Acid-activated [125I]-VacA to cells at 4 degrees C was not saturable, and was only partially inhibited by excess unlabelled toxin. These results suggest that VacA binds either non-specifically or to an abundant, low-affinity receptor on HeLa cells. To study internalization of VacA, we used a protease protection assay. Analysis by SDS-PAGE and autoradiography indicated that the intact 87 kDa toxin was internalized in a time-dependent process at 37 degrees C but not at 4 degrees C. Furthermore, internalization of the intact toxin was detected only if VacA was Acid or alkaline activated before being added to cells. The internalization of activated [125I]-VacA was not substantially inhibited by the presence of excess unlabelled toxin, but was blocked if cells were depleted of cellular ATP by the addition of sodium azide and 2-deoxy-D-glucose. These results indicate that Acid or alkaline pH-induced structural changes in VacA are required for VacA entry into cells, and that internalization of the intact 87 kDa toxin is required for VacA cytotoxicity.
Jianxiao Yang - One of the best experts on this subject based on the ideXlab platform.
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effects of the heating history of impregnated lignocellulosic material on pore development during phosphoric Acid Activation
Carbon, 2010Co-Authors: Jianxiao YangAbstract:Activated carbon samples have been prepared by heating China fir (Cunninghamia lanceolata) wood impregnated with phosphoric Acid in an effort to elucidate the effect of the heating history of impregnated material on the porous texture of the activated carbon. Analysis of the pore structure of the activated carbon in terms of nitrogen adsorption isotherms showed that both using an intermediate isothermal treatment and slowing the heating rate up to 300 °C favor pore development but have a detrimental effect above 300 °C. Therefore, it is recommended that a two-step heating program is applied for phosphoric Acid Activation.
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effects of the crystallinity of lignocellulosic material on the porosity of phosphoric Acid activated carbon
Carbon, 2009Co-Authors: Jianxiao YangAbstract:Activated carbons were prepared from three different lignocellulosic materials or in various lengths of impregnation time by phosphoric Acid Activation. The porous texture of activated carbon was analyzed in terms of the adsorption isotherm of nitrogen, and the crystallinity of lignocellulosic material was measured by X-ray diffraction method. The results showed that decreasing the crystallinity of lignocellulosic material promotes pore development, especially of mesopores. However, excessive impregnation is detrimental to Activation. Impregnation and the selection of parent lignocellulosic material have a similar effect on developing porosity during phosphoric Acid Activation.
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significance of the carbonization of volatile pyrolytic products on the properties of activated carbons from phosphoric Acid Activation of lignocellulosic material
Fuel Processing Technology, 2009Co-Authors: Jianxiao YangAbstract:Abstract Two series of activated carbons derived from China fir (Cunninghamia lanceolata) wood impregnated with phosphoric Acid were prepared in a cylindrical container that was kept in a closed state covered with a lid (the covered case) or in an open state. The effects of the carbonization of volatile pyrolytic products of starting materials on the properties of activated carbon were investigated in the process of phosphoric Acid Activation. Elemental analysis and SEM observation showed that both activating in the covered case and increasing the mass of starting material used favored the carbonization of volatile pyrolytic products. An investigation of N2 adsorption isotherms revealed that the carbonization of volatile pyrolytic products significantly enhanced mesopore development in the final carbons, especially pores with a size range from 2.5 to 30 nm, with little influence on micropores, and therefore produced a large increase in the adsorption capacity to Vitamin B12 (with a molecular size of 2.09 nm). Activated carbons with highly developed mesopores could be obtained in the covered case. The carbonization mechanism of volatiles was discussed and two different carbonization pathways (in solid and gas phases) were proposed during phosphoric Acid Activation.
Patrice Boquet - One of the best experts on this subject based on the ideXlab platform.
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Acid Activation of helicobacter pylori vacuolating cytotoxin vaca results in toxin internalization by eukaryotic cells
Molecular Microbiology, 2000Co-Authors: Mark S Mcclain, Wayne P Schraw, Vittorio Ricci, Patrice Boquet, Timothy L CoverAbstract:Helicobacter pylori VacA is a secreted toxin that induces multiple structural and functional alterations in eukaryotic cells. Exposure of VacA to either Acidic or alkaline pH (‘Activation’) results in structural changes in the protein and a marked enhancement of its cell-vacuolating activity. However, the mechanism by which Activation leads to increased cytotoxicity is not well understood. In this study, we analysed the binding and internalization of [125I]-VacA by HeLa cells. We detected no difference in the binding of untreated and activated [125I]-VacA to cells. Binding of Acid-activated [125I]-VacA to cells at 4°C was not saturable, and was only partially inhibited by excess unlabelled toxin. These results suggest that VacA binds either non-specifically or to an abundant, low-affinity receptor on HeLa cells. To study internalization of VacA, we used a protease protection assay. Analysis by SDS–PAGE and autoradiography indicated that the intact 87 kDa toxin was internalized in a time-dependent process at 37°C but not at 4°C. Furthermore, internalization of the intact toxin was detected only if VacA was Acid or alkaline activated before being added to cells. The internalization of activated [125I]-VacA was not substantially inhibited by the presence of excess unlabelled toxin, but was blocked if cells were depleted of cellular ATP by the addition of sodium azide and 2-deoxy-d-glucose. These results indicate that Acid or alkaline pH-induced structural changes in VacA are required for VacA entry into cells, and that internalization of the intact 87 kDa toxin is required for VacA cytotoxicity.
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Acid Activation of helicobacter pylori vacuolating cytotoxin vaca results in toxin internalization by eukaryotic cells
Molecular Microbiology, 2000Co-Authors: Mark S Mcclain, Wayne P Schraw, Vittorio Ricci, Patrice Boquet, Timothy L CoverAbstract:Helicobacter pylori VacA is a secreted toxin that induces multiple structural and functional alterations in eukaryotic cells. Exposure of VacA to either Acidic or alkaline pH ('Activation') results in structural changes in the protein and a marked enhancement of its cell-vacuolating activity. However, the mechanism by which Activation leads to increased cytotoxicity is not well understood. In this study, we analysed the binding and internalization of [125I]-VacA by HeLa cells. We detected no difference in the binding of untreated and activated [125I]-VacA to cells. Binding of Acid-activated [125I]-VacA to cells at 4 degrees C was not saturable, and was only partially inhibited by excess unlabelled toxin. These results suggest that VacA binds either non-specifically or to an abundant, low-affinity receptor on HeLa cells. To study internalization of VacA, we used a protease protection assay. Analysis by SDS-PAGE and autoradiography indicated that the intact 87 kDa toxin was internalized in a time-dependent process at 37 degrees C but not at 4 degrees C. Furthermore, internalization of the intact toxin was detected only if VacA was Acid or alkaline activated before being added to cells. The internalization of activated [125I]-VacA was not substantially inhibited by the presence of excess unlabelled toxin, but was blocked if cells were depleted of cellular ATP by the addition of sodium azide and 2-deoxy-D-glucose. These results indicate that Acid or alkaline pH-induced structural changes in VacA are required for VacA entry into cells, and that internalization of the intact 87 kDa toxin is required for VacA cytotoxicity.
Vittorio Ricci - One of the best experts on this subject based on the ideXlab platform.
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Acid Activation of helicobacter pylori vacuolating cytotoxin vaca results in toxin internalization by eukaryotic cells
Molecular Microbiology, 2000Co-Authors: Mark S Mcclain, Wayne P Schraw, Vittorio Ricci, Patrice Boquet, Timothy L CoverAbstract:Helicobacter pylori VacA is a secreted toxin that induces multiple structural and functional alterations in eukaryotic cells. Exposure of VacA to either Acidic or alkaline pH (‘Activation’) results in structural changes in the protein and a marked enhancement of its cell-vacuolating activity. However, the mechanism by which Activation leads to increased cytotoxicity is not well understood. In this study, we analysed the binding and internalization of [125I]-VacA by HeLa cells. We detected no difference in the binding of untreated and activated [125I]-VacA to cells. Binding of Acid-activated [125I]-VacA to cells at 4°C was not saturable, and was only partially inhibited by excess unlabelled toxin. These results suggest that VacA binds either non-specifically or to an abundant, low-affinity receptor on HeLa cells. To study internalization of VacA, we used a protease protection assay. Analysis by SDS–PAGE and autoradiography indicated that the intact 87 kDa toxin was internalized in a time-dependent process at 37°C but not at 4°C. Furthermore, internalization of the intact toxin was detected only if VacA was Acid or alkaline activated before being added to cells. The internalization of activated [125I]-VacA was not substantially inhibited by the presence of excess unlabelled toxin, but was blocked if cells were depleted of cellular ATP by the addition of sodium azide and 2-deoxy-d-glucose. These results indicate that Acid or alkaline pH-induced structural changes in VacA are required for VacA entry into cells, and that internalization of the intact 87 kDa toxin is required for VacA cytotoxicity.
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Acid Activation of helicobacter pylori vacuolating cytotoxin vaca results in toxin internalization by eukaryotic cells
Molecular Microbiology, 2000Co-Authors: Mark S Mcclain, Wayne P Schraw, Vittorio Ricci, Patrice Boquet, Timothy L CoverAbstract:Helicobacter pylori VacA is a secreted toxin that induces multiple structural and functional alterations in eukaryotic cells. Exposure of VacA to either Acidic or alkaline pH ('Activation') results in structural changes in the protein and a marked enhancement of its cell-vacuolating activity. However, the mechanism by which Activation leads to increased cytotoxicity is not well understood. In this study, we analysed the binding and internalization of [125I]-VacA by HeLa cells. We detected no difference in the binding of untreated and activated [125I]-VacA to cells. Binding of Acid-activated [125I]-VacA to cells at 4 degrees C was not saturable, and was only partially inhibited by excess unlabelled toxin. These results suggest that VacA binds either non-specifically or to an abundant, low-affinity receptor on HeLa cells. To study internalization of VacA, we used a protease protection assay. Analysis by SDS-PAGE and autoradiography indicated that the intact 87 kDa toxin was internalized in a time-dependent process at 37 degrees C but not at 4 degrees C. Furthermore, internalization of the intact toxin was detected only if VacA was Acid or alkaline activated before being added to cells. The internalization of activated [125I]-VacA was not substantially inhibited by the presence of excess unlabelled toxin, but was blocked if cells were depleted of cellular ATP by the addition of sodium azide and 2-deoxy-D-glucose. These results indicate that Acid or alkaline pH-induced structural changes in VacA are required for VacA entry into cells, and that internalization of the intact 87 kDa toxin is required for VacA cytotoxicity.
