The Experts below are selected from a list of 4255539 Experts worldwide ranked by ideXlab platform
Johan Stenflo - One of the best experts on this subject based on the ideXlab platform.
-
Calcium-dependent interaction between gamma-carboxyglutamic acid-containing and N-terminal epidermal growth factor-like modules in factor X.
Journal of Biological Chemistry, 1994Co-Authors: Carmen Valcarce, A Holmgren, Johan StenfloAbstract:Abstract The N-terminal epidermal growth factor (EGF)-like module in factor X binds a single Ca2+ with low affinity (Kd = 2.2 mM). When it is linked to the gamma-carboxyglutamic acid (Gla)-containing module, however, the affinity increases approximately 20-fold (Kd = 120 microM), indicating an interaction between the two modules and making the site in the N-terminal EGF-like module essentially saturated at physiological Ca2+ concentrations. We have now used the thioredoxin system to probe Ca(2+)-induced conformational changes and interaction between modules in the light chain of factor X. Thioredoxin, in conjunction with thioredoxin reductase and NADPH, allows direct measurements of the rate and extent of disulfide bond reduction. Most disulfide bonds accessible to the reducing agent were found to be located in the light chain of the protein. Moreover, those disulfide bonds that were resistant to reduction by thioredoxin in the presence of Ca2+, but were readily reduced in the absence of the metal ion, were located in the N-terminal EGF-like module and in the Gla module, whereas disulfide bonds in the C-terminal EGF-like module appeared to be equally accessible whether Ca2+ was present or not. Comparison of the rate of disulfide bond reduction in the isolated modules with that in mixtures of modules indicated that a Ca(2+)-dependent interaction occurred between the Gla and the N-terminal EGF-like module. This interaction was mediated by the C-terminal alpha-helical part of the Gla module. The affinity between the modules was low and could not be determined accurately owing to competing equilibria, presumably Ca(2+)-dependent aggregation of the isolated Gla module. By comparing the rates of disulfide bond reduction in Gla module-containing fragments before and after decarboxylation of Gla, we could demonstrate that Ca2+ binding to sites in the Gla module as well as to the single site in the EGF-like module contribute to the interaction between the two modules.
-
The gamma-carboxyglutamic acid and epidermal growth factor-like modules of factor IXa beta. Effects on the serine protease module and factor X activation
Journal of Biological Chemistry, 1994Co-Authors: Jan Astermark, Philip J. Hogg, Johan StenfloAbstract:Blood coagulation factors IX and X are two serine proteases with a similar modular structure. The non-catalytic part of each protein consists of a gamma-carboxyglutamic acid (Gla)-containing module and two modules homologous to the epidermal growth factor (EGF) precursor. We have now found that the NH2-terminal EGF-like module of both factors IX and X inhibits factor Xa formation in a Gla-independent manner, both in the presence and absence of phospholipid and the cofactor, factor VIIIa. In contrast, the COOH-terminal EGF-like module has no such effect. Our data indicate that the NH2-terminal EGF-like module of factor IXa beta interacts either with the corresponding module or with the serine protease module in the substrate, factor X, without affecting the hydrolysis of low molecular weight substrates. Using antibodies as structural probes, we found that Ca2+ binding to the Gla module of factor IXa beta induces a conformational transition in the serine protease module. No evidence was found for a direct interaction between the Gla module and factor VIIIa. We therefore propose that the Gla module in factor IXa beta is indirectly involved in the cofactor interaction, in that Ca2+ binding to sites in this module induces a conformation in the serine protease module that is commensurate with factor VIIIa interaction. In addition, the immunochemical approach revealed a Gla-independent Ca2+ binding site in the serine protease module (apparent Kd of approximately 120 microM) that also might influence its conformation. Antibodies against the EGF-like modules of factor IX were used to probe Ca2+ binding to these modules in intact and in Gla-domainless factor IXa beta. The data indicate a Ca2+ binding site with an apparent Kd of approximately 50 microM in the NH2-terminal EGF-like module of both factor IX species.
-
Effects of gamma-carboxyglutamic acid and epidermal growth factor-like modules of factor IX on factor X activation. Studies using proteolytic fragments of bovine factor IX.
Journal of Biological Chemistry, 1992Co-Authors: Jan Astermark, I Björk, Philip J. Hogg, Johan StenfloAbstract:Factor IX is a vitamin K-dependent zymogen of a serine protease. The NH2-terminal half of the molecule consists of a Ca(2+)-binding gamma-carboxyglutamic acid (Gla)-containing module and two modules homologous to the epidermal growth factor (EGF) precursor. To elucidate the role of these non-catalytic modules of factor IXa beta in factor X activation, we have isolated and characterized fragments of bovine factor IX, containing one or both of the EGF-like modules as well as these modules linked to the Gla module. The fragments were used as inhibitors of factor IXa beta-mediated factor X activation in a plasma clotting system and in systems with purified components of the Xase complex. Fragments consisting of either the two EGF-like modules of factor IX linked together or the NH2-terminal EGF-like module alone were found to inhibit factor Xa generation both in the presence and absence of the cofactor, factor VIIIa. Moreover, a fragment consisting of the corresponding modules of factor X had a similar effect. We therefore propose that factor IXa beta and factor X interact directly through their EGF-like modules on or in the vicinity of a phospholipid surface. We have also found that the isolated Gla module of factor IX inhibits the formation of factor Xa both in the presence and absence of phospholipid but not in the absence of factor VIIIa. Our results are compatible with a model of the Xase complex, in which both the serine protease part and the Gla module of factor IXa beta interact with factor VIIIa. (Less)
Tetsuyuki Ishii - One of the best experts on this subject based on the ideXlab platform.
-
effects of solar spectrum and module temperature on outdoor performance of photovoltaic modules in round robin measurements in japan
Progress in Photovoltaics, 2011Co-Authors: Tetsuyuki Ishii, Kenji Otani, Takumi TakashimaAbstract:The performance of six photovoltaic (PV) modules composed of polycrystalline silicon (pc-Si), amorphous silicon (a-Si), and hydrogenated amorphous silicon/crystalline silicon (a-Si:H/c-Si) modules was investigated at eight locations in Japan from August 2007 to December 2008. In addition, solar irradiance, solar spectrum, and module temperature were simultaneously measured in these round-robin measurements. In this study, we evaluate quantitatively the effects of module temperature and solar spectrum on the performance of the PV modules as thermal factor (TF) and spectral factor (SF), respectively. Furthermore, we investigate the variation in module performance, which is converted into module performance under standard test conditions (STC) using the TF and SF. In the case of the pc-Si modules, the variations in performance ratio under STC (PRSTC) for these modules range from 0.056 to 0.074 through the round-robin measurements. The TF indicates that the contribution of module temperature to the variation in performance is large, between about 15 and 20%. However, the SF suggests that the contribution of solar spectrum is quite small, less than 3%. In the case of the a-Si modules, the contribution of module temperature is about 8%. The performance is largely influenced by solar spectrum, more than 12% at its maximum. Consequently, the variations in the corrected PRSTC of the a-Si modules are between 0.117 and 0.141. These large variations may result from the effects of thermal annealing and light soaking. The variation in PRSTC of the a-Si:H/c-Si module is similar to that of the pc-Si modules. Copyright © 2010 John Wiley & Sons, Ltd.
-
Effects of solar spectrum and module temperature on outdoor performance of photovoltaic modules in round‐robin measurements in Japan
Progress in Photovoltaics, 2010Co-Authors: Tetsuyuki Ishii, Kenji Otani, Takumi TakashimaAbstract:The performance of six photovoltaic (PV) modules composed of polycrystalline silicon (pc-Si), amorphous silicon (a-Si), and hydrogenated amorphous silicon/crystalline silicon (a-Si:H/c-Si) modules was investigated at eight locations in Japan from August 2007 to December 2008. In addition, solar irradiance, solar spectrum, and module temperature were simultaneously measured in these round-robin measurements. In this study, we evaluate quantitatively the effects of module temperature and solar spectrum on the performance of the PV modules as thermal factor (TF) and spectral factor (SF), respectively. Furthermore, we investigate the variation in module performance, which is converted into module performance under standard test conditions (STC) using the TF and SF. In the case of the pc-Si modules, the variations in performance ratio under STC (PRSTC) for these modules range from 0.056 to 0.074 through the round-robin measurements. The TF indicates that the contribution of module temperature to the variation in performance is large, between about 15 and 20%. However, the SF suggests that the contribution of solar spectrum is quite small, less than 3%. In the case of the a-Si modules, the contribution of module temperature is about 8%. The performance is largely influenced by solar spectrum, more than 12% at its maximum. Consequently, the variations in the corrected PRSTC of the a-Si modules are between 0.117 and 0.141. These large variations may result from the effects of thermal annealing and light soaking. The variation in PRSTC of the a-Si:H/c-Si module is similar to that of the pc-Si modules. Copyright © 2010 John Wiley & Sons, Ltd.
Takumi Takashima - One of the best experts on this subject based on the ideXlab platform.
-
effects of solar spectrum and module temperature on outdoor performance of photovoltaic modules in round robin measurements in japan
Progress in Photovoltaics, 2011Co-Authors: Tetsuyuki Ishii, Kenji Otani, Takumi TakashimaAbstract:The performance of six photovoltaic (PV) modules composed of polycrystalline silicon (pc-Si), amorphous silicon (a-Si), and hydrogenated amorphous silicon/crystalline silicon (a-Si:H/c-Si) modules was investigated at eight locations in Japan from August 2007 to December 2008. In addition, solar irradiance, solar spectrum, and module temperature were simultaneously measured in these round-robin measurements. In this study, we evaluate quantitatively the effects of module temperature and solar spectrum on the performance of the PV modules as thermal factor (TF) and spectral factor (SF), respectively. Furthermore, we investigate the variation in module performance, which is converted into module performance under standard test conditions (STC) using the TF and SF. In the case of the pc-Si modules, the variations in performance ratio under STC (PRSTC) for these modules range from 0.056 to 0.074 through the round-robin measurements. The TF indicates that the contribution of module temperature to the variation in performance is large, between about 15 and 20%. However, the SF suggests that the contribution of solar spectrum is quite small, less than 3%. In the case of the a-Si modules, the contribution of module temperature is about 8%. The performance is largely influenced by solar spectrum, more than 12% at its maximum. Consequently, the variations in the corrected PRSTC of the a-Si modules are between 0.117 and 0.141. These large variations may result from the effects of thermal annealing and light soaking. The variation in PRSTC of the a-Si:H/c-Si module is similar to that of the pc-Si modules. Copyright © 2010 John Wiley & Sons, Ltd.
-
Effects of solar spectrum and module temperature on outdoor performance of photovoltaic modules in round‐robin measurements in Japan
Progress in Photovoltaics, 2010Co-Authors: Tetsuyuki Ishii, Kenji Otani, Takumi TakashimaAbstract:The performance of six photovoltaic (PV) modules composed of polycrystalline silicon (pc-Si), amorphous silicon (a-Si), and hydrogenated amorphous silicon/crystalline silicon (a-Si:H/c-Si) modules was investigated at eight locations in Japan from August 2007 to December 2008. In addition, solar irradiance, solar spectrum, and module temperature were simultaneously measured in these round-robin measurements. In this study, we evaluate quantitatively the effects of module temperature and solar spectrum on the performance of the PV modules as thermal factor (TF) and spectral factor (SF), respectively. Furthermore, we investigate the variation in module performance, which is converted into module performance under standard test conditions (STC) using the TF and SF. In the case of the pc-Si modules, the variations in performance ratio under STC (PRSTC) for these modules range from 0.056 to 0.074 through the round-robin measurements. The TF indicates that the contribution of module temperature to the variation in performance is large, between about 15 and 20%. However, the SF suggests that the contribution of solar spectrum is quite small, less than 3%. In the case of the a-Si modules, the contribution of module temperature is about 8%. The performance is largely influenced by solar spectrum, more than 12% at its maximum. Consequently, the variations in the corrected PRSTC of the a-Si modules are between 0.117 and 0.141. These large variations may result from the effects of thermal annealing and light soaking. The variation in PRSTC of the a-Si:H/c-Si module is similar to that of the pc-Si modules. Copyright © 2010 John Wiley & Sons, Ltd.
Jan Astermark - One of the best experts on this subject based on the ideXlab platform.
-
The gamma-carboxyglutamic acid and epidermal growth factor-like modules of factor IXa beta. Effects on the serine protease module and factor X activation
Journal of Biological Chemistry, 1994Co-Authors: Jan Astermark, Philip J. Hogg, Johan StenfloAbstract:Blood coagulation factors IX and X are two serine proteases with a similar modular structure. The non-catalytic part of each protein consists of a gamma-carboxyglutamic acid (Gla)-containing module and two modules homologous to the epidermal growth factor (EGF) precursor. We have now found that the NH2-terminal EGF-like module of both factors IX and X inhibits factor Xa formation in a Gla-independent manner, both in the presence and absence of phospholipid and the cofactor, factor VIIIa. In contrast, the COOH-terminal EGF-like module has no such effect. Our data indicate that the NH2-terminal EGF-like module of factor IXa beta interacts either with the corresponding module or with the serine protease module in the substrate, factor X, without affecting the hydrolysis of low molecular weight substrates. Using antibodies as structural probes, we found that Ca2+ binding to the Gla module of factor IXa beta induces a conformational transition in the serine protease module. No evidence was found for a direct interaction between the Gla module and factor VIIIa. We therefore propose that the Gla module in factor IXa beta is indirectly involved in the cofactor interaction, in that Ca2+ binding to sites in this module induces a conformation in the serine protease module that is commensurate with factor VIIIa interaction. In addition, the immunochemical approach revealed a Gla-independent Ca2+ binding site in the serine protease module (apparent Kd of approximately 120 microM) that also might influence its conformation. Antibodies against the EGF-like modules of factor IX were used to probe Ca2+ binding to these modules in intact and in Gla-domainless factor IXa beta. The data indicate a Ca2+ binding site with an apparent Kd of approximately 50 microM in the NH2-terminal EGF-like module of both factor IX species.
-
Effects of gamma-carboxyglutamic acid and epidermal growth factor-like modules of factor IX on factor X activation. Studies using proteolytic fragments of bovine factor IX.
Journal of Biological Chemistry, 1992Co-Authors: Jan Astermark, I Björk, Philip J. Hogg, Johan StenfloAbstract:Factor IX is a vitamin K-dependent zymogen of a serine protease. The NH2-terminal half of the molecule consists of a Ca(2+)-binding gamma-carboxyglutamic acid (Gla)-containing module and two modules homologous to the epidermal growth factor (EGF) precursor. To elucidate the role of these non-catalytic modules of factor IXa beta in factor X activation, we have isolated and characterized fragments of bovine factor IX, containing one or both of the EGF-like modules as well as these modules linked to the Gla module. The fragments were used as inhibitors of factor IXa beta-mediated factor X activation in a plasma clotting system and in systems with purified components of the Xase complex. Fragments consisting of either the two EGF-like modules of factor IX linked together or the NH2-terminal EGF-like module alone were found to inhibit factor Xa generation both in the presence and absence of the cofactor, factor VIIIa. Moreover, a fragment consisting of the corresponding modules of factor X had a similar effect. We therefore propose that factor IXa beta and factor X interact directly through their EGF-like modules on or in the vicinity of a phospholipid surface. We have also found that the isolated Gla module of factor IX inhibits the formation of factor Xa both in the presence and absence of phospholipid but not in the absence of factor VIIIa. Our results are compatible with a model of the Xase complex, in which both the serine protease part and the Gla module of factor IXa beta interact with factor VIIIa. (Less)
Philip J. Hogg - One of the best experts on this subject based on the ideXlab platform.
-
The gamma-carboxyglutamic acid and epidermal growth factor-like modules of factor IXa beta. Effects on the serine protease module and factor X activation
Journal of Biological Chemistry, 1994Co-Authors: Jan Astermark, Philip J. Hogg, Johan StenfloAbstract:Blood coagulation factors IX and X are two serine proteases with a similar modular structure. The non-catalytic part of each protein consists of a gamma-carboxyglutamic acid (Gla)-containing module and two modules homologous to the epidermal growth factor (EGF) precursor. We have now found that the NH2-terminal EGF-like module of both factors IX and X inhibits factor Xa formation in a Gla-independent manner, both in the presence and absence of phospholipid and the cofactor, factor VIIIa. In contrast, the COOH-terminal EGF-like module has no such effect. Our data indicate that the NH2-terminal EGF-like module of factor IXa beta interacts either with the corresponding module or with the serine protease module in the substrate, factor X, without affecting the hydrolysis of low molecular weight substrates. Using antibodies as structural probes, we found that Ca2+ binding to the Gla module of factor IXa beta induces a conformational transition in the serine protease module. No evidence was found for a direct interaction between the Gla module and factor VIIIa. We therefore propose that the Gla module in factor IXa beta is indirectly involved in the cofactor interaction, in that Ca2+ binding to sites in this module induces a conformation in the serine protease module that is commensurate with factor VIIIa interaction. In addition, the immunochemical approach revealed a Gla-independent Ca2+ binding site in the serine protease module (apparent Kd of approximately 120 microM) that also might influence its conformation. Antibodies against the EGF-like modules of factor IX were used to probe Ca2+ binding to these modules in intact and in Gla-domainless factor IXa beta. The data indicate a Ca2+ binding site with an apparent Kd of approximately 50 microM in the NH2-terminal EGF-like module of both factor IX species.
-
Effects of gamma-carboxyglutamic acid and epidermal growth factor-like modules of factor IX on factor X activation. Studies using proteolytic fragments of bovine factor IX.
Journal of Biological Chemistry, 1992Co-Authors: Jan Astermark, I Björk, Philip J. Hogg, Johan StenfloAbstract:Factor IX is a vitamin K-dependent zymogen of a serine protease. The NH2-terminal half of the molecule consists of a Ca(2+)-binding gamma-carboxyglutamic acid (Gla)-containing module and two modules homologous to the epidermal growth factor (EGF) precursor. To elucidate the role of these non-catalytic modules of factor IXa beta in factor X activation, we have isolated and characterized fragments of bovine factor IX, containing one or both of the EGF-like modules as well as these modules linked to the Gla module. The fragments were used as inhibitors of factor IXa beta-mediated factor X activation in a plasma clotting system and in systems with purified components of the Xase complex. Fragments consisting of either the two EGF-like modules of factor IX linked together or the NH2-terminal EGF-like module alone were found to inhibit factor Xa generation both in the presence and absence of the cofactor, factor VIIIa. Moreover, a fragment consisting of the corresponding modules of factor X had a similar effect. We therefore propose that factor IXa beta and factor X interact directly through their EGF-like modules on or in the vicinity of a phospholipid surface. We have also found that the isolated Gla module of factor IX inhibits the formation of factor Xa both in the presence and absence of phospholipid but not in the absence of factor VIIIa. Our results are compatible with a model of the Xase complex, in which both the serine protease part and the Gla module of factor IXa beta interact with factor VIIIa. (Less)
