Pub Date : 2006-01-31DOI: 10.11311/JSCTA1974.33.20
T. Okuda
Life and death are mutually exclusive states. But some organisms showing no sign of living due to complete desiccation are nevertheless able to resume active life after rehydration. This peculiar biological state of organisms is referred to as cryptobiosis. Larvae of an insect species, the African chironomid Polypedilum vanderplanki, live in temporary rock pools in semi-arid areas and are able to achieve cryptobiosis. P. vanderplanki larvae accumulate trehalose to levels of
{"title":"Trehalose: a Molecule Responsible for Desiccation Tolerance in the Sleeping Chironomid, Polypedilum Vanderplanki","authors":"T. Okuda","doi":"10.11311/JSCTA1974.33.20","DOIUrl":"https://doi.org/10.11311/JSCTA1974.33.20","url":null,"abstract":"Life and death are mutually exclusive states. But some organisms showing no sign of living due to complete desiccation are nevertheless able to resume active life after rehydration. This peculiar biological state of organisms is referred to as cryptobiosis. Larvae of an insect species, the African chironomid Polypedilum vanderplanki, live in temporary rock pools in semi-arid areas and are able to achieve cryptobiosis. P. vanderplanki larvae accumulate trehalose to levels of","PeriodicalId":19096,"journal":{"name":"Netsu Sokutei","volume":"12 3 1","pages":"20-26"},"PeriodicalIF":0.0,"publicationDate":"2006-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78268402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
There are many cold places around the Earth. From the psychrophiles isolated from those environments, cold-adapted enzymes have been isolated. Cold-adapted enzymes have sufficient activity and sufficient substrate-affinity to support the growth, and show low thermo-stability. Artificially cold-adapted enzymes have been obtained by evolutionary engineering from thermophile enzymes. The analysis revealed one of the cold-adaptation mechanisms: the cold-adapted enzymes showed lower enthalpy of substrate-binding thus providing lower activation enthalpy for high activity at low temperature. Some of the cold-adapted enzymes retained high thermal stability of the original thermophile enzyme. The results suggest that it is possible to reconcile high stability with high activity at low temperature. However, the issue needs further investigation. It has been elucidated that life evolved from the hyperthermophilic common ancestor (Commonote). Accordingly, the in vitro evolution experiments for obtaining cold-adapted enzymes from thermophile enzyme are, in a sense, reproducing the evolution of life.
{"title":"Cold Adaptation and Molecular Evolution of Enzyme","authors":"A. Yamagishi","doi":"10.11311/JSCTA1974.33.2","DOIUrl":"https://doi.org/10.11311/JSCTA1974.33.2","url":null,"abstract":"There are many cold places around the Earth. From the psychrophiles isolated from those environments, cold-adapted enzymes have been isolated. Cold-adapted enzymes have sufficient activity and sufficient substrate-affinity to support the growth, and show low thermo-stability. Artificially cold-adapted enzymes have been obtained by evolutionary engineering from thermophile enzymes. The analysis revealed one of the cold-adaptation mechanisms: the cold-adapted enzymes showed lower enthalpy of substrate-binding thus providing lower activation enthalpy for high activity at low temperature. Some of the cold-adapted enzymes retained high thermal stability of the original thermophile enzyme. The results suggest that it is possible to reconcile high stability with high activity at low temperature. However, the issue needs further investigation. It has been elucidated that life evolved from the hyperthermophilic common ancestor (Commonote). Accordingly, the in vitro evolution experiments for obtaining cold-adapted enzymes from thermophile enzyme are, in a sense, reproducing the evolution of life.","PeriodicalId":19096,"journal":{"name":"Netsu Sokutei","volume":"44 1","pages":"2-9"},"PeriodicalIF":0.0,"publicationDate":"2006-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87532684","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-01-31DOI: 10.11311/JSCTA1974.33.10
C. Katagiri
Lipid is one of the major components in organisms; that is, triacyiglycerols and phospholipids are known as an energy source and the major constituent of the membrane, respectively. Their transition between liquid and solid occurs often under the biological environments. Insects are ectotherm of tropical origin. They, however, flourish everywhere on the earth except ocean. We have investigated how they can survive during the cold winter. Insects sometimes avoid and sometimes utilise the thermal transition of the lipids above and hydrocarbons that cover the body surface against dehydration.
{"title":"Phase Transition of Lipids in Overwintering Insects","authors":"C. Katagiri","doi":"10.11311/JSCTA1974.33.10","DOIUrl":"https://doi.org/10.11311/JSCTA1974.33.10","url":null,"abstract":"Lipid is one of the major components in organisms; that is, triacyiglycerols and phospholipids are known as an energy source and the major constituent of the membrane, respectively. Their transition between liquid and solid occurs often under the biological environments. Insects are ectotherm of tropical origin. They, however, flourish everywhere on the earth except ocean. We have investigated how they can survive during the cold winter. Insects sometimes avoid and sometimes utilise the thermal transition of the lipids above and hydrocarbons that cover the body surface against dehydration.","PeriodicalId":19096,"journal":{"name":"Netsu Sokutei","volume":"1 1","pages":"10-19"},"PeriodicalIF":0.0,"publicationDate":"2006-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84655114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-01-31DOI: 10.11311/JSCTA1974.33.27
Nurul Karim, S. Kidokoro
Enzymes, the catalysts of biological systems, are remarkable molecular devices that determine the patterns of chemical transformations. For many decades, a great deal of pure and applied studies have been devoted to enzyme reactions, as the mechanisms underlying the special characteristics of the reactions, such as high specificity and high efficiency, have not only attracted scientific interest but also indicated the possibility of employing enzymes as highly useful catalysts in many application fields. Quantitative evaluation of the catalytic activity of enzymes is inevitably important to reveal the enzymes' reaction mechanisms and to use the catalysts most effectively. To evaluate enzyme kinetics, it is necessary that the transformation of a substrate into a product is accompanied with an observable event. Since the change in enthalpy is one of a reaction's general features, several approaches have been employed to monitor enzyme-catalyzed reactions using calorimetry.1-17) The heat generated as the reaction proceeds is a direct and sensitive observable quantity. Because it allows the direct determination of the reaction rate, which indicates the enzyme activity itself, calorimetry is expected to provide a general and effective way to evaluate enzyme activity. ITC provides one possibility for detecting the catalytic reaction heat as a function of time with high sensitivity and reproducibility. Two calorimetric variables, the compensation power and its integral, can be determined directly and precisely by this method.13-15) Under hydrolytic conditions, the combination of a calorimetric LineweaverBurk plot with these two variables and the non-linear least-squares method was found to be effective for determining enzymatic parameters precisely.13-15) The kinetic parameters, kcat and KM, obtained from calorimetric observables, clearly indicated that the enzyme-catalyzed hydrolysis reaction is well approximated by a simple Michaelis-Menten equation.13-15) Tradit ionally, ITC analysis has used data obtained only after the enzyme solution has been fully titrated.13, 14) However, since the enzyme reaction occurs in the cell even during titration, and since the precise total enzyme concentration in the cell is determined by the titration program, it is possible to use the experimental data gathered during titration for the analysis. To determine the reaction heat and enzyme parameters more precisely, the traditional method has been modified to treat all of the hydrolysis data observed by ITC.15) In addition to activity measurement, inhibition studies of different enzyme-catalyzed hydrolysis reactions have used ITC with great success.8-11,14,15) In most models of
{"title":"Precise Evaluation of Enzyme Activity using Isothermal Titration Calorimetry","authors":"Nurul Karim, S. Kidokoro","doi":"10.11311/JSCTA1974.33.27","DOIUrl":"https://doi.org/10.11311/JSCTA1974.33.27","url":null,"abstract":"Enzymes, the catalysts of biological systems, are remarkable molecular devices that determine the patterns of chemical transformations. For many decades, a great deal of pure and applied studies have been devoted to enzyme reactions, as the mechanisms underlying the special characteristics of the reactions, such as high specificity and high efficiency, have not only attracted scientific interest but also indicated the possibility of employing enzymes as highly useful catalysts in many application fields. Quantitative evaluation of the catalytic activity of enzymes is inevitably important to reveal the enzymes' reaction mechanisms and to use the catalysts most effectively. To evaluate enzyme kinetics, it is necessary that the transformation of a substrate into a product is accompanied with an observable event. Since the change in enthalpy is one of a reaction's general features, several approaches have been employed to monitor enzyme-catalyzed reactions using calorimetry.1-17) The heat generated as the reaction proceeds is a direct and sensitive observable quantity. Because it allows the direct determination of the reaction rate, which indicates the enzyme activity itself, calorimetry is expected to provide a general and effective way to evaluate enzyme activity. ITC provides one possibility for detecting the catalytic reaction heat as a function of time with high sensitivity and reproducibility. Two calorimetric variables, the compensation power and its integral, can be determined directly and precisely by this method.13-15) Under hydrolytic conditions, the combination of a calorimetric LineweaverBurk plot with these two variables and the non-linear least-squares method was found to be effective for determining enzymatic parameters precisely.13-15) The kinetic parameters, kcat and KM, obtained from calorimetric observables, clearly indicated that the enzyme-catalyzed hydrolysis reaction is well approximated by a simple Michaelis-Menten equation.13-15) Tradit ionally, ITC analysis has used data obtained only after the enzyme solution has been fully titrated.13, 14) However, since the enzyme reaction occurs in the cell even during titration, and since the precise total enzyme concentration in the cell is determined by the titration program, it is possible to use the experimental data gathered during titration for the analysis. To determine the reaction heat and enzyme parameters more precisely, the traditional method has been modified to treat all of the hydrolysis data observed by ITC.15) In addition to activity measurement, inhibition studies of different enzyme-catalyzed hydrolysis reactions have used ITC with great success.8-11,14,15) In most models of","PeriodicalId":19096,"journal":{"name":"Netsu Sokutei","volume":"31 1","pages":"27-35"},"PeriodicalIF":0.0,"publicationDate":"2006-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79262519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-11-30DOI: 10.11311/JSCTA1974.32.232
O. Andersson, H. Suga
There are numerous forms of ice including 13 crystalline phases,1) several distinctly different amorphous solid states and various clathrate hydrates. Ten of the crystalline phases, namely, ices II, III, IV, V, VI, VII, VIII, IX, X and XII, are produced at high pressures and three, hexagonal (Ih) and cubic (Ic) ices and ice XI, are produced at ambient pressure. The amorphous forms of solid water are: (i) amorphous solid water formed by hyperquenching micron-sized droplets (HQW) and by vapor-deposition on a cold plate (ASW),1) (ii) high-density amorphous ice,2) (iii) low-density amorphous ice3) and (iv) very high-density amorphous ice.4) While all the crystalline phases of water have been unequivocally established and the similarity between ASW and HQW is reasonably well established, the distinction between the amorphous states produced at high pressures and their relation to ASW is not. One of these amorphous states is formed by subjecting ice
{"title":"On the Unusual Thermal Conductivity of Ices at Elevated Pressures","authors":"O. Andersson, H. Suga","doi":"10.11311/JSCTA1974.32.232","DOIUrl":"https://doi.org/10.11311/JSCTA1974.32.232","url":null,"abstract":"There are numerous forms of ice including 13 crystalline phases,1) several distinctly different amorphous solid states and various clathrate hydrates. Ten of the crystalline phases, namely, ices II, III, IV, V, VI, VII, VIII, IX, X and XII, are produced at high pressures and three, hexagonal (Ih) and cubic (Ic) ices and ice XI, are produced at ambient pressure. The amorphous forms of solid water are: (i) amorphous solid water formed by hyperquenching micron-sized droplets (HQW) and by vapor-deposition on a cold plate (ASW),1) (ii) high-density amorphous ice,2) (iii) low-density amorphous ice3) and (iv) very high-density amorphous ice.4) While all the crystalline phases of water have been unequivocally established and the similarity between ASW and HQW is reasonably well established, the distinction between the amorphous states produced at high pressures and their relation to ASW is not. One of these amorphous states is formed by subjecting ice","PeriodicalId":19096,"journal":{"name":"Netsu Sokutei","volume":"86 1","pages":"232-240"},"PeriodicalIF":0.0,"publicationDate":"2005-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86053929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-11-30DOI: 10.11311/JSCTA1974.32.226
N. Sakai
The data of heat capacity, thermal conductivity, and thermal expansion behavior for materials in solid oxide fuel cells (SOFCs) are reviewed. Most of the SOFC materials are complex metal oxides and their thermal conductivities are generally low, that causes a large temperature distribution during the operation. Since the SOFC consists of metal oxides and composites, a good thermal expansion matching is the most important point in order to fabricate durable cells and stacks. The electrolytes and interconnects are exposed in a large gradient of oxygen partial pressure at a high temperature, and isothermal expansion is observed for rare earth substituted ceria and alkaline earth substituted lanthanum chromites. Although the isothermal expansion in lanthanum chromites can be alleviated by substituting the transition metals, it can not in rare earth substituted ceria. 解 説
{"title":"Thermophysical Properties of Materials for Solid Oxide Fuel Cells (SOFC)","authors":"N. Sakai","doi":"10.11311/JSCTA1974.32.226","DOIUrl":"https://doi.org/10.11311/JSCTA1974.32.226","url":null,"abstract":"The data of heat capacity, thermal conductivity, and thermal expansion behavior for materials in solid oxide fuel cells (SOFCs) are reviewed. Most of the SOFC materials are complex metal oxides and their thermal conductivities are generally low, that causes a large temperature distribution during the operation. Since the SOFC consists of metal oxides and composites, a good thermal expansion matching is the most important point in order to fabricate durable cells and stacks. The electrolytes and interconnects are exposed in a large gradient of oxygen partial pressure at a high temperature, and isothermal expansion is observed for rare earth substituted ceria and alkaline earth substituted lanthanum chromites. Although the isothermal expansion in lanthanum chromites can be alleviated by substituting the transition metals, it can not in rare earth substituted ceria. 解 説","PeriodicalId":19096,"journal":{"name":"Netsu Sokutei","volume":"25 1","pages":"226-231"},"PeriodicalIF":0.0,"publicationDate":"2005-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72846216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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