title: The dependence of enzyme activity on temperature: determination and validation of parameters

authors: Peterson, Michelle E.

subjects: enzyme activity

abstract: Traditionally, the dependence of enzyme activity on temperature has been described by a model consisting of two processes: the catalytic reaction defined by DGDaggercat, and irreversible inactivation defined by DGDaggerinact. However, such a model does not account for the observed temperature-dependent behaviour of enzymes, and a new model has been developed and validated. This model (the Equilibrium Model) describes a new mechanism by which enzymes lose activity at high temperatures, by including an inactive form of the enzyme (Einact) that is in reversible equilibrium with the active form (Eact); it is the inactive form that undergoes irreversible thermal inactivation to the thermally denatured state. This equilibrium is described by an equilibrium constant whose temperature-dependence is characterized in terms of the enthalpy of the equilibrium, DHeq, and a new thermal parameter, Teq, which is the temperature at which the concentrations of Eact and Einact are equal; Teq may therefore be regarded as the thermal equivalent of Km. Characterization of an enzyme with respect to its temperature-dependent behaviour must therefore include a determination of these intrinsic properties. The Equilibrium Model has major implications for enzymology, biotechnology and understanding the evolution of enzymes. The present study presents a new direct data-fitting method based on fitting progress curves directly to the Equilibrium Model, and assesses the robustness of this procedure and the effect of assay data on the accurate determination of Teq and its associated parameters. It also describes simpler experimental methods for their determination than have been previously available, including those required for the application of the Equilibrium Model to non-ideal enzyme reactions.

text: The dependence of enzyme activity on temperature: determination and validation of parameters Traditionally, the dependence of enzyme activity on temperature has been described by a model consisting of two processes: the catalytic reaction defined by DGDaggercat, and irreversible inactivation defined by DGDaggerinact. However, such a model does not account for the observed temperature-dependent behaviour of enzymes, and a new model has been developed and validated. This model (the Equilibrium Model) describes a new mechanism by which enzymes lose activity at high temperatures, by including an inactive form of the enzyme (Einact) that is in reversible equilibrium with the active form (Eact); it is the inactive form that undergoes irreversible thermal inactivation to the thermally denatured state. This equilibrium is described by an equilibrium constant whose temperature-dependence is characterized in terms of the enthalpy of the equilibrium, DHeq, and a new thermal parameter, Teq, which is the temperature at which the concentrations of Eact and Einact are equal; Teq may therefore be regarded as the thermal equivalent of Km. Characterization of an enzyme with respect to its temperature-dependent behaviour must therefore include a determination of these intrinsic properties. The Equilibrium Model has major implications for enzymology, biotechnology and understanding the evolution of enzymes. The present study presents a new direct data-fitting method based on fitting progress curves directly to the Equilibrium Model, and assesses the robustness of this procedure and the effect of assay data on the accurate determination of Teq and its associated parameters. It also describes simpler experimental methods for their determination than have been previously available, including those required for the application of the Equilibrium Model to non-ideal enzyme reactions.

year: 2007

title: How might the use of apps influence students' learning experiences? Exploring a socio-technological assemblage

authors: Calder, Nigel Stuart

abstract: In this paper, we report on primary-school students’ views of their learning experiences when they engaged with mathematical phenomena through apps. The students commented on how they used a range of digital tools within the apps to solve problems, and we consider how the affordances of the mobile technologies, including multi-representation, dynamic and haptic, might influence the learning experiences. In particular, we focus on the interplay between the affordances of the mobile technologies with other social and pedagogical aspects, and ask how the assemblage of social and technological entities might influence mathematical learning experiences.

text: How might the use of apps influence students' learning experiences? Exploring a socio-technological assemblage In this paper, we report on primary-school students’ views of their learning experiences when they engaged with mathematical phenomena through apps. The students commented on how they used a range of digital tools within the apps to solve problems, and we consider how the affordances of the mobile technologies, including multi-representation, dynamic and haptic, might influence the learning experiences. In particular, we focus on the interplay between the affordances of the mobile technologies with other social and pedagogical aspects, and ask how the assemblage of social and technological entities might influence mathematical learning experiences.

year: 2017

title: Te Kahautu Maxwell  | Te Matatini Mātaatua representative [Interviewed by Dale Husband]

authors: Maxwell, Te Kahautu

abstract: This weekend in the Bay of Plenty, twenty-two kapa haka teams, including the reigning Te Matatini winners, showcased some of the nation’s best kapa haka performers during the Mātaatua senior regional tournaments.

text: Te Kahautu Maxwell  | Te Matatini Mātaatua representative [Interviewed by Dale Husband] This weekend in the Bay of Plenty, twenty-two kapa haka teams, including the reigning Te Matatini winners, showcased some of the nation’s best kapa haka performers during the Mātaatua senior regional tournaments.

year: 2024