title: Change in heat capacity for enzyme catalysis determines temperature dependence of enzyme catalyzed ratesnzyme Catalyzed Rates

authors: Hobbs, Joanne K.

abstract: The increase in enzymatic rates with temperature up to an optimum temperature (Topt) is widely attributed to classical Arrhenius behavior, with the decrease in enzymatic rates above Topt ascribed to protein denaturation and/or aggregation. This account persists despite many investigators noting that denaturation is insufficient to explain the decline in enzymatic rates above Topt. Here we show that it is the change in heat capacity associated with enzyme catalysis (ΔC‡p) and its effect on the temperature dependence of ΔG‡ that determines the temperature dependence of enzyme activity. Through mutagenesis, we demonstrate that the Topt of an enzyme is correlated with ΔC‡p and that changes to ΔC‡p are sufficient to change Topt without affecting the catalytic rate. Furthermore, using X-ray crystallography and molecular dynamics simulations we reveal the molecular details underpinning these changes in ΔC‡p. The influence of ΔC‡p on enzymatic rates has implications for the temperature dependence of biological rates from enzymes to ecosystems.

text: Change in heat capacity for enzyme catalysis determines temperature dependence of enzyme catalyzed ratesnzyme Catalyzed Rates The increase in enzymatic rates with temperature up to an optimum temperature (Topt) is widely attributed to classical Arrhenius behavior, with the decrease in enzymatic rates above Topt ascribed to protein denaturation and/or aggregation. This account persists despite many investigators noting that denaturation is insufficient to explain the decline in enzymatic rates above Topt. Here we show that it is the change in heat capacity associated with enzyme catalysis (ΔC‡p) and its effect on the temperature dependence of ΔG‡ that determines the temperature dependence of enzyme activity. Through mutagenesis, we demonstrate that the Topt of an enzyme is correlated with ΔC‡p and that changes to ΔC‡p are sufficient to change Topt without affecting the catalytic rate. Furthermore, using X-ray crystallography and molecular dynamics simulations we reveal the molecular details underpinning these changes in ΔC‡p. The influence of ΔC‡p on enzymatic rates has implications for the temperature dependence of biological rates from enzymes to ecosystems.

year: 2013

title: Observations of shoreline–sandbar coupling on an embayed beach

authors: van de Lageweg, W.I.

subjects: shoreline

abstract: We analyse a seven-year dataset (1999–2005) of shoreline and sandbar variations derived from video observations at the embayed Tairua Beach, New Zealand, to explore sandbar–shoreline coupling and to determine how this coupling is related to alongshore-averaged sandbar–shoreline separation and beach rotation. Our results quantify the coupling between the sandbar and the shoreline which is directly related to the reduced separation between the sandbar and the shoreline. Using a simple predictive shoreline model, we show that this behaviour is related to the energy of the incoming waves. Our observations are obtained from a headland-enclosed beach and show aspects of the morphological state that relate to the existence of headlands that are not considered in the Wright and Short beach state classification. Both the sandbar and shoreline at Tairua Beach rotate relatively quickly (< 1 month) during the winter storm events, when the storms are accompanied by strong alongshore components, gradually returning during the summer months. The sandbar–shoreline coupling length scale is controlled by this rotation, with large wavelengths occurring when the sandbar is strongly rotated.

text: Observations of shoreline–sandbar coupling on an embayed beach We analyse a seven-year dataset (1999–2005) of shoreline and sandbar variations derived from video observations at the embayed Tairua Beach, New Zealand, to explore sandbar–shoreline coupling and to determine how this coupling is related to alongshore-averaged sandbar–shoreline separation and beach rotation. Our results quantify the coupling between the sandbar and the shoreline which is directly related to the reduced separation between the sandbar and the shoreline. Using a simple predictive shoreline model, we show that this behaviour is related to the energy of the incoming waves. Our observations are obtained from a headland-enclosed beach and show aspects of the morphological state that relate to the existence of headlands that are not considered in the Wright and Short beach state classification. Both the sandbar and shoreline at Tairua Beach rotate relatively quickly (< 1 month) during the winter storm events, when the storms are accompanied by strong alongshore components, gradually returning during the summer months. The sandbar–shoreline coupling length scale is controlled by this rotation, with large wavelengths occurring when the sandbar is strongly rotated.

year: 2013

title: A step into the light: developing a culturally appropriate research prcoess to study Maori Rangatahi perspectives of leisure in one setting.

authors: Harvey, Geraldine

subjects: research -- methodology

abstract: There is little knowledge of Maori peoples' leisure understandings, experiences and participation. This article reports on the development of a culturally appropriate research process that investigated the leisure participation, perspectives, and experiences of five Rotorua Maori Rangatahi in one research setting'. Within this exploration there is a focus on the need to conduct leisure research with Maori people in culturally appropriate ways. This research approach incorporates focus group methodology within a Kaupapa Maori research framework which addresses issues of research for Maori. The research process revealed that focus group methodology can be adapted into a Kaupapa Maori research framework and that this research approach could be an important tool when conducting research with Maori Rangatahi, including in educational contexts.

text: A step into the light: developing a culturally appropriate research prcoess to study Maori Rangatahi perspectives of leisure in one setting. There is little knowledge of Maori peoples' leisure understandings, experiences and participation. This article reports on the development of a culturally appropriate research process that investigated the leisure participation, perspectives, and experiences of five Rotorua Maori Rangatahi in one research setting'. Within this exploration there is a focus on the need to conduct leisure research with Maori people in culturally appropriate ways. This research approach incorporates focus group methodology within a Kaupapa Maori research framework which addresses issues of research for Maori. The research process revealed that focus group methodology can be adapted into a Kaupapa Maori research framework and that this research approach could be an important tool when conducting research with Maori Rangatahi, including in educational contexts.

year: 2002