title: Eurythermalism and the temperature dependence of enzyme activity

authors: Lee, Charles Kai-Wu

subjects: enzyme temperature optimum

abstract: The "Equilibrium Model" has provided new tools for describing and investigating enzyme thermal adaptation. It has been shown that the effect of temperature on enzyme activity is not only governed by ΔG‡cat and ΔG‡inact but also by two new intrinsic parameters, ΔHeq and Teq, which describe the enthalpy and midpoint, respectively, of a reversible equilibrium between active and inactive (but not denatured) forms of enzyme. Twenty-one enzymes from organisms with a wide range of growth temperatures were characterized using the Equilibrium Model. Statistical analysis indicates that Teq is a better predictor of growth temperature than enzyme stability (ΔG‡inact). As expected from the Equilibrium Model, ΔHeq correlates with catalytic temperature tolerance of enzymes and thus can be declared the first intrinsic and quantitative measure of enzyme eurythermalism. Other findings shed light on the evolution of psychrophilic and thermophilic enzymes. The findings suggest that the description of the Equilibrium Model of the effect of temperature on enzyme activity applies to all enzymes regardless of their temperature origins and that its associated parameters, ΔHeq and Teq, are intrinsic and necessary parameters for characterizing the thermal properties of enzymes and their temperature adaptation and evolution.

text: Eurythermalism and the temperature dependence of enzyme activity The "Equilibrium Model" has provided new tools for describing and investigating enzyme thermal adaptation. It has been shown that the effect of temperature on enzyme activity is not only governed by ΔG‡cat and ΔG‡inact but also by two new intrinsic parameters, ΔHeq and Teq, which describe the enthalpy and midpoint, respectively, of a reversible equilibrium between active and inactive (but not denatured) forms of enzyme. Twenty-one enzymes from organisms with a wide range of growth temperatures were characterized using the Equilibrium Model. Statistical analysis indicates that Teq is a better predictor of growth temperature than enzyme stability (ΔG‡inact). As expected from the Equilibrium Model, ΔHeq correlates with catalytic temperature tolerance of enzymes and thus can be declared the first intrinsic and quantitative measure of enzyme eurythermalism. Other findings shed light on the evolution of psychrophilic and thermophilic enzymes. The findings suggest that the description of the Equilibrium Model of the effect of temperature on enzyme activity applies to all enzymes regardless of their temperature origins and that its associated parameters, ΔHeq and Teq, are intrinsic and necessary parameters for characterizing the thermal properties of enzymes and their temperature adaptation and evolution.

year: 2007

title: Using the properties of Primate Motion Sensitive Neurons to extract camera motion and depth from brief 2-D Monocular Image Sequences

authors: Perrone, John A.

subjects: biologically-based motion sensor

abstract: Humans and most animals can run/fly and navigate efficiently through cluttered environments while avoiding obstacles in their way. Replicating this advanced skill in autonomous robotic vehicles currently requires a vast array of sensors coupled with computers that are bulky, heavy and power hungry. The human eye and brain have had millions of years to develop an efficient solution to the problem of visual navigation and we believe that it is the best system to reverse engineer. Our brain and visual system appear to use a very different solution to the visual odometry problem compared to most computer vision approaches. We show how a neural-based architecture is able to extract self-motion information and depth from monocular 2-D video sequences and highlight how this approach differs from standard CV techniques. We previously demonstrated how our system works during pure translation of a camera. Here, we extend this approach to the case of combined translation and rotation.

text: Using the properties of Primate Motion Sensitive Neurons to extract camera motion and depth from brief 2-D Monocular Image Sequences Humans and most animals can run/fly and navigate efficiently through cluttered environments while avoiding obstacles in their way. Replicating this advanced skill in autonomous robotic vehicles currently requires a vast array of sensors coupled with computers that are bulky, heavy and power hungry. The human eye and brain have had millions of years to develop an efficient solution to the problem of visual navigation and we believe that it is the best system to reverse engineer. Our brain and visual system appear to use a very different solution to the visual odometry problem compared to most computer vision approaches. We show how a neural-based architecture is able to extract self-motion information and depth from monocular 2-D video sequences and highlight how this approach differs from standard CV techniques. We previously demonstrated how our system works during pure translation of a camera. Here, we extend this approach to the case of combined translation and rotation.

year: 2019

title: Vital evidence: Change in the marine ¹⁴C reservoir around New Zealand (Aotearoa) and implications for the timing of Polynesian settlement.

authors: Petchey, Fiona

abstract: Precise and accurate radiocarbon chronologies are essential to achieve tight chronological control for the ~ 750-years since Polynesian settlement of New Zealand. This goal has, however, been elusive. While radiocarbon datasets in the region are typically dominated by marine and estuarine shell dates, such chronological information has been ignored by those interpreting the timing of key events because a detailed regional calibration methodology for marine shell, comparable to the highly precise Southern Hemisphere calibration curve, is lacking. In this paper, we present the first temporal ¹⁴C marine offset (ΔR) model for New Zealand based on paired estuarine/marine and terrestrial radiocarbon dates from 52 archaeological contexts. Our dataset displays significant offsets between the measured New Zealand data and the modelled global marine radiocarbon curve. These shifts are associated with oceanographic fluctuation at the onset of the Little Ice Age ~ AD 1350-1450 (650-500 BP). The application of a regional and temporal correction to archaeological shell dates provides complimentary information to terrestrial radiocarbon production and has the potential to add structure to the blurred chronology that has plagued archaeological theories about the colonization of New Zealand, and other Pacific islands, for decades.

text: Vital evidence: Change in the marine ¹⁴C reservoir around New Zealand (Aotearoa) and implications for the timing of Polynesian settlement. Precise and accurate radiocarbon chronologies are essential to achieve tight chronological control for the ~ 750-years since Polynesian settlement of New Zealand. This goal has, however, been elusive. While radiocarbon datasets in the region are typically dominated by marine and estuarine shell dates, such chronological information has been ignored by those interpreting the timing of key events because a detailed regional calibration methodology for marine shell, comparable to the highly precise Southern Hemisphere calibration curve, is lacking. In this paper, we present the first temporal ¹⁴C marine offset (ΔR) model for New Zealand based on paired estuarine/marine and terrestrial radiocarbon dates from 52 archaeological contexts. Our dataset displays significant offsets between the measured New Zealand data and the modelled global marine radiocarbon curve. These shifts are associated with oceanographic fluctuation at the onset of the Little Ice Age ~ AD 1350-1450 (650-500 BP). The application of a regional and temporal correction to archaeological shell dates provides complimentary information to terrestrial radiocarbon production and has the potential to add structure to the blurred chronology that has plagued archaeological theories about the colonization of New Zealand, and other Pacific islands, for decades.

year: 2020