title: Review: A new understanding of how temperature affects the catalytic activity of enzymes

authors: Daniel, Roy M.

subjects: enzyme

abstract: The two established thermal properties of enzymes are their activation energy and their thermal stability, but experimental data do not match the expectations of these two properties. The recently proposed Equilibrium Model (EM) provides a quantitative explanation of enzyme thermal behaviour under reaction conditions by introducing an inactive (but not denatured) intermediate in rapid equilibrium with the active form. It was formulated as a mathematical model, and fits the known experimental data. Importantly, the EM gives rise to a number of new insights into the molecular basis of the temperature control of enzymes and their environmental adaptation and evolution, it is consistent with active site properties, and it has fundamental implications for enzyme engineering and other areas of biotechnology.

text: Review: A new understanding of how temperature affects the catalytic activity of enzymes The two established thermal properties of enzymes are their activation energy and their thermal stability, but experimental data do not match the expectations of these two properties. The recently proposed Equilibrium Model (EM) provides a quantitative explanation of enzyme thermal behaviour under reaction conditions by introducing an inactive (but not denatured) intermediate in rapid equilibrium with the active form. It was formulated as a mathematical model, and fits the known experimental data. Importantly, the EM gives rise to a number of new insights into the molecular basis of the temperature control of enzymes and their environmental adaptation and evolution, it is consistent with active site properties, and it has fundamental implications for enzyme engineering and other areas of biotechnology.

year: 2010

title: Uptake of ΣDDT, arsenic, cadmium, copper, and lead by lettuce and radish grown in contaminated horticultural soils

authors: Gaw, Sally K.

subjects: horticultural soil

abstract: Horticultural soils can contain elevated concentrations of selected trace elements and organochlorine pesticides as a result of long-term use of agrichemicals and soil amendments. A glasshouse study was undertaken to assess the uptake of weathered ΣDDT {sum of the p,p′- and o,p-isomers of DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane], DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene] and DDD[1,1-dichloro-2,2-bis(p-chlorophenyl)ethane]}, arsenic (As), cadmium (Cd), copper (Cu), and lead (Pb) residues by lettuce (Lactuca sativa) and radish (Raphanus sativus) from field-aged New Zealand horticultural soils. Concentrations of ΣDDT, DDT, DDE, Cd, Cu, and Pb in lettuce increased with increasing soil concentrations. In radish, similar relationships were observed for ΣDDT, DDE, and Cu. The bioaccumulation factors were less than 1 with the exception of Cd and decreased with increasing soil concentrations. Lettuce Cd concentrations for plants grown on four out of 10 assayed soils were equivalent to or exceeded the New Zealand food standard for leafy vegetables of 0.1 mg kg−1 fresh weight. Concentrations of As, Pb, and ΣDDT did not exceed available food standards. Overall, these results demonstrate that aged residues of ΣDDT, As, Cd, Cu, and Pb in horticultural soils have remained phytoavailable. To be protective of human health, site-specific risk assessments and soil guideline derivations for residential settings with vegetable gardens need to consider the produce consumption pathway.

text: Uptake of ΣDDT, arsenic, cadmium, copper, and lead by lettuce and radish grown in contaminated horticultural soils Horticultural soils can contain elevated concentrations of selected trace elements and organochlorine pesticides as a result of long-term use of agrichemicals and soil amendments. A glasshouse study was undertaken to assess the uptake of weathered ΣDDT {sum of the p,p′- and o,p-isomers of DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane], DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene] and DDD[1,1-dichloro-2,2-bis(p-chlorophenyl)ethane]}, arsenic (As), cadmium (Cd), copper (Cu), and lead (Pb) residues by lettuce (Lactuca sativa) and radish (Raphanus sativus) from field-aged New Zealand horticultural soils. Concentrations of ΣDDT, DDT, DDE, Cd, Cu, and Pb in lettuce increased with increasing soil concentrations. In radish, similar relationships were observed for ΣDDT, DDE, and Cu. The bioaccumulation factors were less than 1 with the exception of Cd and decreased with increasing soil concentrations. Lettuce Cd concentrations for plants grown on four out of 10 assayed soils were equivalent to or exceeded the New Zealand food standard for leafy vegetables of 0.1 mg kg−1 fresh weight. Concentrations of As, Pb, and ΣDDT did not exceed available food standards. Overall, these results demonstrate that aged residues of ΣDDT, As, Cd, Cu, and Pb in horticultural soils have remained phytoavailable. To be protective of human health, site-specific risk assessments and soil guideline derivations for residential settings with vegetable gardens need to consider the produce consumption pathway.

year: 2008

title: Pūrākau, death, and assisted dying: A Māori framework for understanding end-of-life

authors: Karaka-Clarke, Te Hurinui

subjects: Pūrākau, Assisted Dying, Tikanga Māori, Mōair Cosmology, End of Life: Ethics, Mana Motuhake, Wairua, Whakapapa, Relational Autonomy

abstract: This conceptual article addresses several critical gaps in health literature by exploring the ethical, spiritual, and cultural dimensions of assisted dying through the lens of Tikanga Māori and pūrākau (ancestral narratives).  While existing end-of-life policy frameworks often prioritize Western bioethical principles, this article argues for the inclusion of Kaupapa Māori principles such as whakapapa, wairua, mana motuhake, and tapu/ noa as essential components of culturally resonant care.    Drawing upon foundational narratives including the separation of  Ranginui and Papatūānuku, the creation of Hineahuone, the transformation of Hinetītama into Hinenuitepō, and the fatal attempt of Māui to conquer death, we position pūrākau as dynamic ethical texts that guide decision-making.  This article contributes to Indigenous health discourse by offering a whānau-centred, tikanga-informed critique of the End-of-Life Choice Act 2019 and calls for broader recognition of spiritual and relational dimensions in end-of-life care.   We contend that, when under-taken with whānau engagement, spiritual awareness, and cultural integrity, may be ethically compatible with tikanga Māori

text: Pūrākau, death, and assisted dying: A Māori framework for understanding end-of-life This conceptual article addresses several critical gaps in health literature by exploring the ethical, spiritual, and cultural dimensions of assisted dying through the lens of Tikanga Māori and pūrākau (ancestral narratives).  While existing end-of-life policy frameworks often prioritize Western bioethical principles, this article argues for the inclusion of Kaupapa Māori principles such as whakapapa, wairua, mana motuhake, and tapu/ noa as essential components of culturally resonant care.    Drawing upon foundational narratives including the separation of  Ranginui and Papatūānuku, the creation of Hineahuone, the transformation of Hinetītama into Hinenuitepō, and the fatal attempt of Māui to conquer death, we position pūrākau as dynamic ethical texts that guide decision-making.  This article contributes to Indigenous health discourse by offering a whānau-centred, tikanga-informed critique of the End-of-Life Choice Act 2019 and calls for broader recognition of spiritual and relational dimensions in end-of-life care.   We contend that, when under-taken with whānau engagement, spiritual awareness, and cultural integrity, may be ethically compatible with tikanga Māori

year: 2025-09-24