Earth's Climate History Explains Life's Temperature Optima.

Why does the growth of most life forms exhibit a narrow range of optimal temperatures below 40°C? We hypothesize that the recently identified stable range of oceanic temperatures of ~5 to 37°C for more than two billion years of Earth history tightly constrained the evolution of prokaryotic thermal performance curves to optimal temperatures for growth to less than 40°C. We tested whether competitive mechanisms reproduced the observed upper limits of life's temperature optima using simple Lotka-Volterra models of interspecific competition between organisms with different temperature optima. Model results supported our proposition whereby organisms with temperature optima up to 37°C were most competitive.

Structural Evaluation of a Nitroreductase Engineered for Improved Activation of the 5-Nitroimidazole PET Probe SN33623.

Bacterial nitroreductase enzymes capable of activating imaging probes and prodrugs are valuable tools for gene-directed enzyme prodrug therapies and targeted cell ablation models. We recently engineered a nitroreductase ( NfsB F70A/F108Y) for the substantially enhanced reduction of the 5-nitroimidazole PET-capable probe, SN33623, which permits the theranostic imaging of vectors labeled with oxygen-insensitive bacterial nitroreductases. This mutant enzyme also shows improved activation of the DNA-alkylation prodrugs CB1954 and metronidazole.

Ethical Stakes for Past, Present, and Prospective Tuberculosis Isolate Research Towards a Multicultural Data Sovereignty Model for Isolate Samples in Research.

Tuberculosis (TB) is a potentially fatal infectious disease that, in Aotearoa New Zealand (NZ), inequitably affects Asian, Pacific, Middle Eastern, Latin American, and African (MELAA), and Māori people. Medical research involving genome sequencing of TB samples enables more nuanced understanding of disease strains and their transmission. This could inform highly specific health interventions.

Cooperative Conformational Transitions Underpin the Activation Heat Capacity in the Temperature Dependence of Enzyme Catalysis.

Many enzymes display non-Arrhenius behavior with curved Arrhenius plots in the absence of denaturation. There has been significant debate about the origin of this behavior and recently the role of the activation heat capacity (Δ) has been widely discussed. If enzyme-catalyzed reactions occur with appreciable negative values of Δ (arising from narrowing of the conformational space along the reaction coordinate), then curved Arrhenius plots are a consequence.

Characterisation and engineering of a thermophilic RNA ligase from Palaeococcus pacificus.

RNA ligases are important enzymes in molecular biology and are highly useful for the manipulation and analysis of nucleic acids, including adapter ligation in next-generation sequencing of microRNAs. Thermophilic RNA ligases belonging to the RNA ligase 3 family are gaining attention for their use in molecular biology, for example a thermophilic RNA ligase from Methanobacterium thermoautotrophicum is commercially available for the adenylation of nucleic acids. Here we extensively characterise a newly identified RNA ligase from the thermophilic archaeon Palaeococcus pacificus (PpaRnl).