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Microbial metabolisms depend on enzymes that contain trace metals. A synthesis of molecular and geochemical data shows that these metabolic pathways evolved alongside changing marine availability of trace metals during the Precambrian. Life is based on energy gained by electron-transfer processes; these processes rely on oxidoreductase enzymes, which often contain transition metals in their structures. The availability of different metals and substrates has changed over the course of Earth's history as a result of secular changes in redox conditions, particularly global oxygenation. New metabolic pathways using different transition metals co-evolved alongside changing redox conditions. Sulfur reduction, sulfate reduction, methanogenesis and anoxygenic photosynthesis appeared between about 3.8 and 3.4 billion years ago. The oxidoreductases responsible for these metabolisms incorporated metals that were readily available in Archaean oceans, chiefly iron and iron–sulfur clusters. Oxygenic photosynthesis appeared between 3.2 and 2.5 billion years ago, as did methane oxidation, nitrogen fixation, nitrification and denitrification. These metabolisms rely on an expanded range of transition metals presumably made available by the build-up of molecular oxygen in soil crusts and marine microbial mats. The appropriation of copper in enzymes before the Great Oxidation Event is particularly important, as copper is key to nitrogen and methane cycling and was later incorporated into numerous aerobic metabolisms. We find that the diversity of metals used in oxidoreductases has increased through time, suggesting that surface redox potential and metal incorporation influenced the evolution of metabolism, biological electron transfer and microbial ecology.

Oxidoreductases play a central role in catalysing enzymatic electron-transfer reactions across the tree of life. To first order, the equilibrium thermodynamic properties of these proteins are governed by protein folds associated with specific transition metals and ligands at the active site. A global analysis of holoenzyme structures and functions suggests that there are fewer than approximately 500 fundamental oxidoreductases, which can be further clustered into 35 unique groups. These catalysts evolved in prokaryotes early in the Earth's history and are largely responsible for the emergence of non-equilibrium biogeochemical cycles on the planet's surface. Although the evolutionary history of the amino acid sequences in the oxidoreductases is very difficult to reconstruct due to gene duplication and horizontal gene transfer, the evolution of the folds in the catalytic sites can potentially be used to infer the history of these enzymes. Using a novel, yet simple analysis of the secondary structures associated with the ligands in oxidoreductases, we developed a structural phylogeny of these enzymes. The results of this ‘composome’ analysis suggest an early split from a basal set of a small group of proteins dominated by loop structures into two families of oxidoreductases, one dominated by α-helices and the second by β-sheets. The structural evolutionary patterns in both clades trace redox gradients and increased hydrogen bond energy in the active sites. The overall pattern suggests that the evolution of the oxidoreductases led to decreased entropy in the transition metal folds over approximately 2.5 billion years, allowing the enzymes to use increasingly oxidized substrates with high specificity.

Oxidoreductases play a central role in catalysing enzymatic electron-transfer reactions across the tree of life. To first order, the equilibrium thermodynamic properties of these proteins are governed by protein folds associated with specific transition metals and ligands at the active site. A global analysis of holoenzyme structures and functions suggests that there are fewer than approximately 500 fundamental oxidoreductases, which can be further clustered into 35 unique groups. These catalysts evolved in prokaryotes early in the Earth's history and are largely responsible for the emergence of nonequilibrium biogeochemical cycles on the planet's surface. Although the evolutionary history of the amino acid sequences in the oxidoreductases is very difficult to reconstruct due to gene duplication and horizontal gene transfer, the evolution of the folds in the catalytic sites can potentially be used to infer the history of these enzymes. Using a novel, yet simple analysis of the secondary structures associated with the ligands in oxidoreductases, we developed a structural phylogeny of these enzymes. The results of this 'composome' analysis suggest an early split from a basal set of a small group of proteins dominated by loop structures into two families of oxidoreductases, one dominated by α-helices and the second by β-sheets. The structural evolutionary patterns in both clades trace redox gradients and increased hydrogen bond energy in the active sites. The overall pattern suggests that the evolution of the oxidoreductases led to decreased entropy in the transition metal folds over approximately 2.5 billion years, allowing the enzymes to use increasingly oxidized substrates with high specificity.

Many technologies for older adults are designed for them rather than with or by them. These technologies, including everything from home monitoring systems to assistive robots, are often designed to help them age in place. Researchers and designers can be reluctant to involve older adults in the design process, in part due to stereotypes that paint older adults as technology averse. Older adults are a group with a wealth of experience that researchers and designers can support to contribute to HCI, especially a group with a specific skillset, such as older adult crafters. Older adult crafters could contribute to HCI by supporting them to integrate their expertise into tools that make creating with maker electronics easier. Maker electronics -- customizable hardware and software for creating with electronics -- share similarities with crafting. Both require creativity while creating a physical object. Researchers have developed connections between maker electronics and crafting, even including older adults in the design process. However, researchers are missing an opportunity to build on older adult crafters' decades of experience to support older adults without technical expertise to create with maker electronics. In this dissertation, I present my prior work supporting older adult crafters to design a craft-based electronic toolkit with and for older adult crafters. I explored older adult crafters' practices and identified the potential for an electronic toolkit through surveys and participatory design workshops. Next, I developed and evaluated an initial toolkit (Craftec v1). The toolkit showed promise, but I recognized the need for better teaching materials and scaffolded activities to prepare participants. Finally, I remotely co-designed crafted projects with older adult crafters, and developed an updated toolkit design (Craftec v3) for older adult crafters to craft their own projects. I make three key contributions through my work. First, I share a deeper understanding of older adult crafters' practices. Second, I developed a set of craft and maker electronic-based scaffolded activities and teaching materials to teach older adult crafters to create with electronics. Finally, I present Craftec v3, the craft-focused electronic toolkit for older adult crafters that I designed.

All life on Earth is dependent on biologically mediated electron transfer (i.e., redox) reactions that are not at thermodynamic equilibrium. Biological redox reactions originally evolved in prokaryotes and ultimately, over the first ∼ 2.5 billion years of Earth's history, formed a global electronic circuit. To maintain the circuit on a global scale requires that oxidants and reductants be transported; the two major planetary electron conductors that connect global metabolism are geological fluids - primarily the atmosphere and the oceans. Because all organisms exchange gases with the environment, the evolution of redox reactions has been a major force in modifying the chemistry at Earth's surface. First, a review is given of the discovery and consequences of redox reactions in microbes with a specific focus on the co-evolution of life and geochemical phenomena. With the larger picture in mind, the focus is then directed specifically to one of the earliest metabolic pathways on Earth. The reduction of elemental sulfur. is an important energy-conserving pathway in prokaryotes inhabiting geothermal environments, where sulfur respiration contributes to sulfur biogeochemical cycling. Despite this, the pathways through which elemental sulfur is reduced to hydrogen sulfide remain unclear in most microorganisms. We integrated growth experiments using Thermovibrio ammonificans, a deep-sea vent thermophile that conserves energy from the oxidation of hydrogen and reduction of both nitrate and elemental sulfur, with comparative transcriptomic and proteomic approaches, coupled with scanning electron microscopy. Our results revealed that two members of the FAD-dependent pyridine nucleotide disulfide reductase family, similar to sulfide-quinone reductase (SQR) and to NADH-dependent sulfur reductase (NSR), respectively, are over-expressed during sulfur respiration. Scanning electron micrographs and sulfur sequestration experiments indicated that direct access of T. ammonificans to sulfur particles strongly promoted growth. The sulfur metabolism of T. ammonificans appears to require abiotic transition from bulk elemental sulfur to polysulfide to nanoparticulate sulfur at an acidic pH, coupled to biological hydrogen oxidation. A coupled biotic-abiotic mechanism for sulfur respiration is put forward, mediated by an NSR-like protein as the terminal reductase.

We present first measurements of charged and neutral particle-flow correlations in pp collisions using the ATLAS calorimeters. Data were collected in 2009 and 2010 at centre-of-mass energies of 900 GeV and 7 TeV. Events were selected using a minimum-bias trigger which required a charged particle in scintillation counters on either side of the interaction point. Particle flows, sensitive to the underlying event, are measured using clusters of energy in the ATLAS calorimeters, taking advantage of their fine granularity. No Monte Carlo generator used in this analysis can accurately describe the measurements. The results are independent of those based on charged particles measured by the ATLAS tracking systems and can be used to constrain the parameters of Monte Carlo generators.

A measurement of the production cross-section for top quark pairs($\\ttbar$) in $pp$ collisions at $\\sqrt{s}=7 \\TeV$ is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in two different topologies: single lepton (electron $e$ or muon $\\mu$) with large missing transverse energy and at least four jets, and dilepton ($ee$, $\\mu\\mu$ or $e\\mu$) with large missing transverse energy and at least two jets. In a data sample of 2.9 pb-1, 37 candidate events are observed in the single-lepton topology and 9 events in the dilepton topology. The corresponding expected backgrounds from non-$\\ttbar$ Standard Model processes are estimated using data-driven methods and determined to be $12.2 \\pm 3.9$ events and $2.5 \\pm 0.6$ events, respectively. The kinematic properties of the selected events are consistent with SM $\\ttbar$ production. The inclusive top quark pair production cross-section is measured to be $\\sigmattbar=145 \\pm 31 ^{+42}_{-27}$ pb where the first uncertainty is statistical and the second systematic. The measurement agrees with perturbative QCD calculations.