Yeast cytochrome c oxidase: a model system to study mitochondrial forms of the haem-copper oxidase superfamily.

The known subunits of yeast mitochondrial cytochrome c oxidase are reviewed. The structures of all eleven of its subunits are explored by building homology models based on the published structures of the homologous bovine subunits and similarities and differences are highlighted, particularly of the core functional subunit I. Yeast genetic techniques to enable introduction of mutations into the three core mitochondrially-encoded subunits are reviewed

Flowers in Space Attacked by Aliens: Understanding the Spatial Ecology Behind the Devastating Damage by a Thistle Bud Weevil on Pitcher’s Thistle at Whitefish Dunes State Park, WI

One of the most threatened plants in the Great Lakes region is Pitcher’s thistle (Cirsium pitcheri), which inhabits sand dunes along the shorelines of Lakes Michigan, Huron, and Superior. In addition to risks from habitat loss and invasive species, C. pitcheri are imperiled by a thistle bud weevil (Larinus planus) that was originally distributed for biological control of nonnative thistles. During the summer of 2014, we empirically studied the devastating damage caused by L. planus on a population of C. pitcheri at Whitefish Dunes State Park, WI, to determine what factors influence the distribution and intensity of damage. We devised three treatments isolating the effects of elevation and neighboring plants. Our experiment revealed that the low elevation treatment with the greater neighboring plant density experienced the most damage during both the early and late season assessments. Additionally, we demonstrated that different abiotic and biotic factors affect L. planus distribution and damage during the early season compared to the late season. Finally, we analyzed the thistle-weevil system from a spatial ecology perspective. These results have important implications for other studies of plant-insect interactions, offer a cautionary tale about biological control, and inform efforts to conserve C. pitcheri

Option values of low carbon technology policies: how to combine irreversibility effects and learning-by-doing in decisions

In this paper, the political dilemma of the deployment of a large-size low carbon technology (LCT) is analyzed. A simple dynamic model is developed to analyze the interrelation between irreversible investments and learning-by-doing within a context of exogenous uncertainty on carbon price. Contrasting results are obtained. In some cases, the usual irreversibility effects hold, fewer plants of the LCT should be developed when information is anticipated. In other cases, this result is reversed and information arrival can justify an early deployment of the LCT. More precisely, it is shown that marginal reasoning is limited when learning by-doing, and more generally endogenous technical change, is considered. When information arrival is anticipated the optimal policy can move from a corner optimum with no LCT deployment to an interior optimum with a strictly positive development

A few-electron quadruple quantum dot in a closed loop

We report the realization of a quadruple quantum dot device in a square-like configuration where a single electron can be transferred on a closed path free of other electrons. By studying the stability diagrams of this system, we demonstrate that we are able to reach the few-electron regime and to control the electronic population of each quantum dot with gate voltages. This allows us to control the transfer of a single electron on a closed path inside the quadruple dot system. This work opens the route towards electron spin manipulation using spin-orbit interaction by moving an electron on complex paths free of electron

Efficient C-Phase gate for single-spin qubits in quantum dots

Two-qubit interactions are at the heart of quantum information processing. For single-spin qubits in semiconductor quantum dots, the exchange gate has always been considered the natural two-qubit gate. The recent integration of magnetic field or g-factor gradients in coupled quantum dot systems allows for a one-step, robust realization of the controlled phase (C-Phase) gate instead. We analyze the C-Phase gate durations and fidelities that can be obtained under realistic conditions, including the effects of charge and nuclear field fluctuations, and find gate error probabilities of below 10-4, possibly allowing fault-tolerant quantum computation.Comment: 5 pages, 3 figure

First-principles study of high conductance DNA sequencing with carbon nanotube electrodes

Rapid and cost-effective DNA sequencing at the single nucleotide level might be achieved by measuring a transverse electronic current as single-stranded DNA is pulled through a nano-sized pore. In order to enhance the electronic coupling between the nucleotides and the electrodes and hence the current signals, we employ a pair of single-walled close-ended (6,6) carbon nanotubes (CNTs) as electrodes. We then investigate the electron transport properties of nucleotides sandwiched between such electrodes by using first-principles quantum transport theory. In particular we consider the extreme case where the separation between the electrodes is the smallest possible that still allows the DNA translocation. The benzene-like ring at the end cap of the CNT can strongly couple with the nucleobases and therefore both reduce conformational fluctuations and significantly improve the conductance. The optimal molecular configurations, at which the nucleotides strongly couple to the CNTs, and which yield the largest transmission, are first identified. Then the electronic structures and the electron transport of these optimal configurations are analyzed. The typical tunneling currents are of the order of 50 nA for voltages up to 1 V. At higher bias, where resonant transport through the molecular states is possible, the current is of the order of several $\mu$A. Below 1 V the currents associated to the different nucleotides are consistently distinguishable, with adenine having the largest current, guanine the second-largest, cytosine the third and finally thymine the smallest. We further calculate the transmission coefficient profiles as the nucleotides are dragged along the DNA translocation path and investigate the effects of configurational variations. Based on these results we propose a DNA sequencing protocol combining three possible data analysis strategies.Comment: 12 pages, 17 figures, 3 table