Biophysical Characterization Of The Folding, Membrane Topology And Ion Transport Activity Of Ucp2 Using Selective Trp Mutants

Human Uncoupling Protein 2 (hUCP2) is one of five known human UCPs which are found in the inner mitochondrial membrane and have been shown to facilitate the translocation of protons from the intermembrane space to the mitochondrial matrix. The detailed physiological role of UCP2 proton transport, the mechanism by which it mediates this proton transport, as well as its structure has also yet to be elucidated. In order to help determine the topology of UCP2 embedded in the membrane as well as its mechanism of proton transport, the intrinsic fluorescence properties of the two tryptophan residues (Trp) present in its structure (W176 and W283) were used. To this end, three substitution mutants were created by site-directed mutagenesis using primer overlap-extension PCR; these were: W176Y, W283F and W176Y-W283F. The three mutant cDNAs then introduced into a membrane-targeted bacterial expression system from which they were then expressed in E. coli and purified via autoinduction and immobilized metal affinity chromatography (IMAC). Fluorescence and circular dichroism spectroscopy were then used to confirm that the mutants retained native-like conformations. Fluorescence quenching assays with acrylamide were performed to probe the topology of UCP2 embedded in the membrane via the differing accessibility of each Trp to the acrylamide quencher. The final stage of this project involved probing the effects of the Trp residues on the proton transport activity of UCP2 via a proton transport assay previously developed in our lab. Unfortunately, the presence of high background fluorescence, as seen in the W176Y-W283F fluorescence spectra with excitation at 295nm, either due to tryptophan containing-proteinaceous contaminants in the sample, or the presence of a deprotonated tyrosine residue (tyrosinate) in the folded structure of UCP2, has made it impossible to draw any definitive conclusions from the intrinsic fluorescence assays. The results of the proton transport assay for the W176Y-W283F Trp mutant and wt UCP2 indicate a role for the conserved UCP Trp residues in the proton transport activity of the protein based on a 26.7% reduction in the transport rate of the double mutant in comparison to the wt protein

The Great COVID-19 Vaccine Rollout: Behavioral and Policy Responses

Using daily data on vaccinations, disease spread, and measures of social interaction from Google Mobility reports aggregated at the country level for 112 countries, we present estimates of behavioral responses to the global rollout of COVID-19 vaccines. We first estimate correlates of the timing and intensity of the vaccination rollout, finding that countries which vaccinated more of their population earlier strongly tended to be richer, whereas measures of the state of pandemic or its death toll up to the time of the initial vaccine rollout had little predictive ability after controlling for income. Estimates of models of social distancing and disease spread suggest that countries which vaccinated more quickly also experienced decreases in some measures of social distancing, yet also lower incidence of disease, and in these countries policy makers relaxed social distancing measures relative to countries which rolled out vaccinations more slowl

Fall Migration of Ringed Seals (Phoca hispida) through the Beaufort and Chukchi Seas, 2001–02

In a study examining the range, distribution, and habitat use of the ringed seal, Phoca hispida, in Canada’s Western Arctic, eight ringed seals were live-captured, instrumented with satellite-linked (SLTDR-16) transmitters, and released at Cape Parry, Northwest Territories, Canada, on 17 – 19 September 2001 and 7 – 8 September 2002. Locations accepted by the filtering process were received from seven of the eight tagged seals (5 subadults, 1 adult female, 1 pup) over periods ranging from 35 to 207 days (mean 99 d, SD 66). Mean rates of travel were 0.91 m/s (SE 0.011, n = 7) in the Canadian Beaufort Sea, 0.92 m/s (SE 0.014, n = 7) offshore of Alaska’s North Slope, and 0.79 m/s (SE 0.008, n = 5) in the Chukchi Sea. On average, the seals took 32 days (range 19 – 56 d) to migrate between Cape Parry and Point Barrow, almost always remaining within 100 km of shore and over the continental shelf or slope, and covering an average migration distance of 2138 km. Dive depths for all groupings were mainly in the 4 – 80 m range (adult female: 63 – 73%; subadults: 54 – 73%; pup: 64 – 82%), with only the adult female diving deeper than 80 m on occasion, mainly in the Canadian Beaufort Sea (15.1% of her dives). The subadults and pup dove mainly for more than 1 to 5 min (60% and 55%, respectively), while a large proportion of the adult female’s dives were longer (34% for > 1 to 5 min; 31% for > 5 to 8 min; 5.4% for > 8 min). The tracks of the westward migrating seals revealed a routing through three political jurisdictions (including oil and gas industry lease areas in all three) over a period of about two months. This pattern highlights the importance of cooperation between the United States, Canada, and Russia in managing this species.Du 17 au 19 septembre 2001 et les 7 et 8 septembre 2002, dans le cadre d’une étude portant sur le parcours, la répartition et l’utilisation de l’habitat du phoque annelé, Phoca hispida, dans l’ouest de l’Arctique canadien, huit phoques annelés ont été capturés en vie, dotés de transmetteurs en liaison avec un satellite (SLTDR-16), puis relâchés au cap Parry, dans les Territoires du Nord-Ouest, au Canada. Des emplacements acceptés par filtrage ont été reçus de la part de sept des huit phoques marqués (5 préreproducteurs, 1 femelle adulte, 1 jeune) sur des périodes variant entre 35 et 207 jours (moyenne 99 d, SD 66). Les taux de déplacement moyens étaient de 0,91 m/s (SE 0,011; n = 7) dans la mer canadienne de Beaufort, de 0,92 m/s (SE 0,014; n = 7) au large du versant nord de l’Alaska et de 0,79 m/s (SE 0,008; n = 5) dans la mer des Tchouktches. En moyenne, la migration des phoques entre le cap Parry et la pointe Barrow durait 32 jours (écart de 19 à 56 d), et les phoques restaient presque toujours en-dedans de 100 km de la côte et au-dessus de la pente ou du plateau continental. Ils couvraient en moyenne une distance de migration de 2 138 km. La profondeur des plongées de tous les groupements variait entre 4 et 80 m (femelle adulte : 63 % à 73 %; préreproducteurs : 54 % à 73 %; jeune : 64 % à 82 %), et seulement la femelle adulte plongeait à plus de 80 m de profondeur à l’occasion, surtout dans la mer canadienne de Beaufort (15,1 % de ses plongées). Les prérepro­ducteurs et le jeune phoque étaient principalement en plongée pendant plus de 1 à 5 min (60 % et 55 %, respectivement), tandis qu’une grande proportion des plongées de la femelle adulte durait plus longtemps (34 % pour > 1 à 5 min; 31 % pour > 5 à 8 min; 5,4 % pour > 8 min). Les pistes des phoques en migration vers l’ouest révélaient des itinéraires passant par trois compétences politiques (comprenant des concessions de l’industrie pétrolière et gazière dans les trois cas) sur une période d’environ deux mois. Cette tendance fait ressortir l’importance d’une collaboration entre les États-Unis, le Canada et la Russie en matière de gestion de cette espèce

Possible impacts of climate change on freezing rain in south-central Canada using downscaled future climate scenarios

Freezing rain is a major atmospheric hazard in mid-latitude nations of the globe. Among all Canadian hydrometeorological hazards, freezing rain is associated with the highest damage costs per event. Using synoptic weather typing to identify the occurrence of freezing rain events, this study estimates changes in future freezing rain events under future climate scenarios for south-central Canada. Synoptic weather typing consists of principal components analysis, an average linkage clustering procedure (i.e., a hierarchical agglomerative cluster method), and discriminant function analysis (a nonhierarchical method). Meteorological data used in the analysis included hourly surface observations from 15 selected weather stations and six atmospheric levels of six-hourly National Centers for Environmental Prediction (NCEP) upper-air reanalysis weather variables for the winter months (November&ndash;April) of 1958/59&ndash;2000/01. A statistical downscaling method was used to downscale four general circulation model (GCM) scenarios to the selected weather stations. Using downscaled scenarios, discriminant function analysis was used to project the occurrence of future weather types. The within-type frequency of future freezing rain events is assumed to be directly proportional to the change in frequency of future freezing rain-related weather types <br><br> The results showed that with warming temperatures in a future climate, percentage increases in the occurrence of freezing rain events in the north of the study area are likely to be greater than those in the south. By the 2050s, freezing rain events for the three colder months (December&ndash;February) could increase by about 85% (95% confidence interval &ndash; CI: &plusmn;13%), 60% (95% CI: &plusmn9%), and 40% (95% CI: &plusmn;6%) in northern Ontario, eastern Ontario (including Montreal, Quebec), and southern Ontario, respectively. The increase by the 2080s could be even greater: about 135% (95% CI: &plusmn;20%), 95% (95% CI: &plusmn;13%), and 45% (95% CI: &plusmn;9%). For the three warmer months (November, March, April), the percentage increases in future freezing rain events are projected to be much smaller with some areas showing either a decrease or little change in frequency of freezing rain. On average, northern Ontario could experience about 10% (95% CI: &plusmn;2%) and 20% (95% CI: &plusmn;4%) more freezing rain events by the 2050s and 2080s, respectively. However, future freezing rain events in southern Ontario could decrease about 10% (95% CI: &plusmn;3%) and 15% (95% CI: &plusmn;5%) by the 2050s and 2080s, respectively. In eastern Ontario (including Montreal, Quebec), the frequency of future freezing rain events is projected to remain the same as it is currently

Surface Flaw Detection with Ferromagnetic Resonance Probes

Small ferromagnetic resonators have been shown to provide effective electromagnetic detectors for surface flaws in magnetic and nonmagnetic metals. As such a resonator is moved along \u27the surface of a test piece it experiences a frequency shift when it passes over a flaw. lwo detection mechanisms are present: (1) an eddy current effect (2) a perturbation of the dc magnetic bias field used to tune the resonator. Results are given for experiments performed on machined slots in aluminum, titanium and steel and on tightly closed fatigue cracks in titanium. Results are also presented for some measurements on titanium aircraft fasteners

Efficient Cosmological Parameter Estimation with Hamiltonian Monte Carlo

Traditional Markov Chain Monte Carlo methods suffer from low acceptance rate, slow mixing and low efficiency in high dimensions. Hamiltonian Monte Carlo resolves this issue by avoiding the random walk. Hamiltonian Monte Carlo (HMC) is a Markov chain Monte Carlo (MCMC) technique built upon the basic principle of Hamiltonian mechanics. Hamiltonian dynamics allows the chain to move along trajectories of constant energy, taking large jumps in the parameter space with relatively inexpensive computations. This new technique improves the acceptance rate by a factor of 4 and boosts up the efficiency by at least a factor of D in a D-dimensional parameter space. Therefor shorter chains will be needed for a reliable parameter estimation comparing to a traditional MCMC chain yielding the same performance. Besides that, the HMC is well suited for sampling from non-Gaussian and curved distributions which are very hard to sample from using the traditional MCMC methods. The method is very simple to code and can be easily plugged into standard parameter estimation codes such as CosmoMC. In this paper we demonstrate how the HMC can be efficiently used in cosmological parameter estimation