Lack of an Efficient Endoplasmic Reticulum-localized Recycling System Protects Peroxiredoxin IV from Hyperoxidation

Typical 2-Cys peroxiredoxins are required to remove hydrogen peroxide from several different cellular compartments. Their activity can be regulated by hyperoxidation and consequent inactivation of the active-site peroxidatic cysteine. Here we developed a simple assay to quantify the hyperoxidation of peroxiredoxins. Hyperoxidation of peroxiredoxins can only occur efficiently in the presence of a recycling system, usually involving thioredoxin and thioredoxin reductase. We demonstrate that there is a marked difference in the sensitivity of the endoplasmic reticulum-localized peroxiredoxin to hyperoxidation compared with either the cytosolic or mitochondrial enzymes. Each enzyme is equally sensitive to hyperoxidation in the presence of a robust recycling system. Our results demonstrate that peroxiredoxin IV recycling in the endoplasmic reticulum is much less efficient than in the cytosol or mitochondria, leading to the protection of peroxiredoxin IV from hyperoxidation.     

Analysis of potassium iodate reduction in tissue homogenates using high performance liquid chromatography–inductively coupled plasma-mass spectrometry

Potassium iodate (KIO₃) and potassium iodide (KI) are the major salt iodization agents used worldwide. Unlike iodide (I⁻), iodate (IO₃⁻) should be reduced to I⁻ before it can be effectively used by the thyroid. In this study, we developed a new method for analyzing IO₃⁻ and I⁻ in tissue homogenates using high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (HPLC–ICP-MS). We further applied the method to demonstrate the KIO₃ reduction process by tissues in vitro. The effects of KIO₃ on the total antioxidative activity (TAA) and reduced nicotinamide adenine dinucleotide phosphate (NADPH) were also investigated here. Finally, we found that IO₃⁻ can be reduced to I⁻ by tissue homogenates and IO₃⁻ irreversibly decreases the antioxidant capability of tissues. Our studies suggest that KIO₃ might have a big effect on the redox balance of tissue and would further result in oxidative stress of organisms.     

Estimating the human appropriation of land in Brazil by means of an Input–Output Economic Model and Ecological Footprint analysis

As we confront the current environmental crisis, determining the biophysical base (e.g., materials, energy, land, and water) of nations has become paramount. With advanced economies benefiting from the import of resource-intensive primary goods originating from poorer parts of the world, especially emerging nations, these are dilapidating their natural capital. Brazil is one of such emerging economies, whose mining and farming activities, propping up its export-led economic growth, exert great pressure on the environment. In particular, farming has been shown to have one of the world's greatest environmental impacts, especially as a consequence of land use associated with cattle ranching. Since a nation-wide evaluation of land-use types across the whole sectorial spectrum of the country's economy is still lacking, we used the most recently available Input–Output Economic Model for Brazil and the Ecological Footprint method to identify those economic sectors with the greatest potential for appropriating portions of the natural world.Our results show that: (i) the biggest chunk of Brazil's Ecological Footprint is due to its Carbon Footprint and, in particular, emissions from cattle; (ii) only a few economic sectors exhibit high Ecological Footprint values, chiefly those belonging to livestock farming and energy production based on fossil fuels; (iii) excluding the soybeans and slaughter sectors, export-oriented sectors have below-average Ecological Footprint values; and (iv) the percentage of Brazil's Ecological Footprint due to household consumption (excluding imports) is three times bigger than that attributable to exports, with sectors belonging to livestock farming contributing the most to such disparity.These results underscore that the environmental impact of the Brazilian economy can be drastically reduced by tackling the emission-intensive production processes of a few sectors only and disincentivizing the domestic consumption of a narrow range of products, especially with respect to the livestock segment.     

Specificity of Collybistin-Phosphoinositide Interactions: IMPACT OF THE INDIVIDUAL PROTEIN DOMAINS*

The regulatory protein collybistin (CB) recruits the receptor-scaffolding protein gephyrin to mammalian inhibitory glycinergic and GABAergic postsynaptic membranes in nerve cells. CB is tethered to the membrane via phosphoinositides. We developed an in vitro assay based on solid-supported 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine membranes doped with different phosphoinositides on silicon/silicon dioxide substrates to quantify the binding of various CB2 constructs using reflectometric interference spectroscopy. Based on adsorption isotherms, we obtained dissociation constants and binding capacities of the membranes. Our results show that full-length CB2 harboring the N-terminal Src homology 3 (SH3) domain (CB2_SH3+) adopts a closed and autoinhibited conformation that largely prevents membrane binding. This autoinhibition is relieved upon introduction of the W24A/E262A mutation, which conformationally “opens” CB2_SH3+ and allows the pleckstrin homology domain to properly bind lipids depending on the phosphoinositide species with a preference for phosphatidylinositol 3-monophosphate and phosphatidylinositol 4-monophosphate. This type of membrane tethering under the control of the release of the SH3 domain of CB is essential for regulating gephyrin clustering.     

Wildcat population density in NE Portugal: A regional stronghold for a nationally threatened felid

Population density data on depleted and endangered wildlife species are essential to assure their effective management and, ultimately, conservation. The European wildcat is an elusive and threatened species inhabiting the Iberian Peninsula, with fragmented populations and living in low densities. We fitted spatial capture–recapture models on camera-trap data, to provide the first estimate of wildcat density for Portugal and assess the most influential drivers determining it. The study was implemented in Montesinho Natural Park (NE Portugal), where we identified nine individuals, over a total effort of 3,477 trap-nights. The mean density estimate was 0.032 ± 0.012 wildcat/km², and density tended to increase with distance to humanized areas, often linked to lower human disturbance and domestic cat presence, with forest and herbaceous vegetation cover and with European rabbit abundance. Although, this density estimate is within the range of values estimated for protected areas elsewhere in the Iberian Peninsula, our estimates are low at the European level. When put in context, our results highlight that European wildcats may be living in low population densities across the Iberian Mediterranean biogeographic region. No phenotypic domestic or hybrid cats were detected, suggesting potentially low admixture rates between the two species, although genetic sampling would be required to corroborate this assertion. We provide evidence that Montesinho Natural Park may be a suitable area to host a healthy wildcat population, and thus be an important protected area in this species' conservation context.     

The effect of dielectric polarization of the electrode on anomalous temperature effects in the electrical double layer

Monte Carlo simulations and a modified Poisson–Boltzmann (MPB) theory are used to investigate the temperature dependence of the capacitance (around the potential of zero charge) of an electric double layer in the presence of surface polarization due to a dielectric boundary. Within the context of the restricted primitive model planar double layer, whose solvent dielectric constant is ε₂, the cases when the electrode is an insulator (ε₁ = 1), when the electrode and the electrolyte have the same permittivity (ε₁ = ε₂, no polarization), and when the electrode is a conductor (ε₁ → ∞) are studied for the case where the electrolyte concentration is 0.1 M. The simulations reveal a capacitance anomaly, that is, a positive temperature dependence of the capacitance at low temperatures for the former two situations. The MPB theory also shows this effect for these two situations and is in qualitative or better agreement with the simulation data. In these two cases, both the simulations and theory show a dramatic increase of the diffuse layer potential in the temperature regime where capacitance anomaly occurs. However, in the latter situation, where the electrode is metallic, the capacitance always has a negative temperature derivative for the MPB theory and probably also for the simulation data.     

On computational efficiency of the hybrid Monte Carlo method applied to the multicanonical ensemble

Abstract

In the present paper, computational efficiency of the hybrid Monte Carlo (HMC) method applied to the multicanonical ensemble is studied; the HMC is an equation of motion guided Monte Carlo method. As in the standard HMC for the canonical ensemble, the multicanonical HMC calculations with high acceptance ratio show better efficiency; about 60% acceptance yields the best performance for the system examined.