Direct Detection of α-Synuclein Dimerization Dynamics: Single-Molecule Fluorescence Analysis

The aggregation of α-synuclein (α-Syn) is linked to Parkinson’s disease. The mechanism of early aggregation steps and the effect of pathogenic single-point mutations remain elusive. We report here a single-molecule fluorescence study of α-Syn dimerization and the effect of mutations. Specific interactions between tethered fluorophore-free α-Syn monomers on a substrate and fluorophore-labeled monomers diffusing freely in solution were observed using total internal reflection fluorescence microscopy. The results showed that wild-type (WT) α-Syn dimers adopt two types of dimers. The lifetimes of type 1 and type 2 dimers were determined to be 197 ± 3 ms and 3334 ± 145 ms, respectively. All three of the mutations used, A30P, E46K, and A53T, increased the lifetime of type 1 dimer and enhanced the relative population of type 2 dimer, with type 1 dimer constituting the major fraction. The kinetic stability of type 1 dimers (expressed in terms of lifetime) followed the order A30P (693 ± 14 ms) > E46K (292 ± 5 ms) > A53T (226 ± 6 ms) > WT (197 ± 3 ms). Type 2 dimers, which are more stable, had lifetimes in the range of several seconds. The strongest effect, observed for the A30P mutant, resulted in a lifetime 3.5 times higher than observed for the WT type 1 dimer. This mutation also doubled the relative fraction of type 2 dimer. These data show that single-point mutations promote dimerization, and they suggest that the structural heterogeneity of α-Syn dimers could lead to different aggregation pathways.     

Life cycle assessment of automotive fuels: critical analysis and recommendations on the emissions inventory in the tank to wheels stage

Purpose  

As new alternative automotive fuels are being developed, life cycle assessment (LCA) is being used to assess the sustainability of these new options. A fuel LCA is commonly referred as a “Well To Wheels” analysis and calculates the environmental impacts of producing the fuel (the “Well To Tank” stage) and using it to move a car (the “Tank To Wheels” stage, TTW). The TTW environmental impacts are the main topic of this article.     

Effective production of the biodiesel additive STBE by a continuous flow process

A new fuel additive, namely solketal tert-butyl ether (STBE), was developed and optimized under continuous flow conditions using a Corning? Advanced-Flow? glass reactor. STBE was obtained in two steps from glycerol, a renewable building-block produced in large amount in the processing of biodiesel. The advantages of the highly engineered Corning glass reactor included high mixing and heat-exchange efficiency, chemical resistance under corrosive flow conditions and a small hold-up. A robust, continuous, green and safe industrial-scale process is described.     

Phylogenetic ecology of widespread uncultured clades of the Kingdom Euryarchaeota

Despite its widespread distribution and high levels of phylogenetic diversity, microbes are poorly understood creatures. We applied a phylogenetic ecology approach in the Kingdom Euryarchaeota (Archaea) to gain insight into the environmental distribution and evolutionary history of one of the most ubiquitous and largely unknown microbial groups. We compiled 16S rRNA gene sequences from our own sequence libraries and public genetic databases for two of the most widespread mesophilic Euryarchaeota clades, Lake Dagow Sediment (LDS) and Rice Cluster-V (RC-V). The inferred population history indicated that both groups have undergone specific nonrandom evolution within environments, with several noteworthy habitat transition events. Remarkably, the LDS and RC-V groups had enormous levels of genetic diversity when compared with other microbial groups, and proliferation of sequences within each single clade was accompanied by significant ecological differentiation. Additionally, the freshwater Euryarchaeota counterparts unexpectedly showed high phylogenetic diversity, possibly promoted by their environmental adaptability and the heterogeneous nature of freshwater ecosystems. The temporal phylogenetic diversification pattern of these freshwater Euryarchaeota was concentrated both in early times and recently, similarly to other much less diverse but deeply sampled archaeal groups, further stressing that their genetic diversity is a function of environment plasticity. For the vast majority of living beings on Earth (i.e. the uncultured microorganisms), how they differ in the genetic or physiological traits used to exploit the environmental resources is largely unknown. Inferring population history from 16S rRNA gene-based molecular phylogenies under an ecological perspective may shed light on the intriguing relationships between lineage, environment, evolution and diversity in the microbial world.     

Galleria mellonella as a model for studying Enterococcus faecium host persistence

Enterococcus faecium is an opportunistic pathogen responsible for numerous outbreaks worldwide. The basis for the colonization capacities, host persistence and environmental stress response of the hospital-adapted clones emerging from E. faecium are poorly understood. In this study, we propose the use of Galleria mellonella as a simple nonmammalian model to assess E. faecium host persistence. Various strains (n = 10), including hospital-adapted, commensal or animal isolates and a SodA-deficient strain were used to assess the relevance of this model. Compared to Enterococcus faecalis, E. faecium strains do not appear very lethal in a Galleria killing assay. The ability of E. faecium strains to overcome host-immune responses and multiply within the host system was evaluated by monitoring bacterial loads following Galleria infection. Among the E. faecium strains, two hospital-adapted isolates displayed increased colonization ability. In contrast, inactivation of sodA, encoding a putative manganese-dependent superoxide dismutase, significantly reduced survival of E. faecium to Galleria defenses. Galleria appears to be a suitable and convenient surrogate model to study E. faecium survival to host defenses and the role of suspected virulence factors in the colonization process.     

Gain of function of mutant p53 by coaggregation with multiple tumor suppressors

Many p53 missense mutations possess dominant-negative activity and oncogenic gain of function. We report that for structurally destabilized p53 mutants, these effects result from mutant-induced coaggregation of wild-type p53 and its paralogs p63 and p73, thereby also inducing a heat-shock response. Aggregation of mutant p53 resulted from self-assembly of a conserved aggregation-nucleating sequence within the hydrophobic core of the DNA-binding domain, which becomes exposed after mutation. Suppressing the aggregation propensity of this sequence by mutagenesis abrogated gain of function and restored activity of wild-type p53 and its paralogs. In the p53 germline mutation database, tumors carrying aggregation-prone p53 mutations have a significantly lower frequency of wild-type allele loss as compared to tumors harboring nonaggregating mutations, suggesting a difference in clonal selection of aggregating mutants. Overall, our study reveals a novel disease mechanism for mutant p53 gain of function and suggests that, at least in some respects, cancer could be considered an aggregation-associated disease.     

Gold mining in the Peruvian Amazon: global prices, deforestation, and mercury imports

Many factors such as poverty, ineffective institutions and environmental regulations may prevent developing countries from managing how natural resources are extracted to meet a strong market demand. Extraction for some resources has reached such proportions that evidence is measurable from space. We present recent evidence of the global demand for a single commodity and the ecosystem destruction resulting from commodity extraction, recorded by satellites for one of the most biodiverse areas of the world. We find that since 2003, recent mining deforestation in Madre de Dios, Peru is increasing nonlinearly alongside a constant annual rate of increase in international gold price (∼18%/yr). We detect that the new pattern of mining deforestation (1915 ha/year, 2006–2009) is outpacing that of nearby settlement deforestation. We show that gold price is linked with exponential increases in Peruvian national mercury imports over time (R² = 0.93, p = 0.04, 2003–2009). Given the past rates of increase we predict that mercury imports may more than double for 2011 (∼500 t/year). Virtually all of Peru''s mercury imports are used in artisanal gold mining. Much of the mining increase is unregulated/artisanal in nature, lacking environmental impact analysis or miner education. As a result, large quantities of mercury are being released into the atmosphere, sediments and waterways. Other developing countries endowed with gold deposits are likely experiencing similar environmental destruction in response to recent record high gold prices. The increasing availability of satellite imagery ought to evoke further studies linking economic variables with land use and cover changes on the ground.     

IL-22 is produced by innate lymphoid cells and limits inflammation in allergic airway disease

Interleukin (IL)-22 is an effector cytokine, which acts primarily on epithelial cells in the skin, gut, liver and lung. Both pro- and anti-inflammatory properties have been reported for IL-22 depending on the tissue and disease model. In a murine model of allergic airway inflammation, we found that IL-22 is predominantly produced by innate lymphoid cells in the inflamed lungs, rather than TH cells. To determine the impact of IL-22 on airway inflammation, we used allergen-sensitized IL-22-deficient mice and found that they suffer from significantly higher airway hyperreactivity upon airway challenge. IL-22-deficiency led to increased eosinophil infiltration lymphocyte invasion and production of CCL17 (TARC), IL-5 and IL-13 in the lung. Mice treated with IL-22 before antigen challenge displayed reduced expression of CCL17 and IL-13 and significant amelioration of airway constriction and inflammation. We conclude that innate IL-22 limits airway inflammation, tissue damage and clinical decline in allergic lung disease.