Synthesis and RNase L Binding and Activation of a 2-5A-(5′)-DNA-(3′)-PNA Chimera,a Novel Potential Antisense Molecule

Abstract

Fully automated solid-phase synthesis gave access to a hybrid in which 5′-phosphorylated-2′-5′-linked oligoadenylate (2–5A) is connected to the 5′-terminus of DNA which, in turn, is linked at the 3′-end to PNA [2–5A-(5′)-DNA-(3′)-PNA chimera]. This novel antisense molecule retains full RNase L activation potency while suffering only a slight reduction in binding affinity.     

Atomic Layer Deposition of Highly Transparent Platinum Counter Electrodes for Metal/Polymer Flexible Dye‐Sensitized Solar Cells

Atomic layer deposition (ALD) is used to deposit Pt nanoparticles at low temperature (25–150 °C) to fabricate highly transparent counter electrodes (CEs) for flexible dye‐sensitized solar cells (DSCs). The Pt nanoparticles (NPs) are deposited for different number of ALD cycles on indium tin oxide (ITO)/polyethylene naphthalate (PEN) substrates. Rutherford backscattering spectroscopy (RBS) and transmission electron microscopy (TEM) are used to assess the Pt NP loading, density, and size. There is a trade‐off between transparency and catalytic activity of the CE, and the best cell performances of back‐side‐illuminated DSCs (≈3.7% efficiency) are achieved for Pt ALD at temperatures in the range of 100–150 °C, even though deposition at 25 °C is also viable. The best cell produced with ALD platinized CE (100 cycles at 100 °C) outperforms the reference cells fabricated with electrodeposited and sputtered Pt CEs, with relative improvements in efficiency of 19% and 29%, respectively. In addition, these parameters are used to fabricate a large area CE for a sub‐module (active area of 17.6 cm²), resulting in an efficiency of 3.1%, which demonstrates the scalability of the process.     

Ovine pedomics: the first study of the ovine foot 16S rRNA-based microbiome

We report the first study of the bacterial microbiome of ovine interdigital skin based on 16S rRNA by pyrosequencing and conventional cloning with Sanger-sequencing. Three flocks were selected, one a flock with no signs of footrot or interdigital dermatitis, a second flock with interdigital dermatitis alone and a third flock with both interdigital dermatitis and footrot. The sheep were classified as having either healthy interdigital skin (H) and interdigital dermatitis (ID) or virulent footrot (VFR). The ovine interdigital skin bacterial community varied significantly by flock and clinical condition. The diversity and richness of operational taxonomic units was greater in tissue from sheep with ID than H or VFR-affected sheep. Actinobacteria, Bacteriodetes, Firmicutes and Proteobacteria were the most abundant phyla comprising 25 genera. Peptostreptococcus, Corynebacterium and Staphylococcus were associated with H, ID and VFR, respectively. Sequences of Dichelobacter nodosus, the causal agent of ovine footrot, were not amplified because of mismatches in the 16S rRNA universal forward primer (27F). A specific real-time PCR assay was used to demonstrate the presence of D. nodosus, which was detected in all samples including the flock with no signs of ID or VFR. Sheep with ID had significantly higher numbers of D. nodosus (10⁴–10⁹ cells per g tissue) than those with H or VFR feet.     

Reversal in competitive dominance of a toxic versus non-toxic cyanobacterium in response to rising CO2

Climate change scenarios predict a doubling of the atmospheric CO₂ concentration by the end of this century. Yet, how rising CO₂ will affect the species composition of aquatic microbial communities is still largely an open question. In this study, we develop a resource competition model to investigate competition for dissolved inorganic carbon in dense algal blooms. The model predicts how dynamic changes in carbon chemistry, pH and light conditions during bloom development feed back on competing phytoplankton species. We test the model predictions in chemostat experiments with monocultures and mixtures of a toxic and non-toxic strain of the freshwater cyanobacterium Microcystis aeruginosa. The toxic strain was able to reduce dissolved CO₂ to lower concentrations than the non-toxic strain, and became dominant in competition at low CO₂ levels. Conversely, the non-toxic strain could grow at lower light levels, and became dominant in competition at high CO₂ levels but low light availability. The model captured the observed reversal in competitive dominance, and was quantitatively in good agreement with the results of the competition experiments. To assess whether microcystins might have a role in this reversal of competitive dominance, we performed further competition experiments with the wild-type strain M. aeruginosa PCC 7806 and its mcyB mutant impaired in microcystin production. The microcystin-producing wild type had a strong selective advantage at low CO₂ levels but not at high CO₂ levels. Our results thus demonstrate both in theory and experiment that rising CO₂ levels can alter the community composition and toxicity of harmful algal blooms.     

Lipid metabolism in myelinating glial cells: lessons from human inherited disorders and mouse models

The integrity of central and peripheral nervous system myelin is affected in numerous lipid metabolism disorders. This vulnerability was so far mostly attributed to the extraordinarily high level of lipid synthesis that is required for the formation of myelin, and to the relative autonomy in lipid synthesis of myelinating glial cells because of blood barriers shielding the nervous system from circulating lipids. Recent insights from analysis of inherited lipid disorders, especially those with prevailing lipid depletion and from mouse models with glia-specific disruption of lipid metabolism, shed new light on this issue. The particular lipid composition of myelin, the transport of lipid-associated myelin proteins, and the necessity for timely assembly of the myelin sheath all contribute to the observed vulnerability of myelin to perturbed lipid metabolism. Furthermore, the uptake of external lipids may also play a role in the formation of myelin membranes. In addition to an improved understanding of basic myelin biology, these data provide a foundation for future therapeutic interventions aiming at preserving glial cell integrity in metabolic disorders.     

Boosting the Performance of WO3/n‐Si Heterostructures for Photoelectrochemical Water Splitting: from the Role of Si to Interface Engineering

Metal oxide/Si heterostructures make up an exciting design route to high‐performance electrodes for photoelectrochemical (PEC) water splitting. By monochromatic light sources, contributions of the individual layers in WO₃/n‐Si heterostructures are untangled. It shows that band bending near the WO₃/n‐Si interface is instrumental in charge separation and transport, and in generating a photovoltage that drives the PEC process. A thin metal layer inserted at the WO₃/n‐Si interface helps in establishing the relation among the band bending depth, the photovoltage, and the PEC activity. This discovery breaks with the dominant Z‐scheme design idea, which focuses on increasing the conductivity of an interface layer to facilitate charge transport, but ignores the potential profile around the interface. Based on the analysis, a high‐work‐function metal is predicted to provide the best interface layer in WO₃/n‐Si heterojunctions. Indeed, the fabricated WO₃/Pt/n‐Si photoelectrodes exhibit a 2 times higher photocurrent density at 1.23 V versus reversible hydrogen electrode (RHE) and a 10 times enhancement at 1.6 V versus RHE compared to WO₃/n‐Si. Here, it is essential that the native SiO₂ layer at the interface between Si and the metal is kept in order to prevent Fermi level pinning in the Schottky contact between the Si and the metal.     

Efficient, chemoselective synthesis of immunomicelles using single-domain antibodies with a C-terminal thioester

Background  

Classical bioconjugation strategies for generating antibody-functionalized nanoparticles are non-specific and typically result in heterogeneous compounds that can be compromised in activity. Expression systems based on self-cleavable intein domains allow the generation of recombinant proteins with a C-terminal thioester, providing a unique handle for site-specific conjugation using native chemical ligation (NCL). However, current methods to generate antibody fragments with C-terminal thioesters require cumbersome refolding procedures, effectively preventing application of NCL for antibody-mediated targeting and molecular imaging.     

Estimating the frequency of Asian cytochrome B haplotypes in standard European and local Spanish pig breeds

Mitochondrial DNA has been widely used to perform phylogenetic studies in different animal species. In pigs, genetic variability at the cytochrome B gene and the D-loop region has been used as a tool to dissect the genetic relationships between different breeds and populations. In this work, we analysed four SNP at the cytochrome B gene to infer the Asian (A1 and A2 haplotypes) or European (E1 and E2 haplotypes) origins of several European standard and local pig breeds. We found a mixture of Asian and European haplotypes in the Canarian Black pig (E1, A1 and A2), German Piétrain (E1, A1 and A2), Belgian Piétrain (E1, A1), Large White (E1 and A1) and Landrace (E1 and A1) breeds. In contrast, the Iberian (Guadyerbas, Ervideira, Caldeira, Campanario, Puebla and Torbiscal strains) and the Majorcan Black pig breeds only displayed the E1 haplotype. Our results show that the introgression of Chinese pig breeds affected most of the major European standard breeds, which harbour Asian haplotypes at diverse frequencies (15–56%). In contrast, isolated local Spanish breeds, such as the Iberian and Majorcan Black pig, only display European cytochrome B haplotypes, a feature that evidences that they were not crossed with other Chinese or European commercial populations. These findings illustrate how geographical confinement spared several local Spanish breeds from the extensive introgression event that took place during the 18th and 19th centuries in Europe.     

Meiotic analysis of four cross-pollinated generations in a synthetic autotetraploid population of husk tomato (<i>Physalis ixocarpa</i>)

The cultivated husk tomato (Physalis ixocarpa) (2n = 2x = 24) is native from Mexico and Central America and shows a wide genetic variation. Presently, it is the fourth horticultural crop in cultivation surface in Mexico. The working team of this research previously developed an autotetraploid population by using colchicine. The objectives of the present work were to analyze the ploidy level and meiotic behavior of the subsequent generations (C3, C4, C5, C6) from the original (C2) composed only by plants with the duplicated genome from the Rendidora cultivar, and to determine pollen viability. As a diploid control the cultivar Rendidora of P. ixocarpa was used. Ploidy level was determined by flow citometry and meiotic analysis. For the meiotic study, the microsporocytes were prepared by the squash method, stained with carmin and analyzed in diakinesis. Pollen viability was evaluated through 0.01% Buffalo Black staining. The tetraploid condition prevailed through four cross-pollinating generations, maintaining a constant chromosome number 2n = 4x = 48. In diakinesis, the chromosomes of the diploid cultivar were associated into bivalents, whereas in tetraploid plants the chromosomes associated into univalents, bivalents and trivalents. Highly significant differences in bivalent pairing were detected between autotetraploid plants and between generations. Pollen viability did not show significant differences between generations and allowed reproduction. These results indicate that it is possible to develop an autotetraploid cultivar, because the polyploid state is naturally maintained and the plants are fertile. Furthermore, given the differences in bivalent pairing between plants and generations, a response to selection toward meiotic stability is expected.