Real-time assembly of ribonucleoprotein complexes on nascent RNA transcripts.

Cellular protein-RNA complexes assemble on nascent transcripts, but methods to observe transcription and protein binding in real time and at physiological concentrations are not available. Here, we report a single-molecule approach based on zero-mode waveguides that simultaneously tracks transcription progress and the binding of ribosomal protein S15 to nascent RNA transcripts during early ribosome biogenesis. We observe stable binding of S15 to single RNAs immediately after transcription for the majority of the transcripts at 35 °C but for less than half at 20 °C. The remaining transcripts exhibit either rapid and transient binding or are unable to bind S15, likely due to RNA misfolding. Our work establishes the foundation for studying transcription and its coupled co-transcriptional processes, including RNA folding, ligand binding, and enzymatic activity such as in coupling of transcription to splicing, ribosome assembly or translation

Estimativa da precipitação anual média e avaliação de sua influência na produção de milho no polo produtivo de Sergipe.

O Polo de Produção de Milho no Estado de Sergipe vem apresentando desde 2008 um aumento significativo de produção e produtividade, principalmente devido ao alto nível tecnológico adotado com a introdução de insumos agrícolas e práticas de preparo do solo modernas no sistema produtivo da região. A produção do milho nos municípios sergipanos está diretamente relacionada às alturas de precipitações anuais, tendo em vista que não há irrigação nesta região, sendo o cultivo depende de chuva. O presente estudo objetivou avaliar a influência da variabilidade interanual da precipitação, estimada por meio de interpolação matemática, na produção de milho dos municípios de Simão Dias, Carira, Frei Paulo, Pinhão e Poço Verde, em Sergipe, no período de 2003 a 2012. Verificou-se que apenas os volumes anuais precipitados não explicam toda a variação na produção, sendo necessário considerar o comportamento intra-anual da chuva, época de plantio e a aptidão agrícola das terras na região do estudo

On the Structure and Stability of Geometrical Isomers of N3F

The potential energy surfaces for the N3F molecule have been studied using multiconfigurational wave functions. Two new isomers were found, one on the singlet (1 A′) and one on the triplet (3 A″) surface. Both isomers have a three‐membered cyclic structure and C ssymmetry. The singlet cyclic isomer is endoergic relative to the open fluorine azide by 15–17 kcal/mol. Its kinetic stability is close to the stability of the open isomer: the barrier separating the cyclic isomer from the dissociation products N2(X  1Σ+ g )+NF(a  1Δ) is about 13–17 kcal/mol and is lower than the barrier to isomerization. The triplet cyclic isomer is much higher in energy (about 70 kcal/mol), with a barrier to dissociation to N2(X  1Σ+ g )+NF(X  3Σ−) on the order of 15 kcal/mol. Crossings of the 1 A′ and the 3 A″ surfaces may allow the cyclic singlet isomer to predissociate to the ground state products, N2(X  1Σ+ g )+NF(X  3Σ−). It is shown, however, that the singlet–triplet surface of intersection lies ‘behind’ the barrier to singlet decomposition, so that spin‐forbidden predissociation will not preclude detection of cyclic N3F

Hippocampal neurogenesis in the new model of global cerebral ischemia

The study aimed to evaluate the changes of hippocampal neurogenesis in a new model of global transient cerebral ischemia which was performed by the occlusion of the three main vessels (tr. brachiocephalicus, a. subclavia sinistra, and a. carotis communis sinistra) branching from the aortic arch and supplying the brain. Global transitory cerebral ischemia was modeled on male rats (weight = 250–300 g) under chloral hydrate with artificial lung ventilation. Animals after the same surgical operation without vessel occlusion served as sham-operated controls. The number of DCX-positive (doublecortin, the marker of immature neurons) cells in dentate gyrus (DG) and CA1-CA3 fields of hippocampus was counted at the 31st day after ischemia modeling. It was revealed that global cerebral ischemia decreased neurogenesis in dentate gyrus in comparison with the sham-operated group (P<0.05) while neurogenesis in CA1-CA3 fields was increased as compared to the control (P<0.05)

The efficiency of electron acceleration during the impulsive phase of a solar flare

Solar flares are known to be prolific electron accelerators, yet identifying the mechanism(s) for such efficient electron acceleration in solar flare (and similar astrophysical settings) presents a major challenge. This is due in part to a lack of observational constraints related to conditions in the primary acceleration region itself. Accelerated electrons with energies above $\sim$20~keV are revealed by hard X-ray (HXR) bremsstrahlung emission, while accelerated electrons with even higher energies manifest themselves through radio gyrosynchrotron emission. Here we show, for a well-observed flare on 2017~September~10, that a combination of \emph{RHESSI} hard X-ray and and SDO/AIA EUV observations provides a robust estimate of the fraction of the ambient electron population that is accelerated at a given time, with an upper limit of $\sim 10^{-2}$ on the number density of nonthermal ($\ge 20$~keV) electrons, expressed as a fraction of the number density of ambient protons in the same volume. This upper limit is about two orders of magnitude lower than previously inferred from microwave observations of the same event. Our results strongly indicate that the fraction of accelerated electrons in the coronal region at any given time is relatively small, but also that the overall duration of the HXR emission requires a steady resupply of electrons to the acceleration site. Simultaneous measurements of the instantaneous accelerated electron number density and the associated specific electron acceleration rate provide key constraints for a quantitative study of the mechanisms leading to electron acceleration in magnetic reconnection events.Comment: 5 figures, 10 page

Qualidade da água superficial para dessedentação animal na região do polo de produção de milho em Sergipe: diagnóstico preliminar.

No Estado de Sergipe, com a exponencial expansão do Polo de Produção de Milho em função do alto nível tecnológico que se passou a adotar nos últimos anos, está ocorrendo um processo de degradação dos recursos de solo e de água, o que pode comprometer tanto a sustentabilidade da própria atividade agrícola quanto da pecuária. Assim, este estudo tem o objetivo de realizar um diagnóstico da qualidade das águas superficiais para dessedentação animal na região do Polo de Produção de Milho em Sergipe. Para realizar o diagnóstico da qualidade da água superficial para uso animal em cinco pontos (P1, P2, P3, P4, e P5), localizados em áreas de produção de milho no Polo, foram analisados em laboratório os seguintes parâmetros: pH, condutividade elétrica (CE), sólidos dissolvidos totais (SDT), magnésio (Mg2+), demanda bioquímica de oxigênio (DBO) e atrazina. A água do ponto P1 apresenta a melhor qualidade da água, enquanto as águas dos pontos P4 e P5, as piores qualidades para uso na dessendentação animal. Há sinais do processo erosivo resultante das atividades antrópicas na região do Polo

Generation of GeV protons from 1 PW laser interaction with near critical density targets

The propagation of ultra intense laser pulses through matter is connected with the generation of strong moving magnetic fields in the propagation channel as well as the formation of a thin ion filament along the axis of the channel. Upon exiting the plasma the magnetic field displaces the electrons at the back of the target, generating a quasistatic electric field that accelerates and collimates ions from the filament. Two-dimensional Particle-in-Cell simulations show that a 1 PW laser pulse tightly focused on a near-critical density target is able to accelerate protons up to an energy of 1.3 GeV. Scaling laws and optimal conditions for proton acceleration are established considering the energy depletion of the laser pulse.Comment: 26 pages, 8 figure

Finding of the Low Molecular Weight Inhibitors of Resuscitation Promoting Factor Enzymatic and Resuscitation Activity

Background: Resuscitation promoting factors (RPF) are secreted proteins involved in reactivation of dormant actinobacteria, including Mycobacterium tuberculosis. They have been considered as prospective targets for the development of new antituberculosis drugs preventing reactivation of dormant tubercle bacilli, generally associated with latent tuberculosis. However, no inhibitors of Rpf activity have been reported so far. The goal of this study was to find low molecular weight compounds inhibiting the enzymatic and biological activities of Rpfs. Methodology/Principal Findings: Here we describe a novel class of 2-nitrophenylthiocyanates (NPT) compounds that inhibit muralytic activity of Rpfs with IC50 1–7 mg/ml. Fluorescence studies revealed interaction of active NPTs with the internal regions of the Rpf molecule. Candidate inhibitors of Rpf enzymatic activity showed a bacteriostatic effect on growth of Micrococcus luteus (in which Rpf is essential for growth protein) at concentrations close to IC50. The candidate compounds suppressed resuscitation of dormant (‘‘non-culturable’’) cells of M. smegmatis at 1 mg/ml or delayed resuscitation of dormant M. tuberculosis obtained in laboratory conditions at 10 mg/ml. However, they did not inhibit growth of active mycobacteria under these concentrations. Conclusions/Significance: NPT are the first example of low molecular weight compounds that inhibit the enzymatic an

X-ray phase contrast imaging of biological specimens with tabletop synchrotron radiation

Since their discovery in 1896, x-rays have had a profound impact on science, medicine and technology. Here we show that the x-rays from a novel tabletop source of bright coherent synchrotron radiation can be applied to phase contrast imaging of biological specimens, yielding superior image quality and avoiding the need for scarce or expensive conventional sources