Bacterial ribosome requires multiple L12 dimers for efficient initiation and elongation of protein synthesis involving IF2 and EF-G

The ribosomal stalk in bacteria is composed of four or six copies of L12 proteins arranged in dimers that bind to the adjacent sites on protein L10, spanning 10 amino acids each from the L10 C-terminus. To study why multiple L12 dimers are required on the ribosome, we created a chromosomally engineered Escherichia coli strain, JE105, in which the peripheral L12 dimer binding site was deleted. Thus JE105 harbors ribosomes with only a single L12 dimer. Compared to MG1655, the parental strain with two L12 dimers, JE105 showed significant growth defect suggesting suboptimal function of the ribosomes with one L12 dimer. When tested in a cell-free reconstituted transcription–translation assay the synthesis of a full-length protein, firefly luciferase, was notably slower with JE105 70S ribosomes and 50S subunits. Further, in vitro analysis by fast kinetics revealed that single L12 dimer ribosomes from JE105 are defective in two major steps of translation, namely initiation and elongation involving translational GTPases IF2 and EF-G. Varying number of L12 dimers on the ribosome can be a mechanism in bacteria for modulating the rate of translation in response to growth condition

Measurement of the Crab Nebula Spectrum Past 100 TeV with HAWC

We present TeV gamma-ray observations of the Crab Nebula, the standard reference source in ground-based gamma-ray astronomy, using data from the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory. In this analysis we use two independent energy-estimation methods that utilize extensive air shower variables such as the core position, shower angle, and shower lateral energy distribution. In contrast, the previously published HAWC energy spectrum roughly estimated the shower energy with only the number of photomultipliers triggered. This new methodology yields a much improved energy resolution over the previous analysis and extends HAWC's ability to accurately measure gamma-ray energies well beyond 100 TeV. The energy spectrum of the Crab Nebula is well fit to a log parabola shape $\left(\frac{dN}{dE} = \phi_0 \left(E/\textrm{7 TeV}\right)^{-\alpha-\beta\ln\left(E/\textrm{7 TeV}\right)}\right)$ with emission up to at least 100 TeV. For the first estimator, a ground parameter that utilizes fits to the lateral distribution function to measure the charge density 40 meters from the shower axis, the best-fit values are $\phi_o$=(2.35$\pm$0.04$^{+0.20}_{-0.21}$)$\times$10$^{-13}$ (TeV cm$^2$ s)$^{-1}$, $\alpha$=2.79$\pm$0.02$^{+0.01}_{-0.03}$, and $\beta$=0.10$\pm$0.01$^{+0.01}_{-0.03}$. For the second estimator, a neural network which uses the charge distribution in annuli around the core and other variables, these values are $\phi_o$=(2.31$\pm$0.02$^{+0.32}_{-0.17}$)$\times$10$^{-13}$ (TeV cm$^2$ s)$^{-1}$, $\alpha$=2.73$\pm$0.02$^{+0.03}_{-0.02}$, and $\beta$=0.06$\pm$0.01$\pm$0.02. The first set of uncertainties are statistical; the second set are systematic. Both methods yield compatible results. These measurements are the highest-energy observation of a gamma-ray source to date.Comment: published in Ap

Non-canonical Hedgehog signaling mediates profibrotic hematopoiesis-stroma crosstalk in myeloproliferative neoplasms

The role of hematopoietic Hedgehog signaling in myeloproliferative neoplasms (MPNs) remains incompletely understood despite data suggesting that Hedgehog (Hh) pathway inhibitors have therapeutic activity in patients. We aim to systematically interrogate the role of canonical vs. non-canonical Hh signaling in MPNs. We show that Gli1 protein levels in patient peripheral blood mononuclear cells (PBMCs) mark fibrotic progression and that, in murine MPN models, absence of hematopoietic Gli1, but not Gli2 or Smo, significantly reduces MPN phenotype and fibrosis, indicating that GLI1 in the MPN clone can be activated in a non-canonical fashion. Additionally, we establish that hematopoietic Gli1 has a significant effect on stromal cells, mediated through a druggable MIF-CD74 axis. These data highlight the complex interplay between alterations in the MPN clone and activation of stromal cells and indicate that Gli1 represents a promising therapeutic target in MPNs, particularly that Hh signaling is dispensable for normal hematopoiesis.</p

Development of a photosynthesis model with an emphasis on ecological applications

In this paper, a description of photosynthesis in a single leaf is developed that separates physiological sub-processes and that is practical to apply as an ecological tool. Temperature dependencies are emphasized with the ultimate aim of linking such a description of photosynthesis with equations describing the energy budget of particular leaves. The description of photosynthesis can be applied to C 4 plants at this time and is needed to describe photosynthesis in C 3 plants when photorespiration is included. If the model is used to analyze at various times the response of a plant adjusting its metabolism to changes in light, temperature, or other factors experienced during growth, we will obtain a dynamic picture of the acclimation process. It will also be possible to determine the phenotypic plasticity of particular plants with respect to the metabolic sub-processes outlined.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47715/1/442_2004_Article_BF00582888.pd

Gamma-ray Emission from Classical Nova V392 Per: Measurements from Fermi and HAWC

This paper reports on the $\gamma$-ray properties of the 2018 Galactic novaV392 Per, spanning photon energies $\sim$0.1 GeV to 100 TeV by combiningobservations from the Fermi Gamma-ray Space Telescope and the HAWC Observatory.In one of the most rapidly evolving $\gamma$-ray signals yet observed for anova, GeV $\gamma$ rays with a power law spectrum with index $\Gamma = 2.0 \pm0.1$ were detected over eight days following V392 Per's optical maximum. HAWCobservations constrain the TeV $\gamma$-ray signal during this time and alsobefore and after. We observe no statistically significant evidence of TeV$\gamma$-ray emission from V392 Per, but present flux limits. Tests of theextension of the Fermi/LAT spectrum to energies above 5 TeV are disfavored by 2standard deviations (95\%) or more. We fit V392 Per's GeV $\gamma$ rays withhadronic acceleration models, incorporating optical observations, and comparethe calculations with HAWC limits.<br

Study of the Very High Energy emission of M87 through its broadband spectral energy distribution

The radio galaxy M87 is the central dominant galaxy of the Virgo Cluster.Very High Energy (VHE,$\gtrsim 0.1$ TeV) emission, from M87 has been detectedby Imaging Air Cherenkov Telescopes (IACTs ). Recently, marginal evidence forVHE long-term emission has also been observed by the High Altitude WaterCherenkov (HAWC) Observatory, a gamma ray and cosmic-ray detector array locatedin Puebla, Mexico. The mechanism that produces VHE emission in M87 remainsunclear. This emission is originated in its prominent jet, which has beenspatially resolved from radio to X-rays. In this paper, we constructed aspectral energy distribution from radio to gamma rays that is representative ofthe non-flaring activity of the source, and in order to explain the observedemission, we fit it with a lepto-hadronic emission model. We found that thismodel is able to explain non-flaring VHE emission of M87 as well as an orphanflare reported in 2005.<br

Constraints on the very high energy gamma-ray emission from short GRBs with HAWC

Many gamma-ray bursts (GRBs) have been observed from radio wavelengths, and afew at very-high energies (VHEs, > 100GeV). The HAWC gamma-ray observatory iswell suited to study transient phenomena at VHEs due to its large field of viewand duty cycle. These features allow for searches of VHE emission and can probedifferent model assumptions of duration and spectra. In this paper, we use datacollected by HAWC between December 2014 and May 2020 to search for emission inthe energy range from 80 to 800 GeV coming from a sample 47 short GRBs thattriggered the Fermi, Swift and Konus satellites during this period. Thisanalysis is optimized to search for delayed and extended VHE emission withinthe first 20 s of each burst. We find no evidence of VHE emission, eithersimultaneous or delayed, with respect to the prompt emission. Upper limits (90%confidence level) derived on the GRB fluence are used to constrain thesynchrotron self-Compton forward-shock model. Constraints for the interstellardensity as low as $10^{-2}$ cm$^{-3}$ are obtained when assuming z=0.3 forbursts with the highest keV-fluences such as GRB 170206A and GRB 181222841.Such a low density makes observing VHE emission mainly from the fast coolingregime challenging.<br

Impact of diets with different proportions of linseed and sunflower oils on the growth, liver histology, immunological and chemical blood parameters, and proximate composition of pikeperch Sander lucioperca (L.)

The aim of the study was to determine the impact of applying different proportions of linseed (LO) and sunflower (SFO) oils in pikeperch diets on growth, histological changes in the liver, immunological and blood chemical parameters. The fish were fed isoenergetic and isoprotein feeds containing SFO (group 100SFO) or LO (group 100LO) in quantities of 67 g kg/feed, and a mixture of oils: 47 g SFO and 20 g LO kg/feed (group 70SFO/30LO) and 20 g SFO and 47 g LO kg/feed (group 30SFO/70LO). Dietary ratios of polyunsaturated fatty acids from the n-3 and n-6 series (n3/n6 index) were 0.36–2.15. Pikeperch were reared for 56 days in three replicates for each dietary treatment. Various dietary oils and ratios of n3/n6 did not impact fish growth, feed conversion ratio, viscerosomatic and hepatosomatic index, and size of the hepatocytes. Feeding the fish high quantities of LO and SO oils (groups 100LO and 100SFO) reduced the immunological response of the phagocytes and lymphocytes in the fish. Moreover, this resulted in significant differences among groups in the quantity of linolenic and linoleic acid in whole fish bodies, viscera, fillets, and livers. Various quantities of vegetable oils in the fish diets did not impact the quantity of arachidonic, eicosapentaenoic and docosahexaenoic acid in the fillets and livers. The immunological index and low quantities of linoleic acid in the fillets obtained in group 30SFO/70LO indicate that the n3/n6 dietary ratio of 1.35 was the most advantageous for feeding juvenile pikeperch feeds with vegetable oils