1,290 research outputs found

    Ribosomal protein synthesis is not regulated at the translational level in Saccharomyces cerevisiae: balanced accumulation of ribosomal proteins L16 and rp59 is mediated by turnover of excess protein.

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    We have investigated the mechanisms whereby equimolar quantities of ribosomal proteins accumulate and assemble into ribosomes of the yeast Saccharomyces cerevisiae. Extra copies of the cry1 or RPL16 genes encoding ribosomal proteins rp59 or L16 were introduced into yeast by transformation. Excess cry1 or RPL16 mRNA accumulated in polyribosomes in these cells and was translated at wild-type rates into rp59 or L16 proteins. These excess proteins were degraded until their levels reached those of other ribosomal proteins. Identical results were obtained when the transcription of RPL16A was rapidly induced using GAL1-RPL16A promoter fusions, including a construct in which the entire RPL16A 5\u27-noncoding region was replaced with the GAL1 leader sequence. Our results indicate that posttranscriptional expression of the cry1 and RPL16 genes is regulated by turnover of excess proteins rather than autogenous regulation of mRNA splicing or translation. The turnover of excess rp59 or L16 is not affected directly by mutations that inactivate vacuolar hydrolases

    Inferring hidden states in Langevin dynamics on large networks: Average case performance

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    We present average performance results for dynamical inference problems in large networks, where a set of nodes is hidden while the time trajectories of the others are observed. Examples of this scenario can occur in signal transduction and gene regulation networks. We focus on the linear stochastic dynamics of continuous variables interacting via random Gaussian couplings of generic symmetry. We analyze the inference error, given by the variance of the posterior distribution over hidden paths, in the thermodynamic limit and as a function of the system parameters and the ratio {\alpha} between the number of hidden and observed nodes. By applying Kalman filter recursions we find that the posterior dynamics is governed by an "effective" drift that incorporates the effect of the observations. We present two approaches for characterizing the posterior variance that allow us to tackle, respectively, equilibrium and nonequilibrium dynamics. The first appeals to Random Matrix Theory and reveals average spectral properties of the inference error and typical posterior relaxation times, the second is based on dynamical functionals and yields the inference error as the solution of an algebraic equation.Comment: 20 pages, 5 figure

    Dihydrogen Binding to Isostructural S = 1/2 and S = 0 Cobalt Complexes

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    Two isostructural, nonclassical Co(H_2) complexes are prepared from their Co(N_2) precursors using tris(phosphino)silyl and tris(phosphino)borane ancillary ligands. Comproportionation of CoBr_2 and Co metal in the presence of TPB (tris-(o-diisopropylphophinophenyl)borane) gives (TPB)CoBr (4). One-electron reduction of 4 triggers N_2 binding to give (TPB)Co(N_2) (2-N_2) which is isostructural to previously reported [SiP_3]Co(N_2) (1-N_2) ([SiP_3] = tris-(o-diisopropylphosphinophenyl)silyl). Both 1-N_2 and 2-N_2 react with 1 atm H_2 to generate thermally stable H_2 complexes 1-H_2 and 2-H_2, respectively. Both complexes are characterized by a suite of spectroscopic techniques in solution and by X-ray crystallography. The H_2 and N_2 ligands in 2-H_2 and 2-N_2 are labile under ambient conditions and the binding equilibria are observable by temperature-dependent UV/vis. A van’t Hoff analysis allows for the ligand binding energetics to be determined (H_2: ΔHº = −12.5(3) kcal mol^(–1) and ΔSº = −26(3) cal K^(–1) mol^(–1); N_2: ΔHº = −13.9(7) kcal mol^(–1) and ΔSº = −32(5) cal K^(–1) mol^(–1))

    Size Resolved Measurements of Springtime Aerosol Particles over the Northern South China Sea

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    Large sources of aerosol particles and their precursors are ubiquitous in East Asia. Such sources are known to impact the South China Sea (henceforth SCS), a sometimes heavily polluted region that has been suggested as particularly vulnerable to climate change. To help elucidate springtime aerosol transport into the SCS, an intensive study was performed on the remote Dongsha (aka Pratas) Islands Atoll in spring 2010. As part of this deployment, a Davis Rotating-drum Uniform size-cut Monitor (DRUM) cascade impactor was deployed to collect size-resolved aerosol samples at the surface that were analyzed by X-ray fluorescence for concentrations of selected elements. HYSPLIT backtrajectories indicated that the transport of aerosol observed at the surface at Dongsha was occurring primarily from regions generally to the north and east. This observation was consistent with the apparent persistence of pollution and dust aerosol, along with sea salt, in the ground-based dataset. In contrast to the sea-level observations, modeled aerosol transport suggested that the westerly flow aloft (w700 hPa) transported smoke-laden air toward the site from regions from the south and west. Measured aerosol optical depth at the site was highest during time periods of modeled heavy smoke loadings aloft. These periods did not coincide with elevated aerosol concentrations at the surface, although the model suggested sporadic mixing of this free-tropospheric aerosol to the surface over the SCS. A biomass burning signature was not clearly identified in the surface aerosol composition data, consistent with this aerosol type remaining primarily aloft and not mixing strongly to the surface during the study. Significant vertical wind shear in the region also supports the idea that different source regions lead to varying aerosol impacts in different vertical layers, and suggests the potential for considerable vertical inhomogeneity in the SCS aerosol environment

    Parvovirus B19 infection associated with the production of antineutrophil cytoplasmic antibody (ANCA) and anticardiolipin antibody (aCL

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    We described four patients who had clinical diagnosis of erythema infectiosum and presented with skin rash, polyarthralgia, polyarthritis, and mild fever. Anti-parvovirus B19 IgM and IgG antibodies were found in all four patients and parvovirus B19 DNA was detected in three of the four patients by polymerase chain reaction (PCR) in sera using standard methods. Anticardiolipin antibody (aCL) was positive in three of the four patients included three with anti-b2 glycoprotein I (b2GPI). The immunoglobulin isotype of aCL was found to be IgM. Anti-neutrophil cytoplasmic antibody (ANCA) included three p-ANCA and one c-ANCA was detected in all four patients by indirect immuno¯uoresence (IIF). Both anti-proteinase 3 (PR3) and anti-myeloperoxidase (MPO) antibodies were found in two patients whom had polyarthritis for more than 6 months. These data indicate parvovirus B19 may be linked to the induction of an autoimmune response. Lupus (2000) 9, 551±554
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