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  • 1
    Publication Date: 2006-08-26
    Description: In higher eukaryotes, a multiprotein exon junction complex is deposited on spliced messenger RNAs. The complex is organized around a stable core, which serves as a binding platform for numerous factors that influence messenger RNA function. Here, we present the crystal structure of a tetrameric exon junction core complex containing the DEAD-box adenosine triphosphatase (ATPase) eukaryotic initiation factor 4AIII (eIF4AIII) bound to an ATP analog, MAGOH, Y14, a fragment of MLN51, and a polyuracil mRNA mimic. eIF4AIII interacts with the phosphate-ribose backbone of six consecutive nucleotides and prevents part of the bound RNA from being double stranded. The MAGOH and Y14 subunits lock eIF4AIII in a prehydrolysis state, and activation of the ATPase probably requires only modest conformational changes in eIF4AIII motif I.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Andersen, Christian B F -- Ballut, Lionel -- Johansen, Jesper S -- Chamieh, Hala -- Nielsen, Klaus H -- Oliveira, Cristiano L P -- Pedersen, Jan Skov -- Seraphin, Bertrand -- Le Hir, Herve -- Andersen, Gregers Rom -- New York, N.Y. -- Science. 2006 Sep 29;313(5795):1968-72. Epub 2006 Aug 24.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biology, University of Aarhus, DK-8000 Aarhus, Denmark.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16931718" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphate/analogs & derivatives/metabolism ; Adenylyl Imidodiphosphate/metabolism ; Amino Acid Motifs ; Amino Acid Sequence ; Animals ; Crystallography, X-Ray ; DEAD-box RNA Helicases ; Dimerization ; Drosophila Proteins/chemistry/metabolism ; Eukaryotic Initiation Factor-4A/*chemistry/metabolism ; *Exons ; Humans ; Hydrogen Bonding ; Hydrolysis ; Models, Molecular ; Molecular Sequence Data ; Mutation ; Neoplasm Proteins/*chemistry/metabolism ; Nuclear Proteins/*chemistry/metabolism ; Nucleic Acid Conformation ; Poly U/*chemistry/metabolism ; Protein Conformation ; Protein Structure, Secondary ; Protein Structure, Tertiary ; RNA Helicases/chemistry/metabolism ; RNA, Messenger/*chemistry/metabolism ; RNA-Binding Proteins/*chemistry/metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2015-08-20
    Description: The capacity of an advection/diffusion model to predict sand transport under varying wave and current conditions is evaluated. The horizontal sand transport rate is computed by vertical integration of the suspended sediment flux. A correction procedure for the near-bed concentration is proposed so that model results are independent of the vertical resolution. The method can thus be implemented in regional models with operational applications. Simulating equilibrium sand transport rates, when erosion and deposition are balanced, requires a new empirical erosion law that involves the non-dimensional excess shear stress and a parameter that depends on the size of the sand grain. Comparison with several datasets and sediment transport formulae demonstrated the model’s capacity to simulate sand transport rates for a large range of current and wave conditions and sand diameters in the range 100–500 μm. Measured transport rates were predicted within a factor two in 67% of cases with current only and in 35% of cases with both waves and current. In comparison with the results obtained by Camenen and Larroudé (2003), who provided the same indicators for several practical transport rate formulations (whose means are respectively 72% and 37%), the proposed approach gives reasonable results. Before fitting a new erosion law to our model, classical erosion rate formulations were tested but led to poor comparisons with expected sediment transport rates. We suggest that classical erosion laws should be used with care in advection/diffusion models similar to ours, and that at least a full validation procedure for transport rates involving a range of sand diameters and hydrodynamic conditions should be carried out.
    Electronic ISSN: 2077-1312
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by MDPI
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  • 3
    Publication Date: 2017-11-09
    Description: Geological evidence indicates that grounded ice sheets reached sea level at all latitudes during two long-lived Cryogenian (58 and ≥5 My) glaciations. Combined uranium-lead and rhenium-osmium dating suggests that the older (Sturtian) glacial onset and both terminations were globally synchronous. Geochemical data imply that CO 2 was 10 2 PAL (present atmospheric level) at the younger termination, consistent with a global ice cover. Sturtian glaciation followed breakup of a tropical supercontinent, and its onset coincided with the equatorial emplacement of a large igneous province. Modeling shows that the small thermal inertia of a globally frozen surface reverses the annual mean tropical atmospheric circulation, producing an equatorial desert and net snow and frost accumulation elsewhere. Oceanic ice thickens, forming a sea glacier that flows gravitationally toward the equator, sustained by the hydrologic cycle and by basal freezing and melting. Tropical ice sheets flow faster as CO 2 rises but lose mass and become sensitive to orbital changes. Equatorial dust accumulation engenders supraglacial oligotrophic meltwater ecosystems, favorable for cyanobacteria and certain eukaryotes. Meltwater flushing through cracks enables organic burial and submarine deposition of airborne volcanic ash. The subglacial ocean is turbulent and well mixed, in response to geothermal heating and heat loss through the ice cover, increasing with latitude. Terminal carbonate deposits, unique to Cryogenian glaciations, are products of intense weathering and ocean stratification. Whole-ocean warming and collapsing peripheral bulges allow marine coastal flooding to continue long after ice-sheet disappearance. The evolutionary legacy of Snowball Earth is perceptible in fossils and living organisms.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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