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  • ASTROPHYSICS  (6)
  • Biochemistry, Neuroscience  (1)
  • 1
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    Near-atomic model of microtubule-tau interactions (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publikationsdatum: 2018-06-15
    Beschreibung: Tau is a developmentally regulated axonal protein that stabilizes and bundles microtubules (MTs). Its hyperphosphorylation is thought to cause detachment from MTs and subsequent aggregation into fibrils implicated in Alzheimer’s disease. It is unclear which tau residues are crucial for tau-MT interactions, where tau binds on MTs, and how it stabilizes them. We used cryo–electron microscopy to visualize different tau constructs on MTs and computational approaches to generate atomic models of tau-tubulin interactions. The conserved tubulin-binding repeats within tau adopt similar extended structures along the crest of the protofilament, stabilizing the interface between tubulin dimers. Our structures explain the effect of phosphorylation on MT affinity and lead to a model of tau repeats binding in tandem along protofilaments, tethering together tubulin dimers and stabilizing polymerization interfaces.
    Schlagwort(e): Biochemistry, Neuroscience
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Geologie und Paläontologie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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    AKTUELLE ARTIKEL
  • 2
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    Primeval gas clouds and the low-energy X-ray background (1977)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: A model for the appearance of the all-sky low-energy X-ray background on a fine angular scale is presented which is based on primeval hot gas clouds associated with the formation of clusters of galaxies according to the Sunyaev-Zel'dovich (1972) model. It is noted that the background could have both granular and diffuse components if it is due to such gas clouds. The observed appearance of the granular component is predicted along with the observable characteristics of collapsing protoclusters. The effects of distant X-ray-emitting QSOs, radio galaxies, and normal galaxies on the observations are considered, and these sources are shown not to interfere with the possibility of observing the protoclusters. It is concluded that if sufficient heating occurred in an intracluster medium within some clusters of galaxies at the protocluster epoch, the ensemble properties of protoclusters could be observed with an X-ray telescope, and the time at which protoclusters formed could perhaps be estimated.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 218
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 3
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    X-ray astronomy in the Uhuru epoch and beyond /Newton Lacy Pierce Prize Lecture/ (1975)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-16
    Beschreibung: A review of results from the Uhuru satellite is presented. An intensive treatment of two subjects is given, rather than a broad review. First, Cyg X-1, a stellar X-ray source and a candidate for a black hole, is discussed; second, the X-ray source in the Perseus cluster of galaxies, which may be a cloud of hot intergalactic gas, is treated. In both cases, the train of logic used in establishing the nature of these objects is presented and evaluated. For both, while alternative explanations cannot be completely eliminated, they become more difficult to sustain when examined in detail, suggesting that the candidate explanations are more likely correct.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; 197; May 1
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 4
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    A high-sensitivity X-ray survey using the Einstein Observatory and the discrete source contribution to the extragalactic X-ray background (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Surveys of two fields have been carried out utilizing the X-ray imaging instruments of the Einstein Observatory to a limiting flux of 1.3 x 10 to the -14th ergs/sq cm s in the 1-3 keV band, a several hundred-fold increase in sensitivity with respect to previous surveys. Forty-three objects are observed with positional accuracies varying from 5 to 60 arcsec. Optical and radio studies of candidate counterparts are described. The number-intensity relationship for extragalactic sources is evaluated, and the consequences of the findings are discussed with particular emphasis on the discrete source contribution to the extragalactic X-ray background. It is concluded that a large fraction of the background is due to previously unresolved discrete sources.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 234
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 5
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    Studies of cluster X-ray sources, energy spectra for the Perseus, Virgo, and Coma clusters (1975)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Final Uhuru X-ray differential-energy spectra are presented for the Perseus, Virgo, and Coma clusters. Power-law and isothermal bremsstrahlung model spectra with low-energy cutoffs are given, and the energy-dependent Gaunt factor is calculated for the bremsstrahlung. The spectra, which are best fits to the Uhuru data between 2 and 10 keV, are compared with previous observations of these sources in the energy range from 0.1 to 100 keV. The problem of parameter estimation is discussed, error bars with 68% confidence are given for the independently determined slope and cutoff parameters, and the 68% confidence limits are plotted for the fitted spectral functions. The data for Perseus above 20 keV marginally favor the bremsstrahlung fit, those for Virgo between 0.25 and 1.0 keV clearly favor that curve, and those for Coma indicate a low-energy turnover or cutoff. Implications of such a cutoff are briefly discussed.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; 199; July 15
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 6
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    Studies of cluster X-ray sources - Size measurements (1974)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: An examination is conducted of the nine weaker sources in the list of Kellogg et al. (1973) which are well enough observed to be listed in the 3U catalog compiled by Giacconi et al. (1974). The cluster sizes are presented in a table and chi-square plots versus derived core radius and background counting rate are shown in a graph. X-ray luminosities calculated from the 3U catalog counting rates are presented as a function of X-ray size.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; 193; Oct. 15
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 7
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    Parameter estimation in X-ray astronomy using maximum likelihood (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Methods of estimation of parameter values and confidence regions by maximum likelihood and Fisher efficient scores starting from Poisson probabilities are developed for the nonlinear spectral functions commonly encountered in X-ray astronomy. It is argued that these methods offer significant advantages over the commonly used alternatives called minimum chi-squared because they rely on less pervasive statistical approximations and so may be expected to remain valid for data of poorer quality. Extensive numerical simulations of the maximum likelihood method are reported which verify that the best-fit parameter value and confidence region calculations are correct over a wide range of input spectra.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 230
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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