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  • 1
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: A new polarized target for neutron scattering has been designed by CERN and tested successfully using the reactor FRG-1 at the GKSS Research Centre. The nuclear spins are aligned with respect to the external field – parallel or antiparallel – by dynamic nuclear polarization (DNP). To avoid absorption of neutrons by 3He, the frozen solutions of biomolecules are immersed in liquid 4He which in turn is thermally coupled to the cooling mixture of 3He/4He of the dilution refrigerator. Compared with earlier experiments where the sample had been cooled directly by 3He, the rate of detectable neutrons increased by a factor of 30. Another factor of 30 is due to the installation of the cold source and the beryllium reflector in FRG-1. Polarized neutron scattering from apoferritin in deuterated solvent shows that the proton spin polarization is homogeneous in apoferritin molecules. After saturation of proton nuclear magnetic resonance (NMR), polarized neutron scattering is dominated by deuteron spin contrast. With the deuterated large subunit of E. coli ribosomes, three different basic scattering functions are derived from spin-contrast variation, reflecting the known scattering-length-density distribution of the architecture of rRNA and ribosomal proteins. The planned in situ structure determination of a mRNA fragment is discussed in the light of the present results.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 30 (1997), S. 1125-1131 
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: Isotopic substitution methods are widely used in neutron scattering for the determination of the in situ structure of macromolecular components in quaternary structures. The contrast created by the substitution of the hydrogen isotope 1H (proton) by 2H (deuteron) is the most prominent example. A further increase of contrast by a factor of three is possible by polarized neutron scattering from polarized nuclear spins. This offers the possibility of measuring small labels, such as proteins, which contribute less than 0.5% to the whole ribosomal mass, or weakly contrasted molecules, such as tRNA ligands, in the 70S ribosomes. In this study, the positions of the proteins S6 and S10 of the Esherichia coli ribosome with respect to the whole 70S ribosome have been determined by nuclear-spin contrast variation. Furthermore, the localization of two weakly contrasted tRNA molecules bound to the pre- and post-translocational 70S ribosome, respectively, is presented. So far, no other technique has allowed the determination of the in situ structures of these molecules.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: Contrast variation is a commonly employed method of structure analysis by small-angle scattering. Thermal neutrons and X-ray synchrotron radiation have led to a renaissance of non-destructive labelling methods like anomalous scattering and spin-contrast variation for the study of the in situ structure of macromolecular components. Anomalous scattering from sulfur and phosphorus has been used to identify ribosomal proteins and rRNA of the large subunit of the E. coli ribosome. For polarized neutron scattering from dynamic polarized targets, rRNA and the ribosomal proteins were deuterated separately and studied in deuterated and in undeuterated solvents. The structural parameters of rRNA and the whole of the ribosomal proteins obtained by these methods are in good agreement with earlier results obtained from neutron scattering in H2O/D2O mixtures.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 275 (1978), S. 460-461 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] In the first series of experiments two Rabinowitchi (R) strains of M. smegmatis were used: R15 as the viomycin sensitive parental strain and the resistant mutant R33 which has an altered 30S subunit9. Intact 16S RNA from 30S subunits of both strains was isolated by the phenol method10. The ...
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Human genetics 〈Berlin〉 50 (1979), S. 297-305 
    ISSN: 1432-1203
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Cycloheximide(CHM)-resistant mutant Chinese hamster ovary (CHO) and human cells were induced with N-nitrosomethylurea (NMU) and ethyl methanesulfonate (EMS); the mutants were viable and showed unlimited growth in the presence of CHM (7×10-7 M), whereas this concentration inhibits protein synthesis in vivo as well as in vitro. No numerical or structural chromosomal aberrations were found in the mutant cells. In vitro analysis shows that the ribosomes confer resistance against cycloheximide.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Naturwissenschaften 67 (1980), S. 234-250 
    ISSN: 1432-1904
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Allgemeine Naturwissenschaft
    Notizen: Abstract Most of the known antibiotics act at the level of protein biosynthesis probably due to the extraordinary complexity of the translational machinery which can be interfered with at many points. At first a survey is given of our present knowledge covering the structure and function of the prokaryotic ribosome. The most important antibiotics acting at the translational level are integrated into this network of data. The binding sites and the inhibition mechanisms of the drugs, together with the ribosomal components altered in resistant mutants are described. Finally, the points of interference with the translational machinery are indicated in an extended scheme of ribosomal functions.
    Materialart: Digitale Medien
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