Dynamic nuclear polarization and spin-diffusion in non-conducting solids

There has been much renewed interest in dynamic nuclear polarization (DNP), particularly in the context of solid state biomolecular NMR and more recently dissolution DNP techniques for liquids. This paper reviews the role of spin diffusion in polarizing nuclear spins and discusses the role of the spin diffusion barrier, before going on to discuss some recent results.Comment: submitted to Applied Magnetic Resonance. The article should appear in a special issue that is being published in connection with the DNP Symposium help in Nottingham in August 200

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The in situ structure of the L3 and L4 proteins of the large subunit of E. coli ribosomes as determined by nuclear spin contrast variation

Polarized Neutron scattering from dynamically polarized targets has been used to determine the in situ structure of the proteins L3 and L4 of the large subunit of E.coli ribosome. Both proteins (M≈2.3*104) have an elongated shape and radii of gyration of about 19 Å. The orientation of the proteins with respect to that of the ribosomal subunit has been determined. The distance between the centers of mass of L3 and L4 amounts to 125±10 Å

SANS with polarized neutrons

Polarized neutron scattering from dynamically polarized nuclear spin targets has become a method of macromolecular structure research. As the cross-section of coherent neutron scattering of the hydrogen isotopes "1H and "2H differ strongly and evenmore in their dependence on nuclear polarization, methods of specific isotopic substitution are use for the in situ structure determination of selected parts of copolymers or large biomolecules. Selective nuclear depolarization is used to obtain proton spin targets and deuteron spin targets. Extensive studies have been done on the in situ structure of ribosomal RNA and the total ribosomal protein. More recently the polarized neutron scattering from the in situ structure of single ribosomal proteins, L3, L4 and L3+L4 could be observed with an unprecedented accuracy. These results were obtained from the perdeuterated large ribosomal subunit dissolved in a mixture of glycerol-d_n and heavy water. The data show that the structure of the translational apparatus of the ribosome, which is known to take care of the biosynthesis of proteins in each living cell, can be studied in greater detail by polarized neutron scattering from polarized nuclear spin targets. (orig.)Reprinted from: Physica Scripta, v. T49(1993), p. 644-649Available from TIB Hannover: RA 3251(93/E/103) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Architecture of the E.coli 70S ribosome

The 70S ribosome from E.coli was analysed by neutron scattering focusing on the shape and the internal protein-RNA-distribution of the complex. Measurements on selectively deuterated 70S particles and free 30S and 50S subunits applying conventional contrast variation and proton-spin contrast-variation resulted in a total of 42 scattering curves. Processing the data on the basis of the spherical harmonic technique, a four-phase model for the 70S ribosome could be generated, which describes the shape of the particle as well as the protein-and the RNA-moieties of each subunit at about 35 Å resolution