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
URL:
http://dx.doi.org/10.1107/S0021889891011093
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