Nuclear spin order and excitation of inner-shell electrons in macromolecular structure research. An application to the large subunit of the E. coli ribosome

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.