| Structural studies of the various types of samples, including proteins, can be performed by the methods of the solid state nuclear magnetic resonance. Solids and oriented liquid crystalline solutions bear signatures of the anisotropic interactions in their spectra. Spectral line broadening due to the anisotropy can be removed by spinning the sample at the 54.74 degrees with respect to the static magnetic field, but valuable structural information is then lost. Anisotropic interactions, especially the dipolar couplings can be reintroduced back by the two-dimensional switched angle spinning NMR technique. In this method the narrow-line isotropic spectrum is correlated with the broadened anisotropic spectrum, so that the lines are assigned in the isotropic dimension, while the anisotropic dimension provides the information about the degree and the source of the dipolar coupling, and can be used for structural analysis. To perform the angle switching in the course of the NMR experiment, a fast, reproducible and reliable hardware is necessary. Here we present the design of a new pneumatically operated probe for the switched-angle spinning NMR experiments with oriented systems. |
