Design and construction of a quadruple-resonance MAS NMR probe for investigation of extensively deuterated biomolecules.

Extensive deuteration is frequently used in solid-state NMR studies of biomolecules because it dramatically reduces both homonuclear (H-H) and heteronuclear (H-C and H-N) dipolar interactions. This approach greatly improves resolution, enables low-power rf decoupling, and facilitates H-detected experiments even in rigid solids at moderate MAS rates. However, the resolution enhancement is obtained at some cost due the reduced abundance of protons available for polarization transfer.

Modulation of cross polarization in motionally averaged solids by Variable Angle Spinning NMR.

In systems where the dipolar couplings are partially averaged by molecular motion, cross-polarization is modulated by sample spinning. The cross-polariation efficiency in Variable Angle Spinning (VAS) and Switched Angle Spinning (SAS) experiments on mobile samples is therefore strongly dependent on the spinning angle. We describe simulations and experimental measurements of these effects over a range of spinning angles from 0° to 90°.

Pneumatic switched angle spinning NMR probe with capacitively coupled double saddle coil.

Switched angle spinning (SAS) experiments can be used for generating isotropic-anisotropic correlations in oriented samples in a single experiment. In order for these methods to become widespread, specialized hardware is required. Here we describe the electronic and mechanical design and performance of a double-resonance SAS probe.