Rotationally Aligned Solid State NMR

Membrane proteins are inherently dynamic in phospholipid bilayers similar to thier native environment. Among all type of motions, rotational diffusion around the bilayer normal occurs at an intermediate time scale ranging from 10000-100000 per second. This motion can easily be measured using solid state NMR technques. For an example, the motion partially reduces the anisotropic interactions such as chemical shielding and dipolar couplings, whcih are often measured in solid state. Although the motion can be slow down with varying sample temperature, providing useful means to study protein dynamics and membrane biophysics. On the other hand, the motional averaging is not just random, it is predictable and depends on the protein topological arrangement in the bilayers. Therefore, a new class of experiments are developed to measure these motional averaged NMR interactions as a source of structural restraints. The method named as rotationally aligned solid state NMR (RA-SSNMR) that merges the basic elements of static oriented sample and magic angle spinning solid state NMR techniques, has the potential to be a general method for structure determination of proteins in biological membranes.