15N-HSQC spectra of 15N-labeled proteins are widely used to identify ligand-binding sites on protein surfaces, providing a way to assess protein-protein interactions as well as to screen for the binding of small chemical compounds. The method is particularly powerful if the cross peaks in the 15N-HSQC spectrum have been sequence - specifically assigned. The present article reviews the use of paramagnetic labeling to obtain these resonance as- signments quickly with the use of 15N-labeled protein, provided the crystal structure of the protein is known and the protein can be labeled with a paramagnetic ion. The method also yields the anisotropy tensor of the magnetic susceptibility, which can be used to model the orientation of the ligand with respect to the protein.
Available at: http://works.bepress.com/nick_dixon/66/