DETECTION OF INDIVIDUAL CARBON RESONANCES IN SOLID PROTEINS

Natural abundance 13C nuclear magnetic resonance spectroscopy is one of the most informative NMR approaches for the study of proteins.12 A significant number of new ideas on the chemistry, structure, and dynamics of individual residues and the peptide backbone have resulted from 13C NMR of proteins in solution. There are a number of reasons to expect NMR spectroscopy of proteins in the solid state will be of even greater value than the solution studies. The anisotropic character of nuclear spin interactions is retained in the absence of molecular motion;3 therefore angular and distance parameters can be extracted with a variety of experiments. The ultimate l3C resolution in solids may be significantly better than in solution because the isotropic chemical-shift dispersion is the same and experimental procedures can remove static linebroadening mechanisms but not relaxation-induced widths.4 The relatively small globular proteins that are most amenable to high resolution solution NMR are exactly the same ones that crystallize most conveniently for X-ray diffraction analysis; so NMR of polycrystalline proteins will be complementary to diffraction studies. More importantly those proteins not readily crystallized and not water soluble can be studied as amorphous materials. A variety of structural, mechanical, and intrinsic membrane proteins fall in this category; thus solid-state NMR of proteins offers the promise of extending the range of the method. © 1979, American Chemical Society. All rights reserved.