Magic-Angle-Spinning NMR Techniques for Measuring Long-Range Distances in Biological Macromolecules

作者：HONG MEI^*; SCHMIDT ROHR KLAUS

来源：Accounts of Chemical Research, 2013, 46(9): 2154-2163.

DOI：10.1021/ar300294x

The determination of molecular structures using solid-state NMR spectroscopy requires distance measurement through nuclear-spin dipole dipole couplings.However, most dipole-coupling techniques compete with the transverse (T subset of 2 subset of)relaxation of the nuclear spins, whose time constants are at most several tens of milliseconds, which limits the ability to measure weak dipolar couplings or long distances. %26lt;br%26gt;In the last 10 years, we have developed a number of magic-angle-spinning (MAS) %26lt;br%26gt;solid-state NMR techniques to measure distances of 15-20 angstrom A. These methods take advantage of the high gyromagnetic ratios of H-1 and F-19 spins, multispin effects that speed up dipolar dephasing, and H-1 and F-19 spin diffusion that probes distances in the nanometer range. Third-spin heteronuclear detection provides a method for determining H-1 dipolar couplings to heteronuclear spins.We have used this technique to measure hydrogen-bond lengths, torsion angles, the distribution of protein conformations, and the oligomeric assembly of proteins. We developed a new pulse sequence, HARDSHIP, to determine weak long-range H-1-heteronuclear dipolar couplings in the presence of strong short-range couplings. This experiment allows us to determine crystallite thicknesses in biological anocomposites such as bone.The rotational-echo double-resonance (REDOR) technique allows us to detect multispin C-13-P-31 and C-13-H-2 dipolar couplings.Quantitative analysis of these couplings provides information about the structure of peptides bound to phospholipid bilayers and the %26lt;br%26gt;geometry of ligand-binding sites in proteins. %26lt;br%26gt;Finally, we also use relayed magnetization transfer, or spin diffusion, to measure long distances. z-Magnetization can diffuse over several nanometers because its long T subset of 1 subset of relaxation times allow it to survive for hundreds of milliseconds. We developed H-1 spin diffusion to probe the depths of protein insertion into the lipid bilayer and protein-water interactions. On the other hand, %26lt;br%26gt;(19F) spin diffusion of site-specifically fluorinated molecules allowed us to elucidate the oligomeric structures of membrane peptides.

• 出版日期2013-9-17