Cross-relaxation between macromolecular and solvent spins: The role of long-range dipole couplings

摘要: Nuclear spin relaxation by intermolecular dipole–dipole interactions between macromolecular and solvent nuclear moments forms the basis of a widely used method for investigating solvation. In particular, cross-relaxation [or Overhauser effect (NOE)] protein water protons has been to probe mobility molecules interacting with surface. The rests on assumption that NOE is short (4–5 A) range thus provides information about individual in hydration sites near monitored protons. Here, we present theoretical analysis spectral density function (SDF) governs rates laboratory-fixed rotating frames. contrast r–6 dependence intramolecular NOEs structure determination, shown be long-ranged important contributions from thousands molecules. For consistent interpretation such NOEs, it necessary use model explictly incorporates motionally retarded as well unperturbed bulk We formulate diffusion nonuniform solve obtain an analytical expression SDF. Calculations this demonstrate surface are dominated long-range dipole couplings therefore provide little or no dynamics. physical unexpected phenomenon characteristic time scale relaxation-inducing fluctuations longer more numerous remote molecules, despite their higher mobility. results presented here generally applicable dipolar like unlike (nuclear electron) spins variety experimental situations. ©2003 American Institute Physics. (Less)