H-1 NMR dipolar relaxation times and the derivation of internuclear distance

The theory of nuclear spin relaxation via the dipole-dipole coupling mechanism is discussed. Various methods of measuring relaxation rates are described and shown to provide a means for measuring interhydrogen distances in molecules. The methods include the combined use of selective and biselective pulses to invert single resonances together with nonselective pulses. The theory is given with applications from the literature. A modification of the methods - in which one resonance is left noninverted - is described, and some applications of this more efficient approach are shown. The distances obtained from such inversion-recovery relaxation rate measurements are compared with values measured from nuclear Overhauser effect build-up rates. (C) 1996 John Wiley & Sons, Inc.