KINETICS OF HETERONUCLEAR CROSS-RELAXATION IN DIPOLAR COUPLED-SPIN SYSTEMS - APPLICATIONS TO IN-VIVO MEASUREMENTS

Signal intensity changes observed in double-resonance experiments on d ipolar coupled-spin systems in liquid phase are known as the nuclear O verhauser effect (NOE). This article describes the theory of dynamic n uclear polarization of coupled spin-1/2 nuclei along with the experime ntal techniques that permit us to observe the kinetics of heteronuclea r NOE and that help us to determine the cross-relaxation rate constant . Kinetic effects can be detected in coupled I-S spin ensembles when t he period of driving of S spins is varied and the nuclear magnetic res onance signal enhancement of I spins is recorded. Truncated driven and transient NOE experiments on P-31-H-1 and C-13-H-1 spin systems are d iscussed with particular reference to in vivo applications. (C) 1997 J ohn Wiley & Sons, Inc.