Sebastien J. F. Vincent

Suppression of spin diffusion in selected frequency bands of nuclear Overhauser spectra

SummaryA variant of two-dimensional nuclear Overhauser effect spectroscopy (NOESY) is described that yields information about cross-relaxation rates between pairs of spins, while the migration of magnetization through several consecutive steps (spin diffusion via neighboring spins) is largely suppressed. This can be achieved by inserting a doubly-selective inversion pulse in a conventional NOESY sequence.

Measurement of cross relaxation between two selected nuclei by synchronous nutation of magnetization in nuclear magnetic resonance

A novel technique is described that allows one to measure cross‐relaxation rates (Overhauser effects) between two selected nuclei in high‐resolution NMR. The two chosen sites are irradiated simultaneously with the sidebands of an amplitude‐modulated radio‐frequency field, so that their magnetization vectors are forced to undergo a simultaneous motion, which is referred to as ‘‘synchronous nutation.’’ From the time‐dependence observed for different initial conditions, one may derive cross‐relaxation rates, and hence determine internuclear distances. The scalar interactions between the selected spins and other spins belonging to the same coupling network are effectively decoupled. Furthermore, cross relaxation to other spins in the environment does not affect the transient response of the selected spins, which are therefore in effect isolated from their environment in terms of dipolar interactions. The method is particularly suitable to study cases where normal Overhauser effects are perturbed by spin‐diffu...

Chapter 1 Selective pulses in NMR

Abstract The properties of some widely used selective pulses are described, together with methods for calibration. The emphasis is on an overview of what may be expected from a given pulse shape in terms of selectivity, duration, quality of profile, sensitivity to relaxation, and range of applicability.

Towards the accurate measurement of internuclear distances in biological macromolecules by suppression of spin diffusion

The anal. of 2-dimensional NOESY spectra can be misleading if spin diffusion effects are not properly taken into account. An approach consisting in suppressing spin diffusion by selective inversion of the spins undergoing the Overhauser effect, known as QUIET-NOESY (Zwahlen, C. et al., 1994), is described. In addn., the QUIET-EXSY method (Zwahlen, C. et al., 1995), related to the suppression of spin diffusion by QUIET-NOESY, is discussed. [on SciFinder (R)]