- K. Saalwächter, I. Schnell.
REDOR-Based Heteronuclear Dipolar Correlation Experiments in Multi-Spin
Systems: Rotor-Encoding, Directing, and Multiple Distance and Angle
Solid State NMR
22, 154-187 (2002).
We review a variety of recently developed 1H-X
heteronuclear recoupling techniques, which rely only on the homonuclear
decoupling efficiency of very-fast magic-angle spinning. All these techniques,
which are based on the simple REDOR approach for heteronuclear recoupling, are
presented in a common context. Advantages and possibilities with respect to the
complementary application of conventionally X and 1H-inversely detected variants are discussed in relation to
the separability and analysis of multiple couplings. We present an improved and
more sensitive approach to the determination of 1H-X dipolar couplings by spinning-sideband analysis,
termed REREDOR, which is applicable to XHn
groups in rigid and mobile systems and bears some similarity to more elaborate
separated local-field methods. The estimation of medium-range 1H-X distances by analysing signal intensities in
two-dimensional REDOR correlation spectra in a model-free way is also discussed.
More specifically, we demonstrate the possibility of combined distance and angle
determination in H-X-H or X-H-X three-spin systems by asymmetric recoupling
schemes and spinning-sideband analysis. Finally, a 1H-X correlation experiment is introduced which
accomplishes high sensitivity by inverse (1H)
detection and is therefore applicable to samples with 15N in natural abundance.