Sideband patterns from rotor-encoded longitudinal magnetization in MAS recoupling experiments.
Recent multiple-quantum MAS NMR experiments have shown that a change in the rotor phase (and, hence, in the Hamiltonian) between the excitation and reconversion periods can lead to informative spinning-sideband patterns. However, such "rotor encoding" is not limited to multiple-quantum experiments. Here it is shown that longitudinal magnetization can also be rotor-encoded. Both homonuclear and heteronuclear rotor encoding of longitudinal magnetization (RELM) experiments are performed on dipolar-coupled spin-1/2 systems, and the corresponding sideband patterns in the indirect dimension are analyzed. In both cases, only even-order sidebands are produced, and their intensity distribution depends on the durations of the recoupling periods. In heteronuclear experiments using REDOR-type recoupling, purely dipolar sideband patterns that are entirely free of effects due to the chemical-shielding anisotropy can be generated. Advantages and disadvantages of the heteronuclear RELM experiment are discussed in the context of other methods used to measure heteronuclear dipolar couplings.
De Paul
S M
SM
Max-Planck-Institut für Polymerforschung, Mainz, D-55021, Germany.
Saalwächter
K
K
Graf
R
R
Spiess
H W
HW
D000409:Alanine / Q000737:chemistry; D016880:Anisotropy; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D014238:Trichloroacetic Acid / Q000737:chemistry; D014443:Tyrosine / Q000737:chemistry
D014443:Tyrosine; D014238:Trichloroacetic Acid; D000409:Alanine