Bruker BioSpin Solid State NMR, User Manual

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User Manual Version 002 BRUKER BIOSPIN 137 (327)
10
RFDR 10
Radio Frequency-Driven Recoupling (RFDR) with longitudinal magnetization ex-
change is a homonuclear dipolar recoupling experiment. This easy setup tech-
nique is a zero-quantum recoupling sequence that achieves chemical shift
correlation under MAS conditions. The time-dependence of the cross peak ampli-
tudes can be employed to determine inter-nuclear distances. With short dipolar
recoupling times, only spins in close spatial proximity lead to cross peak facilitat-
ing assignment of
13
C resonances in uniformly labelled peptides for instance.
RFDR may also be used in order to correlate chemical shifts and crystallographic
sites on materials samples.
The homonuclear dipolar recoupling is implemented via the application of rotor-
synchronised 180-degree pulses (one inversion pulse per rotor period). The phas-
es of the 180-degree pulses are cycled with Gullion’s compensated XY-8
echo se-
quence in order to achieve efficient recovery of single spin magnetization and to
generate an effective dipolar recoupling Hamiltonian during the mixing period.
The critical experimental point is to avoid
1
H-X recoupling induced by interference
between the
1
H decoupling rf field and
13
C rf recoupling field. This effect can be
removed using a
1
H decoupling rf field 3 times as strong as the
13
C rf field used
for recoupling or by using Lee-Goldburg
1
H decoupling during the mixing period.
References:
1. T. Gullion, D. B. Baker and M. S. Conradi, New, compensated Carr-Purcell sequences , J. Magn.
Reson. 89, 479-484 (1990).
2. A. E. Bennett, J. H. Ok, R. G. Griffin and S. Vega, Chemical shift correlation spectroscopy in rotating
solids: Radio frequency-driven dipolar recoupling and longitudinal exchange , J. Chem. Phys. 96,
8624-8627 (1992).
3. A. E. Bennett, C. M. Rienstra, J. M. Griffith’s, W. Zhen, P. T. Lansbury and R. G. Griffin, Homonuclear
radio frequency-driven recoupling in rotating solids , J. Chem. Phys. 108, 9463-9479 (1998).
4. B. Heise, J. Leppert, O. Ohlenschläger, M. Görlach and R. Ramachandran, Chemical shift correlation
via RFDR: elimination of resonance offset effects , J. Biomol. NMR 24, 237-243 (2002).