6.17 R2SELPULS1—Rotation Resonance with Selective Inversion
01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR
106
Parameters
cpnoesyps uses
UNITY
INOVA and UNITYplus parameters tpwr, tpwrm, dpwr, cppwr,
dipolr, crossp, dblvl2, pw, and cntct. See page 85 for a description of these
parameters.
xpol is set to 'n' for preparation by direct polarization; xpol is set to 'y' for
preparation by cross-polarization.
pw is the observe 90°
° pulse (xpol='n'), or the proton 90° pulse (xpol='y'). pw is in
microseconds.
pwx is the length of pulses two and three and is to pw (if xpol='n'). pwx is in
microseconds.
mix is the mixing period in milliseconds (see also rfdr below). Use caution because
dm='y' during the mix period may lead to an unacceptable duty cycle.
sync set to 'y' is used with rfdr='y' to provide dipolar recoupling during the mix
period. sync set to 'n' provides the usual NOESY mixing period.
rfdr set to 'y' (set sync='y') sets the mixing period to a multiple of 8 rotor periods,
close to the value of mix. The rotor period is obtained from the value of srate.
π pulses
are applied at the middle of each rotor period, with the phase cycle 'xy8' to cause dipolar
recoupling. rfdr set to 'n' sets the mixing period equal to the value of mix and pulses
are not applied.
srate is the actual spinning speed. CPNOESYPS with rfdr='y' requires rotor speed
control.
Reference
Bennett, A. E.; Ok, J. H.; Griffin, R. G.; Vega, S. J. Chem. Phys. 1992, 96, 8624.
6.17 R2SELPULS1—Rotation Resonance with Selective
Inversion
The R2SELPULS1 pulse sequence is used for the rotational resonance experiment with a
selection inversion pulse of Griffin and coworkers. Figure 46 is a diagram of the sequence.
Rotational resonance (r
2
) is obtained between nuclei coupled by the through-space dipolar
interaction when the chemical shift difference between the resonances is an integral
multiple of the rotor speed. At the r
2
condition, each resonance is split into a characteristic
doublet pattern that can be simulated to obtain the coupling constant and internuclear
distance. If one of the resonances is selectively inverted, the two will equilibrate to a
common signal intensity. The recovery curve can also be simulated to obtain the coupling
constant. Rotational resonance is often used for the determination of the structure of
biomolecular materials such as membrane proteins. CPNOESY with rfdr='y' provides
similar information.
Applicability
R2SELPULS1, found in userlib, is available only on
UNITY
INOVA and UNITYplus.
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