Bruker BioSpin Solid State NMR, User Manual

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Relaxation Measurements
User Manual Version 002 BRUKER BIOSPIN 211 (327)
recovery after the saturation, so the carbon signal as a function of recovery delay
gives the proton T
1
value. For T
1
ρ
a variable length proton only spin-lock pulse is
applied after the 90-degree pulse in the CP experiment. The proton magnetization
after this pulse, and thus the carbon signal after CP, depends on the proton T
1
ρ
re-
laxation.
Indirect Proton T1 Measurements 16.3.1
Sample : Glycine
Spinning speed : 10 kHz
Time : 20 minutes
Start from standard CP parameters, as for the X T
1
measurement with CP, and set
pulprog
to cph+1 . Set the saturation loop
l20
to zero, and acquire a spectrum, to
check signal intensity. Signal to noise should be comparable with the standard CP
experiment, so a similar number of scans to that used for the carbon T
1
experi-
ment should suffice.
Saturation parameters can be set as for carbon saturation previously:
l20
= 5-100
and
d20
=
1-50 ms. Acquire a spectrum with these parameters and verify that there is again
no signal.
Make a new data set with
iexpno
and set parameters for 2D acquisition, as for
the previous experiments. D1 can be short, with the same proviso about duty cy-
cle as the X saturation-recovery experiment. A reasonable set of delays for the
vdlist would be: 10 ms, 22 ms, 45 ms, 100 ms, 220 ms, 450 ms, 1 s, 2.2 s, 4.5 s,
10 s.
Data processing
The data should be processed in the same way as for the X saturation recovery
experiment. Both the carbonyl and alpha-carbon peaks derive their carbon polar-
ization from the same proton spins, and so analysis of the two peaks should give
the same result. If you have a sample containing some gamma-glycine (gives
peaks at slightly lower shifts than the more common alpha-glycine form), this
should show different T1 values for the two sets of peaks.
At 500 MHz, the proton relaxation time should be approximately 520 ms at room
temperature.