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
1ρ
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
1ρ
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.
To Next Page
Loading...