Dear NMR experts,
I've been trying lately to run a double-quantum filtered CP/MAS experiment
for my protein users, but I had no luck so far. My first fid is really good,
but the following ones display no signal. There is no signal accumulation
and I can't figure out what is wrong. Since I never before tried this
experiment I cannot be sure I have optimized my parameters properly. So I'm
reaching to you for help. If any of you ever run that sequence, I would
appreciate any tips.
Here are my experimental details:
I'm using a 600 Bruker Avance II and my setup sample was 13C labeled
D-glucose, spinning at 10 kHz.
Within Topspin (1.3), I found the pulse sequence corresponding to my needs:
spc5cp1d. There is other pulse program available, but this one was the
closest to the paper I was following. It is a regular CP with a SPC5 double
quantum filter. The 1d version is used to set up the 2D INADEQUATE sequence.
My CP parameters were already optimized and worked great on their own.
The parameters proper to the DQ filter are the following:
CNST31 (spinning rate) = 10 kHz therefore: B1 = 50 kHz
This implies 90(13C)=5us and I found that to correspond to pl11=5.6 dB
I'm using CW during SPC5 and SPINAL64 during the acquisition. Both are at
100kHz.
Finally I'm using L0=5 as the number of composite cycle.
Thank you,
Celine Schneider, PhD
Research Laboratory Associate
NMR Facility / C-CART
CREAIT Network
Memorial University of Newfoundland
St. Johns, Newfoundland A1C 5S7
Tel: (709)-737-3134
Room: C-1024
Received on Tue Jan 19 2010 - 07:58:50 MST