David,
I attach a pulse program for cpmas - however, you need to determine your
pulses prior to starting cp.
Use Adamantane for that. You can make 13C direct detect using cw decoupling
or better suited for the 600
a TPPM decoupling. The two decoupling schemes you want to play with are in
the directory cdp.dsolids. copy them into the cpd directory the path is
/u/exp/stan/nmr/lists
then paropt the pulse p31 of TPPM.
In order to get an idea you can determine the 90 degree 1H pulse by spinning
10 or 12 or more kHz ( maximum is 15 kHz) approach that slowly in case your
rotor is not packed properly.
The hpdec on Adamantane must be done at about 2 - 2.5 kHz spinning speed.
You can use Adamantane also to setup some of the cp parameters - then use
p15 = 3ms for that. the maximum decoupling power for a 4 mm MAS probe is
for SB systems about 90 kHz, that is 1/90/4=2.78us.
Do not exceed the acquisition time beyond 50 ms if you are decoupling full
power. You can
decouple for about 500ms using maximum 50 kHz -- 5us 90 degree pulse.
Set o1 to 32 ppm ( somewhere between both peaks ) and o2 to 2.5 ppm.
For TPPM you can use the power level of shortest 1H 90 degree pulse you can
get.
The you multiply the 90 degree pulse duration with 2 and subtract 0.2 us.
That gives you p31.
Then you make a fine tune of cp using Glycine - that is the best amino acid
because it is simple
and it has a short T1 of the 1H pool. Spin Glycine with 5 kHz. set dw = 16
us and aq = 35ms.
rg is about 4k, ns = 4 p15, the contact time is 1 ms! o1p is about 100 ppm
and o2p 3.6ppm if the
carbonyl peak is on 176 +- 1 ppm with SR = 0. If not you must reference you
spectrometer properly!
The cp pulse program uses pl12 for the 90 degree excitation pulse in the
proton pool - that is in order to directly measure the decoupling power.
Use the shaped pulse ramp.64 in the wave.dsolids directory - to be copied to
wave. the path is again
/u/exp/stan/nmr/lists.
HH is about reached if one uses the power levels for 4 us pulses for 13C and
1H. If you use the
ramp add 3dB (subtract 3dB from the PL2 level (90 degree 1H pulse)) then
optimize the transfer by
changing either sp0 or pl1 (13C).
I guess that is all for now, please contact me if you have more questions.
I attached two pulse programs and 3 parameter sets. You need to change the
name of the pulse program in the parameter set anything else should work. Of
course the power levels are set to 120 to protect the spectrometer. You
have to change these.
In the KBr parameter set you can do the following change, set
digmod=digital and
set DSPFIRM to smooth and dw=1us and increase TD to 5k.
Everything clear????
The question with backups - I would definitely recommend CD - it is cheaper!
Jochem
-----Original Message-----
From: David A. Horita [mailto:dhorita@wfubmc.edu]
Sent: Tuesday, March 27, 2001 12:12 PM
To: BUM
Subject: cross polarization and data backup questions
Greetings Bruker users:
We have a Bruker Avance 600, and I have a colleague who wishes to do
some 13C-1H cross-polarization experiments on gel-like samples [e.g.,
Sutherland et al. (1979). Biochemistry 18:1797]. Specifically, I need
to do a 1H-13C cross polarization experiment with 1H dipolar decoupling
using standard liquids amps and probes. Since the original experiments
used solids equipment at 1.4 T, I imagine some modifications in
procedure are required for work at 14 T.
If anyone has (or can point me to) a suitable pulse sequence and dipolar
decoupling pattern, I would appreciate the help. Since I've been doing
solution NMR for the last dozen years on V* spectrometers, I'm a bit out
of my element here. Any helpful comments in general would also be
appreciated.
In another vein, we're considering different mechanisms for user data
backup. Can anyone offer comments regarding CD-RW or Zip drives as
useful backup mechanisms? Are data cp'd to a Zip readable on
PC/Mac/Linux platforms?
Thanks for any help.
David A. Horita
-- David A. Horita, Ph.D. Department of Biochemistry Wake Forest University School of Medicine Winston-Salem, NC 27157-1016 Tel: 336 713-4194 Fax: 336 716-7671 email: dhorita@wfubmc.edu
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