Hi Troels,
The relax GUI paper (http://dx.doi.org/10.1007/s10858-011-9509-1), the
2007 review of the Lipari and Szabo model-free problem
(http://dx.doi.org/10.1039/b702202f) and 2008 model-free optimisation
paper (http://dx.doi.org/10.1007/s10858-007-9214-2) that you mention
are specifically for the Lipari and Szabo model-free analysis of
standard R1, R2, and steady-state NOE relaxation. This does not apply
in the same way when studying dispersion processes for the R2
relaxation.
I think there are some papers from the Palmer and Kay labs which talk
about multiple field strength data requirements for relaxation
dispersion studies using R1rho or CPMG-type pulse sequences.
Generally it is better for stability in finding the solution to the
dispersion equations when you have multiple field strength data, and
the bigger the field strength difference or more fields the better.
This is especially important for CPMG-type experiments or non-fast
exchange processes. For R1rho with a process on the fast timescale,
from what I've read I think it is acceptable to use single field
strength data. But please do not trust my answers as I am not an
expert in this area yet, you should look at the dispersion papers
which discuss this issue. Unfortunately I do not remember the exact
references off the top of my head and do not have them at hand, so you
would need to perform a literature search.
Regards,
Edward
On 16 May 2013 15:09, Troels Emtekær Linnet <tlinnet@xxxxxxxxx> wrote:
Hi relax.
I read GUI 2011 paper and the 2007 review.
It mentions the necessity to obtain experimental data at two different
field strength.
We are equipped with a 750 and 800 MHz Varian spectrometer, and
I now wonder if this field separation is "enough".
The 2008,a paper describes 500/600 MHz combination to solve the
double minimum problem. But I wonder if this could be solved also
for a 750/800 MHz data acquisition?
Best
Troels Emtekær Linnet
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Re: Necessary field separation for model-free calculation in nmr-relax