Hi Edward,
I have a general question regarding how to pick signals prior to relaxation
rate fitting.
Following the rationale of [1] fitting the data with a two-parameter
exponential decay is preferable. With relax, I can choose to do so. The
question remains if "picking noise" – i.e. picking signal intensities at the
position of the reference peaks, although the signal has decayed already – is
a good idea.
To me it seems only logical that "picking noise" should not be done. The
signal decays to zero whatsoever (given the pulse sequence is properly set
up) and by picking signals where no signal should be I may pick artifacts
that are not distributed evenly over the base plane of the spectrum. Which
means, I may be introduce artificial offsets.
However relax seems not be happy when I try to use peak lists for T1/T2
relaxation fitting if the lists have different lengths. I always have to do
"noise picking", otherwise already the grid_search fails when encountering a
incomplete time series.
Is the behaviour intended, do I need a complete time series of each amino
acid? Or am I missing something? Or am I completely misguided with my
not-picking-noise approach?
Cheers
Martin
[1] Viles, J. H., Duggan, B. M., Zaborowski, E., Schwarzinger, S., Huntley,
J. J., Kroon, G. J., Dyson, H. J., et al. (2001). Potential bias in NMR
relaxation data introduced by peak intensity analysis and curve fitting
methods. Journal of biomolecular NMR, 21(1), 1–9.
--
Martin Ballaschk
AG Schmieder
Leibniz-Institut für Molekulare Pharmakologie
Robert-Rössle-Str. 10
13125 Berlin
ballaschk@xxxxxxxxxxxxx
Tel.: +49-30-94793-234/315
Büro: A 1.26
Labor: C 1.10
[rx fitting] Dealing with intensities of decayed signals