Hi,
I have a question concerning Rex and its magnetic field dependence vs
how it is treated in relax.
Rex, the contribution from us-ms motions on the transversal relaxation
rate (R2), is scaled quadratically with the magnetic field. When doing
an analysis with relax, one gets a value for Rex.
When working with data from multiple magnetic fields, I realized that
the dataset to which this Rex is associated changes as a function of the
order with which datasets are input into relax. In fact, the Rex value
is associated with the first dataset input.
Here are some results I had with the full_analysis.py script modified to
minimize only tm3 (for a rapid test) :
================================================================
Input_order Association Rex__residue_25
=========== =========== =======================
500-600-800 500 7.0885287044805514
500-800-600 500 7.0885287044182812
600-800-500 600 2.7486344907905164e-13
600-500-800 600 2.7486344897092221e-13
800-500-600 800 -2.1641012543284559e-17
800-600-500 800 -5.3169783493616144e-21
================================================================
As you can see, the Rex value changes with the input order. Most change
comes from the first dataset input, but there is also a small influence
from the subsequent datasets input...
Is this normal ?
Would it be better to always input datasets so Rex gets associated with
the highest magnetic field ? With the lowest ?
Thanks for clarifying this issue !
Cheers,
Séb
--
Sebastien Morin
Etudiant au PhD en biochimie
Laboratoire de resonance magnetique nucleaire
Dr Stephane Gagne
CREFSIP (Universite Laval, Quebec, CANADA)
1-418-656-2131 #4530
Rex vs magnetic field