gbouvignies / ChemEx

ChemEx is an analysis program for chemical exchange detected by NMR.
https://gbouvignies.github.io/ChemEx/
GNU General Public License v3.0
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Chemex fits look weird #283

Open sucha1512 opened 1 month ago

sucha1512 commented 1 month ago

Hi I am trying to analyse my trosy cpmg, and the fits look weird. can you let me know the problem? I have calculated errors from s to n ratio experiments.pdf Can you let me know what to do?

viochemist commented 1 month ago

Hello,

The pdf you show does not appear to have much (quantifiable) exchange, although the R2's are very high so this must have been a real effort to get! These types of fits typically result from poor initialization of parameters. I find starting with simple models on an individual basis helps to find good starting points and locate those residues with the most likelihood of success. Then, when doing a global fitting, use the updated values (R2, DeltaOmega, pb, kex) that you estimate from the initial fits and use only those residues where the exchange appears significant. If you are able to nail down reliable kex and pb values, then create a method with those as fixed values and attempt to fit the rest of the residues.

Just my 2¢

Alex

Dr Alexandar L Hansen https://osu.academia.edu/AlexandarHansen Lead Research Scientist CCIC & Gateway NMR Facility R224 CBEC, 151 W Woodruff Ave, Columbus, OH 43210 614.292.7133 Office / 716.341.8476 Mobile @.*** ccic.ohio-state.edu

On Wed, Oct 2, 2024 at 10:11 AM sucha1512 @.***> wrote:

Hi I am trying to analyse my trosy cpmg, and the fits look weird. can you let me know the problem? I have calculated errors from s to n ratio experiments.pdf https://github.com/user-attachments/files/17230638/experiments.pdf Can you let me know what to do?

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