Backbone Assignment search & match not working properly

Analysis Version 3
1

Hello there,

I am currently assigning a ~300 residue protein by H-detected solid state experiments (hCANH, hCONH, hCAcoNH, hCOcaNH, hcaCBcaNH, …)
I have picked my peaks and assigned them to NmrResidues and now want to start the sequential Backbone assignment. Unfortunately I have run into problems with the Backbone assignment tool.

I want it to match CA, CB and CO, so I checked all three boxes in the menu. For some residues that also works very well. However for a majority of residues it only matches one or sometimes two of the three C-frequencies and shows only one or two of three lines indicating the frequency, even though I know I have peaks picked for all three CA, CB and CO and have also checked if the peaks are labeled correctly.

Here is an example where I then found the CA frequency displayed on the H-axis, why-ever that is and I haven’t found where the CO frequency went to yet:

Screenshot from 2025-06-06 16-23-52
Screenshot from 2025-06-06 16-23-52813×772 50.7 KB

This also only happens to many peaks, not all. For some all is fine and everything works really well, so I don’t think it is a problem related to any general settings…

Does anyone have an idea how to fix this? I can’t do the sequential bb assignment if I can’t match all thee frequencies at the same time.

Thank you!

2

Hi,

this does indeed sound very strange. I think perhaps the best thing might be if you send us your project (so support@ccpn.ac.uk) and we’ll take a look. There is no need to include the spectra.
When sending the data, please also give us some examples of residues that do and ones that don’t work. Hopefully we’ll manage to work out what is going wrong and fix things!

Vicky

3

Thanks for sending the project. It turned out that some of your carbon NmrAtoms had a 1H isotopeCode. (This explains why in your image the @1072..CA NmrAtom has a mark along the 1H x-Axis rather than along the 13C y-axis.) This shouldn’t really have been able to happen - at least not from about version 3.2 onwards. So do make sure you are always using the latest version of the software.
I’ve corrected the isotopeCodes and sent the project back, so hopefully all should be well now!

Vicky