I am new to CCPNmr, I want to know how to delet the assigned NmrAtoms.
For example, I was able to delet the peak for 237CBi, but the reference line for 273CB is still there and CB is still identified in NmrAtoms, which affect the searching in backbond assignment.
at a distance it is slightly difficult to work out exactly what it is you are trying and failing to do. But I wonder if the module you need is the Peak Assigner. You can open this either with shortcut AP or Main Menu/Assign/Peak Assigner or by right-clicking on a peak and going to Edit Peak Assignment...
This pop-up will let you remove assignments from a peak (double-click on the the NmrAtom on the left-hand side to remove it as an assignment - it will then move to the right hand side). But you can also delete the whole NmrAtom if you like (select the NmrAtom on the left-hand side and click Delete).
Alternatively, you can delete NmrAtoms from the side-bar by right-clicking on them and selecting Delete.
Finally, it is worth pointing out that there are occasions when certain things don`t get updated immediately. The Marks for instance, would only be updated when you specifically redraw them by some action or other. The tables should generally update straight away, but occasionally, there are instances where this slips through the net and we have missed a notifier. Closing a table and reopening it is a good way to check that a table really is up-to-date if you think it might not be. If you find a situation like this where a table isn`t updating correctly, then do please let us know and we`ll fix it.
I hope this helps. If this doesn`t seem to do what you were aiming for, then do get in touch on firstname.lastname@example.org and we can perhaps arrange a quick screen share session to discuss what is going on.
Thank you very much for the advice and suggetion it worked.