You can edit a custom modification only if the modification is not currently used in any sequences loaded to the Sequence Manager.

Otherwise, you must first modify the affected sequences to remove the modification. After you edit the custom modification, you can modify the affected sequences again to re-add the edited custom modification.


  1. In the Protein Sequence Editor, select the title bar for the Modification Editor.
  2. The Modification Editor pane opens, displaying all of the side chain, N-terminal, and C-terminal modifications available.
  3. Existing custom modifications appear in purple.
  4. Select Add.
  5. In the Add New Modification dialog box, enter the same name as the existing modification you want to edit and enter the modification information.
  6. Select OK.
  7. The application overwrites the existing modification parameters with the new information.