There are several ways to start Change Chain IDs, a tool in the Structure Editing category. It is also implemented as the command changechains. See also: Build Structure, Renumber Residues, modifying and saving data
The chain(s) to be assigned new identifiers (chain IDs) should be chosen from the list. For each chosen chain, an entry box will be supplied for the new ID, where case is important.
Clicking Apply or OK (which also dismisses the dialog) reassigns chain IDs as indicated, if possible. If the reassignment would give one or more duplicate residue numbers within a chain, an error message will appear and the reassignment will not occur.
Close dismisses the dialog; Help opens this manual page in a browser window.
Handling multiple chains with the same ID. Multiple chains with the same character ID present a problem because the dialog lists them as a single chain. However, if the ID is blank, disconnected chains will be detected and listed separately. Thus, the workaround is to: