    New chain ID            Original chain ID

5exc-pdb-bundle1.pdb:
           A                         A
           B                        aa
           C                         B
           D                        bb
           E                         C
           F                        cc
           G                         D
           H                        dd
           I                         E
           J                        ee
           K                         F
           L                        ff
           M                         G
           N                        gg
           O                         H
           P                        hh
