    New chain ID            Original chain ID

7b6s-pdb-bundle1.pdb:
           A                       AAA
           B                       BBB
           C                       CCC
           D                       DDD
           E                       EEE
           F                       FFF
           G                       GGG
           H                       HHH
           I                       III
           J                       JJJ
           K                       AaA
           L                       BaB
           M                       CaC
           N                       DaD
           O                       EaE
           P                       FbF
           Q                       GaG
           R                       HaH
           S                       IaI
           T                       JaJ
