    New chain ID            Original chain ID

7a7d-pdb-bundle1.pdb:
           A                         A
           B                         B
           C                         C
           D                         D
           E                         E
           F                         F
           G                         G
           a                         a
           b                         b
           c                         c
           d                         d

7a7d-pdb-bundle2.pdb:
           e                         e
           f                         f
           g                         g
