    New chain ID            Original chain ID

6l4u-pdb-bundle1.pdb:
           A                         A
           B                         B
           C                         C
           D                         D
           E                         E
           F                         F
           G                         I
           H                         J
           I                         L
           J                         M
           K                        1u
           L                        2u
           M                         1
           N                         2
           O                         3
           P                         4
           Q                         5
           R                         6
           S                         7
           T                         8
           U                         9
           V                        10
           W                        11
           X                        12
           Y                        13
           Z                        14
           a                        15
           b                        16
