    New chain ID            Original chain ID

9nta-pdb-bundle1.pdb:
           A                        BA
           B                        BB
           C                        BC
           D                        BD

9nta-pdb-bundle2.pdb:
           A                        BE
           B                        BF
           C                        BG
           D                        BH
           E                        BI
           F                        BJ
           G                        BK
           H                        BL
           I                        BM
           J                        BN
           K                        BO
           L                        BP
           M                        BQ
           N                        BR
           O                        BS
           P                        BT
           Q                        BU
           R                        BV
           S                        BW
           T                        BX
           U                        BY
           V                        BZ
           W                        Ba
           X                        Bb
           Y                        Bc
           Z                        Bd
           a                        Be
           b                        Bf
