    New chain ID            Original chain ID

6x6k-pdb-bundle1.pdb:
           A                        AT
           B                        AX
           C                        AY
           D                        BT
           E                        BX
           F                        BY
           G                        CT
           H                        CX
           I                        CY
           J                        DT
           K                        DX
           L                        DY
           M                        ET
           N                        EX
           O                        EY
           P                        FT
           Q                        FX
           R                        FY
           S                        GT
           T                        GX
           U                        GY
           V                        HT
           W                        HX
           X                        HY
           Y                        IT
           Z                        IX
           a                        IY
           b                        JT
           c                        JX
           d                        JY
           e                        KT
           f                        KX
           g                        KY
           h                        LT
           i                        LX
           j                        LY
           k                        MT
           l                        MX
           m                        MY
           n                        NT
           o                        NX
           p                        NY
