    New chain ID            Original chain ID

6fsz-pdb-bundle1.pdb:
           A                         2
           B                        AA
           C                        BB
           D                        CC
           E                        DD
           F                        EE
           G                        FF
           H                        GG
           I                        HH
           J                        II
           K                        JJ
           L                        KK
           M                        LL
           N                        MM
           O                        NN
