    New chain ID            Original chain ID

6kmx-pdb-bundle1.pdb:
           A                        aA
           B                        aB
           C                        aC
           D                        aD
           E                        aE
           F                        aI
           G                        aK
           H                        aL
           I                        aM
           J                        bA
           K                        bB
           L                        bC
           M                        bD
           N                        bE
           O                        bI
           P                        bK
           Q                        bL
           R                        bM
           S                        cA
           T                        cB
           U                        cC
           V                        cD
           W                        cE
           X                        cI
           Y                        cK
           Z                        cL
           a                        cM
