    New chain ID            Original chain ID

4v81-pdb-bundle1.pdb:
           A                         A
           B                         B
           C                         C
           D                         D
           E                         E
           F                         F
           G                         G
           H                         H
           I                         I
           J                         J
           K                         K
           L                         L
           M                         M
           N                         N
           O                         O
           P                         P
           a                         a
           b                         b
           c                         c
           d                         d
           e                         e
           f                         f
           g                         g
           h                         h
           i                         i
           j                         j
           k                         k
           l                         l

4v81-pdb-bundle2.pdb:
           m                         m
           n                         n
           o                         o
           p                         p
