I have a PDB file, and I need to extract its residue sequence numbers (resSeq's). Based on manual inspection of the first few lines of the PDB file (pasted below), I would think that resSeq's should begin with 22, 23. However, Biopython's PDB module suggests otherwise (output attached below as well). I wonder if it's a Biopython bug or if I have problems understanding the PDB format.
ATOM 1 N GLY A 22 78.171 89.858 59.231 1.00 21.24 N
ATOM 2 CA GLY A 22 79.174 88.827 58.999 1.00 20.87 C
ATOM 3 C GLY A 22 80.438 89.415 58.391 1.00 21.89 C
ATOM 4 O GLY A 22 80.362 90.202 57.440 1.00 23.18 O
ATOM 5 N LEU A 23 81.588 89.069 58.972 1.00 21.51 N
ATOM 6 CA LEU A 23 82.895 89.555 58.527 1.00 20.80 C
ATOM 7 C LEU A 23 83.288 89.020 57.162 1.00 22.41 C
ATOM 8 O LEU A 23 82.889 87.923 56.788 1.00 22.93 O
ATOM 9 CB LEU A 23 83.973 89.232 59.560 1.00 20.97 C
ATOM 10 CG LEU A 23 84.225 87.818 60.062 1.00 13.32 C
ATOM 11 CD1 LEU A 23 85.448 87.888 60.939 1.00 15.24 C
ATOM 12 CD2 LEU A 23 83.035 87.258 60.829 1.00 12.21 C
...
for i in chain:
print i.get_full_id()
OUT:('pdb', 0, 'A', (' ', 2, ' '))
('pdb', 0, 'A', (' ', 3, ' '))
...
chain
exactly defined? $\endgroup$