[BioPython] Using Bio.PDB to add atoms to a structure?

[Konrad Forster Koehler]

Using Bio.PDB, I was wondering if there is a way to:

1) read in a structure from a PDB file
2) calculate the position of a new chain/residue/atom
3) add new these chains/residues/atoms to the structure
4) write of the PDB file containing the original + new atoms

I have no problem with steps 1, 2, and 4, but I am stuck on step #3.

I have tried things like:

http://bioinformatics.org/bradstuff/bp/api/Bio/PDB/StructureBuilder_StructureBuilder.py.html#init_chain

builder = StructureBuilder()
chain_x = builder.init_chain("0","X")

error message: init_chain() takes exactly 2 arguments (3 given)

or

chain_x = builder.init_chain("X")
error message: StructureBuilder instance has no attribute 'model'

I have googled for examples or documentation on adding new atoms using Bio.PDB, but I have not found anything.

Can anyone provide me with any pointers, examples, etc?

Best regards,

Konrad