Loading a file

Basically, this is achieved by entering:
x = PDB(``1crn.pdb'')
The PDB constructor can handle different arguments:
PDB(filename,chains,model,hetero management,verbose)

• filename: any name corresponding to a PDB formatted text file. The file can be gzipped (name ending by .gz), compressed (name ending by .Z), or regular.
• chains: a string of chain labels that will be loaded. Specifying something as ``A'' will result in the loading of only the chain A of the file. Specifying ``ABC'' will result in loading chains A, B and C. Specifying ``-AB'' will result in loading anything but chains A and B.
• model: For NMR files, this will install the model number data to be used for further manipulation.
• hetero: Specifying any number but nought will trigger the elimination of any residue not acknowledged as amino-acid or nucleic acid.
• verbose: verbose data processing.