<Verb>ReadPDBfileAsPureCubicalComplex(str):: String --> PureCubicalComplex</Verb>
<Verb>ReadPDBfileAsPureCubicalComplex(str,r):: String, Int --> PureCubicalComplex</Verb><P/>


<P/>
Reads a PDB (Protein Database) file  identified by a string str such as
"file.pdb" or "path/file.pdb"   
and 
 returns a <M>3</M>-dimensional pure cubical complex <M>K</M>. The 
complex <M>K</M> should  represent a (protein backbone) knot but this is not guaranteed.
 A useful check in this direction is to test that <M>K</M> has the homotopy type of a circle.

<P/>If the test fails then  try the function again with an integer
<M>r \ge 2</M> entered as the optional second argument. The integer determines the resolution with which the knot is constructed. 




