[BioC] calculate interaction between aminoacids residues

[Fabien Crozet]

>From a particular PDB file I would like to calculate
the interactions between residues. Two residues are
considered interacting if any of their atoms
(excluding hydrogen) are within a particular cutoff
distance.
The main goal is to compare 2 PDB files with little
differences and then determines the number of
interactions that are disrupted. 
I wonder if there are bioconductor package that can be
adapted for these kinds of statiscal analysis... I
don't know too much about the differents packages and
if someone can give me a suggestion for it, i would
appreciate a lot !
Thanks for help.