Protein Contacts Difference: 
In STING_PCD users can obtain a complete comparison report of the intrachain interactions 
for any two chains described in the PDB format file. The user must supply any 
two PDB ids and corresponding chain ids for the analysis. At the output, a user 
will receive a list of interactions which were preserved in both chains as well 
as the list of those which are present in only one of them. Users can also analyse 
a wild type protein and a corresponding mutant structure with a single point mutantion; 
in this case a user needs to supply at the input, the mutated amino acid name 
and the number.