Example: Modification of the Protonation Degree of Histidines

    The protonation degree of HIS can be changed by using the patch residues HISE and HISD that are defined in file ``tophcsdx.pro", which is located in the ``toppar" directory. The histidine patches can be invoked by using the patch statement; e.g.,

patch HISE 
   reference=nil=( resid 14 ) 
end