
NOC forcefield is generated from GROMACS format forcefield

topology files:
   aminoacid.top	//all amino acid topology
   groups.top		//all hetgroups topology
   nuacid.top		//all nucleic acid topology

forcefile files: 
   name.ntp		//NOC atomname to forcefield atomtype
   name.atp		//forcefield atomtype to bondtype table, mass, sigma, epsilon   
   name_bon.itp		//bondtypes parameter
   name_ang.itp		//angletypes parameter
   name_dih.itp		//dihedraltypes paremeter

note:   
   1. ntp file is generate by command: generate.ff aminoacid.top gmxforcefield.rtp
	#	rename LYS to LYN in GROMACS topology
  	#	ffoplsaa.rtp    rename LYS to LYN
  	#	ffencads.rtp    rename LYS to LYN
  	#	ffencadv.rtp    rename LYS to LYN
   2. atp file is generate by command: generate.ff.merge.atp gmxforcefield.atp gmxforcefieldnb.itp
   3. itp files are derived from gmxforcefieldbon.itp (separate bond, angle, dihedral), by command: generate.ff.bonds gmxforcefieldbon.itp
        #       constrainttypes is skiped
