[gmx-users] proper and improper dihedrals in topology file from other ff

[라지브간디]

Dear gmx users,


I am MD simulation for heme ligated protein where i given all bond and angle, dihedral information in topology file created by pd2gmx ( gromos43a1).


However, i do not know how to interpret the proper and improper dihedrals in topology file? I have looked over the .rtp file and found that gromos mentioned like
 
example:


[ impropers ]
;  ai    aj    ak    al   gromos type
   C2    N1    N3   NA2     gi_1    
  NA2  HA21  HA22    C2     gi_1    
   N3    C2    C4   HA3     gi_1   


But the the parameter  I use from literature where its in charmm and amber format as they mentioned the torsions like following way.


Improper 
CPB-X-X-CR1E    90.0   0.0 
CC - X-X-NB       18.3     0.0           


...............etc


How do i use this improper to utilize in gromos? 


Thanks in advance.