[gmx-users] The promblem of force field

[xiaojiong]

Dear,
My receptor is membrane proteins,then I get protein-ligand complex.I  want to do MD simulations in DPPC.I use the GROMOS96 53a6 force  
 field modified in order to include Berger’s parameters for lipids .The topology for the ligand was created 
employing the server PRODRG 2.5 Beta.
When I finished the command "perl inflategro.pl system.gro 4 DPPC 14 system_inflated.gro 5 area.dat",
 I want to run energy minimization.I submit the command "grompp -f minim.mdp -c system_inflated.gro -p topol.top -o em.tpr".The error like this 
 Back Off!Ijust backed up mdout.mdp to ./#mdout.mdp.4# 
Generated 813 of the 2346 non-bonded parameter combinations 
WARING 1 [file drg.itp,line1]: 
Too few parameters on line (source file toppush.c, line 1501) 

WARING 2 [file drg.itp,line2]:  
Too few parameters on line (source file toppush.c, line 1501) 

WARING 3 [file drg.itp,line17]:  
Too few parameters on line (source file toppush.c, line 1501) 

ERROR 1 [file drg.itp,line 21]: 
Expected a molecule type name and nrexcl 

Program grompp, VERSION 4.5.3 
Source code file:toppush.c, line:1187 

Fatal error: 
Atomtype \par not found 

Is the force field not suitable or others?Thanks!
    
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