[gmx-users] position restrain

[parto haghighi]

Dear GMX users,
I am working on lipid_drg system
my drug molecule has 23 atoms.

[ moleculetype ]
; Name nrexcl
DRG      3

[ atoms ]
;   nr      type  resnr resid  atom  cgnr   charge     mass
     1       CH3     1  DRG     CAA     1   -0.073  15.0350
     2       CH2     1  DRG     CAH     2    0.115  14.0270
     3       CH2     1  DRG     CAI     3    0.367  14.0270
     4        NL     1  DRG       N     4   -0.448  14.0067
     5         H     1  DRG      H1     5    0.346   1.0080
     6         H     1  DRG      H2     6    0.367   1.0080
     7       CH1     1  DRG      CA     7    0.297  13.0190
     8       CH3     1  DRG      CB     8    0.000  15.0350
     9         C     1  DRG       C     9    0.743  12.0110
    10         O     1  DRG       O    10   -0.598  15.9994
    11         N     1  DRG     NAK    11   -0.776  14.0067
    12         H     1  DRG     HAK    12    0.400  1.0080
    13         C     1  DRG     CAP    13    0.470  12.0110
    14       CR1     1  DRG     CAG    14    0.157  12.0110
    15       CH3     1  DRG     CAL    15   -0.072   1.0080
    16       CR1     1  DRG     CAF    16   -0.309  12.0110
    17        HC     1  DRG     HB4    17    0.253  1.0080
    18         S     1  DRG     SAM    18    0.089  32.0600
    19         C     1  DRG     CAQ    19   -0.508  12.0110
    20         C     1  DRG     CAN    20    0.968  12.0110
    21         O     1  DRG     OAD    21   -0.619  15.9994
    22        OA     1  DRG     OAL    22   -0.347  15.9994
    23       CH3     1  DRG     CAB    23    0.178  15.0350

and I have added 12 drugs in bilayer + sol and ion:

[ molecules ]
; Compound        #mols
DRG         12
DMPC        128
SOL         1943
CL          12

At the NVT step:
I have to use position restrain for 12 drug molecules which I have
added in bilayer, so I applied genrestr to make drg_posres.itp

genrestr -f lip_12drg_solv_ion_em.gro -o drg_posre.itp -fc 1000 1000 1000

and I modified end of topology:

; Include Position restraint file
#ifdef POSRES_DRG
#include "drg_posre.itp"
#endif

; Include DMPC chain topology
#include "dmpc.itp"

; Include water topology
#include "gromos43a1_lipid.ff/spc.itp"

; Include Position restraint file
#ifdef POSRES_DRG
#include "drg_posre.itp"
#endif

#ifdef POSRES_WATER
; Position restraint for each water oxygen
[ position_restraints ]
;  i funct       fcx        fcy        fcz
   1    1       1000       1000       1000
#endif

; Include topology for ions
#include "gromos43a1_lipid.ff/ions.itp"

[ system ]
; Name
drug in bilayer in water


[ molecules ]
; Compound        #mols
DRG         12
DMPC        128
SOL         1943
CL          12

when:
grompp -f NVT.mdp -c lip_12_ion_em.gro -p topol_drg.top -o nvt.tpr

Fatal error:
[ file drg_posre.itp, line 28 ]:
Atom index (24) in position_restraints out of bounds (1-23).
This probably means that you have inserted topology section
"position_restraints"
in a part belonging to a different molecule than you intended to.
In that case move the "position_restraints" section to the right molecule.

please guide me if its possile.
Thanks in advance.
P.Haghighi