[gmx-users] charge distribution

[elham tazikeh]

Dear Justin
i really appricite for your help
i want to tell all did work until now, again:


1.total charges in my topol.top was +2, then by genion, i added 2 CL to  my
comlex (HSA+Aspirin)

2.My .itp file (produce by PRODRG) was(consist of 11 atoms) :

[ moleculetype ]
; Name nrexcl
SAL      3
[ atoms ]
;   nr      type  resnr resid  atom  cgnr   charge     mass
     1        OM     1  SAL     O1'     1   -0.765  15.9994 ;'
     2         C     1  SAL     C1'     1    0.354  12.0110 ;'
     3        OM     1  SAL     O2'     1   -0.765  15.9994 ;'
     4         C     1  SAL      C1     1   -0.027  12.0110
     5       CH2     1  SAL      C6     1    0.102  14.0270
     6       CH2     1  SAL      C5     1    0.101  14.0270
     7       CR1     1  SAL      C4     2    0.010  13.0190
     8       CR1     1  SAL      C3     2    0.010  13.0190
     9         C     1  SAL      C2     2    0.130  12.0110
    10        OA     1  SAL      O2     2   -0.191  15.9994
    11         H     1  SAL      H2     2    0.041   1.0080


with topology file and .itp file, after grompp (for produce nvt.tpr)
i encounted to below error :
*system has non-zero total charge : -0.619999*


3.as yor re mentioned, Aspirin has 17 atoms.
for charge distribution, i used of QM (NBO calculation) and my results was:
    1  C  -0.095205
    2  C  -0.077566
    3  C  -0.084684
    4  C  -0.028579
    5  C  -0.223106
    6  C    0.198041
    7  H    0.147099
    8  H    0.106100
    9   H   0.101762
    10  H  0.117238
    11  C  0.443312
    12  O  -0.318010
    13  H    0.247465
    14  O  -0.341986
    15  O  -0.318846
    16  C    0.312765
    17  O  -0.320346
    18  C  -0.281115
    19  H    0.136126
    20  H    0.139768
    21  H    0.139765

these are estimated for* 2-acetoxy benzoic acid *alone (i dont know , must
be calculate for complex HSA+Aspirin or Aspirin alone?)

4. on the other hand, i tried to search in *aminoacids.rtp* file for
*gromos* force field , but saw only charges for ACE group(other aminoacids
and some solvents) and i could not find out the charges of all atoms in
Aspirin molecule.

Overall, in your opinion, where is my problem?

i m looking forward to seeing your advise

cheers