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 -- Gromacs Users mailing list * Please search the archive at http://www.gromacs.org/Support/Mailing_Lists/GMX-Users_List before posting! * Can't post? Read http://www.gromacs.org/Support/Mailing_Lists * For (un)subscribe requests visit https://maillist.sys.kth.se/mailman/listinfo/gromacs.org_gmx-users or send a mail to gmx-users-requ...@gromacs.org.