Send more information. what .itp and .top files are you using? what was your pdb2gmx command? what were the 3 or 4 lines on either side of the error message (cut and paste them)? >hi >i run pdbgmx2 for popc but errore message is here: >wrong format is in ffg43a2.h >line 2 7 ow >whould you please help me? >thanks >mahboobeh