# ERROR 1 \[file topol\_Protein\_chain\_a.itp, line 22\]: moleculetype Protein\_chain\_a is redefined **URL:** \ **Category:** User discussions\ **Tags:** mdp-parameters, mdrun\ **Created:** [July 7, 2022, 12:15am UTC](https://gromacs.bioexcel.eu/t/error-1-file-topol-protein-chain-a-itp-line-22-moleculetype-protein-chain-a-is-redefined/4428 "2022-07-07T00:15:13Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![Hanoriega](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/hanoriega/32/1562_2.png) [@Hanoriega](https://gromacs.bioexcel.eu/u/Hanoriega)\ **Post date:** [July 7, 2022, 12:15am UTC](https://gromacs.bioexcel.eu/t/error-1-file-topol-protein-chain-a-itp-line-22-moleculetype-protein-chain-a-is-redefined/4428/1 "2022-07-07T00:15:13Z")
GROMACS version: version 2020.1-Ubuntu-2020.1-1 GROMACS modification: Yes/No Here post your question Hello, I am a very new user and have been successful to running other simulations. This is my largest, I have attempted (60-mer icosahedral). I got this error and I am a bit unsure as to how I can fix it or by pass maybe?? I copied and pasted below. Please help me and be gentle because I am new to the field. GROMACS: gmx grompp, version 2020.1-Ubuntu-2020.1-1 Executable: /usr/bin/gmx Data prefix: /usr Working dir: Command line: gmx grompp -f em.mdp -p topol.top -c solvate.gro -o em.tpr Ignoring obsolete mdp entry ‘ns\_type’ NOTE 1 [file em.mdp]: With Verlet lists the optimal nstlist is \>= 10, with GPUs \>= 20. Note that with the Verlet scheme, nstlist has no effect on the accuracy of your simulation. Setting the LD random seed to -1437330375 Generated 165 of the 1596 non-bonded parameter combinations ERROR 1 [file topol\_Protein\_chain\_a.itp, line 22]: moleculetype Protein\_chain\_a is redefined There was 1 note * * * Program: gmx grompp, version 2020.1-Ubuntu-2020.1-1 Source file: src/gromacs/gmxpreprocess/toppush.cpp (line 1474) Fatal error: There was 1 error in input file(s) Thank you, Heather Noriega