# How to resolve failing Gromacs Membrane Protein Tutorial Energy Minimization step

**URL:** <https://gromacs.bioexcel.eu/t/how-to-resolve-failing-gromacs-membrane-protein-tutorial-energy-minimization-step/4814>\
**Category:** User discussions\
**Created:** [September 18, 2022, 12:48pm UTC](https://gromacs.bioexcel.eu/t/how-to-resolve-failing-gromacs-membrane-protein-tutorial-energy-minimization-step/4814 "2022-09-18T12:48:25Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![gundalav](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@gundalav](https://gromacs.bioexcel.eu/u/gundalav)\
**Post date:** [September 18, 2022, 12:48pm UTC](https://gromacs.bioexcel.eu/t/how-to-resolve-failing-gromacs-membrane-protein-tutorial-energy-minimization-step/4814/1 "2022-09-18T12:48:25Z")

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GROMACS version: 2021.4  
GROMACS modification: No

I was trying Gromacs membrane protein tutorial.  
I’ve reached [Energy Minimization step](http://www.mdtutorials.com/gmx/membrane_protein/05_EM.html).

But when I ran this code:

`gmx grompp -f minim.mdp -c system_solv_ions.gro -p topol.top -o em.tpr`

I got this error:

```auto
Fatal error:
Cannot find position restraint file restraint.gro (option -r).
From GROMACS-2018, you need to specify the position restraint coordinate files
explicitly to avoid mistakes, although you can still use the same file as you
specify for the -c option.

```

Also with this:

`gmx grompp -f minim.mdp -r system_solv_ions.gro -p topol.top -o em.tpr`

I got the error:

```auto
Error in user input:
Invalid input values
  In option c
    Required option was not provided, and the default file 'conf' does not
    exist or is not accessible.
    The following extensions were tried to complete the file name:
      .gro, .g96, .pdb, .brk, .ent, .esp, .tpr

```

How can I resolve?

G.V.

---

<div class="post-metadata">

**Author:** ![nano](https://avatars.discourse-cdn.com/v4/letter/n/dec6dc/32.png) [@nano](https://gromacs.bioexcel.eu/u/nano)\
**Post date:** [September 18, 2022, 2:36pm UTC](https://gromacs.bioexcel.eu/t/how-to-resolve-failing-gromacs-membrane-protein-tutorial-energy-minimization-step/4814/2 "2022-09-18T14:36:36Z")

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You need to combine -c and -r:

```auto
gmx grompp -f minim.mdp -c system_solv_ions.gro -r system_solv_ions.gro -p topol.top -o em.tpr

```

---

<div class="post-metadata">

**Author:** ![gundalav](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@gundalav](https://gromacs.bioexcel.eu/u/gundalav)\
**Post date:** [September 21, 2022, 1:56am UTC](https://gromacs.bioexcel.eu/t/how-to-resolve-failing-gromacs-membrane-protein-tutorial-energy-minimization-step/4814/3 "2022-09-21T01:56:04Z")

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Thank you! This works.