# Problem during the Protein-Ligand Analysis gmx distance command

**URL:** <https://gromacs.bioexcel.eu/t/problem-during-the-protein-ligand-analysis-gmx-distance-command/5703>\
**Category:** User discussions\
**Tags:** mdrun, analysis-tools\
**Created:** [February 2, 2023, 10:20am UTC](https://gromacs.bioexcel.eu/t/problem-during-the-protein-ligand-analysis-gmx-distance-command/5703 "2023-02-02T10:20:57Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![sreeshma\_raj](https://avatars.discourse-cdn.com/v4/letter/s/439d5e/32.png) [@sreeshma\_raj](https://gromacs.bioexcel.eu/u/sreeshma_raj)\
**Post date:** [February 2, 2023, 10:20am UTC](https://gromacs.bioexcel.eu/t/problem-during-the-protein-ligand-analysis-gmx-distance-command/5703/1 "2023-02-02T10:20:57Z")

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GROMACS version:2022.4  
GROMACS modification: Yes/No  
Here post your question

I was following the Gromacs MD Simulation tutorial, but an error occured in the analysis during “Analyzing Protein-Ligand Interactions and Ligand Dynamics”.  
the command and error are mentioned below.

gmx distance -s md\_0\_10.tpr -f md\_0\_10\_center.xtc -select ‘resname “JZ4” and name OAB plus resid 102 and name OE1’ -oall

Program: gmx distance, version 2021.4-Ubuntu-2021.4-2  
Source file: src/gromacs/trajectoryanalysis/modules/distance.cpp (line 218)  
Function: void gmx::analysismodules::{anonymous}::checkSelections(const SelectionList&)

Inconsistency in user input:  
Selection ‘resname “JZ4” and name OAB plus resid 102 and name OE1’ does not  
evaluate into an even number of positions (there are 1 positions)

How may i correct this inconsistency?

Thank you

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**Author:** ![sshechte1](https://avatars.discourse-cdn.com/v4/letter/s/c4cdca/32.png) [@sshechte1](https://gromacs.bioexcel.eu/u/sshechte1)\
**Post date:** [August 18, 2023, 6:40pm UTC](https://gromacs.bioexcel.eu/t/problem-during-the-protein-ligand-analysis-gmx-distance-command/5703/2 "2023-08-18T18:40:33Z")

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@sreeshma_raj did you ever get an answer to your question? I have encountered similar issue

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**Author:** ![sshechte1](https://avatars.discourse-cdn.com/v4/letter/s/c4cdca/32.png) [@sshechte1](https://gromacs.bioexcel.eu/u/sshechte1)\
**Post date:** [October 30, 2023, 9:41pm UTC](https://gromacs.bioexcel.eu/t/problem-during-the-protein-ligand-analysis-gmx-distance-command/5703/3 "2023-10-30T21:41:21Z")

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Hi, I did not but one time it did not work. The error had to do with the name of the of the ligand name and the residue used for the Hbond calcs. Which file are you using to identify the atom numbers in Pymol?