# Umbrella sampling of ligand pulling towards binding site

**URL:** <https://gromacs.bioexcel.eu/t/umbrella-sampling-of-ligand-pulling-towards-binding-site/12480>\
**Category:** User discussions\
**Created:** [August 3, 2025, 3:00pm UTC](https://gromacs.bioexcel.eu/t/umbrella-sampling-of-ligand-pulling-towards-binding-site/12480 "2025-08-03T15:00:03Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Ranbir720](https://avatars.discourse-cdn.com/v4/letter/r/e495f1/32.png) [@Ranbir720](https://gromacs.bioexcel.eu/u/Ranbir720)\
**Post date:** [August 3, 2025, 3:00pm UTC](https://gromacs.bioexcel.eu/t/umbrella-sampling-of-ligand-pulling-towards-binding-site/12480/1 "2025-08-03T15:00:04Z")

</div>

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

Iam performing umbrella sampling of a ligand getting pulled towards the binding site and again getting dislogded as the pull force increases

The pulling experiment starts from the ligand getting pulled at -1.6 nm from the chosen center of mass and then it binds somewhere at 0.4 nm. But in PMF graph , i see sampling hapenning at -3nm and the sampling ends at 0 nm. Same goes for the histogram. Actually my pulling simulation runs for 543 ps and I have sampled configuration frames till 450ps. The binding happens somewhere near 405 ps. But still I am not able to correlate ANYTHING. Am I missing anything or have something wrong . Can anyone guide me through

 ![Screenshot 2025-08-03 202836](https://europe1.discourse-cdn.com/flex017/uploads/bioexcel1/original/2X/9/9f00837f56ba530d92ac452e4bbde8d971a5c9cd.png)

 ![Screenshot 2025-08-03 202425](https://europe1.discourse-cdn.com/flex017/uploads/bioexcel1/original/2X/d/da374ffa01d923194b18763fb2df79c5999a23dd.png)