# Do we need Pressure coupling while pulling during umbrella sampling

**URL:** <https://gromacs.bioexcel.eu/t/do-we-need-pressure-coupling-while-pulling-during-umbrella-sampling/4638>\
**Category:** User discussions\
**Tags:** mdp-parameters, mdrun, simulation-setup\
**Created:** [August 18, 2022, 8:03pm UTC](https://gromacs.bioexcel.eu/t/do-we-need-pressure-coupling-while-pulling-during-umbrella-sampling/4638 "2022-08-18T20:03:39Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![samapika](https://avatars.discourse-cdn.com/v4/letter/s/9fc348/32.png) [@samapika](https://gromacs.bioexcel.eu/u/samapika)\
**Post date:** [August 18, 2022, 8:03pm UTC](https://gromacs.bioexcel.eu/t/do-we-need-pressure-coupling-while-pulling-during-umbrella-sampling/4638/1 "2022-08-18T20:03:39Z")

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GROMACS version:  
GROMACS modification: No  
Dear gromacs users, I am posting two questions regarding umbrella sampling. I hope to get answers.  
So my first question is, do we need Pressure coupling while pulling during umbrella sampling?  
And, should I position restraint the lipid bilayer during the pulling of a drug molecule through it? I think position restraining will not allow a natural passage for the drug.

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**Author:** ![hess](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/hess/32/416_2.png) [@hess](https://gromacs.bioexcel.eu/u/hess)\
**Post date:** [August 19, 2022, 9:34am UTC](https://gromacs.bioexcel.eu/t/do-we-need-pressure-coupling-while-pulling-during-umbrella-sampling/4638/2 "2022-08-19T09:34:18Z")

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Pressure coupling is is not coupled to umbrella sampling, so you choose pressure coupling, or not, the same way as for a system without pressure coupling.

Why would you want to position restrain the membrane? For pull a drug through a membrane you would usually use the pull code with cylinder geometry for the membrane. Then one should not use position restraints.

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**Author:** ![samapika](https://avatars.discourse-cdn.com/v4/letter/s/9fc348/32.png) [@samapika](https://gromacs.bioexcel.eu/u/samapika)\
**Post date:** [August 20, 2022, 4:49am UTC](https://gromacs.bioexcel.eu/t/do-we-need-pressure-coupling-while-pulling-during-umbrella-sampling/4638/3 "2022-08-20T04:49:45Z")

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Thank you sir for the clarification.