# How do I pull two protein units each in rotation?

**URL:** <https://gromacs.bioexcel.eu/t/how-do-i-pull-two-protein-units-each-in-rotation/1095>\
**Category:** User discussions\
**Created:** [November 16, 2020, 12:39pm UTC](https://gromacs.bioexcel.eu/t/how-do-i-pull-two-protein-units-each-in-rotation/1095 "2020-11-16T12:39:07Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![yenju](https://avatars.discourse-cdn.com/v4/letter/y/9d8465/32.png) [@yenju](https://gromacs.bioexcel.eu/u/yenju)\
**Post date:** [November 16, 2020, 12:39pm UTC](https://gromacs.bioexcel.eu/t/how-do-i-pull-two-protein-units-each-in-rotation/1095/1 "2020-11-16T12:39:07Z")

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GROMACS version: 2018.4  
GROMACS modification: No  
Here post your question

I want to pulling while rotating two units at the same time with their respective rotating shafts, but only one pull-coord1-vec option is applicable. What should I do?

pull-coord1-type = umbrella  
pull-coord1-geometry = angle-axis  
; Select components for the pull vector. default: Y Y Y

; Switch from r1 to r0 in case of dynamic reaction force  
pull-coord1-vec = 0.055499 0.0249185 -0.9918185  
pull\_constr\_tol = 1e-06  
pull-coord1-start = no  
pull\_nstxout = 100  
pull\_nstfout = 100  
; Number of pull groups  
pull\_ngroups = 2  
; Group name, weight (default all 1), vector, init, rate (nm/ps), kJ/(mol\*nm^2)  
pull-group1-name = Protein\_A  
pull-group2-name = Protein\_B  
pull-coord1-groups = 1 2  
pull-coord1-init = 90  
pull-coord1-rate = 0  
pull-coord1-k = 1000  
pull-coord1-kB = 1000

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<div class="post-metadata">

**Author:** ![cblau](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/cblau/32/5_2.png) [@cblau](https://gromacs.bioexcel.eu/u/cblau)\
**Post date:** [November 17, 2020, 9:37am UTC](https://gromacs.bioexcel.eu/t/how-do-i-pull-two-protein-units-each-in-rotation/1095/2 "2020-11-17T09:37:40Z")

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Hi Yenju,

Using more than one pulling coordinate should help you here. Set `pull-ncoords = 2` and then set all values for `pull-coord2-type` accordingly.

Best,  
Christian

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<div class="post-metadata">

**Author:** ![yenju](https://avatars.discourse-cdn.com/v4/letter/y/9d8465/32.png) [@yenju](https://gromacs.bioexcel.eu/u/yenju)\
**Post date:** [November 17, 2020, 9:57am UTC](https://gromacs.bioexcel.eu/t/how-do-i-pull-two-protein-units-each-in-rotation/1095/3 "2020-11-17T09:57:22Z")

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I really appreciate your reply!

Thanks again.

Yeonju.