# How can we change the pH of a solution?

**URL:** <https://gromacs.bioexcel.eu/t/how-can-we-change-the-ph-of-a-solution/8073>\
**Category:** User discussions\
**Tags:** mdp-parameters\
**Created:** [January 18, 2024, 3:12pm UTC](https://gromacs.bioexcel.eu/t/how-can-we-change-the-ph-of-a-solution/8073 "2024-01-18T15:12:23Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![PriZarah](https://avatars.discourse-cdn.com/v4/letter/p/779978/32.png) [@PriZarah](https://gromacs.bioexcel.eu/u/PriZarah)\
**Post date:** [January 18, 2024, 3:12pm UTC](https://gromacs.bioexcel.eu/t/how-can-we-change-the-ph-of-a-solution/8073/1 "2024-01-18T15:12:23Z")

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GROMACS version: 2018  
GROMACS modification: Yes/No  
I want to know whether we can change the pH (pH other than body pH) of a solution containing enzyme we are simulating and how can we do that? Is there any option for that in md parameter file?

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**Author:** ![jalemkul](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/jalemkul/32/18_2.png) [@jalemkul](https://gromacs.bioexcel.eu/u/jalemkul)\
**Post date:** [January 18, 2024, 3:27pm UTC](https://gromacs.bioexcel.eu/t/how-can-we-change-the-ph-of-a-solution/8073/2 "2024-01-18T15:27:38Z")

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You can either set a fixed protonation state with the constituent molecules ionized as they would be at a given pH according to their pKa values, or perform constant-pH simulations, which is a special technique. You do not typically set a value of pH in a simulation system in a standard setup because there are no dissociable protons and the concentration of H3O+ would not be anywhere near realistic.