# CHARMM force field parameters for metal ions Cd(II) and Pb(II)

**URL:** <https://gromacs.bioexcel.eu/t/charmm-force-field-parameters-for-metal-ions-cd-ii-and-pb-ii/5852>\
**Category:** User discussions\
**Tags:** forcefield\
**Created:** [February 22, 2023, 4:46pm UTC](https://gromacs.bioexcel.eu/t/charmm-force-field-parameters-for-metal-ions-cd-ii-and-pb-ii/5852 "2023-02-22T16:46:11Z")\
**Posts on this page:** 3\
**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:** [February 22, 2023, 4:46pm UTC](https://gromacs.bioexcel.eu/t/charmm-force-field-parameters-for-metal-ions-cd-ii-and-pb-ii/5852/1 "2023-02-22T16:46:11Z")

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GROMACS version: 2018  
GROMACS modification: Yes/No  
I want to simulate an enzyme with toxic metal ion Pb(II) using CHARMM force field. Does any one know for FF parameters for Pb(II) ion? Or how to generate parameters for metal ions?  
Thank you.

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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:** [February 22, 2023, 5:02pm UTC](https://gromacs.bioexcel.eu/t/charmm-force-field-parameters-for-metal-ions-cd-ii-and-pb-ii/5852/2 "2023-02-22T17:02:50Z")

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Both of these ions are already supported in the current version of the CHARMM36 port for GROMACS. The parameters come from [dx.doi.org/10.1021/jp309150r](http://dx.doi.org/10.1021/jp309150r) but please note none of these have been extensively validated for interactions with biomolecules and may require adjustment (e.g. NBFIX) to preserve appropriate coordination geometries.

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**Author:** ![Nik](https://avatars.discourse-cdn.com/v4/letter/n/6de8d8/32.png) [@Nik](https://gromacs.bioexcel.eu/u/Nik)\
**Post date:** [October 19, 2023, 6:38am UTC](https://gromacs.bioexcel.eu/t/charmm-force-field-parameters-for-metal-ions-cd-ii-and-pb-ii/5852/3 "2023-10-19T06:38:42Z")

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I have a similar task - to minimize a protein molecule with zinc and cadmium ions. Is it necessary to generate separate topology for each of this atoms and include their parameters to the topology file as we would do for protein-ligand complex? Or using pdb2gmx command is enough in the case when metal ions are already included in the primary PDB file as HETATMs of the protein chain?