Re: Asymmetric concentration gradient

From: Ropon-Palacios G. (
Date: Mon Aug 23 2021 - 23:10:52 CDT

Dear Prof. Gumbart,


My question was on that side, how to do the solvation up and down independently, could you give me an example of the script, to be able to do it please. I find it a bit unfamiliar as this is my first time doing this.


From: "Gumbart, JC" <>
Date: Monday, August 23, 2021 at 11:05 PM
To: NAMD list <>, "Ropon-Palacios G." <>
Subject: Re: namd-l: Asymmetric concentration gradient


Hi Geo,


It’s been a long time since I ran this. But one way I can think of would be to solvate and ionize above and below separately and then combine them with psfgen. I attach an example tclBC script and NAMD input file for running the actual simulation once you’ve built the system.





On Aug 23, 2021, at 10:08 PM, Ropon-Palacios G. <> wrote:


Dear users,


I am trying to simulate a membrane protein system where it has a concentration difference on one side as well as the other, similar to the work of Professor JC Gumbart “Molecular dynamics simulations of membrane proteins under asymmetric ionic concentrations”


My question is, how do I ionize or how do I place the ions on both sides with a difference in concentration? Could you please share a script to do this?.






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