Re: regarding constant PH simulation

From: Jeff Comer (jeffcomer_at_gmail.com)
Date: Thu Nov 19 2020 - 21:25:24 CST

(1) I don’t think there is any explanation on how to do this. You have to
study the files included in the tutorial (and distributed with NAMD) as a
guide.

(2) This is issue is discussed in the paper
( https://doi.org/10.1021/acs.jctc.7b00875 ). If I recall correctly, the
answer is that it doesn’t matter. The idea that PME with charged systems
automatically leads to erroneous results is mostly a myth. Artifacts are
found for small and highly charged systems, but are negligible for most
modern systems with large enough water boxes.

Jeff

On Thu, Nov 19, 2020 at 21:09 zahra nabavi <zahranabavi2001_at_gmail.com>
wrote:

> Dear NAMD Community,
>
> I have two questions regarding constant PH simulation.
>
> 1- I am planning to use it for a new molecule but as far as I know it
> only works for aminoacids. What changes do I need to make so I could use it
> for protonation of my own molecule? Is there any tutorial or guide to help
> me make required changes to the TCL and input files?
>
> 2- When we change protonation states from protonated to deprotonated
> states or vice versa, are there any "ghost" hydrogens somewhere in the
> system to compensate for the movement of the charge between solvent and the
> aminoacid? and if not, isn't it going to affect the PME calculations?
>
> Thank you in advance,
> Zahra
>

-- 
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Jeffrey Comer, PhD
Associate Professor
Department of Anatomy and Physiology
Kansas State University
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Phone: 785-532-6311
Website: http://jeffcomer.us

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