[gmx-users] charmm36 force field

Justin Lemkul jalemkul at vt.edu
Wed Feb 14 14:16:58 CET 2018

On 2/12/18 3:09 PM, farial tavakoli wrote:

First, please note that this line is not doing anything:
> define        =  -DUSE_OLD_C3

If you're trying to use the old CHARMM36 parameters, and not CHARMM36m, 
the correct keyword is -DUSE_OLD_C36. We only included that in the case 
that people wanted to do force field comparisons, because for folded 
proteins, C36 and C36m are almost identical by virtue of how we did the 

> but when I checked nvt.gro by VMD ,  viewed  the receptor and ligand went out of the box, almost completely and ligand was separated from the protein, completely. Is there anyone who can help me and advice me why it was happened?

Sounds like a typical PBC imaging issue. Just use trjconv.



Justin A. Lemkul, Ph.D.
Assistant Professor
Virginia Tech Department of Biochemistry

303 Engel Hall
340 West Campus Dr.
Blacksburg, VA 24061

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