On 10/26/14 10:49 PM, Nathan K Houtz wrote:
Thanks for your help. And actually my version of gromacs does not have genbox 
anymore. (http://www.gromacs.org/Documentation/How-tos/Tool_Changes_for_5.0 at 
the bottom: GENBOX - This tool has been split to gmx solvate and gmx 
insert-molecules.) But it's no big deal, insert-molecules seemed to work just 
fine! Here are the commands I used:

gmx insert-molecules -f tetrolic_acid.gro -ci tetrolic_acid.gro -nmol 499 -o 
tetrolic500.gro
gmx solvate -cp tetrolic500.gro -cs spc216.gro -o tetrolic_solv.gro -p topol.top

where tetrolic_acid.gro and topol.top are files I created myself to define the 
molecule. I checked the output in vmd and it looks like exactly what I want. 
But now I'm stuck on another step and I get a confusing error. I tried to 
minimize the energy via:

gmx grompp -f minim.mdp -c tetrolic_solv.gro -p topol.top -o em.tpr

I stole the minim.mdp file from a tutorial 
(http://bevanlab.biochem.vt.edu/Pages/Personal/justin/gmx-tutorials/lysozyme/Files/minim.mdp).
 I don't know how to properly create an mdp file from scratch, but judging from 
the comments, it seems reasonable and I don't see anything that must be 
specific to the case in the tutorial. Anyway, I don't think it caused my error. 
The output for that command is:

Fatal error:
Atomtype opls_111 not found
For more information and tips for troubleshooting, please check the GROMACS
website at http://www.gromacs.org/Documentation/Errors

The link is not helpful, however. Googling exactly the error turns up very few 
results. The problem seems to be either with my topology file or with the itp 
file for water, which is referenced in my topology file like this:

#include "oplsaa.ff/tip3p.itp"

right after the constraints section. I also tried <#include 
"oplsaa.ff/spc.itp"> but it came up with a nearly identical error:

Fatal error:
Atomtype opls_116 not found
For more information and tips for troubleshooting, please check the GROMACS
website at http://www.gromacs.org/Documentation/Errors

The closest thing to help I found by searching was this blog post: 
http://www.somewhereville.com/?p=114 However, his initial spc.itp file looks 
much different than mine. I think he must just have an older version of gromacs 
or something. Does anyone else know how I could do the energy minimization?


Your topology is constructed incorrectly, but without seeing it in its entirety, it is impossible to say. Please post the file for download somewhere and provide a link, otherwise copy and paste its entire contents into a reply if the message will be small enough.

-Justin

--
==================================================

Justin A. Lemkul, Ph.D.
Ruth L. Kirschstein NRSA Postdoctoral Fellow

Department of Pharmaceutical Sciences
School of Pharmacy
Health Sciences Facility II, Room 629
University of Maryland, Baltimore
20 Penn St.
Baltimore, MD 21201

jalem...@outerbanks.umaryland.edu | (410) 706-7441
http://mackerell.umaryland.edu/~jalemkul

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