[gmx-users] Equilibrate the water around my molecule
Mark.Abraham at anu.edu.au
Fri Mar 23 19:55:09 CET 2012
On 24/03/2012 5:38 AM, Lara Bunte wrote:
> I want to equilibrate the water around my (small) molecule. In the tutorials I found and in the manual is not enough information how to do that if you have an own parametrization of a molecule.
> Here is my situation:
> I have a pdb file and I have a parametrization for this molecule out of a supporting information from a paper. I create a .rtp and .hdb file, changed atomtypes.atp, ffnonbonded.itp and residuetypes.dat.
> In the .rtp file I called my molecule [ ISO ] before the [ atoms ] section starts. In the residuetypes.dat file I write
> ISO Isoalloxazin
The above entry in residuetypes.dat makes it impossible for GROMACS to
recognise your ISO as protein. See manual 8.1.1. This file identifies
the *type* of the *residue* to permit GROMACS and you to agree on broad
categorizations of residues. Telling GROMACS the full name of the
molecule is not helpful here.
> After that I did the calculation described in the tutorial of Erik Lindahl and I got no errors up to equilibrating the water around my molecule.
> In my pr.mdp file is the entry
> tc-grps = protein non-protein
Here you require a protein group to exist. Apparently you have no part
of your system that is protein according to residuetypes.dat, and so
there is no such group. If you'd had another protein element to your
system, then grompp would have regarded ISO as non-protein, and you
might have been left with a hard-to-notice problem.
> I guess this is a problem because I got an error and with best thanks I got this solution from Mark Abraham:
> I read something about make_ndx and about Thermostats but I still have no idea how to go forward with this problem :-(
All three forms of solution I proposed there are still possible. The
second is the easiest: use "ISO Protein" in your residuetypes.dat.
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