Sir,
I have checked the atom types and they seemed fine. So I got all more
confused. In the mailing list, there were previous queries of the same kind
in the past, but could not see an exact response or noone shared how they
dealt with it.
On 26 Apr 2020 21:20, "Carlos Simmerling" <carlos.simmerling.gmail.com>
wrote:
> I'm not a GAFF expert, so Junmei's input here would be great, but what I
> would do would be to look at the atom type assignments, not just the
> parameters in the frcmod. Are the atoms that are becoming non-planar
> assigned atom types consistent with sp2 or sp3 geometries? Once the atom
> types are assigned then you end up with parameters, but maybe it's a
> chemical perception problem. I'd check that first.
>
> On Sun, Apr 26, 2020 at 11:34 AM Sruthi Sudhakar <
> sruthisudhakarraji.gmail.com> wrote:
>
> > Respected all,
> > Even I am facing the same issue using AMBER18 recently. The procedure I
> > followed is almost similar, but my ligand is combined to a G-quadruplex
> > structure in tleap. But in frcmod file, even I am getting such high
> penalty
> > scores and my aromatic ligand also shows planarity distortion. Have
> > enquired regarding the same sometime back but did not get any response.
> > Hope this time someone might be able to give some insight on this.
> > Thank you
> >
> > On Sun, Apr 26, 2020 at 10:20 AM Jenny 148 <jenny.rs140.gmail.com>
> wrote:
> >
> > > > Dear all,
> > > >The following is a recurring problem and I have repeated the
> simulation
> > > multiple times and still the issue persists. Please help.
> > > I have done a simulation on an aromatic ligand which must remain
> planar.
> > I
> > > optimized the structure in Gaussian, done docking on the ligand,
> > calculated
> > > ESP charges for selected conformers in Gaussian again. My ligand has a
> +2
> > > charge. Then I have done the RESP fitting using antechamber and
> generated
> > > the frcmod file.(AMBER18)
> > > > antechamber -fi gout -i ligand.log -fo prepi -o ligand.prepi -c resp
> > > > parmchk2 -i ligand.prepi -o ligand.frcmod -f prepi.
> > > >
> > > > Then I performed restrained minimization, heating and density
> > > equilibration and unrestrained equilibration and 500ns production. My
> > > ligand strangely loses the planarity by the equilibration stage and
> > shows a
> > > really distorted structure which is unacceptable. I have used the gaff
> ff
> > > and Tip3p waterbox in the simulation. My frcmod file looks like the
> > > following:
> > > > DIHE
> > > > ca-ca-cc-cc 4 2.800 180.000 2.000 same as X
> > > -c2-ca-X , penalty score=232.0
> > > > ca-ca-cc-cf 4 2.800 180.000 2.000 same as X
> > > -c2-ca-X , penalty score=232.0
> > > > ca-cc-cf-ha 4 16.000 180.000 2.000 same as X
> > > -cc-cd-X , penalty score=136.0
> > > > ca-cc-cf-cf 4 16.000 180.000 2.000 same as X
> > > -cc-cd-X , penalty score=136.0
> > > > cc-cc-cf-ha 4 16.000 180.000 2.000 same as X
> > > -cc-cd-X , penalty score=136.0
> > > > cc-cc-cf-cf 4 16.000 180.000 2.000 same as X
> > > -cc-cd-X , penalty score=136.0
> > > >
> > > > IMPROPER
> > > > c3-ca-na-cc 1.1 180.0 2.0 Using the
> > > default value
> > > > ca-ca-ca-na 1.1 180.0 2.0 Using the
> > > default value
> > > > ca-ca-ca-cc 1.1 180.0 2.0 Using the
> > > default value
> > > > ca-ca-ca-ha 1.1 180.0 2.0 Using
> > general
> > > improper torsional angle X- X-ca-ha, penalty score= 6.0)
> > > > cc-h4-cc-na 1.1 180.0 2.0 Using the
> > > default value
> > > > ca-cc-cc-cf 1.1 180.0 2.0 Using the
> > > default value
> > > > cc-cf-cf-ha 1.1 180.0 2.0 Same as X
> > -X
> > > -ca-ha, penalty score= 46.8 (use general term))
> > > > c3-ca-na-cd 1.1 180.0 2.0 Using the
> > > default value
> > > > cc-h4-cd-na 1.1 180.0 2.0 Using the
> > > default value
> > > > cc-cd-cc-ha 1.1 180.0 2.0 Same as X
> > -X
> > > -ca-ha, penalty score= 38.9 (use general term))
> > > > Could someone suggest what might have went wrong and how to solve
> this
> > > issue. I am attaching the image of my distorted ligand here.
> > > > My two major doubts are
> > > > 1. Is the frcmod file wrong?
> > > > 2. should I include the -nc flag in the resp fitting since my ligand
> > has
> > > a +2 charge?
> > > When I repeated the procedure to an old ligand which we had then
> > simulated
> > > in AMBER14, the newly generated frcmod files have same components as
> the
> > > old files,but with a high penalty score. Is there something peculiar we
> > > should mention in the latest version?
> > > > Thanks in advance
> > > >
> > > > --
> > > > Jenny R.S
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> > >
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> >
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Received on Sun Apr 26 2020 - 10:00:02 PDT
