I suspect that it isn't the ff14SB or other parameters that you are
loading, but probably is something to do with the new parameters you
created for the modified base. One way to check this : do you have
non-planar problems for standard bases too? even when you do not load a
system with modified bases and new parameters? if it is your parameters,
then you would need so share details about your prepin file and how you
generated any new parameters.
On Sat, Feb 27, 2016 at 4:07 AM, Prayagraj Fandilolu <fprayagraj.gmail.com>
wrote:
> Dear all,
>
> I am again reporting a problem which I had previously discussed here. I
> have done whatever I could, as per the suggestions of Mr. Jason and Mr.
> Carlos. I have not yet got the solution to the problem. Here I am sending
> the error details again…
>
> I am trying to simulate a tRNA system with few modified nucleosides. I have
> generated the parameters for a synthetic nucleoside which was not available
> in leaprc.modrna08
>
> Everything goes fine till I put the system for minimization. In sander
> output of minimization, I found that all the nitrogen atoms (with three
> bonding atoms) lose their planarity and this is affecting the proper atomic
> interactions and base stacking as well.
>
> I tried many other systems but the problem persists with them too.
>
> I guess there is something conflicting within the force fields. I have
> tried leaprc.rna.ff99 & leaprc.ff99bsc0 in combination and individually
> also. Other force fields like ff14SB, ff12SB were also used individually
> but the problem persists.
>
> For each of the above force fields, I am using following commands in leap:
>
> >>> source leaprc.abcforcefield
>
> >>> source leaprc.modrna08
>
> >>> loadamberparams frcmod.ol.dat (only for rna.ff99 and ff99bsc0)
>
> >>> loadamberprep abc.prepin
>
> >>> loadamberparams abc.frcmod
>
> >>> pmf=loadpdb pmf.pdb
>
> >>> solvatebox pmf TIP3PBOX 8
>
> >>> addions pmf Na+ 0
>
> >>> saveamberparm pmf pmf.prmtop pmf.inpcrd
>
> The topology and coordinate files are generated successfully but when the
> system is subjected to minimization for 10,000 steps of SD, all nitrogen
> atoms of the system lose their planarity.
>
> Can someone help me getting into the solution of this error?
>
> Thanks in advance……….
>
> Prayagraj Fandilolu
> Research Scholar,
> Structural Bioinformatics Unit
> Department of Biochemistry
> Shivaji University, Kolhapur - 416004
> (MS) India
>
> On Tue, Feb 2, 2016 at 5:43 PM, Jason Swails <jason.swails.gmail.com>
> wrote:
>
> > On Mon, Feb 1, 2016 at 11:15 PM, Prayagraj Fandilolu <
> fprayagraj.gmail.com
> > >
> > wrote:
> >
> > > Dear Amber users,
> > >
> > > I am simulating a RNA system using the ff14SB in Sander. I am facing an
> > > issue with SP3 planar nitrogen atoms of my system. After minimization,
> > the
> > > orientation of planar SP3 Nitrogen is changing and its planar
> > conformation
> > > is lost.
> > >
> > > I have checked the same system with older ff99bsc0. This ff works fine
> > and
> > > the SP3 planar nitrogen atoms are still planar after minimization.
> > >
> > > I am not getting a clue into this...
> > >
> > > can some one give me a solution to this issue????
> > >
> > > Other parameters being loaded with ff14SB are:
> > >
> > > frcmod.modrna08
> > > frcmod.chiOL4
> > >
> >
> > I'm not sure why you are loading these. The manual describes what force
> > field each leaprc contains. Since you seem to be (??) loading extra
> > parameters aside from what is loaded inside each leaprc itself, you are
> > *not* actually using ff14SB here.
> >
> >
> >
> > > frcmod.ionsjc_tip3p
> > >
> >
> > Loading ion parameters is necessary, as you've done here.
> >
> >
> >
> > >
> > > while in case of ff99bsc0 i am using:
> > >
> > > leaprc.rna.ff99
> > > leaprc.ff99bsc0
> > > frcmod.ol.dat
> > >
> >
> > Same comments above. leaprc.ff99bsc0 (now located in
> > oldff/leaprc.ff99bsc0) is the full specification of that force field.
> >
> > The "extra" parameters you loaded may have been overwriting "good"
> > parameters with bad ones.
> >
> > HTH,
> > Jason
> >
> > --
> > Jason M. Swails
> > BioMaPS,
> > Rutgers University
> > Postdoctoral Researcher
> > _______________________________________________
> > AMBER mailing list
> > AMBER.ambermd.org
> > http://lists.ambermd.org/mailman/listinfo/amber
> >
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Received on Sat Feb 27 2016 - 05:00:06 PST
