Re: [AMBER] Preparation of i-Motif structures

From: Sruthi Sudhakar <sruthisudhakarraji.gmail.com>
Date: Wed, 23 Jun 2021 00:07:02 +0530

Hello Sir,

I tried to fix the column error and try to reload it, still the structure
in both leap as well as in the visualization tools shows error. I am
attaching the pdb here. Other than manually editing the pdb text file, is
there a way to change the residue names?


Regards,
Sruthi Sudhakar


On Sat, Jun 19, 2021 at 3:28 PM Petr Stadlbauer <petr.stadl.gmail.com>
wrote:

> Dear Sruthi,
>
> first make sure your structure is not degraded anymore. What happened
> to your structure reminds me of what happens when one changes residue
> or atom names and fails to keep them in the same columns. It results
> in a shift in the rest of the line and leap (or other visualization
> software) loads the coordinates incorrectly. So add or remove blank
> spaces where needed. There could be some other errors with the names
> and types, but try to resolve the structural problem first.
>
> Regards,
> Petr
>
> so 19. 6. 2021 v 9:37 odesílatel Sruthi Sudhakar
> <sruthisudhakarraji.gmail.com> napsal:
> >
> > Thank you sir for the reply. I have followed the following methodology
> but
> > faced some issues in the preparation of the structure. Initially I have
> > modified the all_prot_nucleic10.lib file by changing the atom types for
> > residues DCP (CH+), D3C (3’-terminal CH+) and D5C (5’-terminal CH+) in
> the
> > following way:
> > "C5'" "CI" -> "C5'" "CJ"
> > "C3'" "CT" -> "C3'" "C7"
> > "C6" "CM" -> "C6" "C1"
> > "C5" "CM" -> "C5" "C1"
> > But in the second stage when I try to change the residue name in the pdb
> > file, the structure seems to be degraded. I opened the pdb text file and
> > manually changed the DC to DCP/D3C/D5C and saved it too. But after this
> > change, when I opened the structure in Pymol to visualize the same, it
> > seems broken and even in leap it got errors. Is there a mistake in the
> > methodology of Changing the residue names.
> > Regards,
> > Sruthi Sudhakar
> >
> >
> > On Wed, Feb 10, 2021 at 11:04 PM Petr Stadlbauer <petr.stadl.gmail.com>
> > wrote:
> >
> > > Dear Sruthi,
> > >
> > > > Dear all,
> > > >
> > > > I would like to know how the preparation of i-motifs ( semiprotonated
> > > C-C+)
> > > > base pairs can be prepared.
> > >
> > > Take your input structure file and designate one of the cytosines in
> > > each CC+ pair with a special residue label, which would correspond to
> > > your parameter files for C+.
> > >
> > > > We could add a hydrogen on to the nitrogen to
> > > > make it protonated,but how different would be the forcefield
> preparation.
> > >
> > > You need to load parameters for C+, which have RESP charges calculated
> > > for C+ and parameters for the angles including the hydrogen on N3.
> > >
> > > > Typically for G quadruplexes we could use the OL15 force field, what
> > > would
> > > > be the case with i-Motifs? Also since there is a semiprotonated
> cytosine,
> > > > do we need any other parametrization to continue with the topology
> > > > generation?
> > >
> > > You can use OL15 for i-motif for sure. You may try to use slightly
> > > obsolete bsc0 parameters for C+ provided in amber. I am not sure
> > > whether it varies among amber versions, but in amber18 you can find
> > > these parameters in files called all_prot_nucleic10.lib and
> > > frcmod.protonated_nucleic, which you need to load. The residue label
> > > corresponding to DNA C+ is DCE then.
> > >
> > > > Thank you for any guidance you can provide.
> > > >
> > > > Regards,
> > > > Sruthi
> > >
> > > Regards,
> > > Petr
> > >
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Received on Tue Jun 22 2021 - 12:00:02 PDT
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