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On 4/23/2011 9:21 AM, majid hasan wrote:
<blockquote cite="mid:533604.60211.qm@web38307.mail.mud.yahoo.com"
type="cite">
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<div style="font-family: 'times new roman','new york',times,serif;
font-size: 12pt;">
<div style="color: black; font-family: 'times new roman','new
york',times,serif; font-size: 12pt;">Okay, thanks, I removed
restraints from water.</div>
<div style="color: black; font-family: 'times new roman','new
york',times,serif; font-size: 12pt;"><br>
</div>
<div style="color: black; font-family: 'times new roman','new
york',times,serif; font-size: 12pt;"> In the final simulation,
I increased the simulation time from 20ps to 2000ps to see if
they wrap around. However in .trr output, CNT and DNA remain
stable, jiggles around and jump across the box in a weird
manner (might have something to do with periodic boundary
conditions?) but don't seem to be attracted towards each
other. </div>
<div style="color: black; font-family: 'times new roman','new
york',times,serif; font-size: 12pt;"><br>
</div>
<div style="color: black; font-family: 'times new roman','new
york',times,serif; font-size: 12pt;">Movie of output is here:</div>
<div><font class="Apple-style-span" face="'times new roman',
'new york', times, serif"><span><a moz-do-not-send="true"
target="_blank"
href="http://phas.ubc.ca/%7Emajid/Project/msteps/cntdna2000ps.mpg">http://phas.ubc.ca/~majid/Project/msteps/cntdna2000ps.mpg</a></span></font></div>
<div><font class="Apple-style-span" face="'times new roman',
'new york', times, serif">and input em.mdp, and md.mdp files
are here:</font></div>
<div style="font-family: 'times new roman','new
york',times,serif; font-size: 12pt; color: black;">EM: <a
moz-do-not-send="true"
href="http://phas.ubc.ca/%7Emajid/Project/msteps/lbfgs.mdp">http://phas.ubc.ca/~majid/Project/msteps/lbfgs.mdp</a></div>
<div style="font-family: 'times new roman','new
york',times,serif; font-size: 12pt; color: black;">MD: <a
moz-do-not-send="true"
href="http://phas.ubc.ca/%7Emajid/Project/msteps/md.mdp">http://phas.ubc.ca/~majid/Project/msteps/md.mdp</a></div>
<div style="font-family: 'times new roman','new
york',times,serif; font-size: 12pt; color: black;"><br>
</div>
<div style="font-family: 'times new roman','new
york',times,serif; font-size: 12pt; color: black;">Commands
that I have been using to build input coordinates, and
topologies are below:</div>
<div style="font-family: 'times new roman','new
york',times,serif; font-size: 12pt; color: black;"><br>
</div>
<div style="font-family: 'times new roman','new
york',times,serif; font-size: 12pt; color: black;"><span
class="Apple-style-span" style="font-family:
arial,helvetica,sans-serif; font-size: 13px;"> For dna:
pdb2gmx -f dna.pdb -o dna.gro -p dna.top -ff select
(Selected amber99sb, and TIP3P water model)<br>
</span></div>
<div style="font-family: 'times new roman','new
york',times,serif; font-size: 12pt; color: black;"><span
class="Apple-style-span" style="font-family:
arial,helvetica,sans-serif; font-size: 13px;">For cnt:
g_x2top -f cnt.gro -o cnt.top -ff select -pbc
(selected amber99sb)<br>
</span></div>
<div style="font-family: 'times new roman','new
york',times,serif; font-size: 12pt; color: black;"><span
class="Apple-style-span" style="font-family:
arial,helvetica,sans-serif; font-size: 13px;">For mixing :
genbox -cp cnt.gro -ci dna.gro -o cntdna.gro -nmol 1
-try 20 </span></div>
<div style="font-family: 'times new roman','new
york',times,serif; font-size: 12pt; color: black;"><span
class="Apple-style-span" style="font-family:
arial,helvetica,sans-serif; font-size: 13px;"><br>
</span></div>
<div style="font-family: 'times new roman','new
york',times,serif; font-size: 12pt; color: black;"><span
class="Apple-style-span" style="font-family:
arial,helvetica,sans-serif; font-size: 13px;">For solvation:
genbox -cp cntdna.gro -cs spc.gro -o cntdnasol.gro</span></div>
<div style="font-family: 'times new roman','new
york',times,serif; font-size: 12pt; color: black;"><br>
</div>
<div style="font-family: 'times new roman','new
york',times,serif; font-size: 12pt; color: black;">I have no
clue what is wrong with the simulation, and any help is much
appreciated. <br>
</div>
</div>
</blockquote>
<br>
You're still not following a sound equilibration protocol. The
velocities you generate at the start are only roughly correct, and
your density is probably a bit off. Check out some tutorials, and
published work on similar systems.<br>
<br>
You also need to consider how far apart these species are. If the
driving force is electrostatic, the forces drop off as 1/r^2, so you
can wait a long time for those to act over a few nanometers, while
re-organizing the solvent between them.<br>
<br>
In real biochemical systems, one doesn't normally observe a single
pair of interacting species mate up smoothly. There's a whole pile
of things that have to happen, and each successful binding probably
results from very many failed attempts. Having many such pairs over
longer periods of times means that statistically the events do
happen, but that's no good to you if you can only simulate a single
pair in a short period.<br>
<br>
Mark<br>
<br>
<blockquote cite="mid:533604.60211.qm@web38307.mail.mud.yahoo.com"
type="cite">
<div style="font-family: 'times new roman','new york',times,serif;
font-size: 12pt;">
<div style="font-family: 'times new roman','new
york',times,serif; font-size: 12pt; color: black;">Thanks,</div>
<div style="font-family: 'times new roman','new
york',times,serif; font-size: 12pt; color: black;">Majid<br>
<div style="font-family: arial,helvetica,sans-serif;
font-size: 10pt;"><font face="Tahoma" size="2">
<hr size="1"><b><span style="font-weight: bold;">From:</span></b>
Justin A. Lemkul <a class="moz-txt-link-rfc2396E" href="mailto:jalemkul@vt.edu"><jalemkul@vt.edu></a><br>
<b><span style="font-weight: bold;">To:</span></b> Gromacs
Users' List <a class="moz-txt-link-rfc2396E" href="mailto:gmx-users@gromacs.org"><gmx-users@gromacs.org></a><br>
<b><span style="font-weight: bold;">Sent:</span></b> Fri,
April 22, 2011 10:59:22 AM<br>
<b><span style="font-weight: bold;">Subject:</span></b>
Re: [gmx-users] DNA not wrapping around CNT in MD
simulation<br>
</font><br>
<br>
<br>
majid hasan wrote:<br>
> Yes, ideally I didn't want to, but I read somewhere on
mailing list that one shouldn't use define = -DFLEXIBLE
while running dynamics. So I thought I will use restrained
water...<br>
> <br>
> I'll move back to -DFLEXIBLE though, if I got a
successful mdrun for restrained water.<br>
> <br>
<br>
Constraints and restraints are separate ideas.<br>
<br>
<span><a moz-do-not-send="true" target="_blank"
href="http://www.gromacs.org/Documentation/Terminology/Constraints_and_Restraints">http://www.gromacs.org/Documentation/Terminology/Constraints_and_Restraints</a></span><br>
<br>
If you *restrain* the water, the molecules won't move. If
you *constrain* (i.e., using rigid water and not -DFLEXIBLE,
which for MD you shouldn't be doing) you fix the geometry of
a molecule while still allowing it to actually move.<br>
<br>
-Justin<br>
<br>
> Thanks,<br>
> Majid<br>
> <br>
>
------------------------------------------------------------------------<br>
> *From:* Justin A. Lemkul <<a moz-do-not-send="true"
ymailto="mailto:jalemkul@vt.edu"
href="mailto:jalemkul@vt.edu">jalemkul@vt.edu</a>><br>
> *To:* Discussion list for GROMACS users <<a
moz-do-not-send="true"
ymailto="mailto:gmx-users@gromacs.org"
href="mailto:gmx-users@gromacs.org">gmx-users@gromacs.org</a>><br>
> *Sent:* Fri, April 22, 2011 10:44:45 AM<br>
> *Subject:* Re: [gmx-users] DNA not wrapping around CNT
in MD simulation<br>
> <br>
> <br>
> <br>
> majid hasan wrote:<br>
> > I just checked and DNA position should not be
restrained because I didn't use define = -DPOSRES in .mdp
file. I am going to run it for a longer time now, and use
position restraints for water<br>
> ><br>
> <br>
> What purpose does restraining the water have? You'll
be trying to observe diffusion of your DNA or CNT through an
immobile solvent.<br>
> <br>
> -Justin<br>
> <br>
> > Thank You,<br>
> > Majid.<br>
> ><br>
> >
------------------------------------------------------------------------<br>
> > *From:* Mark Abraham <<a
moz-do-not-send="true"
ymailto="mailto:Mark.Abraham@anu.edu.au"
href="mailto:Mark.Abraham@anu.edu.au">Mark.Abraham@anu.edu.au</a>
<mailto:<a moz-do-not-send="true"
ymailto="mailto:Mark.Abraham@anu.edu.au"
href="mailto:Mark.Abraham@anu.edu.au">Mark.Abraham@anu.edu.au</a>>><br>
> > *To:* Discussion list for GROMACS users <<a
moz-do-not-send="true"
ymailto="mailto:gmx-users@gromacs.org"
href="mailto:gmx-users@gromacs.org">gmx-users@gromacs.org</a>
<mailto:<a moz-do-not-send="true"
ymailto="mailto:gmx-users@gromacs.org"
href="mailto:gmx-users@gromacs.org">gmx-users@gromacs.org</a>>><br>
> > *Sent:* Fri, April 22, 2011 1:51:47 AM<br>
> > *Subject:* Re: [gmx-users] DNA not wrapping
around CNT in MD simulation<br>
> ><br>
> > On 4/22/2011 6:48 PM, Mark Abraham wrote:<br>
> >> On 4/22/2011 4:54 PM, majid hasan wrote:<br>
> >>> Dear All,<br>
> >>><br>
> >>> I am doing a MD simulation of dna, and
cnt in water. I get a stable simulation in which DNA, and
CNT wiggles around there positions, but they don't seem to
be attracted towards each other. CNT starts in the middle of
the box and just moves a little, and DNA starts at top right
corner of the box and remains there throughout the
simulation.<br>
> >>><br>
> >>> movie of .trr file is here:<br>
> >>><br>
<span>>> >> <a moz-do-not-send="true"
target="_blank"
href="http://phas.ubc.ca/%7Emajid/Project/cntdna.mpg">http://phas.ubc.ca/%7Emajid/Project/cntdna.mpg</a></span><br>
> >>><br>
> >>> My .mdp files are placed here (both .mdp
files are same except for the value of integrator):<br>
<span>>> >> <a moz-do-not-send="true"
target="_blank"
href="http://phas.ubc.ca/%7Emajid/Project/lbfgs.mdp">http://phas.ubc.ca/%7Emajid/Project/lbfgs.mdp</a>
(used for EM)</span><br>
<span>>> >> <a moz-do-not-send="true"
target="_blank"
href="http://phas.ubc.ca/%7Emajid/Project/md.mdp">http://phas.ubc.ca/%7Emajid/Project/md.mdp</a>
(used for MD)</span><br>
> >>><br>
> >>><br>
> >>><br>
> >>> I created cnt, and dna using following
commands:<br>
> >>> For dna: pdb2gmx -f dna.pdb -o dna.gro -p
dna.top -ff select (Selected amber99sb, and TIP3P water
model)<br>
> >>> For cnt: g_x2top -f cnt.gro -o cnt.top
-ff select -pbc (selected amber99sb)<br>
> >>> For mixing and solvation: genbox -cp
cnt.gro -ci dna.gro -o cntdna.gro -nmol 1 -try 20 genbox -cp
cntdna.gro -cs spc.gro -o cntdnasol.gro<br>
> >>> In the dna.top file, amber99sb/ions.itp,
and a position restraint file was also included along with
tip3p.itp. I mentioned it because I am not sure why would it
add ions and position restraints on adding water?<br>
> >><br>
> >> #including molecule .itp files adds nothing
to the system - only the potential to have molecule type(s).
The system is defined in the [system] directive, and must
match the corresponding coordinate file.<br>
> >><br>
> >>> It seems that something is wrong with
non-bonded interactions, but I don't understand what?<br>
> >><br>
> >> Why aren't you following a proper
equilibration protocol before trying to make observations?
You might be using position restraints, have your species
too far apart, or simply have not simulated long enough to
observe any movement. 200ps is an eye-blink.<br>
> ><br>
> > Actually, you simulated 20ps. Your MD timestep is
0.2fs, which is unreasonably short. 100,000 of them is far
too short to see anything happen.<br>
> ><br>
> > Mark<br>
> ><br>
> <br>
> -- ========================================<br>
> <br>
> Justin A. Lemkul<br>
> Ph.D. Candidate<br>
> ICTAS Doctoral Scholar<br>
> MILES-IGERT Trainee<br>
> Department of Biochemistry<br>
> Virginia Tech<br>
> Blacksburg, VA<br>
> jalemkul[at]<a moz-do-not-send="true" target="_blank"
href="http://vt.edu">vt.edu</a><span> <<a
moz-do-not-send="true" target="_blank"
href="http://vt.edu">http://vt.edu</a>> | (540)
231-9080</span><br>
<span>> <a moz-do-not-send="true" target="_blank"
href="http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin">http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin</a></span><br>
> <br>
> ========================================<br>
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-- ========================================<br>
<br>
Justin A. Lemkul<br>
Ph.D. Candidate<br>
ICTAS Doctoral Scholar<br>
MILES-IGERT Trainee<br>
Department of Biochemistry<br>
Virginia Tech<br>
Blacksburg, VA<br>
jalemkul[at]vt.edu | (540) 231-9080<br>
<a moz-do-not-send="true"
href="http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin"
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<br>
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