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Andrey V Golovin a écrit:<br>
<blockquote type="cite"
cite="mid257844426.20050210032128@genebee.msu.su">
<pre wrap="">Dear All!
We added RNA/DNA entries to OPLS-AA/L force field.
If you interested please look at :
<a class="moz-txt-link-freetext" href="http://www.gromacs.org/topologies/force_fields.php">http://www.gromacs.org/topologies/force_fields.php</a>
Some info about testing and building of the records you can found at:
<a class="moz-txt-link-freetext" href="http://rnp-group.genebee.msu.su/3d/oplsa_ff.html">http://rnp-group.genebee.msu.su/3d/oplsa_ff.html</a>
PLEASE take in account that it is alpha-alpha version. Some additional
testing is needed AND careful compassion with the literature is needed
also.
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</blockquote>
bonjour andrey,<br>
<br>
after some work and many "try and error" i have succeeded to <br>
build the various files which are necessary for running Gromacs <br>
calculations on a DNA_decamer with about <b>60 water molecules</b>, <br>
<b>2 Ca++ ions</b> and <b>15 Na+ ions</b> to neutralise the excess
negative<br>
charges due to phosphate groups.<br>
<br>
i get a surprising result after 1ns of simulation ( about 3hours
on a Linux_PC) :<br>
<br>
the double-helix ends up in a dissociated state.<br>
<br>
for this calculation i use - a <b>triclinic box</b><br>
- <b>pme</b> for
electrostatics<br>
- T_coupling at <b>300K</b><br>
- <b>no</b> P_coupling<br>
- <b>oplsaar</b> force field<br>
<br>
my experience in MD_simulations is not tremendous, especially <br>
concerning the simulation parameters.<br>
<br>
- i am wondering if i have choosen the <b>right box form</b> ?<br>
- what about the <b>box dimensions</b> ?<br>
- may be the number of water molecules is <b>too small</b> for this
system ?<br>
- and last but not least i don't know if the <b>periodic boundary
conditions</b> <br>
are on or off ?<br>
<br>
a lot of questions.<br>
<br>
i would appreciate your helpfull advices.<br>
<br>
merci , cordialement<br>
<br>
marc kreissler<br>
<br>
<br>
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