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On 6/04/2011 4:42 PM, mohsen ramezanpour wrote:
<blockquote
cite="mid:BANLkTimGyqxJB1iOqewyo9UdsMetF+PhOw@mail.gmail.com"
type="cite">Dear Dr.Justin<br>
<br>
I had the same problem.<br>
I modified the charges and charge groupsin the topology of a
drug.the net charge of it is zero(I am sure)<br>
though,when I used pdb2gmx it resulted a NOTE like the following:<br>
<br>
NOTE:The system has non-zero total charge: 3.000003e00<br>
I continued simulation and ignored it!<br>
Because:<br>
1- I checked my protein.top and qtot was 3<br>
2-the net charge of my drug was 0<br>
3-Besides,all charges have 3 digit precision,How can it have
0.000003 additional charge?!<br>
</blockquote>
<br>
See <a class="moz-txt-link-freetext" href="http://www.gromacs.org/Documentation/Floating_Point_Arithmetic">http://www.gromacs.org/Documentation/Floating_Point_Arithmetic</a><br>
<br>
Mark<br>
<br>
<blockquote
cite="mid:BANLkTimGyqxJB1iOqewyo9UdsMetF+PhOw@mail.gmail.com"
type="cite">
<br>
What is your point of view?<br>
Thanks in advance for your reply<br>
<br>
<br>
<div class="gmail_quote">On Wed, Apr 6, 2011 at 3:40 AM, Justin A.
Lemkul <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:jalemkul@vt.edu">jalemkul@vt.edu</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid
rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left:
1ex;">
<div class="im"><br>
<br>
김현식 wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px
solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex;
padding-left: 1ex;">
<br>
<br>
> Date: Tue, 5 Apr 2011 23:43:19 +1000<br>
> From: <a moz-do-not-send="true"
href="mailto:Mark.Abraham@anu.edu.au" target="_blank">Mark.Abraham@anu.edu.au</a><br>
> To: <a moz-do-not-send="true"
href="mailto:gmx-users@gromacs.org" target="_blank">gmx-users@gromacs.org</a><br>
> Subject: Re: [gmx-users] How to remove charge of
5e-2 ??<br>
><br>
> On 5/04/2011 11:17 PM, Hyunsik wrote:<br>
> > Dear experts,<br>
> ><br>
> > Hi,<br>
> ><br>
> > When prepare a system, the system had +5.5. So
I add 5 CL- ion to neutralize.<br>
> ><br>
> > But as you know, the Cl charge is -1 and there
still is 5e-2. how can i remove that.<br>
><br>
> Your statements are inconsistent. If you had 5.5
charge and added five<br>
> chloride ions, you could not end up with 0.05.<br>
<br>
oh.. I have mistaken.. I had 5.005 of the system charge.<br>
So even if added five choride ions, the system charge is
not zero. there was 0.005<br>
<br>
that is partial charge?? If like that, topology is
broken or something wrong? abnormal??<br>
<br>
</blockquote>
<br>
</div>
Maybe, maybe not. Rounding errors could account for this
difference, especially if your system is very large. Still,
you should inspect your topology/topologies for
inconsistencies. If pdb2gmx created the topology, keep an eye
on the "qtot" column for a running total of the charge. If
you've made or adjusted any topologies on your own,
double-check your work. If everything looks correct, then the
difference is likely a consequence of floating-point math and
nothing more.<br>
<br>
-Justin
<div class="im"><br>
<br>
<blockquote class="gmail_quote" style="border-left: 1px
solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex;
padding-left: 1ex;"> Thank you,<br>
<br>
Hyun<br>
<br>
><br>
> Mark<br>
> --<br>
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</blockquote>
<br>
</div>
-- <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" href="http://vt.edu"
target="_blank">vt.edu</a> | (540) 231-9080<br>
<a moz-do-not-send="true"
href="http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin"
target="_blank">http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin</a><br>
<br>
========================================
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