[gmx-users] Re: Running Pull Code

[Justin Lemkul]

On 5/17/13 7:16 AM, Shima Arasteh wrote:
> Thanks for your reply.
> It' s around 5 nano seconds that I ran equilibration time on the system, and the average pressure I see as a result, seems sensible. However I am not sure if this criteria is sufficient? Others suggest to evaluate the box-dimension changes using g_energy code to judge of sufficient equilibration time.
>

The box vectors won't tell you anything more than the pressure will since 
they're related quantities.

The better question is, "What is a suitable starting structure for the system of 
interest?"  The umbrella sampling tutorial (which everyone seems to take at 
literal face value as the only way to do things, which it is decidedly not) 
presents a simple, easy-to-understand method.  In the paper I did (upon which I 
based the tutorial), I simulated the protofibril structures for 100 ns before I 
was confident they were suitably stable and representative of viable structures 
for doing SMD and US.  Your mileage will vary and depends on the quality of the 
starting structure and what it is that you hope to determine.  There is no magic 
recipe that is universal.

-Justin

> I appreciate your suggestion.
>
>
> Sincerely,
> Shima
>
>
> ----- Original Message -----
> From: Thomas Schlesier <schlesi at uni-mainz.de>
> To: gmx-users at gromacs.org
> Cc:
> Sent: Friday, May 17, 2013 3:30 PM
> Subject: [gmx-users] Re: Running Pull Code
>
> The three steps (EM, NVT and NPT) are to equilibrate the system. How
> much time these steps need depends on the system. But i would assume a
> ouple of nanosecounds are sufficient for most systems. You could look
> into the literature, how long other people equilibrate systems which are
> similar to ours.
> If the system is equilibrated, you an start to perform the pulling
> simulation to obtain the individual structure for the later umbrella
> sampling.
>
> Greetings
> Thomas
>
> Am 17.05.2013 07:46, schrieb gmx-users-request at gromacs.org:
>> Hi,
>>
>> I have a system composed of POPC/peptide/water/ions. I aim to study ion conduction through the peptide using umbrella sampling.
>> I built the system and ran EM, NVT, NPT successfully, but have not run md yet. I' d like to know if the system is required of passing a few nanoseconds md? Or I might be able to go to Umbrella Sampling straight after NPT?
>> As I studied in Justin's tutorial, running pull code is done after some typical steps of every simulation ( EM, NVT, NPT). But I dont know if is correct generally for other systems as well?
>>
>> Would you please give me any suggestions?
>>
>>
>> Thanks in advance.
>> Sincerely,
>> Shima?
>

-- 
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Justin A. Lemkul, Ph.D.
Research Scientist
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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