[gmx-users]Question about reduced unit for coarse grain

Ye Yang knightyangpku at gmail.com
Thu Jun 23 06:19:39 CEST 2011


 Just no reply from them for some time...
Thank you anyway.

Ye
2011/6/22 Justin A. Lemkul <jalemkul at vt.edu>

>
>
> Ye Yang wrote:
>
>> Thank you very much, Mark.
>>
>> Is there anyway I can know the unit of input from the top file? I am not
>> sure what I am getting from the webtool, although it shows "kj/mol" the
>> instruction on the web says the unit is reduced unit, which makes me
>> confused. In the former case I do not need to convert, but in latter case, I
>> need to convert to standard units. The webtool is from
>> http://smog.ucsd.edu/sbm_faq.**html <http://smog.ucsd.edu/sbm_faq.html>,
>> it is developped by Dr. Onuchic's group in UCSD.
>> Has anyone used this?
>>
>>
> Since this topology was not created by any standard Gromacs utility,
> wouldn't it be more efficient to contact the developers directly about
> implementation details and proper use?
>
> -Justin
>
>   [ angles ]
>>  ;ai  aj   ak  func  th0(deg)   Ka
>>     1      2      3 1  0.95664E+02  0.40000E+02
>>     2      3      4 1  0.91183E+02  0.40000E+02
>>     3      4      5 1  0.89842E+02  0.40000E+02
>>     4      5      6 1  0.91965E+02  0.40000E+02
>>     5      6      7 1  0.90670E+02  0.40000E+02
>>     6      7      8 1  0.91186E+02  0.40000E+02
>>     7      8      9 1  0.92703E+02  0.40000E+02
>>     8      9     10 1  0.91537E+02  0.40000E+02
>>     9     10     11 1  0.91328E+02  0.40000E+02
>>    10     11     12 1  0.92557E+02  0.40000E+02
>>    11     12     13 1  0.93372E+02  0.40000E+02
>>    12     13     14 1  0.94347E+02  0.40000E+02
>>    13     14     15 1  0.99411E+02  0.40000E+02
>>    14     15     16 1  0.98190E+02  0.40000E+02
>> ......
>>  [ dihedrals ]
>>  ;ai  aj  ak  al  func  phi0(deg)   Kd(kJ/mol)  mult
>>     1      2      3      4 1  0.24358E+03  0.10000E+01 1
>>     1      2      3      4 1  0.73074E+03  0.50000E+00 3
>>     2      3      4      5 1  0.22823E+03  0.10000E+01 1
>>     2      3      4      5 1  0.68469E+03  0.50000E+00 3
>>     3      4      5      6 1  0.23172E+03  0.10000E+01 1
>>     3      4      5      6 1  0.69515E+03  0.50000E+00 3
>>     4      5      6      7 1  0.22982E+03  0.10000E+01 1
>>     4      5      6      7 1  0.68946E+03  0.50000E+00 3
>>
>>
>> Thank you very much.
>>
>> Ye
>>
>> 2011/6/22 Mark Abraham <Mark.Abraham at anu.edu.au <mailto:
>> Mark.Abraham at anu.edu.**au <Mark.Abraham at anu.edu.au>>>
>>
>>
>>    __
>>    On 23/06/2011 10:36 AM, Ye Yang wrote:
>>
>>>    Hi,
>>>        Thanks for replying, Yang.
>>>        But I still did not get it fully:
>>>        1. So if we use reduced unit in input, the output and
>>>    calculation is still assumed to be in standard units?
>>>
>>
>>    The calculation uses the same algorithm and whatever values you
>>    input. Nowhere have you specified that these values are in anything
>>    other than the standard units, so how could GROMACS know to change
>>    anything? (Nor can you specify such)
>>
>>
>>     But the calculation itself is different since the constants are
>>>    different, so the result must differed a lot. Does gromacs knows
>>>    that we are using reduced unit?
>>>
>>
>>    No. It's up to you to use a self-consistent set of input parameters,
>>    and to interpret the results correctly.
>>
>>
>>         2. With this program/forcefield to build top file automaticly,
>>>    the KJ/mol it gives is in the top file, so it is still part of
>>>    input, in this case , the gromacs will recognize it in the
>>>    standard unit?
>>>
>>
>>    It doesn't recognize units. It follows an algorithm that is correct
>>    if all the quantities are measured in the standard units. If you
>>    change something, you have to understand all the consequences and
>>    interpret appropriately :-)
>>
>>    Mark
>>
>>
>>         3. in the top file it gives:
>>>          [ angles ]
>>>     ;ai  aj   ak  func  th0(deg)   Ka
>>>         1      2      3 1  0.95664E+02  0.40000E+02
>>>         2      3      4 1  0.91183E+02  0.40000E+02
>>>         3      4      5 1  0.89842E+02  0.40000E+02
>>>         4      5      6 1  0.91965E+02  0.40000E+02
>>>         5      6      7 1  0.90670E+02  0.40000E+02
>>>         6      7      8 1  0.91186E+02  0.40000E+02
>>>         7      8      9 1  0.92703E+02  0.40000E+02
>>>         8      9     10 1  0.91537E+02  0.40000E+02
>>>         9     10     11 1  0.91328E+02  0.40000E+02
>>>        10     11     12 1  0.92557E+02  0.40000E+02
>>>        11     12     13 1  0.93372E+02  0.40000E+02
>>>        12     13     14 1  0.94347E+02  0.40000E+02
>>>        13     14     15 1  0.99411E+02  0.40000E+02
>>>        14     15     16 1  0.98190E+02  0.40000E+02
>>>    ......
>>>     [ dihedrals ]
>>>     ;ai  aj  ak  al  func  phi0(deg)   Kd(kJ/mol)  mult
>>>         1      2      3      4 1  0.24358E+03  0.10000E+01 1
>>>         1      2      3      4 1  0.73074E+03  0.50000E+00 3
>>>         2      3      4      5 1  0.22823E+03  0.10000E+01 1
>>>         2      3      4      5 1  0.68469E+03  0.50000E+00 3
>>>         3      4      5      6 1  0.23172E+03  0.10000E+01 1
>>>         3      4      5      6 1  0.69515E+03  0.50000E+00 3
>>>         4      5      6      7 1  0.22982E+03  0.10000E+01 1
>>>         4      5      6      7 1  0.68946E+03  0.50000E+00 3
>>>
>>>
>>>    Seems to me that this is the standard unit, yet the author of the
>>>    webtool emphasize that this structure based cg model is in reduced
>>>    unit, so what result do I got?
>>>    Has anyone used this webtool to do CG simulation and explain what
>>>    is case?
>>>
>>>    Thank you all very much.
>>>
>>>    Ye
>>>
>>>    2011/6/22 Yang Ye <leafyoung at yahoo.com <mailto:leafyoung at yahoo.com>>
>>>
>>>
>>>        Hi,
>>>
>>>        The unit in output is in assumed to be for the standard unit
>>>        input while the value is in reduced unit.
>>>
>>>        So you need to do your own calculation to figure out what's
>>>        the reduced unit is.
>>>
>>>        Regards,
>>>        Yang Ye
>>>
>>>        On Thu, Jun 23, 2011 at 5:48 AM, Ye Yang
>>>        <knightyangpku at gmail.com <mailto:knightyangpku at gmail.**com<knightyangpku at gmail.com>>>
>>> wrote:
>>>
>>>            Dear all:
>>>                    I see from the user's manual that if our input is
>>>            in reduced unit, the output will also be in reduced
>>>            unit(,ftp://ftp.gromacs.org/**pub/manual/3.1/manual-a4-3.1.**
>>> 1.pdf <ftp://ftp.gromacs.org/pub/manual/3.1/manual-a4-3.1.1.pdf>),
>>>            P25.  On the contrary, if we use standard unit, the out
>>>            put will be in standard unit.
>>>                    This brings the question up when we use coarse
>>>            grain Clementi's model webtool
>>>            (http://smog.ucsd.edu/sbm_faq.**html<http://smog.ucsd.edu/sbm_faq.html>),
>>> according to the
>>>            author, it seems that everything is in reduced unit, so
>>>            the output file should also be in reduced unit, yet I
>>>            found the topology file that the energy unit is KJ/mol.
>>>            What exactly is the unit of the input and out put file?
>>>            When I pull the molecules, do I get the reduced unit
>>>            result or the physical unit result?
>>>                    Since I am an experimentalist, getting the
>>>            physical units is more important to me, so as to compare
>>>            with the experimental results, albeit the intrinsic
>>>            difference. If I get something in reduced unit, there is
>>>            necessity for me to change it into physical unit, or at
>>>            least clarify it in comparison.
>>>                    Thank you very much.
>>>
>>>            Ye
>>>
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> --
> ==============================**==========
>
> Justin A. Lemkul
> Ph.D. Candidate
> ICTAS Doctoral Scholar
> MILES-IGERT Trainee
> Department of Biochemistry
> Virginia Tech
> Blacksburg, VA
> jalemkul[at]vt.edu | (540) 231-9080
> http://www.bevanlab.biochem.**vt.edu/Pages/Personal/justin<http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin>
>
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