[gmx-developers] Umbrella code extension / flat bottom potential

Sabine Reisser sabine.reisser at kit.edu
Tue Feb 17 13:55:45 CET 2015


One more question (I know this conservation starts to belong on the 
users list):
Is there a way to define two variables in "define" in the mdp file? I 
would like distance restraints AND fb position restraints (DISRES and 
POSRES).

Cheers
Sabine

Am 17.02.2015 13:25, schrieb Sabine Reisser:
> Ok, it works! Thanks!
>
> Cheers
> Sabine
>
> Am 17.02.2015 12:41, schrieb Jochen Hub:
>> Am 17/02/15 um 11:23 schrieb Sabine Reisser:
>>> Hi Jochen,
>>>
>>> thanks! In the meantime my PhD student found the -r option, too.
>>> I can also just use editconf to create a shifted reference structure,
>>> right?
>> That depends on what exactly you want. With editconf -translate, the
>> atoms in your peptide will have different Z coordinates.
>>
>> Let's say you want all atoms in your pepetide to feel the same FB-posres
>> potential, with the same center of the potential (e.g. the center of the
>> membrane), then you would need to use the same Z-cooridinate in the
>> posres-reference.pdb file (the one passed with -r) for all atoms in your
>> peptide.
>>
>> Best,
>> Jochen
>>
>>
>>> Cheers
>>> Sabine
>>>
>>>
>>> Am 17.02.2015 09:36, schrieb Jochen Hub:
>>>> Hi Sabine,
>>>>
>>>> the reference positions for the flat-bottom posres are the same as for
>>>> the normal position-restraints. And those can be specified in a pdb/gro
>>>> file given to grompp with option -r. So you need to take your initial
>>>> file, and change the z-coordinate of the restrained atom to the the
>>>> center of of FB-potential, and use grompp -r.
>>>>
>>>> Tip of the day :) : to change the Z-column of a PDB file, you can use
>>>> the bash function:
>>>>
>>>> pdb_replace_z ()
>>>> {
>>>>        local x="$(printf '%8.3f' $1)";
>>>>        sed -E "s/^(.{46})(.{8})(.*)$/\1${x}\3/"
>>>> }
>>>>
>>>> Best,
>>>> Jochne
>>>>
>>>> Am 13/02/15 um 14:41 schrieb Sabine Reisser:
>>>>> Hi again,
>>>>>
>>>>> I think this topic is still interesting.
>>>>> I have just tested Jochens code for flat-bottom position restraints,
>>>>> which works great, but unfortunately it's not suitable for what I need.
>>>>> Here, you can define a layer (with normal in z-direction) with a certain
>>>>> thickness and invert the restraints. The problem is that you cannot
>>>>> define a reference position for the layer, but the reference position is
>>>>> always the initial geometry. That way, particles are pushed away from
>>>>> the layer, but the direction is not defined. So I cannot use this to
>>>>> bind my peptides to one leaflet of the membrane (cmp. my post "Flat
>>>>> bottom position restraints"  on gmx-users). Also I cannot use it to
>>>>> restrain distances between molecules, which I also need sometimes.
>>>>>
>>>>> So I'd be grateful if you could reconsider including the extension to
>>>>> the pull code described below.
>>>>>
>>>>> Cheers
>>>>> Sabine
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --------------------------------------------------------------------------------------
>>>>>
>>>>>
>>>>> I guess you mean flat-bottomed position restraints.
>>>>> I am talking about the pull code (between COM iso atoms).
>>>>>
>>>>> Berk
>>>>>
>>>>> On 02/13/2014 04:05 AM, Mark Abraham wrote:
>>>>>> / It's been in master branch for about a year :-)
>>>>> />/
>>>>> />/ Mark
>>>>> />/
>>>>> />/
>>>>> />/ On Wed, Feb 12, 2014 at 8:20 PM, Berk Hess <hess at kth.se
>>>>> <https://maillist.sys.kth.se/mailman/listinfo/gromacs.org_gmx-developers>
>>>>>
>>>>> />/ <mailto:hess at kth.se
>>>>> <https://maillist.sys.kth.se/mailman/listinfo/gromacs.org_gmx-developers>>>
>>>>> wrote:
>>>>> />/
>>>>> />/     On 02/12/2014 04:55 PM, David van der Spoel wrote:
>>>>> />/
>>>>> />/         On 2014-02-12 15:24, Sabine Reisser wrote:
>>>>> />/
>>>>> />/             Hi,
>>>>> />/
>>>>> />/               "It seems like your potential would not need an extra
>>>>> />/             parameter (it
>>>>> />/             should
>>>>> />/             equal a flat bottomed potential with lower limit 0)."
>>>>> />/
>>>>> />/         A flat bottom potential is already in the code and we have
>>>>> />/         used it extensively. Jochen Hub has implemented it.
>>>>> />/
>>>>> />/     Not in the main distribution.
>>>>> />/
>>>>> />/     Cheers,
>>>>> />/
>>>>> />/     Berk
>>>>> />/
>>>>> />/
>>>>> />/             Yes, this is exactly what I mean.
>>>>> />/
>>>>> />/             Thanks & cheers
>>>>> />/             Sabine
>>>>> />/
>>>>> />/
>>>>> />/
>>>>> />/             On 02/12/2014 03:08 PM, Berk Hess wrote:
>>>>> />/
>>>>> />/                 Hi,
>>>>> />/
>>>>> />/                 This indeed looks like a flat-bottomed restraint
>>>>> />/                 potential. I had
>>>>> />/                 proposed that addition to the pull code for 5.0 in a
>>>>> />/                 request for
>>>>> />/                 feedback, which I also posted to the developers
>>>>> list.
>>>>> />/                 But since I didn't
>>>>> />/                 receive any response on this point I didn't
>>>>> implement
>>>>> />/                 it. Also because a
>>>>> />/                 general flat bottomed potential needs an extra
>>>>> />/                 (distance) parameter. It
>>>>> />/                 seems like your potential would not need an extra
>>>>> />/                 parameter (it should
>>>>> />/                 equal a flat bottomed potential with lower limit 0).
>>>>> />/                 Since it's too late
>>>>> />/                 for 5.0, I would propose to implement the flat
>>>>> />/                 bottomed potential for
>>>>> />/                 5.1.
>>>>> />/
>>>>> />/                 Cheers,
>>>>> />/
>>>>> />/                 Berk
>>>>> />/
>>>>> />/                 On 02/12/2014 02:31 PM, Shirts, Michael (mrs5pt)
>>>>> wrote:
>>>>> />/
>>>>> />/                     Hi, Sabine-
>>>>> />/
>>>>> />/                     So, this looks like the distance restraint
>>>>> />/                     potential (bond function
>>>>> />/                     10) in
>>>>> />/                     section 4.3.4 of the manual that matches this
>>>>> />/                     potential function.  Right
>>>>> />/                     now, this potential can only be applied.
>>>>> However,
>>>>> />/                     there is a planned
>>>>> />/                     fix
>>>>> />/                     for 5.0 that will include the ability to add all
>>>>> />/                     bonded interactions in
>>>>> />/                     between arbitrary atoms in the system, even if
>>>>> />/                     they are not in the same
>>>>> />/                     molecule.
>>>>> />/
>>>>> />/                     I BELIEVE there is an extension to the pull code
>>>>> />/                     that would allow
>>>>> />/                     general
>>>>> />/                     bonded potentials to be used between COMs of
>>>>> index
>>>>> />/                     groups as well but
>>>>> />/                     I'm
>>>>> />/                     not as certain about that.
>>>>> />/
>>>>> />/                     I think that these planned changes will capture
>>>>> />/                     the functionality
>>>>> />/                     that you
>>>>> />/                     are describing.  Is that correct?
>>>>> />/
>>>>> />/                     Best,
>>>>> />/
>>>>> />/                     ~~~~~~~~~~~~
>>>>> />/                     Michael Shirts
>>>>> />/                     Assistant Professor
>>>>> />/                     Department of Chemical Engineering
>>>>> />/                     University of Virginia
>>>>> />/                     michael.shirts at virginia.edu
>>>>> <https://maillist.sys.kth.se/mailman/listinfo/gromacs.org_gmx-developers>
>>>>>
>>>>> />/                     <mailto:michael.shirts at virginia.edu
>>>>> <https://maillist.sys.kth.se/mailman/listinfo/gromacs.org_gmx-developers>>
>>>>>
>>>>> />/                     (434)-243-1821
>>>>> />/
>>>>> />/
>>>>> />/
>>>>> />/                     On 2/12/14, 8:20 AM, "Sabine Reisser"
>>>>> />/                     <sabine.reisser at kit.edu
>>>>> <https://maillist.sys.kth.se/mailman/listinfo/gromacs.org_gmx-developers>
>>>>>
>>>>> />/                     <mailto:sabine.reisser at kit.edu
>>>>> <https://maillist.sys.kth.se/mailman/listinfo/gromacs.org_gmx-developers>>>
>>>>> wrote:
>>>>> />/
>>>>> />/                         Hello,
>>>>> />/
>>>>> />/                         I have implemented an extension to the
>>>>> />/                         existing umbrella code in
>>>>> />/                         Gromacs
>>>>> />/                         version 4.6.3. It is a semiharmonic
>>>>> potential
>>>>> />/                         which sets a maximum
>>>>> />/                         distance between two index groups. When this
>>>>> />/                         distance is trespassed, a
>>>>> />/                         force kicks in and bounces the pull group
>>>>> />/                         back, when the distance is
>>>>> />/                         below the threshold, motions are completely
>>>>> />/                         unrestrained. I use this
>>>>> />/                         code to simulate pores of antimicrobial
>>>>> />/                         peptides, to keep the peptides
>>>>> />/                         in close vicinity without actually
>>>>> interfering
>>>>> />/                         with the pore formation
>>>>> />/                         process.
>>>>> />/                         The code can also be used to make sure
>>>>> several
>>>>> />/                         peptides bind to the
>>>>> />/                         same
>>>>> />/                         side of a membrane or in ligand-binding
>>>>> />/                         simulations.
>>>>> />/                         The relevant part of the extended code is no
>>>>> />/                         longer than 10 lines,
>>>>> />/                         but I
>>>>> />/                         naturally had to change other files in order
>>>>> />/                         to read the modified input
>>>>> />/
>>>>> />/                     >from the mdp files, too. Affected binaries are
>>>>> />/                     mdrun and grompp.
>>>>> />/
>>>>> />/                         Instead of providing this singular modified
>>>>> />/                         Gromacs 4.6.3 as a tarball
>>>>> />/                         for downloading, I would like to get this
>>>>> />/                         extension into the official
>>>>> />/                         release so that it is maintained also in
>>>>> />/                         future releases.
>>>>> />/
>>>>> />/                         What is the procedure to achieve this or who
>>>>> />/                         is the best person to
>>>>> />/                         address?
>>>>> />/
>>>>> />/                         With best regards
>>>>> />/
>>>>> />/                         Sabine Reißer
>>>>> />/
>>>>> />/
>>>>> />/                         ---------------------------------
>>>>> />/                         Dipl. phys. Sabine Reißer
>>>>> />/                         Theoretical Chemical Biology
>>>>> />/                         Institute for Physical Chemistry
>>>>> />/                         Karlsruhe Institute for Technology (KIT)
>>>>> />/                         Germany
>>>>> />/
>>>>> />/
>>>>> />/
>>>>> />/                         --
>>>>> />/                         Gromacs Developers mailing list
>>>>> />/
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>>>>>
>>>>>
>>>>> --
>>>>> Dipl. Phys. Sabine Reißer
>>>>> Karlsruhe Institute of Technology (KIT)
>>>>> Institute of Physical Chemistry
>>>>>
>>>>> Phone +49 (0) 721 / 608-45070
>>>>>
>>>>>
>>>>>
>>>> --
>>>> ---------------------------------------------------
>>>> Dr. Jochen Hub
>>>> Computational Molecular Biophysics Group
>>>> Institute for Microbiology and Genetics
>>>> Georg-August-University of Göttingen
>>>> Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany.
>>>> Phone: +49-551-39-14189
>>>> http://cmb.bio.uni-goettingen.de/
>>>> ---------------------------------------------------
>> --
>> ---------------------------------------------------
>> Dr. Jochen Hub
>> Computational Molecular Biophysics Group
>> Institute for Microbiology and Genetics
>> Georg-August-University of Göttingen
>> Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany.
>> Phone: +49-551-39-14189
>> http://cmb.bio.uni-goettingen.de/
>> ---------------------------------------------------
>
> --
> Dipl. Phys. Sabine Reißer
> Karlsruhe Institute of Technology (KIT)
> Institute of Physical Chemistry
>
> Phone +49 (0) 721 / 608-45070
>
> --
> Gromacs Developers mailing list
>
> * Please search the archive at http://www.gromacs.org/Support/Mailing_Lists/GMX-developers_List before posting!
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-- 
Dipl. Phys. Sabine Reißer
Karlsruhe Institute of Technology (KIT)
Institute of Physical Chemistry

Phone +49 (0) 721 / 608-45070



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