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

Berk Hess hess at kth.se
Fri Feb 13 14:58:49 CET 2015


Hi,

Does https://gerrit.gromacs.org/#/c/3947/ do what you want?

Cheers,

Berk

On 2015-02-13 14:41, Sabine Reisser wrote:
> 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
> />/
> />/
> />/
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> Dipl. Phys. Sabine Reißer
> Karlsruhe Institute of Technology (KIT)
> Institute of Physical Chemistry
>
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